Doors and Windows - exterior steel door install

Hello! I have a question about installing a steel pre hung door. I've installed interior doors but never an exterior door. I tried to get Lowes's or Home Depot to do the install but they said it was about a 3 to 4 week wait. Can't wait that long. My question is I think I may have to make a jamb extension which I think I'll attach with a biscuit joiner. Do I need to re-install the brick mould before installing the door? If the moulding remains then I'll have a hard time to place shims in place. Can I plane the top and sides of the mould enough to get shims along the side? I'm confused! HELP!!!!:wall:

It's usually best if the jamb extension is added between the jamb and the brickmould. You can just pop the brickmould off, pull the nails, add the correct thickness of material to the jamb (cut a 1x4 or 2x4 down to the right size based on your total wall thickness) and then just nail it to the jamb with a few finish nails- glue is optional. Biscuits would not be the best way to attach it. Adding a jamb extension sometimes will make the aluminum threshold too short to work with a storm door, but sill extensions are usually available if your aluminum threshold has a notch in front, you can always order one and add one on.

While you have the brickmould off, you can either install the frame without the brickmould (to make it easier to shim) or put the brickmould back on and shim it from the interior side. When shimming from the inside, you just stick one shim in fat end first, then select a shim that is the correct thickness and slide it in next to it until it gets snug. Not that hard to do. On the hinge side, you especially want shims directly behind the hinges for support.

If your brickmould will need to be shaved to fit, it's best to leave it off when you install the door. When you set the door, be sure you center it between the baseboard on each side, then plumb the sides. Theoretically it should be centered on the old interior and exterior trim lines, provided the old door was plumb- but don't bet on it.

You also want to run a thick bed of sealant across the threshold before you set the door in place. If the door is unprotected from the weather, sealing the bottom of the rough opening with a peel and stick membrane or adding a pan flashing is sometimes a good idea.
(see door pan question at: http://forum.doityourself.com/showthread.php?t=318168)

Thanks for the reply. I'm not sure I understand how I'm supposed to nail the extension on. Do you mean toe nail it in place? Why would biscuits be a poor choice for attaching the extension? I thought of something earlier....how about using the smaller mending or splicing plates? Thanks again!

Not sure what your question is. I think you might be trying to make this harder than it needs to be. Either that or I don't understand what you mean.

In the last post, I mentioned, "It's usually best if the jamb extension is added between the jamb and the brickmould." This might be where you are confused. If I am correct, you are thinking about adding an extension jamb to the interior of the door. This usually is a bad idea, because your door will hit on the extension jamb if it swings open past about 120 degrees. Secondly, you would have to space the jamb away from the edge of the door by about 3/8", (the usual reveal is 3/16-1/4" which leaves you with 1/2" of wood to nail into)... a 3/8" reveal doesn't give you much meat to nail into or screw into or even biscuit into, since the interior side of the jamb is only 3/4" thick. Pocket screws would probably work best, but it's just not usually a good idea.

Additionally, your door latch will probably hit on the extension jamb as the door comes closed, making a nice dent, or scrape on the finish. So that's why I started out my last reply by mentioning that it's usually best if the jamb extension is added between the jamb and the brickmould, which makes the jamb equal to the wall thickness once you have done that.

If you only need 3/8" or so, then an interior extension jamb is not a big deal. But once you get past the point where an interior extension jamb protrudes past the strike plate, it's a good idea to put the extension on the exterior side of the jamb. (or order the door with the correct wall thickness in the first place!)

With that in mind, let me try to explain how this is done:

Let's say the door is a standard 4 9/16" jamb, meant for a 2x4 wall that has 1/2" drywall on one side, and 1/2" sheathing on the other. But your wall is thicker. Let's say you've got 1 1/8" of lathe and plaster on one side, and 7/8" shiplap sheathing on the other which makes your wall about 5 5/8. And instead of getting a door that comes with the right extension jamb preinstalled, you need to install your own.

So you need an extension jamb that is 1 1/16" wide. So you take a 2x4 and rip it down to 1 1/16. Door jambs are usually 1 1/4" wide on the outside, so you'll rip the width down to 1 1/4" so that your extension jamb is exactly the same width as the jamb.

You'll remove the brickmould from the door. If it's a 36" door, you'll cut the top extension jamb 37 1/2" long, lay it right on top of the jamb, and face nail it into the jamb with some 2" or 2 1/2" long finish nails. You will nail right in the center of the extension jamb. Then measure the length of the sides. It will be roughly 80". Line those pieces up onto the side jambs and nail them on. Now the width of your door should be the same as the thickness of your wall.

If your extension that you add is very thick, it might actually build the jamb out past the front of the threshold. This is what I meant when I mentioned: "sometimes this will make the aluminum threshold too short to work with a storm door, but sill extensions are usually available if your aluminum threshold has a notch in front, you can always order one and add one on."

Thank you X Sleeper! You were right in the statement of making it more difficult than it actually is. I just stood back and everything seemed to fall into place. I needed 2 1/2" jamb extension. I used drill bit for pilot hole and countersunk the hole in the extension. Then used an exterior 3" screw. Worked just great. I also placed door in opening without brick mould attached. Thanks again for your help and support.

Glad to help! And thanks for the feedback, we like to find out how things turned out. :thumbup: