Exterior door installation - first timer

Old 04-26-05, 11:17 AM
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Exterior door installation - first timer

Hello hello!

I'm replacing my front exterior door and have decided to take on the challenge and do-it-myself. But have a few questions before I get started...

1.) I bought an in-stock door from HomeDepot. The door jam on the new door is smaller than the existing jam. I guess I have to build out the jam using pressure treated lumber from the outside of the door?

2.) Will this jam difference impact the threshhold? The new door measures 36 X 80 3/4. However, the door opening is 37 1/2 X 80 3/4. I was instructed
to buy 3/4 X 7' quarter round legs to make up the difference in the width.

3.) If my current jam is 5 1/4, should the quarter round legs also be 5 1/4 so as to fit behind the jams? And finally,

4.) will I be installing brick mould set (trim or casing) on both sides of the door/jam (interior and exterior)?

Any other suggestions for my first-time door installation?

Thank you much!
Deerfield Beach, FL
Old 04-26-05, 01:01 PM
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1). Yes, if the door comes with brickmould already attached, you will need to remove it and the jamb will need to be built out so that your door will be the correct thickness for your wall. This can be determined exactly once the door has been removed. Whether or not you use PT wood is up to you.

2). I've never heard of a door with those measurements, but the answer would be "yes". When you build the exterior side of the jamb out, the threshold will appear sunken in, unless you purchase a threshold extension, an option that is available on some doors. If your door is really 36 x 80 3/4, it sounds like you will need to trim the outside of the door with something... as you mentioned (to make it the same size as the old door) in order for your trim to cover the old paint lines.

3). Not necessarily... but if they were, it would make it easier to shim in place. I'd run a bead of sealant on the jamb before you nail them on so that wind doesn't whistle through any gaps.

4). Brickmould should go on the outside, Casing is likely what you want on the inside.

5). Other suggestions: Test fit the door once you've made all your additions. When you are ready to install it, run 2 or 3 beads of sealant along the inner half of the threshold so that the bottom of the door is sealed. Center the door on bottom with the old baseboard, or the old trim lines. Check the top of the door for level. Check the hinges for plumb. Shim at all 4 corners and behind all 3 hinges. Replace 1 screw on the top hinge with a 3" screw that will go back into a stud. The reveal along the top of the door should be straight. If it's crooked, the door is not square. When you finally open the door, bring it 1/8" from closed, and see if the gap is straight. If it's not, the door is not equally plumb on both sides. Adjust each door leg accordingly so that this gap is straight- so that your door will meet the weatherstrip properly. Loosely pack the rough opening with strips of fiberglass, or if you choose to use a foam product, be sure it is low-expanding, and don't use so much that you goop up your new door. If you will be installing a storm door, remember that the storm door will need an opening of 36x81, give or take 1/4", and that the sweep of the storm door will need to sweep onto your aluminum threshold extension. If the top of the door will be exposed to the weather, be sure there is a dripcap under your siding to flash the top of your brickmould. In some areas, it's recommended to install a pan flashing under the door.
Old 04-26-05, 01:36 PM
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Cool Thanks for all the good info...

Yes, you are correct. The new door size is 36X80. Sounds like I will
need to investigate the threshold extension. By the way, what are
quarter round legs? Will I nail the jam extention to both the door wall
opening and new door jam or just the wall? What's the difference between
brickmould and casing? What does plumb mean? And finally, what do you
mean by rough opening?

I live in Florida. Because of hurricanes, the door has to swing outward. Because of this, I don't have a screen and the door is covered from water by a roof cover.

I'm really excited about installing my first door. I learned how to install windows. So, I figured I'd tackle a door next.

Thanks a bunch! ~
Old 04-26-05, 04:10 PM
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Well, perhaps this is some regional door size, but all the doors I've ever worked with here in the midwest are all 37 1/2 x 81 5/8. So I would assume that quarter round legs would be like a jamb... 3/4 x 4 9/16, but rounded on one end (hence quarter round). I've never done such a thing, but it sounds like what they are recommending is that you glue and nail this quarterround jamb onto your prehung door jamb to make it more like a standard size door. Then the door will get shimmed and squared, level and plumb, then nail through the door jamb in about 3 places on each side to hold it in place. ou will also install some 16d galvanized casing nails through your brickmould to attach it to the framing.

I guess my question would be... why the heck didn't they just sell you a standard size door???

Brickmould is a standard trim piece that is used on the exterior of many doors and windows. It is usually 2" wide, 1 1/4" thick on the outside edge, and 1" wide on the inside edge, and has a face profile that will accept storm doors and storm windows.

Casing is trim that is installed around the interior edges of doors and windows. It is usually 2 1/4" wide, two common styles are "ranch" which is a tapered profile with rounded edges, or "colonial" which has several contours and grooves in the profile. In some parts of the country, casing is not used, because they use drywall or plaster returns which come right up to the jamb.

Plumb means straight up and down. "Level" refers to horizontal surfaces. "Plumb" refers to vertical surfaces which are "level", according to the level's vertical vile.

The "rough opening" refers to the size of the opening once your old door is removed. It is the distance between the 2x4 framing on the left and right, and the distance between the floor and the header on top. For a standard 37 1/2 x 81 5/8" door, the "rough opening" might be 38 1/4 x 82 1/2. You need to have the extra room around a door so that you can have room to shim and square it.

Since your door swings outward, I should correct what was stated earlier. You won't need a threshold extension, because you won't be adding an extension to that side of the door. If your jamb is not the correct wall thickness, your quarter round jamb is what will correct for this. Glue and screw or nail it to the door so that the rounded part will serve as a jamb extension. (for example: If your door is 4 9/16, and your wall thickness is 6 9/16, be sure that once you put on the quarteround extension, it sticks out 2" past your door jamb, so that together, they measure 6 9/16.)

Another hint- When you install the brickmould on your door, be sure that the brickmould is 1/16" to 1/8" away from the hinges- otherwise the hinges will rub on the brickmould.
Old 04-26-05, 05:12 PM
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Everything you need to know about door installation

DAM! Could you be anymore detailed? You have crafted your words in
such a way that I can clearly picture in my mind what I need to do. Super Job!

By the way, I'm considering returning the out-of-stock door and just special
ordering the correct size door. It may be an extra $100. But maybe worth
it in the long run. Hey, I'll be saving over $250 by installing the door myself.
You've earned a portion of that $250 savings. Thank you thank you.
Keep up the good work.

All the best!

Old 04-27-05, 01:28 AM
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Ha ha, thanks Paul. If you have any further questions, just ask- there's plenty of people here willing to help.
Old 04-28-05, 01:00 PM
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careful about the door size if i'm correct the 36" reference is the actual door.
Add in 3/4 jambs and you would get an opening or 37 1/2 " and a RO of roughly 38" -38 1/4 ".
So just make sure your measuring the right things.

Also I'd recomend if you could leave the brick molding in place and add the extension jambs to the interior or the door.

Good Luck I always enjoy replacing doors myself. although getting nice gaps can get frustrating. heh


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