Why Curly Birch Ships at 13–15% Moisture

Our slabs and boards leave the yard at roughly 13–15% moisture content. Some customers expect a lower number, especially those used to kiln-dried hardwood at 6–8%. The difference is deliberate, and it helps to know what it means for your work.

How we dry

Curly birch here is dried mostly in the open air, stickered under cover, and finished in a kiln in autumn. Drying takes one to three months depending on the method and the thickness. We do not push it hard. Figured wood with twisting grain is more prone to checking and internal stress than straight-grained timber, and a slow, gentle drying cycle loses fewer boards.

Why 13–15% and not lower

Two reasons.

First, wood does not stay at whatever moisture it leaves the kiln at. It moves towards the humidity of wherever it is. A board dried to 7% and then shipped through a damp warehouse, a ferry crossing and a lorry trailer will pick moisture back up. A board at 13–15% has less to gain or lose on the way, so it arrives closer to the state it left in.

Second, the right final moisture depends on where you are and what you are making. A heated workshop in Canada in January is very different from an unheated one in coastal Scotland. We would rather send wood that is stable and lets you finish the last few points under your own conditions than guess at a number for you.

What happens in your workshop

When a 13–15% board comes into a heated workshop, it gives up moisture until it matches the air. In a dry room in winter, that can mean several percentage points. As it dries it shrinks, more across the width than along the length, and a board that is cut to final size first will end up a little under size and possibly slightly cupped.

That is normal wood behaviour, not a defect, but it changes the order of work.

What to do

Let it sit. Stack the boards with stickers between them in the room where you will work, and leave them for at least two weeks. Longer is better for thick slabs.
Rough out, then wait again. For furniture or anything going into a heated home, cut slightly oversize, let the parts settle for a further few days, then cut to final size.
Measure. A pin meter is accurate enough if you take readings from a fresh cut in the middle of the board, not from the ends, which dry first.
Glue and assemble at the same moisture. A joint glued at 13% that dries to 7% in service is a joint under strain.

When you need it drier

Instrument makers usually work at lower moisture contents than furniture makers, and small knife handles are less fussy than either. If your work needs wood brought lower before it ships, tell us when you ask for a quote. We will tell you whether we can do it for the pieces you want and how long it adds.

For more on letting wood adjust after it arrives, see wood arrived from Finland: let it sit first and moisture content for figured hardwood. Sizes and moisture details are on products.