Drying softwood... a matter of days, weeks, or months???

[Harrris303]

Hi everyone, my problem is this: I'm making a large casement window frame using 2x3 PSE softwood all round, except for the sill, for which I need to start with a piece of roughly 3x6. Obviously I wouldn't find anything like that in PSE so I ended up buying a 2m long 4x8 softwood sleeper and ripping it down roughly, then planing and thicknessing to the required dimensions. Now that I've got it to the right size it seems to me that it's much heavier than I was expecting, so I can only assume it's still pretty wet.

The best thing to do would be to just air dry it down so that it matches the other components but I have no idea how long it would take. My main question is can anyone give me a rough idea how long it would take to dry out a piece of softwood that size? Obviously that depends on how wet it actually is which I can't really say, so just a rough idea of how quickly softwood dries would be great if anyone knows. Or any links to useful webpages would be greatly appreciated? (I have found various webpages relating to this but they're all much more industrial and scientific than I can get my head around!)

The other alternative is to just get on and assemble the frame, but I'm thinking that's a bit risky because if it moves as it dries then it could warp the frame or open up the joints etc. Is that sensible thinking or am I worrying too much??

Any input appreciated! Cheers.

 

[srp]

You probably need to be buying unsorted redwood- 225 x 75 is a standard size and all you need for a cill.
If you want to continue with the sleeper, it's difficult to say how long it would take to air dry as you don't really know how wet it is at the moment. If it's reasonably straight grained, not too many big knots and not boxed heart it will probably dry reasonably straight after you've assembled the frame. Whether any finish you apply will stay put is another matter - might be best to use a micro-porous finish, at least to start with.

 

[ColeyS1]

Only way to know for sure is by having a moisture meter and checking how wet it is to start with. As a stab in the dark I'd say longer than a week, possibly less than a month :? If it's wet its likely to twist/cup as it starts to dry out

 

[marcros]

these "sleepers" seem to be pretty green when they are sold- it doesnt matter much when they are used for landscaping purposes but I would go with the advice above and get a length of unsorted redwood.

For hardwood they say a year per inch of thickness for boards- even if you half that for softwood, it is going to need a year or two.

 

[Jacob]

If it's old seasoned wood which has got wet then it won't take long to dry. If it's green unseasoned it'll take a lot longer.
Seasoning and drying aren't always the same thing.

 

[Harrris303]

Ok thanks everyone. Unfortunately it looks like it is more green than just damp from the rain. Going on what srp said it might dry quite straight as the grain is quite straight and centre of the heartwood isn't far off the centre of the timber. That said I think the window is going to be painted so maybe it's not such a good idea to use it. Maybe I'll just rip it into smaller bits and leave them to season for a while.

Right, I'd better go and find some unsorted redwood then! Thanks for the useful info guys.

 

[Mike.S]

According to Understanding Wood (by Hoadley) the approx time to airdry "4/4 lumber to 20% moisture content" is:

Douglas-fir 20-200 days
Redwood 30-365 days
Eastern White Pine 60-200 days

What I'm not sure of is what 4/4 lumber means but I suspect it follows the USA custom of sizing by quarter inch, so 4/4 means 4 quarters or 1 inch square. That means your 3" x 2" could take some time. The lower number of days is said to apply during spring/summer when better weather prevails.

Alternatively, why not obtain one of those damp meters and compare the moisture content reading of your sill to the PSE softwood - though as wood dries from the outside/ends this may risk you having a 'too wet' core to the large sill piece.

Not sure that's what you wanted but hopefully someone with practical experience will be along soon.

 

[Harrris303]

Thanks Mike I did come across a few of those quarter inch figures in my research and was scratching my head for a while before I figured it out. I would probably try and find a spot in the house to keep it so hopefully it would dry a little quicker than it would outside. But unfortunately the sill piece is actually 3x6 so it'll take even longer!!

I think I will just buy a new bit of wood but even so a damp meter could be quite an interesting little gizmo to have. Just been looking on ebay and as usual was surprised/worried about how cheap some of them are! I don't suppose you have any experience with them? Just wondering if it's a terrible idea to opt for a cheap one instead of investing in a more expensive one...

 

[RobinBHM]

I always thought 4/4 lumber meant 1" (4 quarters), so 6/4 lumber would be 1 1/2" -referring to thickness of the timber, I'm sure one of our American members will advise!

 

[Harrris303]

I begin to see why people started using metric!

 

[Sgian Dubh]

I always thought 4/4 lumber meant 1" (4 quarters), so 6/4 lumber would be 1 1/2" -referring to thickness of the timber...

That's exactly what it means. Americans sell their 'lumber' in 1/4 thicknesses X width in inches X length in feet.

As to the original question the answer is it's likely to take months rather than a few weeks to air dry it to around 20% MC, especially as it's a thick piece of wood, i.e., 3" plus, and we are now in winter. Typically, freshly felled (green) pine will be in the region of 50% to 70% MC. Typical inexpensive moisture meters can't read the high MC values, and tend to max out at about 32% MC. Some moisture meters will read high values, but these meters are generally fairly expensive. An oven drying test could be used to determine the MC, and only needs household scales, paper towels and a microwave.

And, having already ripped the wood, and planed it down to size, if now air dried, the wood will shrink further and distort, so really the piece should have been left oversize so that the shrinkage wouldn't make it too small, and the distortion could be machined out to achieve the desired size. Finally, there's the challenge of setting up to dry right, i.e., keeping it flat on bearers set fairly high off the ground, weighting it down to prevent warp, and finding a situation under shelter with a good airflow to encourage the drying, but not too much airflow which would likely lead to problems such as surface checking, splits, and excessive distortion.

I suspect srp's suggestion of buying some 225 X 75 might be the best option. Slainte.

 

[Mike.S]

I think I will just buy a new bit of wood but even so a damp meter could be quite an interesting little gizmo to have. Just been looking on ebay and as usual was surprised/worried about how cheap some of them are! I don't suppose you have any experience with them? Just wondering if it's a terrible idea to opt for a cheap one instead of investing in a more expensive one...

I bought a cheapo - this one. It just has two prongs and works by electrical conductivity. So, wetter=better conduction=higher reading.

It works fine, though I tend to ignore the actual reading as being accurate - more a figure to be compared to known dry timber e.g. compare freshly bought timber to in-situ wood.

 

[Harrris303]

Unfortunately I'd already machined the timber to the right size before I started to suspect it was a bit heavier than it should be. But even so I don't think I have the time to wait for it to dry so I'll buy something else for the sill and rip the sleeper down to smaller bits for later use.

Thanks for the link Mike. I actually went ahead and bought one very similar just out of interest. Seems like a worthwhile thing to have for the money.

 

[srp]

.... and centre of the heartwood isn't far off the centre of the timber.

That's not good - when it dries you will more than likely get radial shakes appearing. If you go down the unsorted redwood route, try to select a piece which hasn't got the centre ( or heart, or pith, whatever you want to call it).

 

[Hemsby]

STIHL Moisture meter £20.99

http://www.amazon.co.uk/gp/product/B004 ... ge_o04_s00

 

[Harrris303]

Oh right thanks srp, didn't realise that! Useful bit of info!

 

[wills-mill]

The 4/4 style of quarters measurement allows a little for shrinkage I believe. I think most sawyers in The States mill 4/4 at 1 1/8th inches.

Most fresh sawn pressure treated sleepers are UK grown whitewood- Spruce, Hemlock, maybe Grand Fir. Your lump may not give you too many problems if you use it at the moment (I've seen plenty of quite well behaved green Oak window frames), but you probably don't want to have to pull the whole window out and rebuild it at a later date. As a caveat, some places stock very nice Larch or Douglas Fir sleepers- basically they're both a little darker and pinker in colour.

Sensibly you'd be looking at a minimum 2 to 3 months (in somewhere well ventilated and a bit warm) to lose most of the moisture. Your greatest issue may not be movement and shrinkage, but rather the problems of trapping damp timber against a building frame and starting yourself on the road to decay (and doooom).

It maybe worth speaking to local mills to see if they hold any air dried Douglas Fir (or indeed any UK grown softwood) at the right thickness. I've sawn quite a bit of local Western Hemlock for an Estate joiner, he loves it for their weird and wonderful windows.

 

[Sgian Dubh]

The 4/4 style of quarters measurement allows a little for shrinkage I believe. I think most sawyers in The States mill 4/4 at 1 1/8th inches.

You are right of course, and that's normal practice worldwide as far as I know because it's standard to allow for 10% shrinkage in the drying process to bring the wood to 'furniture grade' MC. Furniture grade MC varies a bit from region to region. In North America it's 7% MC ±2%, whereas here in the UK and the rest of Europe most kiln operators aim for about 11% MC ±2%. So, working in metric simply for ease of calculation, milling green boards off the log at 28 mm will result in a dried board finishing at just over 25 mm when dry, although it's likely to end up a little thicker than this because the 10% shrinkage allowance mentioned earlier is deliberately generous. Similarly, milling at 56 mm results in a dried board slightly over 50 mm when dry. All this is predicated on the fact that customers expect 1" (4/4) rough sawn boards to be that size or greater, certainly not less.

The corollary to that of course is that wood destined for joinery grade dryness, i.e., 20% out of a kiln, won't shrink quite as much from green to dry as the furniture grade material. Slainte.

 

[Harrris303]

Sorry only just saw those last couple of messages. Thanks for that guys. Good to have a bit of in depth but understandable information!!