Structural Framing Evaluation
Evaluating structural framing can be difficult for several reasons:
the quality of structural framing work varies widely;
building standards and practices for structural framing have changed over the years; and
different structural framing methods have been used and considered acceptable in different parts of North America.
The following is an overview of evaluating structural framing, as well as a discussion of the limitations of this type of building system.
In evaluating a homes structural framing, at one end of the spectrum are great architectural designs and engineering, quality workmanship, and top-quality materials. At the other end of the spectrum, all those things are poor and failing. Homes that are either in great shape or terrible shape are easy to inspect because they require very little judgment.
In most of the homes, the quality of design, workmanship and material will lie somewhere in the middle. Often we have to decide whether something is a defect or just poor-quality work, whether it’s dangerous and needs immediate correction, or whether it will last and be safe, even though it’s ugly? Making these decisions correctly is really the hard part.
Knowing Structural Framing Fundamentals
Some structural framing work may be several hundred years old, and in all types of homes in between. What was acceptable 80 years ago may not be acceptable now. While this is especially true for parts of the home like the electrical system, basic framing methods haven’t changed as radically.
Most of what can be seen will be variations on western platform framing, balloon framing, or post-and-beam. Once we understand the basic framing methods, you’ll at least have an idea of what structural framing configuration is probably behind the drywall.
Inspecting Structural Framing in Context
Evaluate homes in the context of the time in which they were originally built, taking into consideration locally accepted framing practices, and the general quality of the home. Don’t expect a 300-year-old cottage in Boston, Massachusetts, to be built like a brand new mansion in Pacific Palisades, California.
Speaking of mansions… Don’t assume that high-end homes have been built using good quality materials
or workmanship. Those assumptions can cause you to make major misses, and a major miss in a mufti-million dollar home can make you cry all the way to your lawyer’s office.
Three-hundred years ago, there were highly skilled carpenters, other carpenters whose skills were terrible, and carpenters whose skills lay between the extremes. That hasn’t changed, and the same is true for other occupations connected with the building of homes.
Structural Framing Load Path
Homes are built to transfer the structural load down through the framing to the foundation and soil. This is called the “load path” and it’s where most of the forces in a home’s structural framing are concentrated.
Understanding the different types of basic framing methods will help you to identify load paths in homes built using different framing methods. Being able to locate key point loads will also help you know where to look for structural framing problems.
Point loads are loads that are concentrated in a small area, such as where a post supporting a ridge beam rests on a header above a window. Point loads are high-stress areas.
Load paths don’t always transfer the load downward. Uplift can be a strong force, too. Forces may move down, up, and laterally during an earthquake, so if you live in an area subject to seismic events, such as Northridge, California, you’ll need to learn about the structural framing methods that have been developed to deal with shakers.
Structural Framing Support
Since the structural framing is supported by the foundation and soil, any movement of those components will be reflected in the framing.
Keep in mind that there can be a number of reasons for soil movement, such as:
changes in soil volume with the gain or loss of moisture content. Moisture can cause certain clays to expand as they gain moisture, and some types may contract with loss of moisture. These are called “expansive soils.” Excessive soil moisture can also affect the ability of the soil to bear a load. When expansive soils are the cause, the problem may continue;and/or
inadequate compaction during original construction. When soil is disturbed during excavation, it must be re-compacted by mechanical means before the foundation is installed on it. If soil is not re-compacted, the weight of the structure will cause soil to consolidate as soil particles are pressed together. The result is settling of the soil and anything resting on it. Once the soil reaches a compacted state, settling will stop. This type of problem usually takes place within the first few years after original construction, then stops.
Foundation undermining from erosion can be caused by:
Knowing what to look for will require some knowledge about the soils and construction practices common to the areas in which you work. It takes time to build that library of knowledge, but you can speed the process by talking to local contractors and building officials.
Where to Look For Structural Framing
Much of the structural framing is hidden, so look for evidence of failure in the components you can see, such as the materials covering the floor, walls and roof.
When faced with difficult decisions, remember what we do as a home inspector. You perform a visual General Home Inspection designed to identify safety issues, and system, structural framing and component defects.
Structural Framing Design and Engineering
Structural framing design and engineering are important because the size and strength of structural framing members and the ways in which they’re connected should be adequate. We don’t have to perform calculations in order to determine structural framing adequacy. Instead, we’ll be looking for signs of failure.
Structural Floor Framing
When it comes to inspecting floors, we may do more inspecting with our feet and sense of balance than with our eyes.
Looking for floors that are out of level or not flat. One of the easiest ways to spot these problems is to walk across the floor. If the floor slopes down, you may speed up a little and feel light on your feet. If the floor slopes up, the opposite will be true.
If we find problems with the floor being out of flat or level, your concern will be trying to determine whether the problems were built into the home, which has remained stable, or whether they’re the result of foundation/soil movement, which may continue, eventually causing serious and/or expensive-to-repair damage. Problems can also be the result of a combination of those two conditions.
If the problem is something such as a hump in the floor, we may see studs cut to the wrong length in a basement wall, or the foundation may not have been poured to the right elevation. Both of these conditions indicate that the problem was built in, and the home is probably stable.
If we can see a hump in the foundation beneath a basement wall, the problem may be heaving, in which case we’d look for a source of moisture or ask about expansive soils. A crack in the foundation may also indicate heaving.
One of the places at which to spot movement of floor framing is at doors. If the floor has heaved or settled, the margin above the doors will often be affected.
Again, the sales price or size of the home is no guarantee that work will be high-quality.
You Can’t Always Trust First Impressions
The photos to follow were taken beneath the beautiful 10,000-square-foot log home pictured above. There were no indications of structural framing problems until the inspector entered the crawlspace.
Inadequate post base
Inadequate Post Base
Floor structural framing defects in crawlspaces are often related to a girder that supports lapped floor joists down the middle of a span. These girders are often built up by bolting multiple joists together. Girders should be supported by posts resting on concrete pads.
Improperly Supported Break in Built-Up Girder
Failure to properly construct and install them can result in catastrophic failure. Where girders break, both sides should be supported by a post. The photo above depicts the result of poor workmanship, and could be corrected by a qualified contractor.
Overloaded Structural Framing Girder
Girders are sometimes subjected to heavy loads. Sometimes, failure is obvious, and a structural engineer is needed. The overloaded girder in the photo above is the result of poor structural framing design as well as poor workmanship. Crawlspaces are damp environments. The web of the steel I-beam supporting this post might easily be weakened by corrosion. Since the beam is already failing, eventually, the whole assembly will fail.
In evaluating wall framing, look for walls that are out of plumb, or not flat or straight. If we see protruding drywall in a tall wall, we’ll look to see if it’s at the same height as the floor joists. Upper or lower walls may be out of plumb, or the floor assembly may have components that are not flush.
It’s not unusual to find walls out of plumb because it’s not unusual to find carpenters’ levels that don’t read true. High-quality levels are relatively expensive. Levels with adjustable vials have to be adjusted regularly.
Walls areas that bow in or out may be caused by failure to crown wall studs. All studs have a slight bow in one direction. This is called the “crown,” and in better-quality framing, the studs are all crowned in the same direction.
Walls that are not straight may not have been properly aligned and braced during framing.
Both poorly crowned studs and walls that are not straight are cosmetic issues unless they’re extreme.
Diagonal cracks off the corners of doors and windows typically indicate soil movement. If you see them, look for foundation problems.
Roof Structural Framing Members
For roof framing we can see, such as in the attic, bowed, sagging, cracked or broken framing, and missing structural framing components. We may also be able to see evidence of poor workmanship, such as improper connectors or fasteners, improperly installed purlin bracing, or blocks that prevent air from flowing into the attic from the soffit vents.
Sagging rafters or inadequate rater ties can cause the ridge to sag and the exterior walls to bow out.
Structural Framing In General
For areas in which we can’t see the structural framing directly, we’ll be looking for signs of failure, such as sagging, unevenness, or cracking of the interior or exterior wall coverings.
The point at which poor-quality work becomes defective work can be tough to nail down.
If something looks wrong but shows no signs of failure after 50 years, we’d need a pretty good reason to call for correction. If it’s new and looks wrong, it may fail.
Make sure that if you can’t see it, you can’t inspect it, and you accept no responsibility for confirming its condition.
Part of this job is to limit the client’s expectations. Most inspectors aren’t structural engineers who are also experts in every building trade, although there are people out there who will expect you to know it all.
Quoting Code for Structural Framing
If certain of the year the home was built, know what codes were in effect in that area at that time. Maybe an apparent code violation as can be cited for the structural framing defect.
That said, building codes were developed to help ensure consumer safety, and code books are good reference material for home inspectors.
For conventional roofs, sometimes a qualified contractor experienced in structural framing of roof systems can be helpful. For truss roofs, a structural framing engineer should be consulted because most of the defects related to trusses require calculations.
For other types of structural framing issues, recommendations will depend on what was seen and what our experience tells you.
Recommendations will reflect our confidence in identifying the problem. If we’re not sure, it’s safest to recommend a structural framing engineer, even through it will cost the client money. If we feel confident that we understand the structural framing problem and that a qualified contractor can handle it well, then recommend a structural framing contractor.
Improving Structural Framing Skills
The ability to judge structural framing will improve with experience, especially if we all work at expanding our library of knowledge. Online forums are good venues for learning about how to evaluate structural framing.
We can also learn how buildings should be framed from books and videos, but the practical evaluation of the long-term safety and structural framing performance of a home is learned more easily from experience and remodel contractors… and time spent looking at homes.
Structural Framing Information