Thread: Moisture content working with wet wood

Originally Posted by havabeer69

How do I tell what moisture content I should get the boards down to? Or is the 8% basically it.

14-20% is too much. I've found Blackbutt to be fairly forgiving of MC, but even so I'd be aiming for the 10-12% range at max.

Should I size the boards down to their approx size but leave a few mm on them then try and dry them out a bit more?

You can do, but the real problem will be cupping. At 200x50 (let's say 180 wide after jointing) I'd expect to need to thickness off 5-7mm, on average, to remove cupping and/or twisting. Some pieces would probably require more. Which means there's an inherent risk of shorting yourself when "leaving a few mm." Even after removing 5-7mm, that's usually one good surface and one with minor blemishes, which can be hidden inside the carcase.

You don't say what thickness the top/panels will be, nor whether the boards are quarter-sawn, flat-sawn or... I guess you can rough down to 30mm and hope for 20mm panels and to 40mm for a 30mm top. And still have a few mm wiggle room. (But not much!)

Should I dry them in my garage or bring them into the house? If I do bring them in the house should I just pump the dehumifier to speed up the drying?

I'd leave 'em in the garage. Just ensure they're properly stickered and have air flow around 'em. Household AC tends to work too fast and can cause surface checking, if not more serious problems.

Am I over thinking all this and should just build it and it will shrink together as one solid unit as it's dries when installed.

At 510mm depth, I think you'll risk "flatness issues" (due to the aforementioned cupping) if you proceed with the timber at that MC. Best to let it dry a bit longer. Sorry if that's bad news, but it's the price one pays for cheap timber. On the brighter side, at least it wasn't cheap because of defects.

Originally Posted by havabeer69

....
My questions:
How do I tell what moisture content I should get the boards down to? Or is the 8% basically it.

Should I size the boards down to their approx size but leave a few mm on them then try and dry them out a bit more?
.......

I think Skew's pretty well nailed it.

When I worked in the timber industry many years ago, we used to dry timber to two different standards:

• 12% moisture by weight - default measure, most sales.
• 8 % - timber destined for commercial furniture and fit-outs. Offices, hotels, etc are airconditioned and hence drier than most homes.

For air drying the usual rule of thumb was 12 months per 25 mm thickness, and we painted the ends to slow drying and minimise internal tensions.

!2% is the rough standard for dried timber. 8% for permanent air con. A happy medium is around 10% for most furniture. As already stated by others Blackbutt is reasonably accommodating, provided drying is not rushed. Fast drying may cause collapse. A year in the garage and you should be some where near it. Maybe a job for next year.

If you want the entertainment unit now, and the blackbutt is just the top, why don't you make the entertainment unit base to suit roughly what you intend on making and just sit the blackbutt on top.

Then in a year or so, when moisture content has stabilised to the environment secure top with what means you choose to do so.

Obviously if you're making the entire unit from the Blackbutt, the above is null and void.

Yes I agree with the guys above. 30mm thick should dry quite quickly depending on your location and where you put
them. Space them out well with good air flow now through summer they could be dry enough in 6 - 8 weeks if they
are already down towards the 14 or under 20. Make sure you paint the ends with something to stop splitting. Can be
oil base anything or a good thick coat of anything pretty much, colour doesn't mater. Good luck.

Sorry should have stated I intend on laminating 3 panels together and use the black butt as the sides, top and bottom with ply as the back plus internal dividers/supports.

Does sound like its far too moist for use. Might have to buy something else and either store or sell the current boards on

When working with wood, there are two general rules.

1 ~ Wood will move and there is nothing that you, I nor JC can do about it.
2 ~ When in doubt, refer to rule number 1.

There is another rule don't beat me up for Imperial measurements.

When timber is cut, moisture content can be as high as 30%. (Even higher) The number is not too important because most of us buy timber that is KD. (Kiln Dried)
OK, KD is usually 6% to 10% MC. So let the timber sit in your shed for two to three weeks and the moisture content stabilizes. The number isn't really important just that the timber has reached equilibrium.

So, what do we do about wood movement? I have come up with an approximation. One eighth inch per foot or 3.75MM per 30MM. That number is how much you can expect the wood to move. Remember that the one eighth number is from equilibrium to use environment.

How do you use this information? It is simple. Think of a lower shelf in a hall table. The shelf is 10 inches wide. The shelf is attached by tenons to the lower rails between the legs.
You cut the mortises in the rails about ½ inch wider than needed on each side. Then rather than a single 10 inch tenon, cut 4 two inch tenons with a ¼ inch between the tenons. Glue everything in place and sleep at night.