versaengine
Geotechnical
- Jul 4, 2003
- 11
I am looking at 1/2 of a duplex house with severe differential movement and recurring interior cracking. One story wood frame, stucco, on poured concrete basement foundation on stip footings with rear walk-out to grade, with slab on grade garage attached to front. House has a common concrete block party wall separating the two units. There are load bearing partition walls on the basement floor which is fully finished. The neighbor reports they have not had any significant problems, including the party wall.
The center of the house appears to have heaved up, but it may actually be settlement of exterior perimeter, or maybe a combination of both. The center is approximately 4" higher than the perimeter and there is alot of interior cracking in the upper level above the center area. The exterior perimeter has one recurring crack but most of the exterior walls have performed ok.
The site was filled with uncontrolled concrete rubble several years prior to development and instead of recompacting the existing fill the developer brought in more fill some of which is high plastic clay and then placed a temporary surchage of earth fill to approximately 6' deep above finish grade to preload the site prior to home construction. Stormwater is detained on the site with a micro-detention rain garden along the uphill side yard of the home. It was discovered the stormwater had been draining to beneath the house by being in contact with the sewer lateral backfill along the same side of house.
The builder corrected the water problem, and assuming the water was the primary cause of movements, then repaired the previous interior cracking and other interior damages.
Most damages came back over the following year, just less severe than the original.
I am not sure if the differential movement is due to settlement of the exterior walls or heaving of the center of the home. I could set up a monitoring survey tied to an exterior remote benchmark and monitor for any elevation changes but this takes time.
HOWEVER, I was wondering if anyone knew of anything else that could be done to try to DETERMINE IF THE EXTERIOR IS SETTLING OR IS THE INTERIOR HEAVING??
The center of the house appears to have heaved up, but it may actually be settlement of exterior perimeter, or maybe a combination of both. The center is approximately 4" higher than the perimeter and there is alot of interior cracking in the upper level above the center area. The exterior perimeter has one recurring crack but most of the exterior walls have performed ok.
The site was filled with uncontrolled concrete rubble several years prior to development and instead of recompacting the existing fill the developer brought in more fill some of which is high plastic clay and then placed a temporary surchage of earth fill to approximately 6' deep above finish grade to preload the site prior to home construction. Stormwater is detained on the site with a micro-detention rain garden along the uphill side yard of the home. It was discovered the stormwater had been draining to beneath the house by being in contact with the sewer lateral backfill along the same side of house.
The builder corrected the water problem, and assuming the water was the primary cause of movements, then repaired the previous interior cracking and other interior damages.
Most damages came back over the following year, just less severe than the original.
I am not sure if the differential movement is due to settlement of the exterior walls or heaving of the center of the home. I could set up a monitoring survey tied to an exterior remote benchmark and monitor for any elevation changes but this takes time.
HOWEVER, I was wondering if anyone knew of anything else that could be done to try to DETERMINE IF THE EXTERIOR IS SETTLING OR IS THE INTERIOR HEAVING??
