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Drying fresh cut lumber

GarageBand's picture

Recently I cut a cherry log into slabs.  One end is the crotch of the tree.   However, once we go into it, we found that the other end was pretty extensively rotten.  There was a knot in the center that went first, but the lumber on either side of the knot is still good.  Plus there is enough of the good lumber that the whole piece should be pretty interesting once it is dry.  I would like to save as much as I can, but I am worried about keeping the decayed part throughout the drying time.  The part that had turned to mud/dirt has fallen out (some of it I vacuumed), but should I remove the rest or should I leave in as much as I can, let it dry and see what is salvageable/interesting once the whole thing is dry.  Will the rotten/spalted/punky part cause problems with the drying of the rest of the slab?

Thanks,

Thomas 

RalphBarker's picture

dry (post #153852, reply #1 of 4)

I like martinis very dry, which may have affected the MC of my jokes, too.

I'm not, however, an expert on wood drying. But, if the rot is at the ends of the boards, I'd probably cut it off, so the good wood could be properly sealed to avoid splitting.  Rotted interior sections might be wire-brushed away and the internal edges sealed, as well.

Someone with real knowledge on the subject will respond eventually.

SgianDubh's picture

I suggest you remove the (post #153852, reply #2 of 4)

I suggest you remove the worst of the rotten wood and then sticker it up to dry. I'm assuming you are intending to air dry and I don't know where you are based, your climate, nor how thick the boards are that you've cut. Air drying takes time of course, but if you can get the wood stickered up properly so that it will dry, then once you get it below 20% MC all fungal activity will stop-- most fungal activity will give up at about 30% or 40% MC, but 20% MC is what's known as the dry rot safe point. Dry rot is (incidentally) a quite rare fungus in the natural environment, and humans tend to create the ideal conditions for it to thrive.

There is obviously much more to drying wood than this simplistic answer, such as sticker size and placement, shelter for the wood, airflow, preventing end checking and surface checking, etc, but you didn't ask those questions. Slainte.

GarageBand's picture

more specifics (post #153852, reply #3 of 4)

Thanks for the specifics on moisture content.  As far as the other specifics - the slabs are 2-2.5 inches thick; climate wish, I live in central Virginia;  I will be drying it under my deck which, since I live on a hill, is dry and shaded; and I have ash stickers that are placed one foot apart.  I have dried a portion of an old walnut tree which was already standing dead for a year in this location, but I am a little worried about the cherry slabs.  Given these conditions, do you think I should do something to increase air flow?  Secondly, what are the things I should be doing to prevent surface and end checking?  I have already coated the ends, but I have not been maticulous about the rotted areas.  

 

Thanks,

Thomas

SgianDubh's picture

Thomas, if you've had success (post #153852, reply #4 of 4)

Thomas, if you've had success before under this deck, there's a good chance you'll succeed again. As long as the deck provides shade that will help reduce the chance of surface checking, particularly on the top boards.

You have already sealed the ends and this helps reduce the severity of end splitting. The spacing of your stickers is suitable-- they could be further apart, but there's no harm that I can see having them fairly close, provided they are lined up exactly one above the other to eliminate the chance of causing bowing. You have no control over natural air movement but you can slightly adjust how fast air passes between each layer of boards. You do this by adjusting the sticker size, but as long as they are 3/4" thick that does for most drying purposes. Thinner sticks, eg, 5/8" will slow drying rather, and 1" will speed it up. You do need a reasonable air flow, particularly at the early stages of drying because the air movement carries evaporated moisture away.

I'm guessing your stack is no wider than 6', so place the boards close together horizontally-- you don't want to expose too much surface area compared to the volume of the wood as too much exposure can lead to too rapid drying, which could lead to drying faults. I'm not sure what the weather conditions are at this time of year in Virginia. I imagine it's pretty hot and humid so drying will be influenced by this-- you don't really want a very dry atmosphere at the initial stage of timber drying as this can cause surface checking. Here in the UK winter is generally favoured for initial air drying because the high atmospheric RH slows the process down.

You are dealing with thick material, and it's often said you should allow a year per inch to get the wood down to its final moisture content. This maxim is generally not very useful, but I suspect that in this case it's not a bad rule of thumb-- so expect 2 to 3 years to dry the wood as much as it will. Here in the UK I've never found air dried wood below about 17% MC, and 20% is typical. Again, because you are in Virginia, I don't really know how dry the wood could get. To estimate this you'd need to know the general annual RH range and extrapolate from that the lowest moisture content the wood might achieve. Temperature has only a minor influence on wood MC in air drying-- it's relative humidity that is the big driver of MC. I hope this is enough to go on with. Slainte.