Reusing Existing Wood Members

[ash060]

I am currently working on a project where the owner wants to reuse some existing wood rafters, posts and beams for a new project. The wood was taken from an old (about 80 to 100 years) barn. The wood would be used for a porch overhang around the perimeter of the new building. I am in Florida so the wind loads can get pretty high. They are going to get the wood re-planed, so the new dimensions will probably be dressed sizes. I was going to ask the owner to send me a sample, so I could take a look at it even though I have no idea how to deduce anything by looking at it.

I don't know the species or anything else. What would be some way of assessing the structural properties of this material? Are there any code guidelines for unknown species?

Thanks

 

[msquared48]

There have been strings on this in the forums in the past. You might want to do a search here.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[woodman88]

If you know what the sizes are to be and how the old lumber is to be used. You can calculate what the required values that will be needed. If the required values are less then the minimum values in the NDS Supplement you are probably okay.
If they are not, have the owner measure the sg of the lumber. You can do this by checking the moisture content, weighting and measuring the volume of each member. Take the lowest sg that you get and compare your require values to the values of lumbers in the NDS Supplement that match that sg. You may want to apply a personal safety factor to this calculated sg.

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.

 

[ron9876]

Maybe a testing lab to determine allowable stresses.

 

[1freewun]

Hello,
Is there any way of estimating the loads the members carried previously?

Geoff

 

[boo1]

100 year old bard wood from FL, will be old growth Cypress or heart SYP. Visual observations will tell you real quickly what one it is.

 

[ash060]

The barn is not from Florida it is from the Midwest somewhere, I think Ohio, the owner is bringing the lumber down to Florida to re-use

 

[MiketheEngineer]

Look at it. See what you think. You might be able to find a local visual grader (licensed or experienced).

I have often used an Fb in the 1,000 psi range with a good Safety Factor - so that you might really only be using about 700-800 psi - about as low as any visual lumber goes.

Also, look at its use - just a porch?? Who cares if it fails unless you are sitting underneath it.