By Howard “Buck” Barker, PE, Forensic Engineer, ConstructionU Instructor of Preventing Litigation
A home owner noticed the carpet in his basement was pulling away from the outside wall of his walkout basement. When he pulled the carpet back to check it out, he was shocked to see two three-quarter inch wide cracks. One along the wall and a second about 10 feet away running roughly parallel to the outside wall. “Is the wall moving,” he thought.
He hired a home inspector to investigate the situation. The wall is about 12 feet from the top of a slope that runs down to a river behind the house. The inspector reported the opening cracks did accurately indicate movement causing the wall to be out of plumb by an inch and a half. The second floor was sloped 2% toward the outside wall. His conclusion was the footings were indeed sliding down the slope. Would the wall collapse like a home on mud slide in California? Can it really happen in Wisconsin? He moved his daughter out of her bedroom located next to wall to protect her. He didn’t use any of the rooms adjacent to the sliding wall. He wasn’t going to take a chance.
Who is responsible for making sure soil conditions under a building will support the structure? That question was posed to me by the lawyer representing the contractor who built the home. The short answer is whoever accepts responsibility for designing the foundations. The contractor wrote a simple contract that said, “I will build a home in accordance with the plans you provide”. However, the plans did not include a foundation design. The contractor shrugged it off saying, “I know how to build a foundation.” What he didn’t realize is by doing that he accepted responsibility for designing the foundation he built which includes verification of the strength and stability of the underlying subgrade soils. The lawyer admitted that it looked bad for the contractor.
Verification of subgrade soils – there are two basic ways:
1. Hire a geotechnical firm to do soils borings that are analyzed by a Professional Engineer (PE). The drill rig will perform Standard Penetration Tests (SPTs) that measure the soil bearing capacity or strength of the soils while collecting samples for classification. The PE will also evaluate the stability of the slope to judge if the structure is too close to the slope.
2. Wisconsin’s Administrative Code SPS 321.15 titled “Footings” states, “The soil-bearing values of common soils may be determined through soil identification.” Simple auger borings or test pits can be used to classify the soils. Those soil types can be compared in Table 321.15 (3) to presume a soil-bearing capacity.
Neither one of these two methods were implemented for this project. In addition, SPS 321 states, “No footing or foundation shall be placed upon unprepared fill material, organic soil, alluvial soil or mud unless the load will be supported.” If any one of these soil situations are present, SPTs must be performed to verify soil bearing capacity. The contractor’s excavation for foundations encountered fill on this site. The contractor did not report it. It looked even worse for my client, the contractor.
I have a 4-step routine for working on a case like this:
What was the outcome? The CSM showed a storm sewer easement between the owner and his neighbor’s property that discharged to the river. My Protocol included taking survey shots on the outfall, but it couldn’t be found. The municipality televised the pipe from an upstream manhole. The camera ran into a wall of soil. The pipe was never extended to the slope. Since the subdivision was built, the soils next to the home were saturated during every rain storm. The added weight of water plus the lubricating affect on soil particles cause the slope to slowly fail.
Once the pipe was extended, would the slope continue to move? I placed crack monitors at every crack in the foundation wall. They are a two-part device, each part is mounted on opposite sides of the crack. One side has a graph on it. The other has a red dot. Every month for a year the home owner took a picture of each monitor to see if the dots were moving in relation to the grids. After a year, no movement was documented. The owner dropped the case against the contractor with one stipulation. The crack monitors were required to be left in place. The owner never contacted the contractor again and his daughter moved back into her beloved bedroom that overlooks the river.
One good test is worth a thousand expert opinions.
This is one of 11 case histories studied in the ConstructionU course Preventing Litigation taught by By Howard “Buck” Barker, PE, Forensic Engineer, Instructor of Preventing Litigation. The course is available for in-house instruction at your facility. Contact ABC for more information.
