Wood Warping 3

[theshearstud]

What precautions can be taken to minimize the amount of warping for lumber with exposure to moisture?
-Will a No.1 warp less than a No.2?
-Will treating the wood prevent warping?
-Would a quarter-sawn piece of lumber warp more than a flat-sawn cut? If so, is it typical to specify this?

This is for the roof members of a large pergola, so it will see essentially zero load and any warping will be visible.

Thanks

 

[woodman88]

You should be using old (weathered) lumber or design the connections so the members can be replaced as needed.

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.

 

[jayrod12]

Warping is highly depended on what part of the trunk the piece is cut from and less about the quality of wood (No. 1 over No. 2) or the treatment.

You can try and specify it all you want but in the end the contractor will be buying whatever lumber is available and installing it.

The only piece that will be unlikely to warp is a piece cut perfectly from the centre of the trunk. The shrinkage on each face would be roughly equivalent and would help prevent warping.

 

[woodman88]

The Wood Handbook, Wood as an Engineering Material has more information than you need about wood in general and warping of wood. It is a free download from the below web site.

http://www.fpl.fs.fed.us/products/publications/several_pubs.php?grouping_id=100&header_id=p

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.

 

[theshearstud]

Thanks for the quick responses.

 

[Ron]

Quarter sawn lumber will generally not warp as much as flat sawn lumber. Flat sawn, particularly near the outside of the log, will also cup more than near the center of the log.

No. 1 lumber is less likely to warp than No. 2 lumber, since No. 2 lumber is allowed to have more aberrations than No. 1 that are likely to contribute to warping issues.