20. industry standard practices related to slab foundation performance

20. What you need to know about accepted industry standard practices related to slab foundation performance

There is nothing in the TREC SOP that requires you to take into consideration industry standard practices when forming your opinion about how well or poorly a foundation is performing. So, what precisely are these practices and what do they require? 

The International One & Two Family Dwelling Code

The way this would be applied to virtually every required system in the SOP, is to first consult  the IRC to see what it says. Unfortunately all the IRC deals with is how a foundation on expansive soils should be designed. This is also true of the other relevant codes are related materials such as the IBC, the ACI 318, and the design manuals from the PTI and the WWI. These are all design documents and do not provide much specific information related to foundation performance.

From an engineer’s perspective, not all is lost. These documents specify, for the most part, that a reinforced concrete beam be designed so that the calculated overall deflection is limited to 1/360. As an example, this means simply that the calculated deflection due to soil movement should not exceed 1 inch when the length of the slab is 30 feet.

This seems at first glance to be pretty specific and concrete, but that first glance is leading. You might think that if an engineer uses a deflection ratio of 1/360 in his design, then if the slab was constructed properly, it should not deflect more than 1 inch across 30 feet. Unfortunately, that is just not true.

It turns out that a reinforced concrete beam subjected to a design load will deflect more than 30% more than the calculations indicate. Even under laboratory conditions, graduate students will find that reinforced concrete beams that they build under tightly controlled conditions will deflect between 20 to 30% more than what the calculations indicate.Under field conditions, the deflection would be even more than under laboratory conditions. 

US Army Corps of Engineers

The Army Corps of Engineers is highly regarded as one of the premier engineering organizations in the world.  oedd one of the most  isrid rhw  You should never recommend a second opinion unless you believe it is in your client’s best interest. In addition, you should understand in your own mind why you are recommending a second opinion. The most common reasons are these:

  1. Most houses built on expansive soils will show some damage and distress during the life of the house.
  2. Most damaged houses should not have the foundation repaired because the damage is not severe enough to justify foundation repair.
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Texas Section America Society Of Engineers

You should never recommend a second opinion unless you believe it is in your client’s best interest. In addition, you should understand in your own mind why you are recommending a second opinion. The most common reasons are these:

  1. Foundation performance should be assessed on the basis of distress and damage due to foundation movement and on elevation measurements used to estimate overall foundation bending and tilt.
  2. If a house is found to be unsafe due to foundation movement the repair may be one option among others.
  3. If the foundation performance is found to be inadequate, then alternatives should be considered. These would include restoration, adjustment, remediation, or use alternatives. Recommendations made by the engineer should be cost effective, practical, projected future performance and the needs of the client.
  4. One option that is always available when there are no safety issues involved is to make periodic cosmetic repairs and door adjustments rather than comprehensive foundation underpinning.

Foundation Repair Association

  1. Most foundations fail, or underperform, due to lack of proper maintenance, especially poor drainage and tree issues.
  2. Foundation repair cannot make your house like new again.
  3. Foundation repair can make the areas  not underpinned less stable.
  4. If the owner does not follow proper maintenance procedures, the warranty may be voided and foundation performance will be degraded.  

Appraisal Guidelines

You might think that guidelines written for appraiser’s,might not give us much useful insight into what a home inspector needs to know about reporting on foundations. If that describes you, bear with me for a few minutes and hear me out.

FHA Appraisal Guidelines Regarding The Foundation

The Appraiser must examine the foundation for readily observable evidence of safety or structural deficiencies that may require repair. If a deficiency is noted, the Appraiser must describe the nature of the deficiency and report necessary repairs, alterations, or required inspections in the appraisal where physical deficiencies or adverse conditions are reported.

Notice these terms: “may require repair,” “report necessary repairs, alternations or required inspections.” They are clearly referring to repairs, alterations, and inspections that are required or necessary.

The mortgage company is required by FHA to do the following:  

The Mortgagee must confirm that the Structure of the Property will be serviceable for the life of the Mortgage.

The Mortgagee must confirm that all foundations will be serviceable for the life of the Mortgage and adequate to withstand all normal loads imposed.

In practice, the mortgage relies on the appraiser to report any conditions that indicate that the house may not meet these criteria. 

Fannie Mae Appraisal Guidelines

The appraiser is instructed to look for and identify items in need of immediate repair. If the appraiser sees an adverse condition but does not feel qualified to determine if immediate repair is needed, then the property must be appraised subject to an inspection by a qualified professional.    

Freddie Mac Appraisal Guidelines

Freddie Mac ahs guidelines very similar to Fannie Mae. Any adverse conditions that affect the habitability, safety or structural integrity of the house.        

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