The title of this page is the title of a document published by the Texas section of the ASCE (American Society of Civil Engineers). The self-described guidelines are for use by Texas Professional Engineers when evaluating the performance of a slab-on-ground foundation.
It is my opinion that real estate agents and TREC (Texas Real Estate Commission) home inspectors would be well served to be familiar with some key provisions
Where these guidelines came from
In 1998 the Texas Board of Professional Engineers (TBPE) issued what they call a Policy Advisory regarding design, evaluation, and repair of residential foundations. The policy advisory stated that the TBPE received a disproportionate number of complaints against PE license holders performing design or evaluation of residential foundations.
The TBPE decided, in response to the complaints, to form a committee to study the situation and make recommendations to the TBPE, especially concerning poor communications and procedures. The board also made it clear that in the case of a complaint they would refer to the recommendations when assessing whether the engineer was competent.
The Policy Advisory was roundly challenged when it was published, especially by the Texas Section of the ASCE. The main criticism was that the professional organizations should have been the ones to develop the document. The consensus was that the Texas Section ASCE should take over and develop a new document concerning both foundation design and the evaluation and repair of residential foundations.
Why these guidelines are important
Professional engineers are required to do “competent” work. Should a complaint be filed against a Texas PE, the Texas Board of Professional Engineers (TBPE) may consult the Texas Section ASCE guidelines when making a judgment concerning competency.
Levels of evaluation
The Texas Section ASCE guideline follows the lead of the TBPE Policy Advisory 23 in recognizing three levels of reporting: level A, Level B and Level C.
Level A reports are visual and do not include any elevation measurements. A Level B report is visual but does include enough elevation measurements to convey the overall shape of the slab surface. A Level C report includes everything in a Level B report, but it also includes material testing and/or destructive or intrusive inspections.
I have never seen a level C report used in a real estate transaction. Normally a level C report would only be used in a litigation situation.
Regardless of the level of inspection or report, the data collected should be analyzed using normal engineering methods. This is a very general description. The authors seem to be leaving the details to the engineer making the evaluation. That is consistent with admonitions from TBPE that the engineer making the evaluation use his or her engineering judgment. Under no circumstances should a Texas Professional Engineer issue a cookie-cutter check-box inspection.
From an engineering perspective, foundation performance evaluations have three related components: structural integrity, structural safety, and structural performance. Performance issues, usually minor, are common, but structural integrity and safety issues are not common with the exception of doors that bind – something that is easy to repair.
Structural integrity issues
Structural integrity is a phrase that is thrown around a lot. To a structural engineer, the phrase has a fairly specific meaning: it refers to the ability of the foundation to support the design loads in a way that does not tear the frame structure apart and does not prevent the structure from serving its core function.
For example: if the slab foundation bends excessively and pulls rafters away from the ridge and, if it was severe, that could be considered a structural integrity issue.
Another example: if the concrete surface on one side of the crack is either higher or lower than on the other side, that could an indication of a lack of structural integrity. However, in the case of a driveway, and other flatwork, if the flatwork can still perform as expected the crack would still be a performance issue and not a structural integrity issue. On the other hand, if the difference in elevation could be a tripping issue, then the crack and the elevation difference would be a structural integrity issue.
Structural safety issues
The most common structural safety issue due to foundation distortion is doors that serve as a fire escape door, but which a small child can not open.
Slab foundation performance issues are a completely separate issue from structural integrity and structural safety issues. In almost every case, what concerns the home buyers and homeowners most are performance issues.
There are two reasons why homeowners focus on performance issues: they can usually see them, especially cracks and separations and they are afraid that they may be indications of a more serious structural issue.
Performance issues include the following:
When judging how well or poorly a foundation is performing, the guideline recommends you look for the following visual indicators of performance. Note that the following indicators are in bold letters. My comments are below each indicator:
Cracking or separating of exterior walls:
This is vague, to say the least. I assume they are talking about cracking/separating in exterior brick veneer and stucco walls.
Rotating, buckling, or deflecting masonry veneer panels:
The concern here appears to be masonry veneer panels that are free standing and not tied to the wood frame structure. If the masonry veneer panels are constructed in a normal manner with steel ties embedded into the mortar and fastened to the studs, there is effectively no chance that the brick veneer will collapse or fall to the ground.
This same issue was in version 1 of this guideline. I asked a friend why it was, included in view of the fact that, for all practical purposes, brick veneer is always attached to the frame structure via ties. The answer was that this was reportedly a problem in the College Station – Bryan area. I suppose I could make an Aggie joke out of this, but I will just say that it does not pass the reasonableness test in my mind.
Just to be clear, I have seen situations where you could push on the brick and watch it move. My contention is that this is never, or virtually never, due to foundation distortion or movement. It is far more likely due to a lack of brick ties. Even if it is due to foundation movement, it can best be repaired by adding brick ties.
Cracking of concrete foundation elements:
The only concrete foundation element in a slab-on-foundation is the entire foundation. Any slab of concrete is at risk of cracking. Visible cracks need to be reported, but the reality is that cracks and separations in slab foundations are rarely a significant structural issue.
Cracking of gypsum board walls and ceilings:
Gypsum board (aka sheetrock) will crack at the corners of window and door openings when subjected to foundation distortion.
Ceiling cracks are most likely due to age or the wood frame sagging over time.
Separating of walls from ceilings or floors:
I have never seen a house where the walls were separating from the ceilings. I have seen situations where the walls were separating from the floor. In every case where it was obvious that the wall had lifted off the floor, the owners had ignored the situation for a long time or the separation was likely due to a previous foundation repair.
Separating of rafters from a ridge board:
A separation between rafters and the ridge can be due to normal shrinkage of the rafters and the ridge board. If the rafters are racked the likelihood of the separation is due to foundation distortion goes up. Ditto if the separations are widespread or large, say 1/2 inch or more.
Racking of door and window frames:
Door frames are very sensitive to foundation distortion, especially doors on the ground floor. Upstairs door issues may be due to floor framing irregularities.
Window frames can be racked by slab foundation distortion just as doors can. The difference is that windows in southeast Texas are likely to be used only rarely. It is my experience that even in new homes, half or more of the windows do not work as easily as they should.
Separating or racking of other structural framing:
Typically the only place you will see this is in the attic. How much separation is acceptable is a matter of subjective judgment. Some, perhaps in some cases, all of the separation may be due to rafter shrinkage.
Cracking, buckling, or separating of floor coverings:
The clearest example is floor tile that is fractured such that the fracture runs across one tile to another tile and across the second tile. A single fractured tile might or might not be due to foundation distortion. The grout between floor tiles is a cementitious product that is subject to separating due to shrinkage.
Separating of initially tight joints:
Inside you will mostly see this in the trim material at doors and in the baseboard and crown molding.
Deflecting or tilting of structural elements:
This indicator is most easily applied to pier and beam foundations. Typically in a slab foundation, the only element is the entire slab. Without as constructed elevation measurements, any apparent deflection or tilt is an estimate or approximation only.
It is not easy to identify how this would be applied to a slab-on-ground foundation. I suppose that missing or deteriorated grout at the live anchors in post-tensioned slab foundations would qualify. So would exposed rebar or horizontal cracks in conventionally reinforced slab foundations.
Following the laundry list of performance indicators, there are two general comments that need to be understood:
Observation of some of the listed conditions does not necessarily imply inadequate structural performance or insufficient stiffness.
The importance of any of these indications may depend upon the age of the structure and any previous repairs.
The first comment above is definitely true for several reasons. First, because each of the items could be due to excessive slab foundation movement. Second, the distress could be due to normal and expected foundation movement. Third, it could be due to age. Fourth, even if a house showed every listed indicator, the house could be habitable and thus not in need of repair.
The second comment is true but needs to be expanded. For instance, there is nothing about how important any of the indicators are when applied to a specific house. The reliability of any given indicator at a specific house is always a matter of engineering judgment.
Deflection & tilt
Deflection and tilt are performance issues since they both lead to sloping floors. It is virtually impossible for tilt to create a structural integrity issue. Deflection, on the other hand, if severe enough, can result in the frame structure being pulled apart.
When we speak of overall deflection, we are speaking of defection as calculated across a profile that runs from side to side or front to rear.
You could take profiles across diagonal profiles. I do not do that for a couple of reasons. My profiles match the profiles that are used in the design methodology.
When you use a profile that runs diagonally you are necessarily evaluating two-way bending, not one-way bending. Slab foundations are designed for one-way bending in each primary direction, not two-way bending across a diagonal.
Local deflection is deflection over some distance short of across the entire slab. Evaluating for local deflecting is difficult since the shorter the span involved, the more the degree of curvature along a profile is heavily influenced by the as-built surface geometry and the less it reflects actual deflection.
Since the design methodology ignores local deflection I choose to ignore it. In my opinion, estimates of local deflection are inherently misleading for this reason: in the case of overall deflection, I choose profiles that go across the foundation from side to side and from front to back. I take 3 elevation measurements along the profile: one at each end and one in the middle area. I say “area” because the middle measurement I use is the one that gives me the highest deflection ratio. That way the calculation should be conservative. Notice also that the measurements at each end of the profile are necessarily on the finish floor above a perimeter grade beam. Since a slab-on-ground foundation is also always screeded to the form boards, the end measurements should be pretty reliable.
If you want to reliably estimate local defection, I would argue that you need to take measurements above two stiffening beams and the 3rd measurement halfway between the two beams. The problem is that there is no way to know where the stiffening beams are without as-built drawings..
Tilt is where the foundation rotates but does not change shape. Generally, tilt increases the slope of the finish flooring. Tilt can be reliably estimated. Tilt does cause distress or damage to the house. It can increase floor slopes and create higher elevation differences.
Consider a slab foundation 60-feet long. Sixty feet is 720-inches. One percent is 7.2 inches. The difference in elevation over 60-feet is 7.2 inches. This elevation difference would normally be considered acceptable because it does not exceed 1%.
You will rarely see this. The reason I point it out is to emphasize that when you have high elevation differences, it is frequently due to high tilt, not excessive bending. Another common cause of high elevation differentials is that the measurements being considered are not on the same side to side or front to rear profile.
In the context of slab foundation performance evaluations, remediation refers to changes that can be made to improve foundation performance.
Unsafe due to structural inadequacies
The following quotes are from the Texas Section ASCE document:
If the residence is found to be unsafe due to structural inadequacies, the client and/or civil authorities should be informed immediately.
How many times have you seen this happen? Never. Are engineers blind, don’t really care or what? The truth is that wood frame houses are structurally very safe. It is rare for a need to inform the client or the civil authorities that a wood frame house structure is unsafe. Expansive soil distortion can create structural inadequacies, but that is unusual and the structural safety issues are normally easily corrected.
Expansive soil movement can create safety issues that should be corrected, but the correction almost always does not involve foundation repair. For example, if a fire escape door binds so tightly that a 2-year old cannot open it this is a clear safety issue and should be corrected posthaste. Note that the sticking door can be corrected without underpinning the foundation. In most cases, underpinning will not correct a sticking door.
Structural integrity issues due to structural inadequacies
From the document:
The engineer should recommend repair, remediation, adjustment, or use alternatives if the structural integrity is inadequate.
There is an unstated assumption in this statement. The assumption is that the potential benefit outweighs the risk that the house and/or the foundation will be damaged.
The engineer should provide alternatives for the client’s consideration if performance is inadequate.
Here is a common real-world example. Imagine a house that has cosmetic drywall cracks, some brick veneer cracks and a door that does not latch. You could have a repair contractor just repair the drywall and brick veneer cracks and adjust the door. On the other hand, the owner might tell you that these issues come every summer when we have dry weather. This should suggest the need for an automatic foundation watering system system.
Recommendations and alternatives should be commensurate with the nature and the cause of the inadequacy, and the seriousness of its consequences.
This is an important point. If the problem is a sticking door, that is no reason to recommend foundation repair.
The engineer should consider the cost effectiveness and practicality of the recommendations, the projected performance, and the needs of the client. For example, an owner may choose to perform periodic cosmetic repairs and door adjustments, rather than comprehensive foundation underpinning.
The key phrase here is that homeowners should feel free to make to cosmetic repairs and door adjustments. From a real estate agent’s perspective, this is a key issue.
Engineers owe their clients their best, true, independent assessment of the situation. If there are structural integrity or safety issues and slab foundation repair could be a viable option, then there is a case for recommending foundation repair. But if there are no structural integrity or safety issues, then doing nothing is a viable option.
Risks of continued diminished performance are involved in all remedial measures.
This is a problem that I see far too often: TREC inspectors and some engineers recommending foundation repair with no warning that underpinning may not solve the problem and indeed make things worse, even much worse.
What all this means
If there are any visible structural safety issues, the client and the Building Official and/or other civil official should be notified immediately. This comes straight from the Texas Engineering Practice Act.
If there are structural integrity issues, the investigating should recommend repair, remediation, adjustment, or use alternatives depending on the situation. Note that “repair” could include foundation repair or repairs to the house itself.
If the performance of a slab foundation performance is judged to be inadequate, the investigating engineer should provide options for the client to consider. Any options provided should be cost-effective, practical, and commensurate with the cause of the inadequacy and the seriousness of the situation.
Foundation repair is always an option, but not necessarily a good option. Compared to other potential options, foundation repair is inherently risky, it is expensive and, because it does not address the underlying cause of poor performance, may make the problem worse, not better, especially in the long run.