Sunday, February 12, 2012

High Bearing Values

High Bearing Values and ABC Geotechnical Schedules

Here is one response that can be placed in the cover letter that sets out the limits where the bearing values are a bit on the high side.

The bearing value provided in the geotechnical investigation report (GI) is higher than we would typically provide within that formation and area. There is no test data contained within the GI report support such a value based on conventional data conversion for typical construction. The value is acceptable for flexible construction.

We are therefore proceeding on the basis that we are accepting the bearing value at face value; however, differential movements may be excessive for some styles of construction and suitable for others. No information has been provided on the structure or performance expectations.

Thursday, February 9, 2012

Insurance and Foundation Movement

In general, home insurance does not cover foundation movements. Some insurance may cover damage due to foundation movement. You fix your foundation (the big cost) they may cover the damage to interior (drywall patches, painting).

We are located in what was a glacial lake, which became a mud flat after the lake drained. Much of this area has high plastic soils. We have had a number of dryer years, the big tree now have roots through the desiccated crust, into the moister soils, drawing water from them, and in effect thickening the desiccated crust, with accompanied movements. Recent rains have created some surface swelling, with associated lateral pressures.

We can do an inspection of the damages and provide an opinion as to the probable cause(s). With residential construction, there are often additional problems to the foundation movements. Poor design, that the expected performance is not satisfactory, wrong construction, poor construction, incomplete construction, poor repairs, and may other problems exist. Inspections are conducted at a hourly rate, including travel time, inspection time, any research time digging through archives, and report writing time.

We can also conduct a geotechnical investigation to determine soil index parameters, or actual values, and an indication of the swelling potential a number of ways. The next step is typically a minimum four deep macro-core test holes, with moisture contents, Atterberg limits, remaining linear shrinkage to oven dry estimates, hand auger holes inside the structure, site surveying, house level survey, drafting of the collected data, and a engineering report. The current cost are typically $7000 to $15000.