I am curious how much checking effects a timber? I have not been able to find much on the topic. I am under the impression that up to a 1/4" is ok, am I right on that? I have customers ask all the time but really don't know the answer to this one. I use mostly Douglas Fir, Pine or Larch. Also, is there a way to tell if the timber is going to check before it does, to try and cull out the trouble ones?

Thanks,

Tim

Howdy Tim,

Try this link: [url=Wood Behavior]http://www.tfguild.org/forums/ubbthreads.php?ubb=showflat&Number=20924&page=1[/url]

Personally, I like checks. It seems that if timbers were culled for potential checking the price of timber would rise dramatically.

Hi Tim,

In very simple terms my experience with Douglas fir is that you are alright to use centrally located boxed heart timbers up to 6 x 6 without much fear of checking. Using timbers above that size is bound to result in checks opening up. With larger timbers where its a requirement to limit checking then it would be better to use free of heart or halved timbers, this way the wood can shrink back upon itself without checking about the heart. Keep in mind that other drying distortion patterns will take place depending on where the cut is positioned in the cross section of the tree. Checks run back to the heart and the juvenille wood and so when checks open up then this forms a perfect path for beetles to enter a timber and do their worst so they don't call timber framed buildings in England "half [halved]timber buildings" for no good reason.

Regards

Ken Hume

Oh,yes I can help you about this matter. and i suggest you to visit this site : http://www.careyandfox.co.uk/ which provide complete solution of Timber Related Problem.

Checks aren't problems.

Hi careyandfoxuk, I could not find anything regarding Checking in Timbers, could you be more specific as to where to find info on your site? Thank you

only when they say "checks in the mail....."

Hi Mo,

I wonder if you could expand a little on your statement above that "Checks aren't problems" please ?

Might not the location and extent to which a check opens up become a legitimate concern ?

Regards

Ken Hume

Well Ken, I guess I shouldn't be so absolute when I really have no idea of what I'm talking about. I guess I just said it, cause I like the way they look.

Maybe I should have said, "Checks aren't cosmetic problems."

Does anyone know of a case where a check caused a structural failure?

Well, If a check is discontinuous and not excessively large...I guess it's easier to show someone, but sufficed to say, "normal" checking is not considered a defect in timbers, and there is no need to reduce the rated strength of the timber. Checking is a natural part of the drying process whereby local stress is relieved. It occurs from uneven drying/shrinking of the timber. It is desirable to minimize it as much as possible. White pine will can commonly have timber with no significant checking, but hardwoods will usually have some degree of checking. Oak for example will usually check to some degree. We minimize checking by sealing the end grain with a wax based sealer (Anchorseal is a common brand used). The end grain of a piece of wood is the exposed capillaries of the wood. Water will run out/dry out very quickly from the ends if not sealed. This will lead to uneven drying/shrinking. Sealing those ends stops water from leaving allowing drying to only occur from the sides of the timber. Water will dry from the sides much more slowly and evenly. Slowing the drying and making it more even will allow the timber to shrink more uniformly and therefore reduce the internal stresses that lead to checking. When working with green wood, always seal the end grain, whether it's the end of the log, or the end grain within the mortice you just finished cutting.

As you state, Brad, checking is a natural occurrence. Your statement on working green wood may be a personal approach, one does not have to always seal the end grain. I see end grain sealing as an adoption taken by modern joinery to try to solve the naturally occurring checks. If you have a timber which is going to check so badly it will become a problem, I am sure a little anchor seal wouldn't help.

Tim

I agree with Tim to some degree here, however it is not unheard of for some old buildings to have had their joints sealed with tar, or to have had the insides of the joints painted. In some areas the entire timbers might be coated with tar to seal them off and to protect them

I am in the habit of mopping the ends of timbers and inside mortises with raw linseed oil. Always done it. Just seems to me that wood will lose moisture excessively from any end grain. Raw linseed oil won't completely seal but will slow it down some.

sada

Im almost sheepish to mention this, but Eric Sloane mentions some interesting historical methods for eliminating or mitigating checking. Off the top of my head, a few worth noting included submerging in a cold, fast moving stream for months; burying in sawdust, painting the ends with pitch....

With white oak at least and some cedar, I have had similar success slapping on any type of tar, pitch, latex paint on the ends of the wood and this has had a tremendous benefit of slowing up checking to near non existent levels.

I would heartily agree that the "linseed slathering" is historically accurate for green furniture where cracking or checking is far more serious aesthetically and structurally and it is my understanding that the darkened timbers we often see are partly a result of years of annual oil slathering.

Another point worth mentioning is that split logs, and particularly hand hewn logs do seem to split/check far less than cut logs. Ive witnessed this first hand with my lumber. Those logs I have split lengthwise and/or hand hewn show far less tendency to split, particularly after a paint, tar, pitch, or linseed slathering.

Ive used roofing tar and basement sealant tar on the ends of my logs. A little bit goes a long way, and seals tighter than a steel drum. No issue with molding/mildew etc.

cheers
Drew

Mo,
Thanks for the concise reponse to careyfox. I didn't open their link. I'm suspicious and cautious of one-time posters who don't enter into the discussion with information or Qs. Anyone who drops in a link as their sole contribution is suspect - reason to avoid. They gave no info in their profile either. hope you didn't get bad cookies or a virus.
Jim, you got their number too. where's the beef?
Back to the legitimate Q and A.
Cyber death to spammers and pfishers!

Steve

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Hello,
My understanding is that checks, and cracks or splits are not the same.
checks
A crack or split
a split developed from a check.

That checks should be prevented as much as possible is an issue relating to joinery and not aesthetics because they occur at the end grain and are not usually substantially in sight. Splits or cracks, which occur at the surface are more than anything something aesthetic and only rarely concern the structural integrity of a timber.

Don Wagstaff

Seasoning checks ARE a grading criteria in some species in higher grades and are limited to 1/4 to 1/2 thickness. Since boxed heart timbers will usually only check to the heart, the check will not go all the way through the timber (then it would be a "split" in grading terms). It's possible that a check could be a split (which also have specified limits) in reclaimed resawn timber, free of heart, I suppose. If that check happened to be right where there was a reduction on the end of a joist, it could be a problem.