Doors and Windows - HOW to install a door in a existing wall

I want to install a service door in my garage to the outside. The block wall comes up about 6" to the 2x4 wall. My question is how do I measure for the door to cut the hole, and Iam thinking of replacing the concrete floor "someday" so should I cut the block? Because it wouldbe nice not to have to step up to go out. I was going to frame the bottom in green treat if I did cut the block. Thanks for all your help!

First off, you need to consider if it will be okay if the door only opens to 90 degrees or not. When a door is installed in an opening where the cement block (8" wide... assuming you have 8" block walls) is sticking out on the inside farther than your wall is (4 1/2" wide) the door will hit the cement block on the bottom as it swings past 90 degrees. (actually hits at about 110 degrees or so)

If that's okay, then knock the block out. Since the ends of the blocks will show from the interior side, it's often best to remove the rest of the blocks from either side of the door opening, replacing them with ones that are solid on the ends. There would be no need for treated lumber framing anywhere in this equation. The rough opening for the door will be exactly as wide as the rough opening in the blocks, and the door will slip behind. You just won't nail anywhere in the bottom 6".

The rough opening for a 36" prehung door is usually about 38 1/4", and a r.o. for a 32" prehung would be 34 1/4".

Once you knock the blocks out, you may find that you want the height of the door to be 2" higher, and if that's the case, you will want to get a 2" SOLID, which is a cement block that as the name indicates, is solid concrete. Mortar them in, making sure they are nice and level, then let it set up for a day or two before you set the door in. Don't put treated wood under the door instead, that would be really crummy.

What about the header size? Should it be 2x6 doubled up or bigger? I have 2x4 walls. Thanks for all the help.

Hey XSleeper...
You didn't even mention an outswing door. Any reason why?
That would mostly eliminate the amount of swing limitation.

Just wondering....


Hey Kellwhy...

How old is the house? Was it custom or pretty much a tract or spec (?) home. Reason I ask, many houses are framed for a door in case the buyer decides they want one. Happened with me, but they wanted almost $1000 for the door install. I let 'em build it and cut out and put it in myself later.

No reason, gunguy... I just didn't mention it. Call it an intentional oversight. ;) Personally, I hate most outswinging doors (especially the ones sold at big box stores), and would only install them if it was demanded by local code... or maybe at the top of a basement staircase where there is no landing at the top of the stairs. For exterior doors, I prefer inswinging doors with an exterior storm. But I guess the OP didn't say what type of door he was thinking about. If he was thinking inswinging, I wanted to mention that wall thickness problem- something that might be easily overlooked.

As for the header, a 2x6 header should be fine. Depending on the wall height, it's sometimes easier just to fill up the entire wall height with header- for instance, using a 2x12 might save you from installing short cripples between the header and top plate.

Thx X, I don't like 'em either unless there's no other way. Always seems to be a leak problem, and yer right, the Box models are cheap. More like buy and flip items.

It would be a good solution for a small garage that doesn't have much space in the first place, so it's good you that you mentioned it. Some ppl might not like a door banging into their nice new car. :eek: Yeah, the thing I hate about the cheap-o outswinging doors are the thresholds. But they definately have their place.