Structure 101

Introduction

In this lesson we will cover structural components of a typical residential home. We will learn about footings, foundations, framing floors, walls and roofs. After we learn about how a house is built, we will look at some common defects an inspector is likely to encounter. These lessons are copyrighted for the exclusive use of the Global Inspector Training Association.

Objectives & Outcomes:

At the end of this lesson the student will have a good understanding of how a house is built, be aware of common defects, where the defects generally are found, how to recognize them and document them in a professional home inspection report.

Standard Of Practice

The Global certified inspector shall:

Describe:

1. Methods for inspecting: Attic structure, ceiling structure, floor structure, foundation, roof structure.
2. The type of foundation as basement, crawl, slab, brick, block, poured concrete.

Inspect:

All visible and accessible components including but not limited to:

1. Visible framing such as walls ceilings and floor joists.
2. Foundation, piers, support posts and poles.
3. Wood in contact with the soil.
4. Evidence of past or present water infiltration.
5. Modifications to structural components such as over notching or drilling.

The inspector is not required to:

1. Endanger their self by climbing into or onto areas that may be unsafe.
2. Give engineering advice on causes or repairs.
3. Give cost estimates on repairs.
4. Crawl or walk through attics that do not have an adequate and visible walking or crawling surface.
5. Enter into crawlspaces in which the inspector cannot fit and safety traverse.

Checking for prior knowledge

As a home inspector you will be required to write reports therefore, we emphasize writing. Practice your writing and write down on a piece of paper what you know about the structure of a house. Can you name some or all of the structural components in a house. Can you describe the process of how a house is built?

To better understand the structure of a house and how it preforms over time, we are going to learn how one is built and then look at some common structural issues.

Building a house starts with a set of drawings like these. These drawings are called blueprints because once upon a time the process used to duplicate them made them turn blue.

Today, the blueprints look like this and are still usually called “blueprints”, “drawings” and just “prints”.

This is one of the houses my students and I built when I was still teaching high school construction. In this class we built a real house each year and these are some of the prints we used. This is a two-story house with a basement, and we can see the basement foundation plan as well as the first and second floor plans.

This is a more detailed drawing of the foundation plan within the set of blueprints. This drawing has the dimensions, windows, placement of furnace, water heater, sump pit. Based on these drawings, building codes, a survey, site plan an excavator comes out to the site and digs the basement.

Foundation

At the beginning of each school year, we broke ground for a new house, and we did almost everything ourselves. However, some things, like digging the basement, we had to hire out to a contractor.

Here the excavator is digging our basement for us while the students watch. In class, we also taught lessons about different types of soils, drainage, and hydrostatic pressure.

After the digging of the basement is complete, we got in the hole and did some fine tuning of the bottom which needs to be flat and level.

This hole in the ground that will become our basement. In my opinion, a basement is nothing more than a hole in the ground with a drainage system around and under it…and eventually, all drainage systems fail and the basement leaks.

If you have a background in construction and think this looks like clay soil, you are correct. Clay soils are known to hold water, expand when wet, shrink when dry and inhibit drainage. When wet dirt and water push inward on a foundation, it is called hydrostatic pressure, and the force is so great that it can buckle the foundation.

In our future basement, a student is digging a hole for the Stanchion pads . These pads are a foundation/footing for the metal poles that hold up the steel beam.

We can also see the wood forms for the foundation footing behind the student. Those forms will be filled with concrete to create the footing for the foundation which the basement walls will sit on. After the concrete is dry, the forms are pulled off and used again at another job.

The hole the student is digging will also be filled with concrete at the same time the footing forms are filled. The Stanchion poles will rest on top of the pads, and the steel main beam will sit on top of that. The concrete basement floor is not the footing for the Stanchion poles, the concrete stanchion pad under the floor is footing. Many times, homes are modified, and stanchion poles are moved, and the concrete stanchion pad isn’t dug and poured. And the supporting pole doesn’t have a proper footing.

This is what a completed Stanchion pad, pole and main beam look like. Notice the concrete pad under the basement floor. Again, this is what actually supports the Stanchion pole, not the concrete basement floor.

This student rakes dirt up against the bottom of the footing forms so none of the wet concrete oozes out the bottom as it is poured in. These forms are not just sitting on the ground, they have stakes holding them in straight, square and level.

Here students use a transit level to check the elevation of the bottom of the basement and to make certain all the forms for the footings are level and at the correct height. It is very important that the footing is level and square. If you start a house on a foundation that is not level and square, carpenters will be fighting it until the last piece of trim is nailed on.

Once the forms are level and square, concrete is then poured into the wood footing forms and allowed to dry. Bleeders AKA weeping tiles are run through the footing to allow ground water to flow through and into the sump pump system.

This is the completed footing. The concrete has been poured in the forms and allowed to dry.

The entire house sits on the footing which is deep in the ground and cannot be seen by home inspectors once the house is completed. After the footings are dry the forms for the basement walls are brought in on a truck. Then the crew sets the forms for the poured concrete walls.

Students observed as the forms are set into place with a crane. The sections of wood forms are bolted together to prepared for the concrete to be poured inside of them.

Notice that there are two walls that create the forms, and a threaded steel rod runs between them, and a nut goes on each side.

The nuts and bolts keep the forms from pushing apart when the wet concrete is poured in between them. It takes about 28 days for concrete to cure to 98% of its full strength. But, after a couple of days the concrete is firm enough for the crew to come back and strip off the wood forms, the threaded steel rods are knocked out with a hammer and the holes are filled with concrete, hydraulic cement or other similar products.

After the forms are stripped off, we can see the beam pocket for the steel support beam AKA “I beam” that holds up the center of the floor structure. We also see something called a “cold joint in the concrete.

A cold joint is where two different concrete pours meet. Cold joints are formed when the concrete truck dumped its load and then another truck comes and pours on top of the previous load. And that line in shows us where that happened. We can also see the rod holes which haven’t been filled yet. Rod holes are an important issue with home inspectors because they are known to leak water.

Our students dump and spread about 4″ to 6″ of medium sized and small gravel which is below the basement slab. This provides the base for the concrete basement floor and the voids between the gravel provide drainage. The perforated PVC weeping tiles leading to the sump pit are buried under the gravel. The white PVC pipe sticking out of the ground is a “rough in” for a future basement bath as well as the connections to the sanitary sewer for the first and second floors.

Floor Framing

About the time the forms are being stripped off of the new foundation walls, the lumber is delivered to the jobsite so that framing can begin. In the picture we see dimensional lumber as well as the Oriented Strand Board (OSB) used to build and sheet the floors and exterior walls. The words OSB and plywood are commonly used interchangeably, but they are actually different materials.

In this picture students are measuring the top of the completed foundation walls so we can cut our first piece of sill plate AKA mud sill which is what attaches the concrete foundation to the wood structure of the house. Also, notice the circled the brick ledge in this picture.

The brick ledge is where the exterior brick veneer sits on the foundation of the house. Home inspectors may not be able to see the foundation of a house but seeing a crack in the brick veneer MAY be an indication that the foundation is moving.

Also notice the large pile of dirt behind the house which is there because we have not backfilled around the house yet. It is not a good idea to backfill around a house until the floor structure is secured to the top of the foundation walls. This is because the floor structure actually holds the foundation walls out and keeps them from leaning inward. The weight of the dirt and hydrostatic pressure could push the foundation walls inward.

In this drawing we can see how the concrete foundation is attached to the wood sill plate AKA mud sill with a J bolt. The hydrostatic pressure on the basement walls will push the walls inward unless the flooring system is properly attached to the foundation. In the drawing we see the foam continuous sill sealer between the foundation and wood mud sill.

This drawing is to reinforce the concept of the floor structure holding the basement walls out against the pressure of the soil. When the flooring system is securely connected to the top of the masonry walls with J bolts, it actually creates a strong box. This box holds the top of the walls out against the hydrostatic pressure of soil and water. The top of the foundation must be connected to the floor structure otherwise, the walls can lean it. Once the 4″ thick concrete basement floor is poured, it holds the bottom of the walls out against the pressure at the bottom. The deeper the foundation goes in the ground, the more pressure on it. This hydrostatic pressure can move the foundation walls and cause cracking & leaking.

Here we see students putting down foam sill sealer which stops air leaks, insects, moisture, and other penetrations under the wood mud sill.

This is not one of the houses we built but, we can see that the foundation was not poured level and then the carpenters came to start framing. They discovered the issue and compensated with some shims under the mud sill. That is a lot of shimming for a new foundation. The shims are only on the end and once the walls are framed and drywall & siding are installed, on both sides, the treated 2×6 mud sill will compress. This may cause can cause drywall cracks.

The floor structure of a house is started by installing the steel support beam AKA “I-beam” which the wood floor structure rests on. In the picture, we just set the steel beam, and my students are using levels to make certain they are plumb before attaching them. In construction, plumb means to be perfectly vertical, or straight up and down, like a wall or a pole.

After the steel support beam is set in place, the wood floor joists can be installed and secured to the mudsill with framing nails AKA 16d nails. Floor joists are generally installed 16″ on center (OC). These pictures are a mixture of different houses we built. Therefore, in some pictures you will see dimensional lumber floor joists as well as I-Joists being used.

Next wood or metal bridging between joists is installed. During construction, the bridging keeps joists from twisting out of place. After construction, and for the life of the building, the bridging helps strengthen the joists by connecting them together so that some of the load is transferred from one joist to another.

After the floor joists are laid out and secured, the Oriented Strand Board (OSB) plywood subfloor is put down and secured with construction glue, nails and screws.

Screws are better than nails in this application because they are less likely to pull out and start squeaking. This is not the same 7/16″ OSB that is used for exterior wall sheathing (not sheeting). This floor was sheeted with 23/32″ tongue and groove AdvanTech. Underlayment like cement board for ceramic floor tiles go on top of the subfloor.

Video

In this video I am in a house that is under construction and discuss some of the structural components that may not be visible during a typical home inspection.

When a blueprint calls for a wall to run parallel to… and fall between two floor joists, carpenters will frame something called a ladder into the floor structure. Here, 2x4s were ran perpendicular to the 2×10 floor joists and are resting on top of more 2×4 cleats. This is a common framing method and adds additional support for the wall above.

This video shows the same sort of carpentry technique but the 2x4s are “on the flat” or sideways. So, there is more than one way to accomplish the same thing. And all carpenters think their way is the only correct way!

Wall Framing

Once the floor is framed, the walls are built on the floor deck and stood up in place. Let’s look at the parts of a typical wall from the top down.

The double top plate is at the very top of the wall.

Headers are structural members that carry the load over openings like doors and windows.

Trimmer studs are what the headers rest on at each side of the opening.

Rough sills are the bottom of the window framing.

Cripple studs can be above or below a window. In this picture cripple studs are above and below the window are there simply to make the opening smaller.

Sheathing is 7/16″ OSB in 4’x8′ sheets which covers the outside of the wall studs and drywall covers the inside.

The walls are framed on the ground and then stood up in place and braced. Students nail the wall assembly together with 16d framing nails.

Here we see a wall that is braced with a 45-degree 2×4 board coming off of the corner connecting the wall to the rim joist. Most of the time, professional carpenters will build the wall sections on the ground including sheeting the stud walls with OSB before standing them up.

Once an abutting wall is ready to stand up the 45-degree horizontal brace can be pulled off. Then the new abutting wall is nailed to the first and a double top plate is put on overlapping and connecting the two walls.

The 7/16″ thick OSB sheathing provides bracing against the wind and no metal corner braces are needed in this situation.

In this picture we can see how the double top plate overlaps from one wall to the next connecting the two walls together. The joints are staggered and again, this strengthens the entire structure against lateral forces like wind loads. This keeps the walls from racking and keeps them square.

Sheathing is the OSB plywood that is nailed across the wall studs and trusses.

The standard nailing pattern for plywood wall sheathing is an 8d which is 2.5″ x 0.131″ no more than 6″ apart at the edges and 12″ apart everywhere else. Again, this adds lateral strength to the building and gives us a good surface to nail siding over.

The corners in a building also help strengthen the structure against wind loads. This is a typical 2″x6″ framed corner of a house. Notice that an interior corner is created for screwing and gluing drywall to the studs.

Also, the bottom of the wall is called the bottom plate, and it is nailed to the wood floor decking. Also, the exterior wall sheathing overlaps down on the rim joist of the house holding the entire structure to the foundation.

Video

This video discusses how a home inspector can identify a load bearing wall.

After the walls are up the roofing structure can be built. In this case, we used trusses. The green objects are truss spacers to make certain the that the trusses are laid out properly. Roof trusses are generally laid out 2′ (two feet) on center. Conventional framing is generally 16″ (sixteen inches) on center.

Here, students are actually in the trusses nailing the 4’x8′ sheets of OSB onto the trusses. As the OSB and trusses are nailed together, the green spacers are taken off. Framing guns which shoot framing nails are used in most situations because it is faster than using a hammer.

This is another picture of students sheathing the roof. Residential trusses are generally set by hand while larger commercial trusses may require a crane. We had about 20 teenagers in each class, so we had plenty of muscle to lift the trusses in place. Some roofs are still conventionally framed but trusses are used the majority of time in the Detroit area.

Here we are nearing the end of the framing portion of our project house we built that year. We also built our own stairs to the basement and second floor. Let’s take a look at how stairs are constructed.

Stairs

During the framing of the house, the same carpenters may also build the stairs.

There is information about inspecting stairs in the basement and living space sections of this program. But those lessons don’t cover how stairs are built.

In the drawing we can see the three major parts of a simple staircase, tread, riser, stringer. There is also a preferred angle of 30-35 degrees so that the stairs are not too steep or not steep enough.

Private home inspectors are NOT code enforcement, but it is wise to be familiar with the codes. The 2018 IBC building code for rise and run for stairs is a maximum 7″ rise and minimum 11″ run (tread depth). The OSHA standard for rise and run of stairs is maximum 9.5″ rise and minimum 9.5″ run (tread depth). The OSHA standard is likely different because it encompasses commercial and industrial applications. A wise, old builder once told me… “Matt, the perfect stair is 7/11, 7″ rise and 11″ run, and is easy to remember…7/11 just like the store.”

The two main types of stair stringers are routed AKA house stringers and saw tooth stringers. In the picture we see a saw tooth stringer at a job site. Home inspectors will most commonly see this type of stringer on outdoor decks. Stringers like these can be purchased at some lumbers stores but, when building a house, the carpenters framing the house will typically make the stringers out of 2″x12″ lumber.

Here we are making our stairs at school using a metal jig and router to cut the grooves in the stair stringers. These are routed AKA “house stringers” which are generally found inside of homes.

After the stringers are completed, the treads are risers are screwed and glued into place inside the stringers.

After we completed framing the stairs we stood them up against a wall to test them!

Video

A nicely done set of stairs installed in a home under construction.

Inspecting Structures

EXTERIOR

Now that we have learned the basics about how a house is built, let’s look at inspecting them.

Remember that in most cases, brick is a veneer siding and not actually a structural component of the typical residential home. On this house we can see just one layer (wythe) of brick. Also, in this picture we can see the wood structure behind the brick. In a house like this, the brick isn’t structural, the wood framing behind it is. And as we learned earlier in this lesson, the brick sits on the brick ledge on the foundation.

If the brick starts cracking and/or moving that can be an indication that the foundation has moved as well. Keep in mind that brick can simply come loose from the wood structure that is behind it and lean out and fall off like it is here. There weren’t any cracks or any bowing in the foundation of this house. The foundation was perfectly straight, level and plumb, so, what happened to the brick on this house? I suspected that the brick ties that hold the courses of brick steady to the house had simply rusted out. It was also a tall two-story 100-year-old house making the brick more apt to lean and pull away from the house.

Notice that there is no house wrap like Tyvek or even tar paper under the brick. This is an old house and just has brick over wood. Also, a house this old will rarely have any insulation between the wall studs.

This is a horizontal crack in a brick house and if you look closely, the vertical mortar joints below the crack are pointing slightly inward indicating that the foundation is bowing inward and is pulling the brick in with it.

Remember, the brick on a house sits on the brick ledge which is part of the foundation. When a foundation is bowing inward, it is almost always a block or brick foundation and almost never a poured foundation. With a horizontal crack like this, there will very likely also be a horizontal crack in the foundation which may be visible from the basement. If the basement is finished, someone MAY have finished it just to hide the cracks and/or repairs to the foundation.

Going inside the basement for just a moment, we see a horizontal crack in the foundation wall. When the foundation cracks like this, it is pushing inward. As the foundation pushes inward, it pulls the exterior brick in with it as we saw in the last picture. These two cracks are related to each other.

Inspector sample comments: There is a horizontal crack several feet long on the exterior brick. This is likely related to the horizontal crack in the block foundation. The foundation appears to be pushing inward, and a foundation repair company should be contacted for further evaluation and cost of any repairs.

If the basement is finished, cracks like this may not be visible and that should be documented in the report in writing and with pictures.

Inspector sample comments: “There is a horizontal crack several feet long on the exterior brick and this may be an indication of the foundation is cracking and pushing inward. However, the basement was finished, and I could not determine if the foundation is cracking/moving. A qualified contractor should be contacted for further evaluation.”

In our reports we actually stopped putting the phrase, “A qualified contractor should be contacted for further evaluation” in every marginal or defective item of the report. Instead, we put it in all capital bolded letters in our contract and at the beginning of every section of the report.

“IF ANY INSPECTION ITEMS ARE RATED AS “MARGINAL OR “DEFECTIVE”, WE STRONGLY ADVISE THAT THE CLIENT CONSULT WITH A LICENSED & QUALIFIED CONTRACTOR FOR FURTHER EVALUATION AND COST OF REPAIRS BEFORE YOU PURCHASE THE PROPERTY, NOT AFTER.” This phrase appears at the beginning of each section of the report for a total of about 23 times.

This is a classic step crack in a brick house which is a good example of possible differential settlement. Step cracks in corners can occur for a number of reasons but foundation settlement is a major reason. Downspouts are very often in the corners of homes and if they are depositing water too close to the foundation, the water can soften the dirt and cause settling.

Differential settlement cracks are characterized by cracking in a building’s foundation and/or the exterior cladding, and/or interior finished surfaces. This happens when different parts of a building’s foundation settle at different rates, and are caused by a number of issues:

Soil: Different types of soils expand, contract, and shift at different rates. If part of a building rests on solid bedrock and another part of the building rests on loose soil, the section on the soil will settle more over time.
Nearby structures: Large trees with large roots, downspouts, waterpipe leaks, and excavations close to the building can also cause differential settlement.
Foundation dimensions: The dimensions and depth of the building’s foundation can also be a factor in differential settlement.

In this video, structural engineer Joe Vaglica PE, Phd discusses a step crack in a commercial building we inspected together. Joe discusses several different possible reasons for the cracking. The brick veneer was cracked but the CMU block wall behind the brick was visible and was not cracked.

In the picture, the top portion of the brick has shifted outward and overhangs the bottom. This sort of movement is generally called cracked with displacement or sheer.

We can also see that the mortar has been repaired in the past. Repairing the mortar just fills the crack and keeps the water out but doesn’t repair the cause. This was the corner of a front porch, and many times porch foundations are not as deep in the ground as the house and the porch can sometimes settle and pull (rotate) away from the house.

Inspectors should site (look) down each side of a building that they are inspecting. If it looks like it is crooked or leaning, it probably is. However, it could also be an optical illusion. Putting a level on it is a great way to document the actual condition of the wall.

In the picture, I had to pull the level over an inch away to get the bubble in the center.

Attics Structure

This is a drawing showing the names of the different rafters in a roof.  The most common and important ones to remember are:  Ridge, valley, common, hip and valley rafters.   We can see in the drawing that the ridge rafter is the peak of the building.  The valley rafter is the rafter under the valley and runs from the ridge to an inside corner.  The hip rafters are the angled ridges running down from the ridge to the top of the walls on and outside corner.  Any one of these rafters can split or bow and should be visually inspected as best you can from the attic and the roof. ​

Inside an attic we see 2″x4″ rafters on 2′ (two foot) centers, spanning about 13′ (thirteen feet).  We call this over-spanning meaning that the structural member is too small to span that far. I drew the white straight line which shows how much the 2″x4″ behind the white line is bowing. It appears to be about a 2″ bow in the rafter.   Today, at least a 2″x6″ would be used here and would be on 16″ centers, not 24.”  This is a structural defect, but the repair is fairly easy to repair with a knee wall AKA pony wall.  ​

​1″ of snowfall on the roof weighs approximately one pound per square foot. So, a 1,500 square foot home with 1″ of snow on the roof has an additional 1,500 pounds of weight called snow load to support.​ Ten inches of snow could weigh 15,000 pounds. This much weight can obviously cause a poorly framed roof to collapse.

A simple solution to sagging roof rafters is a knee wall AKA pony wall like we see at both sides of this picture. Very old roof structures tend to be undersized by today’s framing standards.

This was a 100-year-old house with 2″x4″ rafters 2′ OC (On Center). This house also had no ridge board at the peak however, it was not failing in any way. No sagging or splitting of any of the rafters. That is probably because there is a knee-wall at the bottom third is supporting the 2″x4″ rafters. If something isn’t framed to today’s standards but isn’t failing, it isn’t a good idea to call it out as a defect and make a big deal of it. We always commented on it and took a picture for the report but very few people are going to fix something in a 100-year-old house if it isn’t failing.

Inspector sample comments: The roof rafters are 2″x4″ and 24″ on center. Today, 2″x6″ rafters 16″ on center would likely be required. However, the framing isn’t bowing, splitting or failing in any way. This is just an FYI.

This is damage to the plywood sheathing on a roof. There was no damage to the roof shingles in this area. I am guessing a large tree limb may have fallen on the roof in the past and damaged the plywood. Then the roof may have been replaced which is why I didn’t see any exterior shingle damage. This area was a little soft and we called it out as a defect in the inspection report.

This is another attic with 2″x4″ rafters but these are sagging and notice that there is no knee-wall at midspan to support. This picture was taken when there wasn’t any snow on the roof. Many houses will have 2 layers of shingles on the roof because the code allows it. A 1,200 square foot house with two layers of shingles weighs about 5,760 pounds.

Using blocks to support roof rafters is never a good idea! These are blocks installed incorrectly in a barn attic to support the roof. Even in a basement or crawlspace stacking blocks end to end is improper construction.

Additionally, the weight of the blocks of course makes this a bad idea. None of this was fastened together and had a lot of loose shims at the top. Any improper modifications done to the structure should be photographed and documented in the report as a defective item requiring further evaluation by a qualified contractor.

This is not a split. It is called a scarf joint and has been there since the house was built. A scarf joint is a type of framing joint used to lengthen a rafter. In other words, they didn’t have a sick of wood long enough for the span, so they made one. In my view, this is not a great way to frame a roof, but it is allowed and there are videos online demonstrating different techniques for scarf joints. We can see in the picture that the joint has spread apart by about 1/8″ in a 50-year-old house. We didn’t call this out as a defect.

This is another roof rafter that was lengthened and there is a knee-wall under it to support it. We can see inside the cracked portion on the left and the wood looks much lighter in color indicating that the split is newer rather than older. This may have cracked when there was a heavy snow load on the roof.

It is not a good idea to notch a structural beam on the bottom because they tend to split like this.

Inspector Sample comments: Crack in roof rafter approximately 1 foot long and in need of repair.

This is fire damage in the attic of an occupied home which is not that unusual. This is one of those “out of sight, out of mind” issues that pops up. Many times, sellers of property forgets to mention damage like this in the seller’s disclosure documents and it is up to the home inspector to find it. Fire damage is sometimes painted over in attics. However, this is not necessarily to hide the damage but is to kill the burnt smell that will permeate the house. The two main reasons to paint an attic are fire damage and mold growth.

Inspector sample comments: “There is significant fire damage in the attic. Ask the seller about past fires in the house and who did the repair. Was the repair sealed by a structural engineer and were permits pulled.” Or, “Attic was painted, ask the seller if they know why this was done. The two most common reasons are fire damage and mold growth.”

Video

In this video, Joe Vaglica, PE, and I are using my sewer camera to inspect trusses in a building. The city had some issue with the type of trusses used on the project and they required a structural engineer to inspect and sign-off on the trusses. I removed a recess can light in the kitchen to give us access to the ceiling cavity so we could do the inspection. We used my sewer camera to see inside the ceiling. Sewer cameras can also be used to inspect the interior of a metal or brick chimney as well as French drains and sump pump lines. It is my opinion that sewer cameras are one of the best investments an inspector can make.

Living Space Structure

This home was only about ten years old, but the door at the left wouldn’t close, and the drywall had a stress crack. Issues like this are a little unusual in such a newer home.

The area below was an open floor plan, no supporting wall directly below. So, I suspected that the beam spanning this area was sagging. Definitely an item for the inspection report.

If the house were 100 years old, I would expect something like this. This is a much more serious issue in a newer home.

These are routed AKA house stringers as we saw earlier in this lesson. As an inspector goes up or down a set of stairs, that is a great time to inspect them. We can see in the picture that the stair treads are pulling out of the stringers, and this is certainly a structural defect. Stairs like this can suddenly fail and people could be hurt.

Believe it or not, head clearance can be an issue in homes. This was a very nice 1920s mansion with inadequate head clearance on the main stairs. When this house was built, you would think that code officials would have caught this and required modifications but apparently not. Also, people have gotten taller since the 1920s. Even though something like this is generally “grandfathered-in” it should be called out in the inspection report.

Basements Structure

Let’s looks at some common structural damage seen in basements from the top down.

When in a basement, look up! In the picture, Joe Vaglica, is looking up at the structure of a commercial basement we inspected. Basements are one of the places in a building where much of the structure may be visible so, take your time and inspect the visible structure thoroughly.

Most of structural the damage in a basement will be water related, and almost all of that damage will be at the top and bottom of the basement. The top because there are water sources like pipes, sinks and toilets above and the water can drip down and cause extensive damage to the wood or metal structure. There is also commonly water damage at the bottom of a basement because that is where the most hydrostatic pressure is located. Hydrostatic pressure is the pressure exerted by a fluid at rest due to the force of gravity. The force is increased with depth of the fluid. Dirt has water in it and the deeper the foundation, the more pressure it has on it.

At the top of the basement, structural steel beams should be inspected closely for rust damage. This is especially under porches and the exterior walls where there is typically more moisture.

In the picture the ceiling is a concrete porch slab. The porch was three stories and had a roof covering it. Notice how the rust is much worse at the outer wall where there is more moisture.

At the top, this is a rotten subfloor under a bathroom, and this is structural damage. The plywood subfloor is rotted because a toilet was dripping a few drops of water for many years. To properly repair, the rotten section would have to be cut out and replaced. New cement board and ceramic tile would have to be replaced as well.

At the top, water damage can be found at the upper portion of a basements. Sliding doors and their tracks are known leak problems. This is especially true if there is no overhang on the house which exposes the door-wall to more rain and snow.

Inspectors should inspect door-walls for leaks when they are testing the function of the door and also from underneath. In the picture, we can see here that I bring a step ladder into the basement when I inspect a house. I pulled out the insulation under the door-wall and found water damage to the subfloor.

This is how you can go from a zero to a hero in the inspection business. Knowing what kind of damage to expect and then taking the time to actually find it. I have known plenty of home inspectors that would never bring a step ladder into a basement and pull-out insulation under a door-wall. Keep in mind I didn’t pull out insulation all across the basement, just under the door-wall because that is a problem area.

Splits in wood floor joists may be visible and generally repaired pretty easily by sistering on another joist. We generally walk from one end of the basement to the other just looking the floor joists with special attention focused under the wet areas like bathrooms, the laundry and kitchens.

At the top, this is water coming through the brick and into the basement at the rim joist. This happens when the grade is too high around the house. If a house has raised brick flower boxes around it, this sort of issue can easily occur so be watching for it.

Foundation Walls

Lasers are great for checking walls for bowing but don’t work well outdoors. A simple piece of string can tell an inspector a lot. This is a situation where a concrete foundation wall was poured crooked. I am guessing that the forms slipped out of place during the pour, and no one noticed until it was too late to fix it. Foundations can be built crooked and may not have moved due to settling.

Let’s look at common issues found in the middle of a foundation wall. This is a block foundation which is bowing in the middle of the wall about halfway between the floor and the ceiling. Some folks call this a cinder block foundation, and others will call it a Concrete Masonry Unit (CMU) foundation. There is a difference between cinder block and CMU blocks but that is a subject for another time, and we will just call them block foundations in this lesson.

The portion of the wall sticking out is a block pilaster on a block basement wall. These pilasters are generally installed at the time the house is built and are meant to help stiffen the basement wall and protect the middle portion of the wall from bowing inward. These pilasters are generally found on the longest walls in a basement and not on the short ones. This is because the longest walls are more likely to bow and crack. If you look about halfway up the wall, you can see a crack that has been patched. This is the classic horizontal crack in a block foundation. The longest walls generally crack first, and it is usually about halfway up the wall like this one.

I am using a hand signal to show that the pilaster isn’t loaded at the top. In other worlds there is no load on it. The pilaster doesn’t go all the way to the top of the wall, and the weight of the house isn’t sitting on pilaster. If the weight of the house was sitting on it, that would make it much stronger. This can be demonstrated by stacking up three empty pop cans on top of each other. If you take one finger it is easy to knock them over with very little force. Then, put one hand on top of the cans and apply a little weight. Then take your finger and try to knock the cans over again with the same amount of force. When the pop cans have a load on the top, they cannot be knocked over with the same amount of force.

Video

The video above discusses some of the issues related to the bowing of brick and block foundations.

This foundation wall and pilaster are bowing but there was no visible crack in the wall. If it was patched, we certainly couldn’t tell.

There is a slim possibility that if a wall is crooked, it may have been built that way. Even if a wall was built crooked, it is still a defect to be put in the report.

Ironically, this bowing pilaster does go all the way up to the flooring structure and appears to be loaded with weight of the house which should strengthen it. Didn’t work this time!

Notice the brick opening at the window left of the water pipes. We can see how out of plumb it is. Also, a gap has formed between the two layers (wythes) of brick in the foundation. Separation of wythes of brick is a common defect.

Different house, same situation. This crack looks like it was patched in the past and now has re-cracked.

Again, the crack is about halfway up the wall, and we can see a pronounced bowing of the wall. Customers always ask if the crack will get worse and, in my opinion, the answer is always yes. Slowly but surely, over a long period of time the crack will get worse.

As an inspector, you simply need to advise them to get further evaluation by a qualified contractor. In this case, a qualified contractor would be a foundation repair company, and they likely recommend bracing with steel beams. Repairs like this are typically tens of thousands of dollars.

Let’s discuss hydrostatic pressure a little more in-depth. This drawing is a very good depiction of what actually happens. If you were to take a stick in your hands and bend it until it breaks, it will almost always break in the center third… and foundation walls are no different.

The cracks will usually be present and widest in the center third of the wall and the crack may stop before it gets to the corners of the foundation.

The shortest walls are the least likely to bow and crack and the longest walls are most likely to bow and crack. The corners of the foundation are the strongest points, and the middle portion of the walls are the weakest points against lateral pressure which is also called hydrostatic pressure.

The formula for hydrostatic pressure is p = pgh. This simply means, the deeper you go in the ground and the more water present, and the more pressure exerted on the foundation walls.

Here we see that three mortar joints between the block have cracked and been patched. When there are multiple cracks in a wall, you should add the width of all the cracks to get a total amount of movement in the wall. The total combined width of the cracks in a wall tells you how much it has moved. When cracks are patched it is difficult to tell how wide they are but, putting a level, laser or a piece of string on the wall can remove any doubt.

Working our way down to the bottom of the basement foundation wall, home inspectors may see this. This is another block foundation, but it wasn’t bowing in the middle. Instead, the second row (course) of block has pushed inward slightly. This is called wall shear and this is a classic example. The first block cannot push inward because the concrete basement floor holds it in place. So, the second course of block pushes inward.

This is another much worse case of wall shear. This wall has pushed in much farther and the third row of block has pushed inward which is unusual. Part of the reason is that hydrostatic pressure increases with depth. If you have ever swam in a pool and dove to the bottom, you felt the pressure increase on your eardrum, this is a similar concept. The deeper in the ground the foundation is, the more pressure on the basement walls.

When a wall is bowing inward or, has wall shear, obviously the wall has moved inward. Eventually the exterior soil will sink as the wall bows inward. If there is a concrete drive or slab on the exterior, it may crack as it also sinks with the soil under it. Negative grade and concrete cracking like this MAY just be settling of the soil. But it may also be a sign that the foundation is moving inward. Double check that basement wall when you see sunken concrete like this!

Another structural issue that can be found at the bottom of a basement is rusting Stanchion poles. This is a metal Stanchion pole in the basement of a 100-year-old house. There is moisture in the ground and over time the metal posts simply rust off at the bottom and the weight of the house pushes down and crushes the metal pole at the rusty bottom. This can be subtle, and inspectors have to look closely.

Inspectors should probe at the bottom of the metal Stanchion poles with a screwdriver like this and don’t be surprised if your screwdriver actually goes into the poles which are hollow inside.

If your screwdriver goes into the pole, it is rusted out and will require replacement.

Just to drive home the point, let’s look at this drawing a second time. This drawing shows how the metal Stanchion pole goes into the concrete floor and actually rests on top of the concrete Stanchion pad. Because there is moisture in the ground, the metal poles will eventually rust off. Here in the Detroit area, this seems to take about 80-100 years. So, homes built in the 20s – 40s are especially prone to rusted metal poles.

Also, note that metal Stanchion pole sits in the center of the footing/Stanchion pad. If the load isn’t in the center of the footing, it can rotate/tilt to one side. This is an engineering concept called eccentric loading.

So, that’s some of the most common structural issues a home inspector is likely to see in a basement. If you find issues like the ones we covered, customers may ask you how it could be repaired. Next let’s take a look at how some of these issues are repaired.

Problems & repairs To Block Foundations

Video

Here I discuss the bracing of a block foundation wall and point out what I like about it. This was generally a pretty good job.

This is another block foundation that was bowing inward. The owner had these 4″ steel beams installed to reinforce the wall. There’s just one problem, the steel beam wasn’t touching the wall it was supposed to be supporting. I am sticking my finger behind the beam to emphasize the point in my inspection report.

I don’t know why there would be a gap between the steel beam and the wall it was supposed to be supporting. However, this was in an area of soil with high clay content. As mentioned earlier, clay soil is very expansive and when it rains, it swells, when the weather is dry clay soil shrinks. We can see the date on the picture is July 9 and this is a time of the year when it tends to be hot and dry. The soil may have shrunk reducing pressure on the wall causing it to spring back straight. I know from talking to foundation repair crews and civil engineers that this can actually happen. In any case, the gap between the steel beam and the wall could be filled with mortar to touch and support the wall. Mortar should fill the gap of any voids between beam and the wall it supports because this will give even support to the wall from top to bottom.

When these steel beams are installed to support bowing walls, the most common spot for failure is at the top bracing. There is a protocol for doing repairs like this, and the repair manuals I have found online call for bolts and not nails to attach the supports together. They also recommend having the supports be at least 6′ ) feet) long and these clearly aren’t. So, in this example, the wood braces are nailed and not bolted. Also, the braces are just a couple of feet long. This is a poor job.

Also, there were so many nails in the new wood that they had split in several places.

Here is a very good way to connect a steel beam to the flooring system. This is a 1/4″ thick steel plate with 12 bolts holding it. That’s not likely to fail.

When the braces are running perpendicular to the floor joists, wood braces are sometimes placed between every joist to carry the force over several floor joists for additional support. Otherwise, the floor joists can twist like this one is. We can see that the cold air return is buckling because the floor joist is twisting at the bottom and toward the left under the force from the foundation wall to the right.

If you live in an area that has these sorts of issues, aside from this lesson, I recommend you read everything available in the web to educate yourself as much as possible. As an inspector, you will certainly run into this situation so be prepared.

This method of bracing a steel beam against a foundation wall is far superior to the last picture. We can see this a 2″x8″ butting up against the steel beam and goes across five floor joists and is bolted to all of them. These joists are not likely to twist.

At the bottom, in my opinion it is best to set the steel beams in the concrete floor. This technique is pretty failsafe and not much can go wrong. Sure, the steel beam will eventually rust off but that will take 80-100 years.

Another technique for attaching the steel beam to the basement floor is by bolting it with an angle iron welded to the steel beam. This one looks ok, but we have seen bolts like this pulling out of the floor due to so much pressure from the basement wall pushing inward.

In this picture we can see a pretty good foundation bracing job. The steel beams are about 4-5 feet apart, nice and tight against the foundation wall in most places…just a couple of gaps which can be filled with concrete. Also notice that the basement floor was busted up along the perimeter wall. That is because a French drain/weeping tile was also put in. This helps drain water from behind the wall and relives the hydrostatic pressure on the wall.

This is another technique for stabilizing a bowing or leaning foundation wall. These large metal plates have a hole in the middle and there is a long metal rod going out several feet into the yard.

To install this system, first holes are drilled in the wall and metal rods go through the holes and several feet out into the yard.

At the other end of the rod is another metal plate or block of concrete which acts as an anchor. On the basement side, the rod is threaded and there is a large nut and washer. I know a realtor who had this done to his house and he said the company that did this repair actually gave him a huge wench to tighten the bolt as needed. I had to laugh at that one!

This is a job proposal on a foundation bracing job. You can see that it isn’t cheap and as an inspector you certainly don’t want to miss a bowing foundation.

Let’s look at some other foundation situations.

This is an interesting picture because this is both a poured and block foundation. Earlier in this lesson we saw how basement foundation walls are poured with forms. Here, the foundation contractor only had standard height forms, and the job called for a taller basement. So, two courses of block were laid on top of the poured foundation. This is perfectly acceptable as long as the two are properly connected. Can a home inspector tell if the poured concrete and block are properly connected? Not likely, however, we also know that the wood floor structure must be connected to the masonry foundation and a home inspector may be able to see that.

This is a cracked pilaster in a block foundation. Looking closely, we can see that the cracking is directly below the steel support beam. This type of crack is a common defect. This crack is a bit more serious than most and a step crack has also formed in the block wall to the right of the pilaster. This is something I would call out as needing further evaluation and repairs. Small hairline cracks under a steel support beam are common and not a serious issue.

Poured Concrete Foundations

Structurally, poured concrete foundations are fairly problem free here in the Detroit area. I have never seen one bowing inward due to hydrostatic pressure, but they do crack and leak! Earlier in this lesson we learned why rod holes are created in the foundation. In the basement lesson we learned that rod holes tend to leak and to watch out for them.

I am mentioning it for a third time because this is such a common issue and inspectors are likely to see. Keep in mind that if the basement is finished, you will not be able to see this kind of damage. You may just see a water stain at the bottom of the drywall and assume, as many would, that the leak is where the basement floor meets the foundation wall. That would be a good assumption but not always correct. If the water table is high in the soil, the water can come through higher on the wall.

Poured concrete foundations can crack and the outside corners are a common spot for inspectors to find issues. Any cracks should be noted and photographed for the inspection report.

Shrinkage cracks occur when concrete cures. As the water evaporates out of the concrete, it can shrink leaving cracks. Shrinkage cracks are from hairline up to about 1/16″. The crack in the picture is a little too wide to be a shrinkage crack and I would call this out as a stress crack. Also note that the crack is wider at the top than at the bottom indicating that some movement is happening.

Another house with a very similar crack but a bit worse. This crack was approximately 1/4″ at the widest point. But if you look closely, there are actually three separate cracks.

When evaluating cracks, it is of course a very good idea to use a measuring tape to document the width.

A finger, ink pen or pencil in the picture will also give the crack scale. Cracks in foundations can be repaired in several different ways. Epoxy type products which claim to be stronger than concrete and can effectively fill and hold cracks together. There are also carbon fiber stitches and straps that are used on cracks. If done correctly, these repairs can be effective in stabilizing structural issues.

This is a crack monitor kit which is mounted to a surface over the crack. The crack monitor is centered over the crack, and the screws are used to mount the monitor on either side of the crack. There is a grid that is marked by the installer and if the surfaces move it will be obvious.

This is a carbon fiber strip which are used for various crack and foundation repairs. The strips are attached to the damaged area with an epoxy type product and the strips go from one end of the crack to the other.

This was a vertical crack in a poured concrete foundation, and it had been injected with urethane and patched with what looked like carbon fiber strips. However, we can tell it had started leaking again by the water marks on the fresh patching material. Even the best techniques can fail if the technician doesn’t do something correctly.

Insulated Foundations

Many newer homes are also insulated on the exterior side of the foundation. Rigid insulation on the exterior of concrete or masonry basement walls has several advantages over interior insulation.

1. When installed correctly, it will provide continuous insulation with no thermal bridging. Thermal bridging is where heat or cold flows easily through certain areas of a building’s structure. 2. Foam insulation protects the waterproofing and masonry wall with more moderate temperatures. 3. Exterior foam insulation reduces moisture condensation problems on the interior side. 4. Exterior insulation doesn’t reduce interior basement floor area. 5. From the basement or crawlspace, homeowners can see the foundation wall, cracks or any leaks that may occur.

Interior insulation is actually more common in most areas. New energy codes are requiring that foundation walls be insulated like this making it impossible to see most of the foundation.

This insulation is often held in place with fasteners and inspectors are not required to pull the insulation back to inspect. Simply put in your report that the foundation was not visible, not inspected, the condition is unknown and be sure to take pictures.

This was a newer home with a blanket of insulation covering the top half of the wall, but I spotted these water marks at the bottom of the blanket. Because the insulation was secured to the foundation at the top and bottom, I wasn’t able to look behind it. I just put it in the report as a defective item to be checked into further. This was probably a rod hole leak.

Crawlspace Structure

We covered crawlspace structural issues in the crawlspace lesson. However, these issues are so common that it deserves a second short look. Beware of moisture, rot, mold and insect damage in crawlspaces. Improper repairs are also very common and should not be missed.

In the picture is a rotted 8″ wood main beam in a crawlspace. And where there is rot, there is a good chance for insect damage. We can see a newer white PVC pipe above the rotted area. I’ll bet the old metal drainpipe rusted out and leaked on this beam for many years. Because it was in a crawlspace, no one saw the leak. Crawlspaces are out of site and out of mind to most people and are neglected. The 2″x4″ and concrete blocks are a half-hearted attempt at a repair. MOST of the time, when people add blocks like this in a crawlspace they are just sitting on top of the ground and don’t have a footing.

You can’t inspect what you can’t see, and you should put that in your report. If insulation covers the structural components be sure to document it. Mention that you cannot see it and cannot inspect it, and the condition is unknown. We can see a couple of pieces of insulation hanging down and inspectors may be able to get a limited view of the structure there.

Where you can see the structure, be sure to have a probe and test suspicious areas like this. Telling your customer the wood is rotten is one thing, but pictures are worth a thousand words.

Improperly installed supports are probably the most common structural defect an inspector will find in a crawlspace. Some blocks are laid on their side and they are not designed for that. This is “dry stack” because there is no mortar between the blocks. And using a screwdriver as probe, inspectors can determine that the blocks had no footing and were just sitting on top of the ground.

Wrap-up And Review

In my career of teaching construction and inspecting, I have taken over one million pictures, and this is my favorite.

This is a picture I took when I was a judge in a statewide high school building trades contest where three high school kids built an 8’x8′ shed in a day-long timed competition.

Below is the review, good luck on the test.

Review

Test yourself, do you know the names of the structural components of a roof?

Test yourself. Do you know the names of these items?

Test yourself. Do you know the names of these items?

This is an exploded view of a typical house and displays many of the concepts we cover in this lesson. Click the blue dots to read the descriptions.

Supporting members like Stanchion poles and piers require a footing.

Framing techniques from decades ago are not the same as they are today.

The brick veneer sits on the part of the foundation called the brick ledge. If the foundation moves, the brick may or may not crack but cracks are a good indication that the foundation has moved.

Horizontal cracks in a foundation wall can be a serious structural issue. The larger the crack and the more cracks there are, the more the wall has moved. This is especially true with brick or block walls.

Not all soils are the same, some drain better than others. Soils that don’t drain well tend to apply more pressure on the foundation walls. This is called hydrostatic pressure.

Some soils are better than others at supporting a load.

Because of moisture and “out of site, of mind” crawlspaces tend to have structural issues like rot and insect damage.

Pilasters are put in basement walls to strengthen them but don’t always work at holding the foundation straight.

There are several different techniques for bracing foundation walls and many times the job is done incorrectly.

Snow and shingles weigh a lot and can cause the roof structure to sag or even collapse.

Lesson tags: California Colorado Georgia Hawaii home inspection training, California home inspection training, Michigan home inspector training, Minnesota home inspection training

Back to: Structure 101