post and beam cracks ?

[Warren Lake]

Past customer asked me about cracks in his post and beam home. said he was going to fill with Epoxy and I said you will need a filler to do that and kind of messy. Have no experience with it but can see logic in not wanting to have water get in and freeze. He was also concerned about if it had lost much strength.
I guess pine is the standard or fir for this construction and looks like pine. Is the stuff air dried or? Looks like most of these types of posts contain the center of the tree and in cabinet stuff that is not used. These posts are outside on his porch so they see weather changes. Size is 8 x 8"
I asked about the epoxy repair question and he said he got it online and that one company in the US sells a product made for this type of thing and is used in historical restorations.
Anyone have experience with this and how do you deal with the cracks or always leave it. Id think if a repair was good and didnt really show tons then its a good idea to keep water out as it can be so destructive.

how should he approach this or just ignore it or?

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[Maurice Mcmurry]

You are spot on about timbers containing the pith. I use foam backer rod followed by polyurethane caulking compound (caulk) when its exterior. I worked on a big, fancy, timber frame restaurant that was made from un seasoned oak timbers. They are all from whole logs. The whole building looks like your image and worse. I am disappointed with the way it looks and some of the pegs have broken and joints have failed.

[Alex Zeller]

I don't think it would be possible to dry logs that big so they are all put up wet. Of course as the wood dries it checks. Often it may want to twist but being mortised on both ends it can so you get those long cracks. For a post there's no loss of strength. There's lots of exterior post and beam (as well as wood carvings) around here. Freezing doesn't seem to be an issue. I would try to brush or spray what ever finish that was used on the wood into the cracks. If I was going to try to fill them in I would look into chinking as the best option. It works for log cabins so it should work with post and beam.

[Edward Weber]

I don't think it would be possible to dry logs that big so they are all put up wet. Of course as the wood dries it checks.

You're right, many are put up wet, most likely too wet.
If the logs were allowed to sit a couple of months to years and season, this would not be as much of a problem.

[Kevin Jenness]

You're right, many are put up wet, most likely too wet.
If the logs were allowed to sit a couple of months to years and season, this would not be as much of a problem.

Timber frames, unless made from recycled timbers, are built from wet, usually green timber with a boxed heart. Naturally, you get checks. That is the nature of the beast. Letting the logs season a few months would make no difference to the core moisture content. If the checks are filled it should be with a flexible compound over a backer rod as Maurice describes, and after the major shrinkage has occurred. It takes years for thick timbers to dry completely at the center, if they ever do.

[Edward Weber]

Timber frames, unless made from recycled timbers, are built from wet, usually green timber with a boxed heart. Naturally, you get checks. That is the nature of the beast. Letting the logs season a few months would make no difference to the core moisture content. If the checks are filled it should be with a flexible compound over a backer rod as Maurice describes, and after the major shrinkage has occurred. It takes years for thick timbers to dry completely at the center, if they ever do.


I wasn't suggesting that it would dry completely or eliminate checks and cracks but letting them acclimate for a certain amount of time does relieve stress and some moisture. Rule of thumb 1" per year of drying, an 8"x8" takes 4 years. Let them sit, warp and check for a while before you mill them, so at least some of the internal stresses are relieved. YMMV

[Kevin Jenness]

I wasn't suggesting that it would dry completely or eliminate checks and cracks but letting them acclimate for a certain amount of time does relieve stress and some moisture. Rule of thumb 1" per year of drying, an 8"x8" takes 4 years. Let them sit, warp and check for a while before you mill them, so at least some of the internal stresses are relieved. YMMV

That rule of thumb is not at all applicable to big timbers. Letting logs sit around and dry out before milling timbers from the heart will just degrade the material. There's a reason you see sprinklers running on the log piles at big mills. https://www.fpl.fs.fed.us/documnts/techline/storage-of-softwood-logs.pdf

[Maurice Mcmurry]

The gentleman who built the frame for the restaurant also acknowledged that building green is the way it is done. He did his best to deal with the inevitable checking and shrinking.

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[Tom M King]

Timbers with the heart boxed in the middle are more likely to stay straight, and not twist or bow. Such timbers are going to check. Structures have been built like this with timbers as green as possible for many Centuries. It was figured out Long, long ago that this was the best way.

No one had time to cut timbers big enough without the heart and let them sit for years until you knew if they were going to be straight, or worth the time to mill straight pieces out of crooked ones. You could certainly do that these days when it's much less work to mill a dry timber now than back then, but I've never seen anyone decide to do it this way for a whole building. You would need to cut 6 or 8 times the material, and let it dry for 10 or 12 years, and then start your build.

The checks don't hurt the big pieces strength enough to matter. It's also the reason it's almost impossible to find wide boards milled out of old beams without checks in them.

[Edward Weber]

That rule of thumb is not at all applicable to big timbers. Letting logs sit around and dry out before milling timbers from the heart will just degrade the material. There's a reason you see sprinklers running on the log piles at big mills. https://www.fpl.fs.fed.us/documnts/techline/storage-of-softwood-logs.pdf

You seem to want to argue, I do not.
Your link is for "storage" of logs, not drying.
It is not uncommon to buck logs to a rough size and air dry until final milling before construction.
Timber frame construction can be done in any number of ways, green or dry with each method having it's pro's and con's.
Mankind has been successfully air drying timbers for thousands of years.

[Kevin Jenness]

Edward, I apologize for coming off as argumentative. That is not my intent. I do enjoy discussion.

When you said "If the logs were allowed to sit a couple of months to years and season, this would not be as much of a problem." I assumed you were suggesting drying in log form rather than rough milling followed by seasoning and re-milling as we typically do in furniture and cabinetmaking. If you were in fact talking about seasoning the logs in the round the link makes clear why that is problematic for softwood logs.

I have a wonderful book about Japanese temple joinery https://www.amazon.com/Genius-Japanese-Carpentry-Secrets-Ancient/dp/4805312769 that shows massive halved hinoki logs stacked for 3 years of seasoning followed by milling with industrial machinery, so I recognize that that is done in some cases. I would think that hinoki would be less subject to degrade than species like pine and spruce. I don't believe that it is at all common in the trade as most frames are cut as soon as possible after sawing the timbers and very few shops have the equipment to re-mill such large material. I will ask my son who is a professional timber framer about this. I know he typically works with freshly milled stock when he builds new frames.

I really doubt that seasoning boxed heart timbers would prevent the type of checking that occasioned this thread. Timber containing the pith is bound to check for the same reason that log "cookies" almost always do. In theory timbers could be sawn free of the pith, but there are sound reasons for not doing so aside from the fact that unusually large logs would be required.

[Warren Lake]

thanks for all the posts. A friend who builds mega mansions 5 mill and up stuff said they never treated the cracks in anyway and they were part of the character. Thats from a builders point of view., From a home owner and your own place logic is you take care of stuff the way you want. Stopping water getting in makes sense to me if possible. I rust proof all my cars, they last 25 years and more. A builder once told me when he designs his number one thought pattern is what damage is water going to do.

I know cabinetmaking and timberframing are night and day different so very much appreciate your input. I think my friend Bruce asked a good question. I can see the school of thought you want to fill it because if done well it might look better and last longer, then the one friend its part of the character. So two different view points there. I cant see too many builders wanting to fill stuff as its more time, reality the material will keep moving as well so id think there needs to be flexibility in any filling work.

[Mark Hennebury]

I believe that the Japanese run a saw kerf to the pith, prior to construction. some glue in a wedge after the wood has settled.

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https://covingtonandsons.com/2020/01/11/the-sewari-kerf/

https://thecarpentryway.blog/2013/12/

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[Kevin Jenness]

Mark, I had forgotten that detail, although I thought it sensible enough to do it on my floor joists 35 years ago. Thanks for the reminder.

[Scott T Smith]

Interesting discussion. I'll chime in with a few comments from a milling and drying background.

1 - Wood shrinks both radially and tangentially, with tangential shrinkage being much greater than radial. Different species have different ratio's, red and white oak is around a 2:1 ratio, southern yellow pine (SYP) and doug fir around 1.6. The photo's in Mark Hennebbury's post show the impact of this. See how the kerf cut opens up more towards the outside of the pith-centerd post? That's because the tangential shrinkage is 2X the radial. Another factor come into play though, and that is the percentage of shrinkage. Doug fir and SYP only shrinks 4.5% - 7.3% as it dries (and is only around 30% MC fully green), whereas white oak shrinks 5.6% / 10.5% as it dries, thus it has much greater wood movement than Doug Fir. So typically oak posts and beams will develop larger surface checks as they dry than SYP / Doug Fir.

2. In hardwoods, pith wood is comprised of juvenile wood cells and they have a much greater ratio of shrinkage than mature wood. That's why hardwood logs almost always crack from the center out.

3. As Tom and Kevin mentioned, Timberframes are commonly built with green posts, beams, etc. The reason why is that (with the possible exception of an RF Vacuum kiln), it is not feasible to dry thick posts and beams milled from most wood species in a kiln w/o damaging the integrity of the wood. Some species (such as doug fir) are a notable exception because the MC% in the green wood is so low. The joinery is much easier to do on green timbers, which is also a factor.

4. In most locations, when logs are allowed to age before milling insects will get into the logs, causing short and long term damage. Additionally, a log aged 2-3 years is typically as green in the center as it was the day that it was dried.

5. The so called "one year per inch rule" is BS. It only really applies to extremely slow drying species such as oak. Softwoods dry much more quickly than 1 year per inch, as does fast drying hardwoods such as poplar. As an example, 1" pine and poplar will fully air dry from green down to EMC% in around 60 - 75 days in a hot summer in the southern US.

6. As Edward stated, checking in timbers is typically lessened by allowing the timbers to dry very slowly. All things being equal, a modern timberframe home will develop more extensive checking on interior wood versus exterior, because the HVAC system dries the interior air to a lower RH%, thus drying the wood more quickly inside than out.

7. Structural engineering guidelines for timberframes typically are based upon using green material and take the anticipated checking into account when determining allowed capacities.

8. The checking shown in the posts from the OP's initial photographs are not due to pithwood. The grain pattern on the surface of the timbers makes that obvious.

9. Edward Weber is correct in stating that when logs sit the internal stresses can be reduced. I see this a lot with low grade logs that we allow to spalt before milling. That's not usually a setback when milling and drying "character" lumber, but may be problematic when structural integrity for timberframe material is a concern (ie weakened wood cells). If log seasoning is desired, it makes a difference to fell the logs during the winter when the sugar content (sap) is lower in the log, versus felling in the summer when the flowing sap/sugers are higher. The summer felled logs will start to degrade much more quickly than winter felled, and attract a lot more bugs.

We've actually milled oversized, seasoned, kiln dried and then milled a second time on some timberframe components in the past. This was done in order to net some straight, KD 7" x 14" beams, but it's a time consuming and very costly process.

[Maurice Mcmurry]

Where is a log like the one in Scott T Smith's avatar when you need one? Thats helpful data.

[Warren Lake]

its in my back yard now.

[Maurice Mcmurry]

The one in Scott's avatar is a monster, I keep trying to zoom in on it. Is it looks like a Cypress.

[Edward Weber]

Thanks for the additional info.
Also #8, the checking in the OP's photo. to me, looks like what I've seen when a timber is installed wet and some type of forced hot air heat source is turned on. I'm not saying that's the cause, it just has that look as if it happened quickly. JMO

Some more info for anyone interested
https://www.structuremag.org/?p=18396

[Kevin Jenness]

I talked to my son, whose business is building and restoring timber frames, about this. He said that almost all new frames are built with once-milled green wood as soon after sawing as possible so as to cut the joinery before the wood moves significantly due to drying. Occasionally he will have to replace a twisted piece before erection (he is fortunate enough to have his own bandmill). He knows of one timber framer in Maine who makes a practice of rough milling then seasoning and re-milling his material. Obviously that is a considerable additional cost for an arguable benefit. He had heard of boring out the pith to reduce checking but has never seen it done. Sawing a kerf in a hidden area makes sense but he does not do it. When he has logs on hand a significant amount of time before he will need them they are cut into oversize cants to reduce degrade and sawn to finished size when it's time to cut the joints.

[Stan Calow]

So, I was following this discussion, and cant quite figure out if the consensus is to fill those cracks with epoxy, or leave them alone. If yes to epoxy, then its just for aesthetics, right?

[Kevin Jenness]

I would leave them alone. If they were to be filled it should be with some flexible chinking.

[Warren Lake]

I think he has decided to spray some finish inside best as he can and not fill. I believe the posts are outside on the front porch area.

[John K Jordan]

Warren,

I live in a timber frame house built about 40 years ago. A good friend lives in one he designed and had built about 25 years ago. I know of several others who have timber frame houses. The timbers in mine range from 4x6" for exterior porch rafters to 6x6 for 2nd story floor joists to 8x14" for the ridge beam. The posts are from 6x6 to 8x8" depending on what they are supporting. All of my interior timbers had been painted with a thin "pickling", thin enough for the grain to show through. The light-colored pickling makes the interior much brighter than when the wood naturally darkens as it ages. I don't think there is any finish that will prevent cracking.

All timber frame buildings I know of are made from green softwoods, most pine, one doug fir. The pins are all green wood. I have never seen a failed joint or broken pin.

Most large timbers these days contain the pith since finding domestic trees large enough to eliminate the pith is difficult and would probably be incredibly expensive. You'll notice even the lowly PT 4x4s you can buy these days are cut from small trees and have the pith in the center and sometimes wane on the corners. For my own sawmill I rarely get logs large enough to cut 6x6s without the pith.

All of the interior and exterior timbers I've seen have developed cracks (except for a few 4x6 porch rafters on my own house.) I can't see that the cracking has hurt anything. I think it adds to the charm of the structure.

From my research the cracks are normal and are rarely a structural issue. Here is the first article Sir Google gave me: https://www.homesteadstructures.com/blog/why-are-there-cracks-timber-my-new-timber-frame-structure

I'd consider carefully before applying any filler to the cracks. Besides the effort and the mess a non-flexible filler might separate from the wood as the wood moves with the seasons. In addition, if the timbers in your pictures have not yet come to moisture equilibrium and the cracks may widen further. If anything, I might consider adding a penetrating oil finish such as BLO. But before I did anything, I'd consult with an established and respected timber frame company. For example, there is one near where we live in East TN: https://www.alhloghomes.com/

I do know some who have encased posts with thin wood boards, some mitered at the corners, some with butt joints. If done right these can look great and won't crack. 20 years ago I resawed a 12' long 2x12 doug fir board into four thin boards for my friend with the timber frame house to encase one of his beams to match the others in his house. During construction, he couldn't source enough of the size he needed.

JKJ

[Scott T Smith]

The one in Scott's avatar is a monster, I keep trying to zoom in on it. Is it looks like a Cypress.

Actually red oak. Here are a few pix of some different logs that we've milled.


Meredith College 72" red oak.

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Pittsboro, NC 54" red oak.

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NC - 43' oak beam

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Greensboro, NC. Large oak from Blandwood - the ancestral home of Governor Moorehead.

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One of my favorites - from Fine Woodworking Magazine "Tools and Shops" Winter 2020 issue.

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[Ronald Blue]

Looks like you are holding your pruning saw in that first photo Scott.

[Maurice Mcmurry]

Our son moved to Durham NC a few years ago. The first sentence of his first phone call was "Dad you won't believe the trees around here"

[Scott T Smith]

Looks like you are holding your pruning saw in that first photo Scott.

Nah, this is the "pruning saw".... :D

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