Old growth wood species values 1

[AlpineEngineer]

I have a project that was built in 1973, they want to add another roof system on top of the existing roof (all wood framing). The beams can not support the new weight using modern calcs and wood values. Do you guys know where I can find values for these older growth wood species? Is 1973 even considered old growth wood? I thought most of the old growth value stuff dissapeared in the 50's and 60's. I just ordered SEI/ASCE 11-99 are there values in that publication?
Is there any way to tell if the timber beams are old growth?

Thanks,

 

[SlideRuleEra]

Old growth timber is not defined by when the lumber was cut, but by the conditions that the trees lived in. If a forest is not disturbed for CENTURIES the trees living there grow & mature in more or less steady-state conditions. This means that they grow slowly (closely spaced tree rings) and at a steady rate (uniform structural properties). These two conditions result in superior lumber.

It is highly unlikely that wood harvested in the 1970's is old growth. However, you can contact the USDA Forest Products Lab to help identify the existing lumber, here is a link:

http://www2.fpl.fs.fed.us/

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[dougantholz]

There are several wood species experts out there who can grade wood based on a small core sample. It is likely for "quick and dirty" purposes to use select structural - HOWEVER use caution. In the midwest US I typically use dense select structural for wood older than 1930's, and select structural for wood older than that. Worst case you can flitch plate things, but you probably have all sorts of problems.

 

[RARWOOD]

The strength of lumber is determined by the presence or lack of strength reducing charteristics, such as knots or splits. Lumber from old growth might not be as strong as second growth if more knots are present or the lumber has a steep angle of grain.

Old growth would be stronger if it qualified as dense material. With Douglas fir there is very very little lumber that would qualify as dense.

 

[RareBugTX]

I was in a similar situation before, where we dealt with an heavy timber 120+ years old building. Column was investigated for additional load. I used SPF #1 with corresponding values for Fc and Fc perp.

I agree with the fellow who suggested using flitch plates as another option.