Prehung Doors with 8" posts

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Forum topic by docspencer posted 03-23-2013 01:24 AM 736 views 0 times favorited 4 replies Add to Favorites Watch
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354 posts in 1943 days

03-23-2013 01:24 AM

I hope the title makes sense. I’m stalling prehung doors in my shop (sorry for those who have read my prior post – the next part is redundant). The jambs are standard width but the trick is the posts that form the rough opening are 8-9” thick, so I’m looking at some major jamb extensions.

I can get regular 3/4” pine stock and plane it do thickness, but how to attach the extensions to the jambs? I’m guessing I shouldn’t just glue? I do have a dowel jig (the kind that centers the hole). Is this a good idea?

Never installed a prehung door much less built jamb extensions. I’d love to hear any ideas or suggestions.

4 replies so far

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3379 posts in 3083 days

#1 posted 03-23-2013 02:37 AM

When I hung prehung doors in my thick wall, I just bought an extra frame from the door outlet, and after I
fastened the door to the opening, I just shimmed and attached the extra frame, trimmed to width to the
opening on the inside of the building, butting it firmly against the first frame. No problems 10 years later.

-- As ever, Gus-the 79 yr young apprentice carpenter

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354 posts in 1943 days

#2 posted 03-23-2013 02:38 AM

What a great idea, Bluepine. I wonder what an extra frame costs?

View toolie's profile


2121 posts in 2626 days

#3 posted 03-23-2013 12:18 PM

here’s what i did with MDF that i ripped down:

just taper ripped to final width and butted against door jamb, with 1/8” reveal. then shimmed and nailed to framing.

-- there's a solution to every just have to be willing to find it.

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354 posts in 1943 days

#4 posted 03-23-2013 11:08 PM

Quick update – picked up the door. A steal at $120. Got it home only to discover the two beams, while a perfect 38 1/2” at the bottom were nowhere plumb (note – these are 8 X 8” posts; god knows how they ended up that far out of plumb). Spent the day tacking in strips of wood to make up the 1 1/2” gap at the top of the hinge side and using the circular saw to shave 1/2 on the other side on top. Took all day, but the door actually fits square and plumb – I think.

This is my first door install and what a doozie! I’ll take some pics tomorrow before I put the door in and screw it in.

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