beam strength comparison chart

[Sawyerfortyish]

My employee is building an addition on his house. He wants a 4x10 white oak beam where the new doorway from the old house is to the new section. It's a 12'doorway and the building inspector said that it can't be used unless he can see a strength chart comparing oak to doug fir. The inspector said to use 2 doug fir 2x12 from the lumber yard. If you nail them togeather you only have 3 1/4 x 115/8. The white oak beam would be just as strong and a lot nicer to look at. Is there a chart that compares strength values of differant speices of wood in beam form somewhere?

[Don P]

An east coast inspector designing your beam and specifying a west coast wood. Yup he's competent on two counts :

The design strength values are here table 4a;
http://www.awc.org/Publications/DA/index.html#DA6

You'll lose based on those numbers as will anything but SYP I think. The question isn't species its size. You do not care so much about the strength per square inch as about the strength of the overall beam, lower strength numbers usually mean a larger beam. He chose one of the 2 species with the highest assigned strength values in common use and said "beat this"... that ain't the question. I doubt he will be swayed by anything short of an engineer's and grader's stamps.

[beenthere]

Don P said it well.

Maybe a solution would be to use the D fir and trim it out with a cladding of oak. That is if the depth can be increased to accomodate it.

As I understand, much depends on the grade (internal knots, soundness, and grain angle) of the oak beam for its strength, as it's size (mostly depth).

Possibly offering to set up a test of the two beams, for the inspector to see, would help convince him (depending on how far one wants to take this).
By supporting the beams at 12', hang equal weight on each, and measure the deflection. Then add more weight and measure the deflection again. See which has more stiffness (less deflection) and either prove to the inspector that the oak is better, or your employee can prove to himself that the inspector is correct.

Other than that, put in the D fir until after the inspection, then replace it with the oak.

[MrMoo]

You might want to look in Glover's Pocket Reference. You can usually pick them up at Ace hardware for $9. I have seen stuff about strength of different woods in there.

[zopi]

or..put the soft wood beam in and, as we know, a bandsawmill will cut really nice veneers...come to think of it, he could build a laminate beam
out of the same wood, using (for example) West system marine epoxy.I've seen some boat frames out together like this that take an amazing amount of abuse..

or he can come and look at the white oak main beams under my house..been holding it up for 180 years! lol

[Don P]

Whoops, I posted the wrong link, those were the tables of beam formulas. This link is to the strength values of different woods;
http://www.awc.org/pdf/2005-NDS-Supplement.pdf