Timber Framers Guild Forums General General Forum Questions Kerfing to control checking

I am working on a spruce frame and am considering kerfing the timbers on the concealed side to direct the checking. Just wondering what everyone's experience of this is? In the Japanese tradition I think they normally kerf to the pith. I can see a kerf that deep being problematic structurally where it intersects joinery. How many have tried this?

You don't necessarily need to kerf to the pith. You are trying to force the check to the kerf. Every couple of feet you want to add a dry oak wedge to the kerf. You don't want drive them to hard, You don't want to split the piece, but you don't want the piece to close back on itself. I have done this on rafters, girts, and posts.

I'll definitely give it a try on this frame. I'll be interested to see how much of a difference it makes. I try to get people to get on my schedule in enough time to get some fall cut timber that can sit all winter. But I still get those people that contact me in June and want a frame in August. I'll Anchorseal the endgrain and try the kerfing, then see how it compares.

I'm guessing that when the timber is done drying you would end up with a stronger timber. If you minimize checking in other areas and direct it to one major check, which is wedged, all the grain radially would be in compression, thus minimizing loss of strength. It might be an interesting question for an structural engineer. I would never design around this as a factor, but it might be an added plus in demanding designs. What do y'all think?

I've used this before. The challenge is getting back there and remembering which ones you kerfed and how deep etc. probably worth making some notes for later.
The placement of the pith within the timber is probably just as important for checking.

I try to place the side closest to the pith on the outside, also anchor sealing the ends. On this current frame, I kerfed some of the timbers but not others, so I will see how it affects things. I can already see checks gravitating toward the kerfs.