7 1/2" square post in timberframe home (RF/V kd red oak) is undergoing some substantial checking. Frame was raised 6 months ago in midwest. This is the most heavily loaded post in the home under a splined joint of 8x12 beams (rafter plates) plus supports top ends of pair of valley beams. Checking is to the heart with widest point about 1/2-3/4" spread and runs vertically 6'. It is a 16' post with 2nd level floor girt tenoned into it with shoulder. My immediate fix is to band it with 1/4" steel plate "bracket" that can serve to attach balcony/stair railing fairly inconspicuously.

Thoughts??? Thanks in advance.

Will,

Oak is very likely to check, the bigger timber the wider checks and 16" post is pretty massive one. I've seen splits over 1.5" wide so you could fit your hand in. Over time the check will progress and you'll see more of them all over the posts and beams. Those shall be located on sides close to the centre line.

Bending strap as you described is fine, but might not be necessary. Take a closer look at post/beam joint to see what happened to bearing face. Was housing deep enough to allow for movement? I presume housing should be at least 2" deep for this size of oak post and loaded beam.

I'm afraid we need to see some pictures to provide proper advice in this particular case. Can you upload some?

Michal
TFDesign.cz

I'm a newbie myself, but I am wondering...was the oak post green when you cut and fit the joints? I also have a few oak posts that have some decent size checking to them, but not as bad as what you describe. They are seasoned now and should not check any further. I wonder if there is a way to slow the drying of green oak to reduce checking? I wonder if anchor seal applied to the exposed end grains would have helped? There must be a way to control checking to some degree. Maybe mills have a technique? I'd love to hear anyone with knowledge on this.

7 1/2" square post 16' long. It was radio frequency/vac kiln dried red oak. Milled after kiln drying.

As I look at this post checking, it seems to me the tenon of the beam it supports (Hundegger machined) might be acting as a wedge into the mortise. The check or split is centered right up the mortise side of the post above and below the mortise. The shoulder for the beam is not very much over 1" deep. A handcut square tenon could rest in a square mortise without causing a splitting force, but a rounded machine cut tenon unless undersized on the bottom, could act as a wedge, it seems to admittedly non-expert me. Thoughts?

Again, a picture is worth a thousand words... If you don't know how to post pics, let us know and we can tell you how. It's an immensely useful tool when you can show people what you are talking about.

A square cornered mortise probably has more reason to initiate a check out of the sharp corners than the round cornered mortise IMHO.

Hope these pics help and hope the consensus is I worry too much. Again, this is a 7-1/2"x7-1/2" post that is about 16' high supporting part of a balcony and also supporting roof plate that includes top ends of two valley beams. Red oak radio frequency vacuum kiln dried. House standing < 6 months.

This long check goes to the heart on mortise side. Top check to the tenon is opening up in last few days about an inch to right of the long check. Pic shows 2x4 collar to support temp 2x4 railing. These are full res images so they're big files.

http://www.wcctonline.org/House 074.jpg
http://www.wcctonline.org/House 073.jpg
http://www.wcctonline.org/House 072.jpg

Thanks

Linky no Worky.

cut and paste the entire line. The space in the link broke the link.

or, use these links
http://www.wcctonline.org/House%20074.jpg
http://www.wcctonline.org/House%20073.jpg
http://www.wcctonline.org/House%20072.jpg

Thanks.

looks normal to me.... I do not see any signs of the balcony joint failing.

Shot #73 shows some gap between the beam and the posts, hopefully that's just a shadow on the left side, not a gap between the stringer and the beam.....

That is indeed a vertical gap that has opened up between beam and post. The check on the mortise side of that post effectively pushs that beam away as that post face is no longer flat but now is raised at the check.

click on the picture and you can zoom right in and practically count the rings.

Do those pegs go all the way through?

yes. There is also a girt beam/joist perpendicular to the beam you see in this photo that connects to this post.

Will, ok I thought I saw that, but do these pegs go all the way through next to that girt? If you can tap one end of the peg does the other end move? I'm worried that these are fake pegs and that they aren't doing their job....

Pegs go all the way through. They're not fake. Raising crew sawed then off flush on girt side. I'll check to make sure they're snug, however. I would imagine they're REALLY snug now. Thanks for input. Stair stringers are pocket screwed into the girt -- perhaps I should unscrew them and let strings float on top, though I can't imagine they'd move the girt/post much either way.

While that is a significant size check, it doesn't seem all that unusual from what I've seen from green oak. As someone else said, the thicker it is, the larger the checks are going to be. It also depends on how it was cut from the tree - the ring pattern in that post. Steve Chappell's book shows how checks can occur based on how it was cut.
It's hard to know if you have a problem with that floor joist mortise without knowing the shape of that mortise, it's dimensions and where the check is relative to the bearing surface. Is the bearing surface sufficient and will it split further? is the question. That gap you show sure is ugly unfortunately. That looks like a full 1/4 inch. I'm wondering how it could be that much if the joint was properly fit to start with and the peg holes were draw bored. Were they? If that were the case and the joint were tight fit to start with, I wouldn't think it would open up THAT much.
So what will prevent things like this? I am now working with some white oak that is seasoned 5 or 6 years. It is stable and not bad to work with a sharp chisel. Maybe oak should be cut oversize and allowed to season and hence stabilize, then remilled to size? I'm also thinking that there must be techniques to minimize checking and movement in oak. Anyone have any knowledge here?
Recently I took a timberframing class where we had red oak stock for the braces. This stock was 3 inches thick if I remember correctly and was fairly dry and stable. We ended up being short of material but they had an oak log and a band saw mill on site and cut come stock from the log. As we began to cut the newly cut stock, it was noticeably more wet/green than the other stock we worked with. The pieces were cut for tenons and a curve cut on the stock for looks. The following day as we began the raising, you could see that the newly cut stock was starting to move - twist a little bit and small checks were starting from the wet wood drying so quickly over two days. The question I asked myself was...what had been done differently with the first stock we started with so that is was very square and stable? I concluded that there must have been some technique to drying that stock, or it had cured and was then cut to dimension. Any insights from anyone with timber knowlege of this type is appreciated.

Actually, all my red oak was radio frequency/vacuum kiln dried. Thought that would have made things more stable. This post by far has the most checking of anything in my house. Maybe this was really green when put in the kiln. Could be as I understand these longer timbers were harvested late -- or so I was told. These timbers were milled with a Hundegger so tenons and mortises had the curved ends. Many of the tenons were not bored until put into the mortises and held by come-alongs -- then they were bored and pegged. Obviously not offset bores!

I am an experienced engineer, but a novice timber framer. So, take these comments for what they're worth.

Looks like you've still got about 3/4" of bearing between that beam and the post. That's probably sufficient, but you might want to check your loads.

It's also fortunate that the check is perpendicular to the pegs, so it doesn't compromise the tension-perp-to-grain strength.

My guess: you don't have a structural problem here, only an aesthetic one.

I don't think you're getting any wedging action from the rounded edge tennons.

It looks to me like you're getting splitting and shrinking due to drying. I know you said they are RF kilned. Did you put a moisture meter on them? If so, did you check internal MC?

I might be barking up the wrong tree, but isn't RF drying pretty tricky to get right? Maybe the surface of the timbers were dry, but internal MC was still high.

That post sure looks like a "cut green, dried in place" timber to me.

I have to second jshaw in the first place.

What else to say... It is not a wedging because the post is split above mortise even more than below and goes all the way up. From the pics it is obvious that girt does not twist and the way it checks below mortise is typical moisture movement. I think the post was green when cut.

As to stabilize beams, there is only one way. Proven by centuries. Log your trees in winter, bark them, and season them for at least 6 months. Then you can mill them. 75% of moisture content movement will happen in those 6 months, providing it was barked

Michal

So if you remove the bark and let the log season for 6+ months, will the log check? Will that checking be much less than if you milled it? What would be a guess as to how much it could be reduced?

if you don't like checking work with steel.

Arborite anyone?

Timber is warm, has texture and will check no matter what you do.

If you season timber before milling, checks will be smaller than in unseasoned wood and beam will be more stabilized (less twisting, smaller changes in size).

There isn't any advantage to seasoning in the round or even very much oversized as I see it. The larger the timber, the greater the stresses as it dries. 1x and 2x stock doesn't check very much compared to larger stock. It is hard to keep a pile of round stock piled safely or supported adequately.

The surface checking and movement of the fresh sawn brace mentioned earlier was caused by too harsh a drying environment. If the surface dries enough to shrink before the core has begun to shrink, the buttons are gonna pop. As soon as drying stress ecxceeds tension perp, a check initiates. Much like tearing a piece of cloth, it may be relatively hard to start the tear, but once begun it keeps tearing pretty easily. Oak needs a pretty mild drying environment.

PEG might help reduce checking but can cause finishing problems. Other glycols have been reported to have some of that benefit... they dry very slowly and might help to keep the surface cells bulked while the core loses some moisture. Remember a cell doesn't begin to shrink until it is below around 28%.

Moisture content is basically the same winter or summer, sometimes even higher in winter with no transpiration going on. Always way above the fiber saturation point of around 28%.