prehanging french doors

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Forum topic by rogerw posted 01-22-2011 07:34 PM 1337 views 0 times favorited 3 replies Add to Favorites Watch
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262 posts in 2716 days

01-22-2011 07:34 PM

A year or so ago I acquired a set of french doors out of an old lady’s garage. I would like to use them to replace my aging sliding glass doors leading onto my florida room.

My question is this: What is involved with making them into “prehung” doors? I am sure I could use them as is but assume it would be easier to install as if I purchased them as a prehung set from the store. I have never installed a door into a hole before and this would be a first.

I used to be a member of HCOA and asked this question on there but never got a response.

Thank you in advanced for your responses.

-- >> my shop teacher used to say "do the best at everything you make for your mom because you're going to see it for the rest of your life!" <<

3 replies so far

View Colin 's profile


93 posts in 2837 days

#1 posted 01-22-2011 11:52 PM

If you can find a shop that prehangs doors, it will probably cost somewhere around $60 to have them do it. Doing it without all the jigs and machinery is possible but it is easy to make mistakes and it would probably take you a day to do it since you have never done it before. So my vote is for taking it to a shop.


View northwoodsman's profile


242 posts in 3773 days

#2 posted 01-23-2011 04:50 AM

Are you talking interior or exterior. I’m not sure what a Florida room is. If they are interior, it’s a fairly simple process. You can actually buy a kit at many of the big box stores, or you just purchase the materials to do it yourself. You will need 3 pieces of door jamb, 3 pieces of door stop, 6 hinges, and casing. Measure the width of one door, double that (for 2 doors) and add 1/4”. This will be your finished inside opening width. For example if you have 2 – 30” foors your inside opening would be 60 1/4” (30” door + 30” door + 1/8” gap in center and 1/16” gap on the hinge side of both doors). Since the door jambs are normally 5/8” thick, and you will want to cut rabbets into your side jambs 1/2 way through to connect the top to the sides, your top piece in this example would be 60 7/8”. Your side jambs would be the length of the door + 5/8” for the rabbet joint on top and + about 1/2” – 1” for the gap on the bottom sepending on the type of flooring. If you had a hard surface floor on the swing side of the door, a half inch gap is good. So again in this example if your door is 80” tall, your side jambs would be 81 1/8” tall. Measure all of your pieces, double and triple check your calculation, cut your pieces to length (mark them left, right and top), cut your rabbets into the top of the side jambs and assemble using glue and #8 screws (or nails). Measure the thickness of your door. It’s probably around 1 3/8” thick. Transfer that measurement to the correct side of the jambs and install your door stop. Next measure and install your hinges. Nail a piece of scrap wood near the bottom on one side of the jams, connecting the two sides to prevent movement. Next cut and install the casing to the side of the jambs opposite from your scrap wood stabilizer. This will make it easier to achieve the correct placement in the opening. Square it up, check your gaps to make sure they are correct and even olong the top and down the center between the doors on the flush side of the unit, and secure in place. It will take about 3 – 4 hours if you haven’t done this before. Go to a big box store and look at an example before you begin as a reference.

As Colin stated, if you can find someone to do this for $60.00, it may be the best $60 you ever spent. Materials will be at least $45.

-- NorthWoodsMan

View Colin 's profile


93 posts in 2837 days

#3 posted 01-23-2011 06:43 AM

The above post is a pretty good step by step but leaves a couple things out like using an astragal with header and footer bolts (not necessary but preferred in most situations) beveling the edges, how to install properly aligned hinges… the hinges are what will make the biggest difference in how your door functions and I imagine it would be difficult to do the first time with no jigs and nobody to show you what to do;

If you don’t use an astragal, you can install roller catches on the tops of the doors but you have to do something to keep the doors from being able to open themselves.

I regularly have my doors prehung for me because I don’t want to shell out the $10,000 in equipment that my local shop has that allows them to pre-hang a door in 20 minutes with consistent accuracy. A pair of doors takes about 45 minutes. So I can’t compete with that doing it all by hand. Sometimes I just have them mortise the hinges in the jamb and door edge. That only costs me $7.50 and it saves me time.


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