LumberJocks

estimated shrinkage

  • Advertise with us

« back to Wood & Lumber forum

Forum topic by Partridge posted 01-05-2011 08:03 PM 1317 views 0 times favorited 10 replies Add to Favorites Watch
View Partridge's profile

Partridge

296 posts in 3422 days


01-05-2011 08:03 PM

i am trimming out house windows with 1 1/2×4 rough cut ceder and i just cut from the tree. how much shrinkage do i expect.

-- I get out in the shop when I can


10 replies so far

View Colin 's profile

Colin

93 posts in 2277 days


#1 posted 01-05-2011 08:33 PM

Don’t do it. Let it season for at least a year, stickered and protected from the sun. If you install now, the shrinkage will be enough to crack the trim wherever there is a nail/screw. It will still move some after you have let it season but probably no more than 1/8” through the year. It will not just shrink but expand as well depending on humidity.

You can rough cut your lengths now to speed up the drying process. Still at least a year but if you leave them in long lengths, it could take a lot longer.

-- http://www.columbiawoodscreendoors.com

View Greedo's profile

Greedo

470 posts in 2426 days


#2 posted 01-05-2011 09:06 PM

cut off and plane a small piece of that lumber and take it indoors and watch what happens!

i tried that once with a piece of fresh oak, it started warping at eyesight and withing a few hours it was completely cupped with gigantic cracks. the following weeks it slowly took back it’s initial shape and the cracks disappeared.

View Bill Davis's profile

Bill Davis

226 posts in 3390 days


#3 posted 01-06-2011 08:21 AM

It depends on several factors: 1) The species of wood – though you did mention cedar there quite a range of them, 2) The starting moisture content of the wood – can be measured with a MC meter, 3) the average year around relative humidity at your location and the length of swings to the min and max %RH, 4) What direction relative to the tree rings – wood swells/shrinks quite differently in the radial, tangential and longitudinal grain directions, 5) what type of and how much finish you apply to the wood – a finish MAY somewhat mitigate but not eliminate moisture sorption and thus control shrinkage and swelling.

Since shrinkage and swelling are ongoing facts with wood as the RH changes, I would recommend first finding the average year around %RH in your area then have the wood acclimated to that level before cutting the pieces to size. Whether you finish the wood or not that is the best starting point.

View Colin 's profile

Colin

93 posts in 2277 days


#4 posted 01-06-2011 05:22 PM

I agree with Bill except when it comes to waiting to cut to size. Don’t cut to finish size but rough cut to length and that will speed up the drying process. But it won’t make much difference if the lengths are pretty short to begin with.

-- http://www.columbiawoodscreendoors.com

View Bill Davis's profile

Bill Davis

226 posts in 3390 days


#5 posted 01-06-2011 10:40 PM

+1 to what Colin said. He knew what I wish I meant.

View Partridge's profile

Partridge

296 posts in 3422 days


#6 posted 01-07-2011 06:39 PM

thank you for all the info. it is all cut and drying,, i will have to ruff cut as they are all the boards are 9 foot long
but i noticed that the heart wood of ceder is in the 20-25%. the sap wood is were all of the moister is. i wll dry for a two or 3 weeks and then use a oil varnish on wood. i will try to stay clear of sap wood.

-- I get out in the shop when I can

View childress's profile

childress

841 posts in 3008 days


#7 posted 01-07-2011 06:47 PM

In general, wood takes a year per inch to (air)dry. So if it’s 1” thick, 1 year to dry, 2” thick, 2 years to dry, etc.

2 to 3 weeks isn’t going to do much of anything…

-- Childress Woodworks

View childress's profile

childress

841 posts in 3008 days


#8 posted 01-07-2011 08:16 PM

LOL….frightened turtle, huh?

I don’t know about you, but I have A TON of shrinkage with that.

(ok, someone had to say that) ;-P

-- Childress Woodworks

View dbray45's profile

dbray45

3187 posts in 2242 days


#9 posted 01-07-2011 08:29 PM

From my research -

If you are in the colder areas where the tempurature gets and stays in the low to mid 30s, without rain or snow, wait 3 months with the wood covered and sides open to allow air movement. Use 1” stickers. You need the wood to get down to at least 12% MC for outdoor unfinished use – from what I am told, 8% is better. The problem with wetter climates is that if the wood gets wet, may actually dry the outside of the wood faster but not the inside, making the wood check and crack.

Depending upon the wood, cut, and moisture, you can get up to 10% shrinkage. The slower the wood dries, the less twist, cup, warp, checking, etc… because everything shrinks together. I had a local lumber mill that cut the wood and stickered it to air dry for at least a year, white oak for 2 years, before finishing with the kiln.

There is a big difference in building all new construction with green lumber and adding to existing with green lumber.

-- David in Damascus, MD

View draaierjozef's profile

draaierjozef

11 posts in 2451 days


#10 posted 01-08-2011 12:36 AM

Cedar lumber will shrink different amounts depending on the direction with which it was sawn from the log.

i.e. if it was plain-sawn, and was fully hydrated when sawn and not allowed to dry out before cutting to the final size, it may shrink as much as 10% in width, and it may “cup” as a result of drying. If it was 1/4 sawn, then it may actually be rather stable (~4% shrinkage or so), with little cupping to be expected.

To minimize the effect of cupping, apply shellac, or other sealer to both sides of the boards, to slow down uneven dehydration from the exposed side when compared to the side against the house. ONce dry, cedar is actually rather stable. Hope this helps.

Have your say...

You must be signed in to reply.

DISCLAIMER: Any posts on LJ are posted by individuals acting in their own right and do not necessarily reflect the views of LJ. LJ will not be held liable for the actions of any user.

Latest Projects | Latest Blog Entries | Latest Forum Topics

HomeRefurbers.com