"Green" spruce planks - how much shrinkage

[mointainwalker]

hi

I bought some planed spruce planks - 3500 x 200 x 22 from my local saw-mill in November and stored them- separated by bearers -
in my unheated but well ventilated shed

I see that they have now shrunk by 3%-4% in width and would like to know for how much longer they are likely to continue to shrink.

An old local carpenter told me that it takes 1 year per 10 mm for wet wood to dry which was a hell of a surprise and although he ought to know what he is talking about, it was so far off what I reckoned ( 6 months) that I thought I would ask you.

Another question on the same lines.

Is wood that you buy packaged in sheds/merchants air-dried or kiln-dried to get it down to 12% ?

 

[Jasonb]

General rule of thumb is one year per 25mm plus a year so for your 25mm boards 2 years so around the same as you were advised. It will depend somewhat on what time of the year the tree was felled, how long between felling and milling and relative humidity where you have it stored.

Yes store bought timber will be kiln dried. If you intend to use your wood indoors then it will need further conditioning to bring it down from airdried.

Jason

 

[mointainwalker]

hi

Just an update.

My planks shrank by an astonishingly ( to me) uniform 15 -16 mm ( 7.5% ) over 5 months and no movement at all since. They are still in a well -ventilated, covered area open to outside .

Is it likely ( not asking for guarantees ) that shrinkage has finished if movement has stopped over several months ?


Thanks

 

[WoodYouLike]

It seems it has for the environment in ventilated area, the situation could still change when you stack them in the house.

Can you test with a small stack to see if natural movement occurs again?

 

[big-all]

the wood will further shrink if the moisture content reduces
it will also expand if the moisture content increases

what are you using it for and where will it be used[on or near a radiator /damp room /in the house in general/outside but protected]

 

[mointainwalker]

I will be using the planks as wall-cladding in the un-heated annexe/work-shop where they are currently stored.

In view of the possibility of expansion, what would be the minimum gap when fitting ?

Not sure what finish i will put on them. however since they are only 20 mm thick, I presumably don't have to bother with coating the reverse face to prevent warping, do I ?

Thanks

 

[big-all]

i wouldn't worry to much about expansion unless there's dampness present
are you going to cut a t&g on the edges ?

 

[mointainwalker]

b-a

No t&g . This being my work-shop, I don't mind a small gap.

Should i butt the planks or leave a gap ?

 

[big-all]

if you don't do t&g it wont be neat as you will have gaps
you can butt up tight with 2 fixings and the expansion will be held in check except around the edge