# Poplar door jambs



## Lettusbee (May 8, 2010)

So, I needed a 1x8 door jamb. Got some s4s poplar, 4/4 x 8.

Routed the hinges, rabbeted the jamb legs where they meet the head, rounded the edges, and primed the show side. Now they are cupped. Not much, just enough to bug me. 
Could this have been avoided if I'd made a relief cut on the backside?


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## StrongTower (Mar 4, 2010)

That wide, I would have ripped in half, flipped one side and glued back together, maybe 3 kerfs in the back and primed all sides. Poplar just moves like crazy in my experience. 


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## Lettusbee (May 8, 2010)

I've never dealt with poplar 1x that wide. I considered priming all sides and kerfing it, but thought I'd take a chance. 
Learned something.

Thanks


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## Leo G (May 12, 2005)

Did you prime one side or 2?


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## Leo G (May 12, 2005)

Ah yes, primed the show side.

This is where you went wrong. You need to put coatings on both sides of wide boards like that. Otherwise you'll get uneven transfer of moisture, which causes cupping. If it was humid out the board cupped so the primed side was concave. If it was dry, the prime side would be convex.


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## hdavis (Feb 14, 2012)

Interior trim. You can't just use it, you still have to let it equilibrate.

Anything like this, I use doug fir. I still let it equilibrate.

You can also have issues with the kiln schedule that will mess it up. I make two frames and use the best one.

Edit - just to emphasize Leo's identification of the major problem, you painted one side. I usually don't use relief cuts, and I never paint just one side - seal the whole thing, or just leave it bare until you're ready to seal the whole thing.


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## VinylHanger (Jul 14, 2011)

I've had pretty good luck with 1x pine. Don't remember if I've gone 8 wide but 6 wide has been no problem. Just prime and paint one side after install.

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## Leo G (May 12, 2005)

Well, once it's nailed in place it won't go anywhere.


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## pinwheel (Dec 7, 2009)

Leo G said:


> Well, once it's nailed in place it won't go anywhere.


Bullchit:laughing:


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## Leo G (May 12, 2005)

If you shim it properly and nail sufficiently 1x material isn't going to put the nails unless you are using 18ga.


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## pinwheel (Dec 7, 2009)

Leo G said:


> If you shim it properly and nail sufficiently 1x material isn't going to put the nails unless you are using 18ga.


So long as you don't get any huge swings in moisture, it'll lay flat.


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## Texas Wax (Jan 16, 2012)

Leo G said:


> Well, once it's nailed in place it won't go anywhere.





pinwheel said:


> Bullchit:laughing:





Leo G said:


> If you shim it properly and nail sufficiently 1x material isn't going to put the nails unless you are using 18ga.





pinwheel said:


> So long as you don't get any huge swings in moisture, it'll lay flat.


.... and if you run the cup of the board out, hell you can run 12" pole barn screws (like tnt), covered by the stop. That'll suck the edges tight to the shims, for ever and ever Amen.

Must be getting old and taught by by old old guys .... this chit is basic finish carpentry. Well back in the day before yesterday anyway :jester:


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## JFM constr (Jul 26, 2014)

Leo G said:


> Well, once it's nailed in place it won't go anywhere.


I agree .Have done wide jambs ,yes they can cup.they do need kerfs ,I do not see how it effects it's use . avoid hinge mortise area .otherwise do what you have to flatten them out . I have had them cup and no they were probable not back primed . Casing adds alot to keeping them right . 
Just my experience .Hope it goes good for you .
last set i did I used pine .cut out of 1x12 . they were probable moving as soon as i left the store but really changed when they were ripped.they were only 6" or so wide .


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