Construction Allowing for drywall when framing an interior room

Stephen Tashi

Science Advisor
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Summary
What are good methods for framing the addition of an interior room so both old and new drywall are supported?
What are the best methods for framing the locations where a new interior room meets the wall and ceilling of an existing interior room?

I'll be adding a small closet to a room of a house. The rectangular closet will have 3 new walls and use one existing interior wall. The new walls will be framed with (USA) 2x4 inch lumber and then covered by drywall. I see 3 choices for how the new framing can be joined to the old wall and old ceiling.

1) Leave the old drywall in place and attach the new wooden framing to the old framing, leaving the old drywall between them.

2) Cut away just enough old drywall so the new framing can be attached directly to the old wooden framing.

3) Cut away large sections of the old drywall and attach the new framing to the old framing as if it were all new construction.

Methods 1) and 2) are convenient.

Method 1) leaves any problems with replacing or repairing the old drywall to the future. Where the walls are concerned, this doesn't bother me. However, the closet will hold a gas furnace and holes must be cut in the ceiling to allow for the ducts and flue. A contractor will install the furnace and I don't know exactly how this will be done yet. Reparing drywall on the ceiling may be necessary right away. Also, I'd prefer that the new framing meets the ceiling joists directly to give the joists good support instead of having a sheet of drywall between them.

Method 2) leaves the edge of the old drywall unsupported unless by some happy coincidence there is old lumber behind the edges that are left after you cut away part of the drywall.
 
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I think (1) is the normal approach. the new framing supports only the new drywall and closet door. unless you're making more changes above, the new walls are not structural. so there's no reason to do the extra work in (2) or (3).
 
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If doing # 2 and end up with unsupported edges then I'd just stick in extra studs or blocks as needed to support the new edges.

If putting in a new furnace I'm surprised its just dry wall and you don't have to do any fire proof materials?

Regarding which of the three is the best, heavily depends, having lived through the nightmare of matching new dry wall to old plaster and lath, my default (perhaps somewhat brutal) is now almost exclusively #3, I prefer to open up the walls to at least the next sheet seam (if its already dry wall, if its anything else it all comes off), re frame as needed, often the insulation is crap and wiring dodgy, so opening the walls gives you a chance to go over that. I find it almost just as easy to hang full sheets and crack fill a new wall than spending a lot of time getting small annoying spots that never look right.

Obviously if its in the basement or something where you don't care then do what ever.
 

marcusl

Science Advisor
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#1 sounds bad to me. You don’t want something weak and friable between your framing. I second essenmein on doubling up studs to provide a surface on which to nail off the drywall. I’ve seen pros do this. #3 would work as well, obviously.

I can suggest a forum called doityourself.com that resembles PF in the sense of having many specialty sub forums (plumbing, electrical, etc), being well moderated, and having expert advice available for your questions . Click on Forums and start scrolling to the forum on Interior Framing.
 

Tom.G

Science Advisor
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If putting in a new furnace I'm surprised its just dry wall and you don't have to do any fire proof materials?
If I recall correctly, here in Southern California 3/4 inch drywall is considered a fire proof barrier between living units in an apartment building and between a living unit and any common areas such as an attic. Check your local building and fire codes for details, and also the furnace installation instructions for required minimum clearance for both safety and service access. Also, some areas require that outside air be used for combustion air.

Cheers,
Tom
 
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I'm not sure what the code allows around here, but in the few closed in furnaces I've seen its been 1/2" concrete board or fire rated drywall, although not at 3/4", its 5/8" here, there is regular 5/8 drywall, and I'm told the fire rated stuff has other fillers which give it more hold up time in a fire, eg glass fiber. But what is or isn't permitted varies quite a bit with regions so I'd check with local codes about that, esp in the case of furnace or something, any excuse the insurance companies can use to get out of paying, trust they'll take it, and the furnace not being installed with sufficient fire rated materials if a pretty big out for them!
 

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