how to install pre hung doors

I have dabbled in home improvement projects and like giving advice to others on what not to do.

"How not to replace a door—?"

Easy. Don't wait this long to do it.

Not my fault the door whose shredded remains you see in this photo was clearly not meant for exterior use, or that the plywood repair was inadequate. But I sure didn't have to let it get this bad.

OK, it wasn't really causing a problem, in the sense that it's out of sight, and gives access only to a small furnace (no longer working anyway.) But by letting it sit so long I allowed water to get into the wall itself and got a nice rot problem going in some of the framing. Not good.

And it's not as if the repair itself were very hard, or very expensive. It was probably 6-8 hours work, spread over three afternoons, and less than $200 all told.

So do as I say—and not as I did.

Below are pictures of the "stuff"—a basic steel-sheathed door (pre-hung of course, it's way easier), a vinyl brick molding kit, a lockset, and some spray caulking. It's not too tough to cartop the door home, as you can see.

The door was in stock at about $115 at a prominent "big box" retailer. It pays to shop around, apparently; the other guys would have had to special-order a "left-hand outswing" door and would have charged about $75 more.

For those unfamiliar with this terminology, "left-hand" means that the knob is on the left, and "outswing" means that the door opens outward, toward you. "Outswing" was necessary since there wasn't enough clearance inside for the door to open, and "left-hand" was desirable to keep the user safely away from the edge of the deck onto which this door opens. (You'll see the layout in some of the later pictures.)

Note that the terminology is not always consistent--although the foregoing reflects the discussion I had at the store (a somewhat confusing one!), this type of door is elsewhere termed a "right-hand reverse" door. (See comment by reader "D Best" below.) This reflects the placement of the hinges, not the knob, while "reverse" refers to the "outswing"—since an outswinging door is the less common of the two possibilities. A diagram and discussion are here:

Door Swinging

Preassembled doors may not be too hard to cartop home. (Does not apply to doors with elaborate windows built in.)

A vinyl brick molding kit, lockset, and spray caulking are also needed.

Preassembled doors may not be too hard to cartop home. (Does not apply to doors with elaborate windows built in.)

The first step is to pry off the old brick molding—that's the trim that surrounds an exterior door. It's quite straightforward, as illustrated in the photo. If you're lucky, it may be possible to remove it in one piece and reuse it—but it's hard not to break a piece, even if you are careful. I'd already decided to replace the molding, so I didn't even try.

Use a pry bar to remove old brick molding.

Here's the decayed framing I mentioned above. You can see a bit of the white door casing at the top of the frame; I cut it away in places to facilitate its removal.

Clearly, this rot damage is a very, very Bad Thing.

Here, I've cut away all the decayed wood in the studs (the upright pieces.) Still to be removed is the rotted portion of the joist (the horizontal piece resting on the concrete floor.)

Cutting away the rotten joist wood was the hardest part of this repair—it's tough to saw up to the edge of the wall, but not into it, and there was very poor access to the area I needed to work on. I actually used a small chainsaw, working with elaborate caution. (I don't think I'd recommend that to you—but that is what I used.)

Decayed studs cut away, removing all rotted wood.

Having removed the rotten wood, the next need is clearly to replace it with sound wood. The method I used was to "sister" pieces together. That means that in addition to the piece replacing the rotted wood, a "backing piece" which overlapped the joint between new and old wood was added for strength and stability.

That's part of the reason that the two old studs were cut away at different heights, as shown in the photo above: it created that overlap in joints, giving decent rigidity to the repair without the need of a separate sistered backing piece.

The photo below shows the sister piece atop the joist.

Sistered joist installed.

New segment of stud fitted in place to be sistered.

Sistered joist installed.

I thought I had a nice picture of the sistered studs, but apparently not. Still, you probably get the idea.

Before you start installing your door, read the instructions.

Or perhaps I should say, "read the instructions as best as you can?" The ones that came with my door were quite generic, relating to many different models in the company's product line, and were not always as clear as I could have wished. Still, I was glad I took the time; reading them was more helpful than not.

Start by fitting the door into the rough opening to see how well—or ill!—it fits. In my case, somewhat on the "ill" side; I'd made some sort of error in the vertical measurement, and the rough opening was too big for the door I had purchased! Possibly I was guilty of assuming that the existing door was the standard 80 inches, whereas it appears to have been roughly 82, or possibly I confused the dimensions of the door with those of the rough opening. Author Scott Grice gives the allowances for sizing the rough opening thus:

". . . 3/4 in. for the jamb, 3/4 in. for finish flooring, 3/8 in. for underlayment, and 3/4 in. for wiggle room at the top of the door, and the top of the trimmer (the bottom of the header) needs to be 82 5/8 in. above the subfloor."

(Since my door would be over the concrete, no allowance for flooring or underlayment is required, reducing the correct rough opening size to 81 1/2".)

It probably wouldn't have affected my buying decision, had I realized the discrepancy prior to buying the door—it's cheaper and faster to adjust the framing a bit than to custom order a special sized door. Still, good luck isn't guaranteed, and you should exercise the care that I somehow failed to. (You can clearly see the gap between the original rough opening and the top of the door in the closeup photo.)

Well, easier to fill in space than to enlarge it. I just added a piece to the top of the rough opening to adapt opening to the door.

That done, the door could be "shimmed" in place. "Shims" are wedges, used to adjust and secure doors and windows in place prior to nailing or screwing them to the framing. You can buy packages of them cheaply anywhere building supplies are sold.

The whole point is to ensure that the door or window is really and truly plumb and level. ("Plumb" means exactly vertical; "level" means exactly horizontal—in BOTH horizontal dimensions!) If this is neglected, you are putting your installation at risk of not operating properly—your door may not latch properly, may not close, or may tend to swing open annoyingly.

Use your level liberally, and recheck as much as you need to to be certain! I did.

Unfortunately, I was so intent upon this laudable and necessary goal that I forgot something else.

Door fitted in place, but not installed.

One of the best parts of the installation instructions I got was the bit about how to shim the door correctly. Basically, it had you start at the bottom, then do the top corners, then work from the bottom up, checking and rechecking as you went.

The first thing it said was the center the door in the opening. I didn't.

You see, the opening was a bit on the large side, and I was a bit short of shims and didn't want to run out for more. Since I had already found that the stud at the right side of the doorway was beautifully plumb, I decided to shim hard against that stud instead. What I didn't realize was that that would complicate caulking and the installation of the brick molding when the time came to accomplish those steps of the process.

So do as I say, and not as I did. . .

Here's the door, installed and the gaps around the frame caulked. You can see the ragged edge created by the spray caulking on the left, and contrast it with the nice clean line at the right. Note, too, the gap filled at the top.

Well, the "uncentered approach" wasn't the best way to do things, but it wasn't too, too terribly bad, either.

Typical!

Pre-routed pocket for latch assembly.

The next thing was the installation of the lockset. Pre-hung doors come with the appropriate pockets already routed into them, and into the casing, so installation is pretty easy—just a matter of checking that latch and strikeplate line up OK, and screwing the hardware in place. Everything you need is included, barring tools of course.

You can probably figure it out on your own, but it may be a bit easier securing the knobs before the latch or vice versa, so check the instructions for the recommended sequence.

Once your door is latching correctly, you are ready for the brick molding. Here, you can see that I need to trim the siding a bit. That's one of the consequences of my failure to center the door in the opening.

One of the other consequences is that I had to be a bit more careful in placing the nails I used to fasten the brick molding; the nails had to go into the wood, not caulk, after all!

By the way, a simple mitre box is invaluable in trimming the brick molding to size, especially if you need to trim the header (top piece) or if you are cutting molding from stock pieces since in either of those cases you are going to have to make a 45-degree cut. (If you can use a kit "as-is" you may be able to skip this cut—but apparently, kits are all made for a 36-inch door, so I had to cut the header to fit my 32-inch door correctly.)

Okay, so installing the brick molding took a little extra trimming and will still take a little extra caulking. Still, it looks pretty good, doesn't it?

Well, except for that bit at the top, where the old siding doesn't even come close to meeting the brick molding.

New siding is indicated. You can see the sequence below.

Freeing the old siding. You need to go 1 row higher than the row you are replacing.

The photos pretty much speak for themselves, I think—the only slightly tricky bit was nudging the new siding into place under the piece above; the fit was just a bit tight. I used a piece of scrap wood, carefully tapped with a hammer, to ease the new piece of siding into its spot without damaging anything.

With that done, it was straightforward to caulk and seal around the edges of the door. I began with the spray filler/sealer. Be careful with this product, as there are a couple of variants of this stuff, and it's important to use the version intended for use with doors and windows—the other type expands more (and more forcefully!) and can bend frames, causing windows and doors to jam.

But it's very useful material. Once that base layer cured, I added a layer of latex sealer to give a better surface for painting. Truth to tell, if you look closely it's not that great a surface even now. A sandable product could have been used to allow a really good finish.

But as I said, this door is relatively little-seen anyway, so it didn't seem worth the time.

Priming around the door, once caulking has been applied and allowed to dry. Dog is optional.

Finish coat appied. Now we can say this project is done!

Priming around the door, once caulking has been applied and allowed to dry. Dog is optional.

A couple of "finishing" photos—the first shows a coat of primer/sealer applied to the brick molding and wall. (I plan to paint the door at a later date, too--once the color is negotiated successfully!)

The second is the "after" picture, showing that even a duffer l like me can get a reasonable result in the end, despite the odd detour, error and workaround. And I'm hoping that, as a result of reading this Hub, you'll be spared one or two of those!

This article is accurate and true to the best of the author's knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.

Doc Snow (author) from Camden, South Carolina on August 19, 2017:

Thanks, Juliet. It may take a while for my next "how-to," as we are quite literally in a different place. However, there is definitely construction in our future, and I suspect I *will* be writing about it!

juliet james on August 15, 2017:

Nice article. Thank you for sharing this. Its really helpful. Step by step instruction on door replacement is good. We expect more from your side

Doc Snow (author) from Camden, South Carolina on January 07, 2013:

Not to worry (too much.) It's an 'outside closet,' which doesn't give access to the interior.

Good catch, though, and perhaps I should have pointed that out for the unwary...

mch on January 07, 2013:

Did you just install an exterior door on your house with the hinges in the exterior of the house??

Hope crime is a non-factor where you live.

Doc Snow (author) from Camden, South Carolina on May 16, 2012:

Thank you, D Best--appreciate your detailed comments!

Yes, the door itself is 80", not 82". The project (and article) is now about 18 months ago, so I'm not sure what I was trying to say at the time. But I'll clean up the wording in the article to be clearer.

Same goes for the 'handedness.' I recall a somewhat lengthy discussion with the sales associate, and being rather puzzled by the description--but time has blurred the details, I'm afraid.

And thanks for your comments on the rot. There are a lot of things I don't know about carpentry of all sorts, but one that *was* drummed into me is that rot will spread. You've got to cut it out. And then, of course, you have to replace the structural strength that's been lost.

I will say, though, that 18 months on this job is holding up well; the door operates smoothly and the finish--inelegant though the caulking was--is holding up OK so far as well.

Thanks once again for dropping by!

D Best on May 16, 2012:

Are you sure your door was 82 high? Most Doors the Average height is 80 not 82. Could your door have been that instead, and you made the opening for an 82 door? Did they (big Box store) ask you which side the hinges were on? LH doors are not as easy to comeby as RH. They do not sell as much. Your door hinges are on the right so it is actually a RH door that's why you got it cheaper. Standing outside looking at the house, if the hinges are on the right it is a RH Door etc. It's good the way you cut out the rot extra and did the joining well. A lot of people don't realize fix the small problem while it is still small. It turns into abigger problem overtime and costs 3 times as much the longer you leave it!

Doc Snow (author) from Camden, South Carolina on October 28, 2010:

Great! I hope it does really help, and good luck with your project! Thanks, as always, for dropping by.

Hello, hello, from London, UK on October 28, 2010:

Very well explained and as you yourself said the pictures speak for themselves. Thank you for a great help. I need doing this as well as the windows.