Installing an interior door in an unfinished basement

Factual Questions
1

The Devil’s house has an unfinished basement. We’ve long had a problem with cold air coming into the house from down there, and given the recent cold snap I’ve been (kind of) taking care of it in small pieces.

Step one was to line the unfinished stairwell walls with foamcore insulation.

Step two is to put some sort of barrier at the bottom of the stairs. My initial idea was to make this awesome blanket fort, but Mrs. Devil kind of vetoed that. So I want to install a basic interior door.

I have no idea what I’m doing. But since it’s a non-structural interior door, I figure this is a great chance to learn.
I don’t know if it’s typical, but the bottom of the stairs end oddly—one bannister pokes out a little and the other side has a dangly bit. That means I can’t just press a door up against the existing stairwell and be done with it. So here’s what I’m thinking of doing:

Attach foot-long 2x4s to the basement floor (would those be sill plates?).

Carefully balance a pre-hung door on top of the plates.

Okay, that’s about as far as I get. No, wait. I figure I’ll just extend the foamcore insulation from the end of the stairs to the new door. Hopefully without knocking it over.

How do I attach the sill plates to the cement floor? Those blue-coloured screws in the hardware department? Do I [del]get[/del] need to buy a nail gun? I have a small compressor (2.6SCFM @90PSI), if a pneumatic tool would help.

So, now that I have the wood attached to the floor, do I just nail the door down? Do I then just nail it to the joists overhead? Or should I attach another sill plate up there and then nail the door to that? Given the vagaries in construction and whatnot, won’t I likely run into a door that’s slightly too big or slightly too small? What then? Install it on an angle?

Hey. Wait a second. Now that I’ve gone and attached all this wood to the floor, won’t bottom-step-to-floor-ratio be off? Will that result in comical pratfalls? Should I move the door out by more than a foot to create a landing of sorts or am I overthinking things?

Where was I? Oh, I’ve got a door nailed to the floor and nailed to the ceiling. Am I done? Or do I need to connect it to the existing studs? Now am I done?

This’ll be easy, right?

Before heading to Lowes, I’m hoping for three things. A reality check on the above, an idea of the measurements I need to make before heading out, and an over-inclusive shopping list (I’d rather have to return things than make a second trip). Here’s what I have on the list so far: 2x4s, a door, a tool to attach the 2x4s to the floor, fasteners to attach the 2x4s to the floor, and fasteners to attach the door to the sill plates. I have basic hand tools (e.g. circular saw, hammers, drill, Band-Aids), but an idea of everything that I’ll need would be great.
Yours in entryways,

Rhythm

2

It’s hard to tell from your description what you have at the bottom of the stairs, but a door hangs from hinges on one side, and shuts against the other side. So you need something on the sides to mount a door frame. In general you should get a prehung door (a door already mounted in a frame), and create a framework to attach that to. Those side pieces have to be secured at the floor level, but you don’t need anything else under the door itself (except you’ll want to attach a sill there to seal the bottom of the door). Your best bet is to concentrate on insulating the basement and stop the constant loss of heat through there. Once insulated you can add a zone to heat the basement, most of that heat will rise to heat the rest of that house. If it’s still uninsulated, heating your basement is like trying to heat the whole town you live in.

ETA: If you have to attach something to concrete, it depends on the concrete. In order to use those screws you have to drill into the concrete (there’s usually a bit supplied), and that doesn’t always work that well. I use a nail shooter that uses .22 cartridges, they can be rented, but a simple tool operated with a hammer costs less than $50.

3

My advice - get a carpenter.

Failing that you should first take a close look at existing doors to see how they are constructed.

4

I would recommend that you first enclose the other three sides of the staircase with a 2x4 wall (you don’t need to put up drywall). It is a much easier project than properly hanging a door. It will also be a good starting point for the door frame.

5

This makes me think you have a lot of air infiltration in the basement. Have you tried caulking everywhere you can get to? If wind can’t push air into the basement, what’s there should stay in the basement, not come upstairs.

6

Get a carpenter? What fun is that? I’d definitely go professional if there was anything structural or significantly complicated, but this is a good chance to learn and do.

Unfortunately (or fortunately, come to think of it), all the other doors are in living areas–there’s nothing else in the basement to serve as a model.

One side of the stairs is completely framed, the other was fairly open (I attached simple 1x2s to hang the insulation). There is a door at the top of the stairs.

My hope is that this is something of a babystep project. Not that I’m saying anything is easy or getting overconfident, but my hope is that by getting a pre-hung door I’ll avoid a lot of the headaches associated with hanging a door. A few years ago I had to replace another interior door. The frame was intact, all I needed to do was put hinges on it and hang it. It took a bit of work with a Dremel router attachment and a handful of frustration to get it ‘right’, but it’s there, opens fine, and looks good. But won’t the pre-hung/pre-hinged route save me the hardest part of hanging a door?

You’re spot on with the amount of air that leaks into the basement. Funny thing is, the rest of the house is incredibly insulated. There are actual, measurable gaps in the basement that lead to the night sky. I’ve plugged most (those that I can find) with insulation, but I know there is more–much more–work to be done. In the short term, I’m just looking to stem the direct airflow into the house.

7

get a prehung door.

construction adhesive will glue wood framing to the floor. you can also anchor by drilling holes in the floor and inserting anchors for screws or bolts.

8

This is do-able. Basically you want to build a 2x4 opening for a pre-hung door to fit in.

Here’s a video of the basics: YouTube

Build the opening about 1/4" wider than the pre-hung door casing. Without seeing your exact situation it’s hard to know whether you need to attach anything to the floor or not. You wont need a 2x4 under the door, weather stripping will stop the air circulation, example: http://www.homedepot.com/Tools-Hardware-Hardware-Weather-Stripping-Door-Bottoms/h_d1/N-5yc1vZc3e0/R-100174107/h_d2/ProductDisplay?catalogId=10053&langId=-1&storeId=10051#.UQaJ8ZG9KSM. If the opening that the door is going into is already pretty close to the right size, construction adhesive will do just fine for the bottom “plates”. If you do need to attach the bottom plates to the floor use a .22 nail gun as suggested above.

You will also need a package of wood shims. Frame up the opening as true as possible, screw the door in place using the shims as spacers to make sure it’s level, fill the gaps with expanding foam (let cure) then put on trim.

9

Ok, so the first step is to build a 2x4 wall at the bottom of the stairs. Cut 2 2x4s the width of the stairwell opening. These are your plates. Pressure treated is recommended for the bottom plate which will be in contact with the concrete floor. One will be attached to the basement floor, the other to the ceiling. Line the pair of them up one the floor, small edge up. Now you will mark your stud locations. You will need at least 1 stud one either side of the door opening, which needs to be 2" larger than the nominal size of the door. For example: a 30" door requires a 32" opening.

You likely also need 2 additional studs, one on each end of the wall. Additionally, you need a header , or horizontal 2x4" at the top of the door opening. For a standard 80" door, 82" from the floor works nicely. Measure the height of your wall at the bottom of the stairs, checking for the lowest point. Subtract 3 1/2" inches from that number to get your stud length. (Plate thickness+ 1/2" clearance) Cut your studs.

Now, lay the plates down on the basement floor, lay the studs in between, on your marks. Nail in from the top/bottom of the plates using 2 16d framing nails per stud. Mark the header location 82" from the bottom of the bottom plate, to the bottom of the header.

Now stand it up and move it into place. Use a level to get plumb. (plumb is straight up and down, perpendicular to level.) Nail or screw the top of the wall into the ceiling joist or beam. Now, use concrete screws or hardened concrete nails to nail the bottom plate down. Don’t nail into the plate directly under the door, as you will be cutting that out. Concrete screws are the best option, but will require a hammer drill to install. Nails are cheap and just require a hammer, but will be more difficult.

Cut the door sill out with a handsaw or recip saw (sawsall).

Now you’re ready for some kind of sheeting. If air infiltration is your main concern, just use 1/2" ridgid foam, nailed up with roofing or button cap nails. Cut out the door opening in the foam and you’re ready for your door.

To install a prehung door with attached casing.

Unwrap the door, take out all the nails/staples holding the door shut/trim on. You should be able to pull one side of the casing(trim) out of the frame as a unit. Set that aside.

Take a shim or 1/2" piece of scrap wood on the floor, right on the hinge side of the door. This is going to help you have some play when you try to level the door header.

Set the hinge side of the frame right on the scrap, sliding the whole unit into position. Use a level to plumb the hinge side door, nail in place with finish nails behind each hinge through the casing. Now, look at the gap between the door and frame on the hinge side. That space is called the reveal. Move the door header up and down until the reveal matches, then nail it in place. Likewise for the lock side of the frame.

Now, open the door, shim carefully behind each hinge and the lockset. Check door for proper operation and nail in place at each shim location. Score and snap the shims at the edge of the frame. Insert the remaining trim back in the frame and nail.

Caulk the door frame and wall to help with your air problems.

Robert is your mother’s brother. :wink: Hope that helps.

10

If you already have a door on the main floor, what is the rationale for installing one in the basement?

How about the walls on the main floor surrounding the staircase? Are they cold to touch? A bit of insulation there could go a long way. What is the usual temperature in the basement anyway?

If actual air flow up the stairs is a problem, put up plastic sheets all around the staircase in the basement. You could also have a closer look at that door. Is there a gap between the door and the floor (common in most houses)? If the door feels cold, you may consider upgrading it for an insulated door.