The missing foundation

Mar 23, 2011 by

The owners of a house in Southern California decided to strengthen their home to better survive “the next big one”. They called a local earthquake retrofit contractor for a price. One of the improvements they were looking for was to bolt the wooden house structure to the concrete foundation.


The contractor arrived and, after taking exterior measurements, wiggled into the tight crawl space under the house to see what needed to be done there. When he later emerged, he reported to the home owners that a portion of their foundation was missing.

GEI was hired by their insurance company to inspect the site to identify and determine the predominant cause and approximate age of the missing foundation.

Our expert visited the residence and conferred with the owners. They showed him the report of estimated costs that had been prepared for them to install foundation bolting to comply with the voluntary earthquake preparedness provisions of their city codes. Their property was a single-family, timber-framed building, aligned principally north-south, with an integral garage to the north, built circa 1923, according to the County Tax Assessor’s office.

The living room to the residence was entered from the front door in the west wall. The floor of the southeast corner had some minor separation from the wall, but the separation was normal for a building of this age. There were no other sagging or developing cracks in existence that were the result of a missing foundation. The under-floor support was comprised of a series of 4-inch by 4-inch beams carrying 2-inch by 6-inch floor joists. The beams were supported on individual timber support posts bearing on concrete or concrete/brick amalgam pads. The property was built prior to the enactment of laws requiring permits for construction (permits were not required in the county unincorporated areas until 1933). As such, the building might not meet current standards for protection of public health and safety. The area under the front door, which was claimed to be without a foundation, did have the required support. It had stood for the last 88 years, apparently without damage. The support was provided by timber beams and concrete pads instead of the expected poured concrete foundation strip found elsewhere.

The foundation supports varied throughout the residence crawl space, but appeared to be solid. The exception to this was the support by the west end of the foundation beams on a variety of concrete/brick/stone pads and by burial in the front (west) wall foundation strip. None of the west end beam supports included any form of waterproofing that could be discerned without lifting the beams. While the beams were not currently deteriorating from dry rot, it was advised that they treat the buried and supported west ends of the 4-inch by 4-inch beams to prevent possible dry rot and/or insect attack.

Our expert also noted that the downspout by the front door was not functional and could be discharging rainwater near the foundation strip and beam-ends. Also noted was the fact that the crawl space did not meet current code requirements (most of us would describe the crawl space as claustrophobic). The current crawl space code requirements are not retroactive unless the crawl space is altered.

 

Based on the foregoing, it was the expert’s opinion that the predominant cause of the perceived missing foundation was a misinterpretation of the principles of foundation engineering and of framed construction. The approximate age of the residence was 88 years, and the foundation had been in existence since that time, with no apparent structural issues.

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