MC for pine pavilion

[alanh]

I just milled some pine for an open porch/pavillion that I plan to build this fall. I cut 6x6 for the truss/purlins and 1x6/8`s that`ll be v match tongue and groove for the ceiling. Im air drying them in an enclosed trailer with both ends open. (I close it up on rainy days) The existing outside cedar on the house and locust deck are around 9%. What MC would be safe to build with without the pine shrinking out of the grooves?

[Cazzhrdwd]

If the other deck wood is 9%, I'd try to get close to that. Seems a bit dry for outside though, did you take several readings? Maybe some readings not in direct sunlight?

[GeneWengert-WoodDoc]

The average MC in much of New England is 12% if protected from rain.  Perhaps your meter is off, or you have had some dry weather.  The issue if you install at 9 or 12% MC is that after some foggy and damp weather, you might approach 25% MC which means the pieces will swell about 3% to 4%...1/4" for 6" widths.  If you put the pieces at 9% tight, then there is no room for swelling, so it will buckle.  Also, will there be heat from the roof that might some days dry and shrink the pieces a bit more?  So, make an extra long tongue and deep groove.  Fasten at one edge only so they can move.  Non-corrosive fasteners might be worthwhile.