Installing A replacement door

Old 06-04-20, 05:39 PM
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Installing A replacement door


have a question in install. Currently replacing the interior entry and storm door on Front of my house built in about 1950. Existing is a 36 door and replacing with a leaded glass fiberglass ore hung door. My question is once I rip out the old doors and frame down to the rough opening, what happens if the rough opening is not big enough to accept the new door. What are some tips and tricks. It is a brick sided front. Thx
Old 06-04-20, 07:05 PM
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Your old door likely has a sloped sill. That will likely get removed as you tear out the old frame. Most often, the floor joists were notched so that the door sill would sit down lower. So don't be surprised if you need to add some blocking between the joists, or shim them up where they have been notched. You usually want to lay a new, flat, level sill down for the new door to sit on. Generally you want the top of that sill to be about 1/4-1/2" lower than your finished floor is. As you assemble all this, give some thought to air sealing the layers of wood you put on, since air will blow right through the framing and under the door if you don't.

The height of a standard prehung is usually 83 1/4" if measured from the aluminum sill to the top of the brick mold trim on the outside. And the rough opening usually needs to be about 82 1/4 for it to fit between your new sill and the header. So you could measure that right now. If you measure from your brick on top to your flooring inside... if that measurement is at least 83 1/4 you should be okay. If it's not, you will need to cut the top edge off your brickmold (the exterior trim on a prehung door is called brickmold) or possibly remove it altogether.

Occasionally you run into door openings that are too short. In some cases, they have laid a 2x4 flat under the header, and if so, it is okay to cut that flat 2x4 out to gain another 1 1/2" of height.

As far as width is concerned, 36" prehung doors will have trim (brickmold) that is 40" wide. 32" doors will have trim that is 36" wide. If you measure the width of your brick opening, it should be close to that. If it's not, you will either need to trim the brickmold, or remove it and replace it with something else. If its wider than 40", for example, you could replace it with something wider.

If you have to replace the brickmold with something else, you will need to use trim that is 5/4 thick (1" thick) Since you will be putting on a storm door, you will need that thickness for the storm door z-bar to mount on.

LP Smarttrim 5/4 is good for this sort of thing, if you need something wider than 2" brickmold. You will also likely need something in front of/under your new door sill as well.

The biggest mistake people make is buying a stock door from a box store without thinking about their wall thickness. Box store doors are often just for 4 9/16" walls. You really should determine your exact wall thickness and get a door that is made for that thickness of wall. This ensures your aluminum sill will be wide enough to span and cover what it needs to.

Otherwise with a a stock door, you can usually get a sill nose extension that snaps onto the aluminum sill. Then you need to remove the brickmold and add a custom filler to the standard 4 9/16" jamb. If your wall thickness is, say 5 1/2... or 7"... or what have you. Ordering the door the right thickness saves a lot of work, and it's a factory finish that you dont have to mess with.
Old 06-05-20, 06:50 AM
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Remove the inside trim and measure the r/o.

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