Hi all, I’m getting ready to build a large custom door jamb and was wondering why the backs of old jambs are often kerfed?
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It helps them stay flat, resist cupping.
Edited 6/22/2004 8:47 pm ET by jim blodgett
To prevent it from warping, cuping, twisting. You'll see the same thing on the bottom of hardwood flooring, back side of baseboard and I'm sure other things.
Doug
keeps the jambs from drastic cupping,breaks up the continuity of the grain.
What I thought too, but just like when you rip a nice straight 2x whatever into two curvy pieces, wouldn't I have to kerf my stock & then re-joint it flat...
You could, but that's a whole lot of face jointing. This is exactly why most door and window jambs/sash are tradionally made from vertical grain lumber. It's far more stable than flat sawn and stays more uniform as it swells and contracts with seasonal humidity fluctuations.
point taken, but lumber & lumber costs being what they are these days, how would I know vertical grain stock & could I afford it?...way back when we made our own jamb stock out of #1 pine, dado'd the heads & eased the edges...nowdays it's off to HD & buy 7/16 jamb sets...
made one like that today, working on a remodel with an odd size jamb...interior door, used some nice #1, even beveled the edges a little bit on the jointer...made me thankful I learned the trades when I did...
Still have an exterior jamb to make, ~12" wide, I planned to use good 5/4 white pine (from a local yard, most likely flat sawn), fit the door & then add 1/2 stock with a kerf for vinyl weatherstrip...would you kerf the bak of the 5/4?