Expansion gap for shiplap quarter sawn Sapele

[Samuel Lee]

I’m building an exterior door jamb and door using quarter sawn sapele here in MA. The plan for the door is to use shiplapped joints between 5-6 boards to form a 39” wide door.

According to the wood EMC and dimension change coefficients, the expansion I’d have to account for is 1/16” across the entire width of my door (39” wide). But some places I read mention an expansion gap that’s nickle sized or 1/16” between each board. I’m assuming the calculator is the way to go and if so, can I install the shiplap boards tight and have the 1/16” reveals on either side of the door account for the gap?

[John TenEyck]

When I look at the Shrinkulator for QS Sapele, going from 8 to 12% moisture, the expansion is 39.26 from an initial 39.00 inches. I don't know what parameters you used, but you might want to take another look at it. 1/16" seems far too little for an exterior door made with solid stock.

John