How to Turn a Window Into a Door
LESLIE: Our next caller is from Wisconsin.
Mary, how can we help?
MARY: I was wondering – I have an older house and I would like to take a window out in the bedroom and put a small door that goes out into the deck.
MARY: And I was wondering if it would be – if it’s something I should do because there’s a furnace vent right under the window.
TOM: Ah. Well, that’s a great question.
TOM: Well …
LESLIE: You would have to relocate that duct.
TOM: You’re going to have to relocate that vent. But by the way, it’s improper construction to have a furnace vent under a window. In fact, if it’s built correctly, you’re not supposed to have a furnace vent within I think it’s 10 feet of a window, unless it’s above it. Yeah, because …
LESLIE: Why is that?
TOM: Well, because see here’s why. Because if you have the window open and the home becomes depressurized because of high winds – so the pressure in the house is lower than the pressure outside – those gases from the furnace vent can get drawn into the house and of course that can cause carbon monoxide poisoning. So regardless of whether you put the door in, it’s probably a good idea to relocate that furnace vent.
Now as to installing the door, you know, the hardest part of putting in a window or a door on an exterior wall is maintaining the structural integrity of that wall because it’s probably load-bearing. But what’s nice is if you have a window there, you already have a header. So the trick here is to preserve that header and if the header happens to be high enough, you can actually just lower – remove the wall section under the window and use the same header to support the door. And so it doesn’t have to be a …
LESLIE: Because the side rails on either side of the window are going to go all the way down to the floor.
TOM: Right. Right, exactly. Now there may be a rule, in terms of egress here, in terms of how narrow that door can possibly be. And also remember that – you said it’s going to go out to a deck – you have to be very careful about how you flash the door against the deck; you know, at the bottom of it. Because it’s a real common place for leaking and what you probably are going to want to do is use fiberglass flashing to go up and over the sill before you put the door in, so it’s a completely watertight seal.
TOM: If you have a good contractor do it, that shouldn’t be that hard to do.
MARY: I measured the top of the window and it’s 82 inches.
TOM: That’s perfect.
LESLIE: Yeah, that’s standard door height.
TOM: That’s perfect. Yeah, you’re …
LESLIE: Now Tom …
LESLIE: … if she’s going to be putting a door in the place of the window, where should she relocate that furnace vent to?
TOM: Well, that’s going to kind of be …
LESLIE: Since you’re still – you’re now creating a larger opening.
TOM: Yeah, it’s going to be – the answer to that’s going to really depend on where in the house it fits. You know, in an ideal situation, she might want to run that up through a closet and maybe through the roof and out above the house.
What kind of furnace is this? Is this the furnace for the whole house that comes out there?
TOM: Is it a newer furnace or an older furnace?
MARY: I would say the furnace is probably less than 10 years old.
TOM: It’s probably not a high-efficiency, condensing furnace; which could account for why the vent is where it is. I would suggest to be relocated. I can’t tell you where without seeing the house but an HVAC contractor ought to be able to lay out your options for you.
MARY: But having a fireplace also wouldn’t make a difference.
TOM: Wouldn’t – no, it wouldn’t change anything. It would just add to the complication level because you’ve got to vent that as well.
MARY: Oh, OK.
TOM: Alright, Mary?
TOM: Thanks so much for calling us at 1-888-MONEY-PIT, 888-666-3974.
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