A.Carl Hagstrom responds: I had a foundation sub who always claimed that his work was within 1/4 inch. After talking to other builders in my area, I realized that he meant his work was always within 1/4 inch of being close enough. While I’m unaware of any universally accepted standards for foundation and framing tolerances, the Handbook of Construction Tolerances by David Kent (McGraw-Hill) lists hundreds of suggested tolerances for various phases of construction.

According to the Handbook , horizontal building layout (including the foundation) involves both dimensional accuracy and squareness. For measurements less than 10 feet, the tolerance is 1/8 inch; between 10 and 100 feet, it’s 1/4 inch (see illustration, below). For squareness, the tolerance for the dimension of the 5-leg in a 3-4-5 triangle...

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