Quick question - I’m building a custom jamb for an antique door to be installed in new construction. Already have the head jamb width figured out. For the jamb legs, do I just give it a 1/4-1/2” gap between the top of head jamb and the bottom of rough opening header? At the bottom of the jamb legs, do I bring them all the way down to finished floor height then just use an oscillating tool to cut a bit off to install floors?

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Posted by 9rocket

Member since Sep 2020

1215 posts

Posted on 4/30/24 at 6:44 am to AyyyBaw

1/2” at least for the head jamb. More won’t hurt. This allows you to square the door up.
Either set the jambs on the subfloor and cut off with an oscillating tool using a scrap of flooring as a guide, or set the door after the finished floor is installed.

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Posted by AyyyBaw

Member since Jan 2020

1063 posts

Posted on 4/30/24 at 2:43 pm to 9rocket

Appreciate it. Looks like I’ll have about 1/2” space between jamb legs and 2x4s on each side but only about 3/16 between head jamb and 2X header. That’s with the leg jambs resting on the subfloor and a 1/8” gap between doors and jambs with a 1/2” gap between door and finished floor. It’s gonna be tight! Worse case scenario I’ll pull the doors and cut doors and jamb legs down an inch or so. Appreciate the information.

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Posted by 9rocket

Member since Sep 2020

1215 posts

Posted on 4/30/24 at 4:55 pm to AyyyBaw

You will be okay IF the jack studs are plumb and the floor is level (enough). This is the main reason for the 1/2” at the head jamb. Make sure they are before you start installing. If they’re not there are all kinds of ways to make this work out.

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