residential foundation settlement review.

[versaengine]

looking for opinions regarding two approaches related to the use of elevation surveys in determining if a foundation needs stabilization.

My "competitor" likes to do a relative levelness survey and assumes the house was built level. Depending on the conditions and how much the house is out of level he will likely recommend whole house piering.

I don't feel comfortable assuming a house was built level. I like to put more emphasis on structural performance and the condition of the house. I like to do an elevation survey IF I think I may survey again as part of monitoring, looking for a change and I also feel a remote stable benchmark is important because in theory I can determine if some or part of the house is going up instead of assuming one area is stable and a lower area is settling.

How do folks feel about "monitoring" considering soils may lie dormant until a significant soil moisture change occurs, which might take years. How reliable can monitoring be? Perhaps suitable for new construction or when nearby changes due to construction operations occur?

 

[oldestguy]

I've done the relative elevation thing for short term changes only. It works good for setting a large house trailer level also.

For long term changes, outside marks on the structure perimeter usually are tied to solid bench marks, as for checking over a period of years.

In many cases, you can see problems in the foundation with cracks. In those cases marks across the cracks are monitored say once every 6 months to check for continuing movement.

For soil moisture change effects on clays some of each method have been used. However, where I'm called in due to a messy condition, such as wall cracks so large you can see outside, and with fast growing trees right there, no readings. Just go immediately to adding moisture and cutting down the trees. That usually fixes things permanently. Client has to know about steady watering in dry seasons however.

Our areas are not blessed with much for shrink-swell conditions, but they do crop up now and then. Most settlements are due to soft subsoils compressing, including peats and ash fills.

 

[apsix]

I've done the relative level survey to help build the picture.
I wouldn't use that only as a basis for recommendations.
In my experience the level survey results are usually compatible with visual observations.

"emphasis on structural performance and the condition of the house" sounds good to me.

 

[darthsoilsguy2]

i did a long-term settlement study on my house with a benchmark i placed on a tree in my backyard. the house has settled a foot now, but i can't tell the difference.

just kidding.

i've done some work similar to that of your competition. i stay from all residential work now, but in the cases i had been involved with.

1. the owner wants recommendations now for a variety of reasons. (i.e. time left on warranty, the contractor is the client and looking to get the project to bed, the owner is on edge until the issue is resolved)

2. by the time we got involved, it was obvious to all that settlement was in effect. the main thing we had to stay vigilant on would be to answer the question - Is this localized? or are we sliding down a hill?

3. However, forensic hand-auger borings and cone penetrometer testing (plus review of grading plans and inspection of the building for cracks) were usually performed to get an idea of the soils. i would not feel that i had done due diligence to recommend underpinning without investigating the underlying soils below.

i have worked on one project similar to the long-term scenario you describe... but it's for a large office tower so they don't mind waiting, and paying, for good monitoring and evaluation techniques.