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RE: Timber floor level tolerances

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Thank you everyone who responded.  Some excellent references to follow up.  I conclude the following generalizations.


1)      David Ballast’s book could be worth getting.

2)      Subject to structural distress there are no prescribed/specified tolerances for standard timber framed structures.  There are some for post & beam assemblies.

3)      Tolerances should be determined/agreed upon before beginning of project.  I see there are several checklists available on line, which makes me wonder why there are no agreed tolerances.

4)      Generally allowed: ¼” between adjacent joists and ½” to ¾” over 20’-0”. (Our Home Warranty scheme gives floor slopes a tolerance of 1” in 20’-0” [L/240?])

5)      Whether tolerance(s) are adequate, or not, should probably be the buyer’s “beware” awareness … ?

6)      In our present case, we had a closet that was intimately connected to a long span beam in second floor directly seated on the main floor.  We concluded that the upper beam/closet assembly put the main floor joists in to sag, possible when the joist were still not 100% KD and the set has “set”.  No rebound when closet/beam joint removed … a number of usually unrelated details adding up to create a problem.  We evened out the floor but now the Owner sees all the other warts and the only explanation available is that the as-built tolerances, while sensed, are not outside possible construction inaccuracies … but there is still a general slope trend over the entire floor extent.




Thor A. Tandy P.Eng, C.Eng, Struct.Eng, MIStructE
Victoria, BC