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How bad is bad?

 

A little old lady calls out a repair foundation repair company to assess her foundation. She asks them how bad is it? Remember that the person answering the question has little engineering experience and is paid on a commission for everything he sells. What do you think his answer is going to be? Some of our customers are telling us that a repair contractor advised them that the house was in imminent danger of collapse! Something I have never seen in the 20 years in the business and certainly not with the house in question.

Regardless of what you think of the qualifications or motivations of this person the answer invariably will be a subjective description with no consensus backed scale of any sort that can offer any legitimacy to the assessment.

Is that the way it has to be? The answer is a resounding no! There are objective consensus arrived at measurements to provide a severity scale to foundation movement. Both the foundation performance Association (FPA) and the Texas ASCE have arrived at consensus opinions for acceptable foundation movement. They give allowable tolerance of movement for both tilt and deflection.

Tilt is relatively easy to understand it is simply slope, rise over run from one side of the house to the other. The consensus arrived at tolerance is 1%. That means on a 50 foot wide structure 6 inches is considered the tolerance for movement. This can simply be arrived at by taking elevations and subtracting the high from the low and measuring the distance between them.

Deflection is less understood. In basic terms it is the hump or dip, or deviation of movement between two points. In order to get this measurement a complete topological map must be drawn of the house and a section line with the elevations on it taken in order to calculate the maximum deflection between any two points. This obviously cannot be done unless elevations are taken in the entire house to create topological map.

Of the two measurements deflection by far is more important. I have seen houses with 9 inches of tilt and no deflection and houses with 5 inches of deflection. Even though the overall elevation differences less, the 5 inches deflection created way more severe damage than the house with 9 inches of tilt.

See my earlier blogs…Deflection vs Tilt for a more complete discussion on tilt and deflection. In order to get deflection the more important of the two, a complete cross section must be done which requires complete mapping and topo lines of the entire house not just a few points.

Without this objective analysis all you are left with is subjective opinions that have little validity especially when coming from someone who benefits from their interpretation.

If you would like more information or would like to have Bob consult with you, please either leave a comment or email us at elizabeth@azrm.net

 


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