Okay, so you’ve dropped your metal boxes, replaced the wood floors with concrete and now – you’re faced with interior space.
It’s time to start divying up that “Corten Castle” into rooms. Just like in a “normal” home, you’re going to cut some holes or build some partition walls to start creating bedrooms, bathrooms and other areas. This means that you’re going to be installing doors. In most ISBU Homes, the partition walls inside the home are built from dimensional lumber, just like their counterparts in “normal society”.
We do this for a lot of reasons. It allows you to use regular materials that you’re already used to. It allows you to buy (or reuse-recycle-repurpose) materials anywhere and it allow you to use your ‘idiot brother-in-law” to help you without having to worry that he’ll cut off his own hand with a plasma cutter.
Sure, the self-inflicted wound will cauterize itself, but he’ll still cry like a little girl. You don’t want your kids to see that, do you?
And that brings up a question I get asked a LOT;
“What size should the rough opening for my doors be?”
Today, we’re going to talk about “swinging doors”. Pocket doors are abit more challenging and it’s a separate discussion. Trust me on this.
Look, determining your rough openings for doors is one of those parts of construction where it’s important to get it right on the first attempt.
Creating rough openings for doors is really pretty simple;
“Just add 2″ to the WIDTH of the actual door size you intend to install.”
Now, once you know how WIDE you’re going, you need to determine how HIGH that opening should be;
“We add 2.5″ to the height measurement of the actual door. This allows you ample room to space to door frame off your sub-floor.”
We like 30″ wide doors. In the trades, they call these “2/6″ or 2’6″ wide doors.
Add 2 inches to the width. What do you get?
You get 32″.
Yep, that’s how wide your opening is going to need to be.
Now, your door height is probably going to be 80″.
Again, we do some math. Add 2.5″ to 80″ and you get…
82.5″ – which translates to “6/8″ or 6’8″ in “doorspeak”.
There are a handful of reasons why a rough opening needs to be bigger than the door and it’s frame;
First, it’s called a “rough opening” for a reason. These openings aren’t usually done by surgeons, they’re usually done by guys in a hurry. That means that the door opening isn’t going to be perfectly square or in some cases, even PLUMB.
You need room to adjust the door and frame (plumb, level and square) in it’s opening.
There’s no such thing as a “universal” door size. Door sizes vary by manufacture. We’re not talking about HUGE differences, but the differences are enough that you could end up with a jamb that is too tight, or a door that doesn’t work properly. You will probably need room to persuade that door to fit.
And, that wall isn’t going to remain that exact size forever. The wall will expand and contract throughout the seasons by taking on humidity and then drying out. Expansion/Contraction. We’re not talking about a LOT, but it’s enough “material movement” that you will want to allow the door to work, year round, without sticking or refusing to close (and more importantly “latching”) properly.
And then there is floor covering…
If you’re going to install carpeting, you will want to shim your door framing up a little bit (about 3/8th of an inch) so that the carpeting can be tucked UNDER the jambs. That way, your door never rubs or chafes the carpet.
Remember also that not all doors are level. Providing some “fudge room” allows you to move your latch jamb into the correct position so that your door will close properly.