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poorhomeboy
Basement - 24" gap btwn foundation and framing

Background: Newer construction, poured foundation with rubberized membrane and Dow blue foam on the exterior of foundation, perforated tile at footings on interior and exterior emptying into sump well. Experienced two years of seasonal changes – never any leaks, seepage, or signs of water (besides the tile network doing it’s job and emptying into the sump). The basement remains cool in summer, warm in winter – ductwork is installed above, but we keep the grates closed.

I’m planning on finishing our basement in stages.

Right now, I’d like to put up some walls to divide the mechanical area from the future finished space (mainly so my three sons don’t explore where they shouldn’t be exploring….). I also want to frame out space around our sump pump (make it look like a corner closet/pantry area.

The mechanical area – about 1/3 of the square footage – would remain unfinished storage. The future finished area would become one large rec room/home theater/bar area.

I have enough floor space that I can build most of the walls – excluding the egress window area where I’ll build window seats – far enough away from the foundation to access the space later (I’ve mapped out a 24” perimeter around all the exterior walls that’ll be finished with chalk to sketch the space). My thought is this – with enough space to maneuver between the foundation and backside of the finished studwall, I can install whatever types of wiring we need in the future, allow for air to circulate around and over the walls (suspended/drop ceiling), and monitor for any leaks down the road.

In the unfinished storage area, I’ll be running a dehumidifier to balance humidity regardless of my method of finishing.

Is it still necessary to use a vapor barrier between the foundation and the finished, drywall covered studs?

canuk
Re: Basement - 24" gap btwn foundation and framing
poorhomeboy wrote:

Background: Newer construction, poured foundation with rubberized membrane and Dow blue foam on the exterior of foundation, perforated tile at footings on interior and exterior emptying into sump well. Experienced two years of seasonal changes – never any leaks, seepage, or signs of water (besides the tile network doing it’s job and emptying into the sump). The basement remains cool in summer, warm in winter – ductwork is installed above, but we keep the grates closed.

I’m planning on finishing our basement in stages.

Right now, I’d like to put up some walls to divide the mechanical area from the future finished space (mainly so my three sons don’t explore where they shouldn’t be exploring….). I also want to frame out space around our sump pump (make it look like a corner closet/pantry area.

The mechanical area – about 1/3 of the square footage – would remain unfinished storage. The future finished area would become one large rec room/home theater/bar area.

I have enough floor space that I can build most of the walls – excluding the egress window area where I’ll build window seats – far enough away from the foundation to access the space later (I’ve mapped out a 24” perimeter around all the exterior walls that’ll be finished with chalk to sketch the space). My thought is this – with enough space to maneuver between the foundation and backside of the finished studwall, I can install whatever types of wiring we need in the future, allow for air to circulate around and over the walls (suspended/drop ceiling), and monitor for any leaks down the road.

In the unfinished storage area, I’ll be running a dehumidifier to balance humidity regardless of my method of finishing.

Is it still necessary to use a vapor barrier between the foundation and the finished, drywall covered studs?

There would be no advantage of introducing a vapour barrier with the method you are proposing. Besides, the vapour barrier wouldn't be toward the foundation side ( since that would be the colder surface.

Personally, you are loosing quite a bit of square footage by keeping the walls out 2 feet and seems unnecessary.
I would cover the foundation walls with one or two thick rigid foam ( depending where you live ) -- frame the walls touching the foam and then finish drywall. This wouldn't require any additional vapour barrier -- the open stud bays would allow easy access for any future wiring --- and you would gain some valuable space.

If you do enclose the sump pit and it doesn't have a tight cover seal then you want to make sure the enclosed space has ventilation--- either louverd doors or vents. Otherwise you could end up with mold / mildew issues within that space from the humidity form the water in the sump pit.

2 cents worth

Mastercarpentry
Re: Basement - 24" gap btwn foundation and framing

In the city here, if you wall in an area and the wall will contain plumbing or electrical, the building codes require a minimum of 12" clear space behind the wall to allow service and inspection. Since you're not really likely to need to get back in there that is enough space to work in. I know you want to work in stages but it's far better to rough-in the plumbing and electrical before covering the wall with sheetrock. At the very least plan now and do all your drilling while the wall is open. Walling off the mechanical areas now is a good idea, especially if you're not putting plumbing or electrical in it or can get the that from behind later on easily. If you've got gas-fired appliances they will need an air supply either from outside or from the newly-created room. A quick call to your codes inspector will get you a few answers for free. Sounds like a great project for you and a good approach to it.

Phil

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