Drying a Large Oak Timber for a Mantelpiece

      Drying large timbers takes time however you do it. Here are some thoughts about practical approaches. November 16, 2011

I am building a new home and had a large oak tree taken off my property. I had a 15' piece of the trunk saved (measuring 94" around the outside of the bark) with plans to find a sawmill to mill corbels and a fireplace mantel to be used in the new home, along with some 8/4 planks to be used, hopefully, for a countertop in the basement bath. It's been since November 2009 when the tree was dropped and waiting for me to find a sawmill. I now have a sawmill that can handle the job, but my builder wants to be sure it's dried. Do I have to find someone to kiln dry it after it's milled, or what other methods can be used and how long does it take? Do I have it milled oversized to allow for shrinkage, and how much? I know virtually nothing about wood and sawing, just thought it'd be a nice touch to have a mantel made from a tree from the property.

Forum Responses
(Sawing and Drying Forum)
From contributor B:
Yeah, you will need to have it kiln dried; not just to dry it, but to kill the potential bugs and their larvae that may be in it. Have it cut a little bigger than you want, then machine it after it is dried. How long it takes to dry is up to how dry it currently is. Have your sawyer/kiln operator test it when it is cut. One thing, oak is notoriously difficult to dry without splitting, so don't try to hurry things; plan on a couple months to be safe.

From contributor A:
The mantel, if made from a solid piece of wood, will check and move some. A piece that is say 6 inches thick and 12 inches wide will take years to dry. Short of a vacuum kiln, you can just put it up after it is cut and wait. I had some 4 inch hard maple in the kiln for 8 months and dried 6 loads of lumber on top of it and it is around 12% now in the middle but is fine for a mantel or slab furniture.

Just mount it so it can be removed and recut if needed. Most of the time if it is well sawn it will lay right there. Being down for so long did not allow it to dry, but it does make the wood more stable. It is a good thing you are doing by using the tree in the home.

From contributor T:
Would it be the same with southern yellow pine? I have a 12x10 live edge mantle sitting in my shop for about 2 years waiting for it to dry enough to install. Should I go ahead and finish and install or wait?

From contributor A:
The SYP will be pretty dry. If it has not moved by now it is not going to. I would leave the back edge unsealed so any moisture in there can weep out the back side.

Even at 12x10 it will dry out a lot faster then oak. SYP will most of the time move in the first 3 months of drying on large timbers. Now a timber that is re-wetted and then hit by the sun may twist more, but it is not due to internal stress but to external stress created by being wetted and dried on one side more then the other.

From the original questioner:
So I'm thinking of knocking down the roughness (if any), maybe a little color, sealing it on all but the backside, and installing it but keeping an eye on it. The sawyer I'm talking to agrees with letting it air dry in place. He says, like someone else did, oak checks easy when kiln drying.

From contributor T:
All the beam style mantles that I have done in the past have been installed with fresh cut green wood and I have never had a problem or upset client. I always explained to the client that checking is expected, and the wood will be kiln dried as the heat rises when the fireplace is used. Warping or twisting can be a problem once installed, so I pay attention to the log while sawmilling to see if any tension is being released. It really depends if you are going for a rustic look or not. Drying out a single piece of wood that thick is really going to have a lot of overhead tied up on it, making it very pricey. Your only other options are to dry it out yourself and wait years, find a standing dead tree, use old barn beams, or do not attach the mantle to the corbels and rotate it every couple months to ensure the moisture is not being relieved too much on just one side. I imagine if you put up a soaking wet mantle and blasted the fireplace several times, the bottom side would shrink and the top would move little, causing a bow, but flipping would solve that. It can be a hassle however you look at it.

Bugs should not be a problem. Oak is usually not a problem unless the bugs are already present.

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