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Foundation Movement – Part III

05 Feb

Foundation Upheaval

In previous blogs, we discussed that foundation movement can be categorized into two types: foundation settlement (the most common) and foundation upheaval (the most difficult to remedy by foundation repairs). Today, I will discuss the latter: upheaval.

As a Structural Engineer, I recently represented a homeowner of a new custom home (costing about $1mm) where the foundation heaved upwards over 5” – within the first year! The slab was constructed over drilled concrete piers; which is the type of foundation I would design for myself if I ever built a new home (shoot me dead first).

The homeowner called me to check out his foundation after the builder (and his engineer) had inspected the home and told the homeowner that “it was just normal settlement” (however, it did not settle, it heaved upward). As part of my inspection, I reviewed the foundation design and determined it to be a good design. So, if it was a good design, why did the foundation move and cause numerous sheetrock cracks, slab cracks, etc.?

The answer to this very good question is that it moved primarily for 4 reasons:

  • The foundation was constructed on a lot with highly plastic clay soils (soils that expand and lot when the soil moisture content increases and shrinks a lot when the soils dry).
  • The builder did not follow the engineer’s specifications for site preparation.
  • The builder did not provide adequate drainage conditions around the foundation.
  • The builder built the foundation in 2006, during a record breaking drought in North Texas.

I will focus my brief discussion on the last reason, which I consider being the primary problem.

This particular residence is built in a suburb of Dallas that is well known for its highly expansive clay soils. Prior to designing the foundation, the builder obtained a geotechnical report that indicated that the soils at the site were such that 6 inches of PVR were possible. PVR is “Potential for Vertical Rise”; this means that under the “right” conditions, the soils could expand upward over 6 inches. The geotechnical engineer recommended several measures the builder should take to minimize any foundation movement. However, the builder did not follow the recommendations and the foundation heaved upwards about 5” in the first year.

In 2006, when the slab was built, the highly plastic clay soils, because of a record breaking drought, were in an extremely “shrunken” state. Unfortunately, when the drought ended and the rains returned, the soils expanded significantly and lifted the slab up off the piers. Because of the large size and shape of the house, a satisfactory remedy was not economically feasible.

It should be said that even if the drainage conditions around the foundation had of been perfect (and they were not), the slab would have still been lifted up off the piers by the expanding clay. When the rains returned, the soils were going to be re-hydrated no matter what the drainage conditions.

As a side note, the builder also built the slab too close to the ground surface, plus it was a flat lot so the surface water had no place to run. I guess the builder was not aware that water runs down hill.

Fortunately, the homeowner retained an experienced attorney who was able to get the builder to buy the house back. The builder told me that he now pre-swells the soils prior to installing a foundation (which was one of the recommendations his geotechnical engineer had made originally). After the builder bought the house back, he fixed the cosmetic defects in the house and then resold it in an “as is” condition at a discounted price.

For more information on foundation movement and foundation repairs, go to www.GeoDFW.com

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4 Comments

Posted by on February 5, 2011 in foundation repair

 

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4 responses to “Foundation Movement – Part III

  1. Amanda

    August 21, 2011 at 3:15 am

    We desperately need the contact information of the attorney used in this case. Our house was built and completed by end of October 2001. The lot also was flat and in a no flood zone, however the adjoining older neighborhood behind our lot floods and drains right into our backyard and fills up all the way up to the house. In June 2006 or 07 the water actually came into the house. There are no wells on either side of the house as the engineers plan showed that should be in place. Now, I have noticed the brick on each side of the house is splitting from slab foundation to roof line. When the lot flooded we contacted the City of Fort Worth and basically got nowhere, as well as FEMA and our insurance and got the runaround by them stating we are in the highest rated zone for no flooding and the “flood” itself did not meet the definition of a flood. In addition, Woodhaven Homes was the builder and I have been told they filed bankruptcy and closed, however I am not completely certain of this. Any information would be greatly appreciated.

     
    • Jim

      August 21, 2011 at 12:57 pm

      amanda
      the name of the attorney is Mr. Mark McQuality @ 214 780 1400. Mark is excellent and most experienced in handling problems concerning foundation problems. sounds like you may also need a civil engineer to study the topography around your home (including the area of the older homes). also, any recent current damage to the foundation is probably the result of the drought, which causes settlement. flooding (too much water) causes upheaval.

      good luck
      Jim McNeme, P.E.

       
      • wombatstail

        March 14, 2013 at 11:42 am

        Why would concrete piers be your pier of choice (if you were to hypothetically build your own home)? We are trying to pier our foundation in Garland, TX and figuring out if concrete or steel piers are best.

         
      • Jim

        March 14, 2013 at 7:55 pm

        call our office to discuss this

         

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