huangyhg

existing lumber
i need to verify the species and grade of existing roof joists. any ideas on how to go about this? none of the local testing in my area are able to help.
wood identification by the usda forest products laboratory. here is a link
find out the age of the building.
if it was built later than the 80's the joists may have stamps on them that indicate the species and grade.
if no stamps, go to the applicable wood code of that time and use those values based on the wood type.
as far as grade, look at the lumber and classify it per applicable visual grading standards.
if your doubtful about your assumptions, use the lowest reasonable allowable stresses.
checking the actual stresses is always a good place to start.
the surest way is to cut a coupon sample of the joist and send it in a zip-loc bag to the forest products lab in madison, wi. they can tell you the species. as far as grade, i would pick the stresses for either "construction grade" or "#2 and better", which is what most lumberyards carry for structural lumber. higher grades are usually special order.
i assume spf #1/#2 when i don't know otherwise. it has relatively low (and therefore conservative) values.
it is interesting to look at older nds specifications--lumber properties (such as fb) have actually decreased over the years (i think due to using faster growing trees these days).
daveatkins

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