​​​​​​​Pine boards - tangential movement - 5/4 x 10 inches wide

[Howard Rosenberg]

I'm starting a new bench for the front porch. That means Toronto, Ontario, Canada cold / heat / humidity 12 months of the year.

Any thoughts / opinions / knowledge how much 10 inch-wide boards 5/4 thick would move?

Thanks.

Howard

[Steve Demuth]

Depends of course on whether the boards are flat sawn or vertical grain. Assuming the former, you'd use a change coefficient of about .0025. So a ten inch board would move .025" per percent moisture change. If you figure a 5% change in EMC over the course of a year, that gives you .125" = 4mm. You should probably do a little digging for your area though, to see what the relative EMC change for outdoor wood is in your area.

[John TenEyck]

For future reference, you can use the Shrinkulator on Woodbin.

https://woodbin.com/calcs/shrinkulator/

John

[Jamie Buxton]

It is a little counterintuitive, but in the snow belt, the humidity swing indoors is usually larger than outdoors. The wider indoor swing is caused by heating (and therefore drying) the air in the winter.

[Kevin Jenness]

I think he's asking about seasonal width movement, not weight capacity. But providing the thickness of the wood is confusing.

The "shrinkulator" is what it sounds like, a calculator for estimating wood movement relative to moisture content, as opposed to the "sagulator", a beam strength calculator.

[Warren Lake]

16 foot white pine I used for facias was air dried at 12 percent approx. stuff used for indoor cabinets now is kiln dried. If I did facias again id use the air dried.