What’s the best way to build a storage room in my basement?

October 7, 2008 9:07 AM

What’s the best way to build a storage room in my basement?

I want to build an 8x14 storage room in my basement. I have the usual crap to store, a few pieces of furniture, some camping gear, some old photos, etc. I know the basement isn’t the ideal place for some of this stuff but, well, it’s really the only place I have for it. I’d like to build an area that will offer the best quality storage possible in a basement.

I have a new, very dry basement. There’s no issue with water other than humidity in the air. Walls and floors are dry to the touch, the walls are waterproofed and insulated on the outside and there’s a vapor barrier under the slab. We had a slight problem with mold growing on some stuff (but not on the house itself) that we seem to have solved with de-humidifiers.

The floor will be PT 1x sleepers with plywood flooring over it. Given that there’s already a vapor barrier under the slab, should I put an additional one under the wood floor?

Two of the walls will be framed with wood studs with OSB (or plywood) walls to separate them from the unfinished part of the basement. Is there any reason to use sheetrock instead? I want this to be quick and easy and the OSB will be lighter and easier to work with. The other two walls will be against the concrete exterior walls. Given that the concrete is dry, is there any benefit to putting up wood walls on these sides with a vapor barrier behind the OSB? Would that offer any better protection?

Is there any reason to put a vapor barrier on the interior walls?

Should I attempt to seal this room off from the rest of the basement and make it as airtight as possible (via poly barriers) or should I do the opposite and allow air to circulate in and out with a couple of air vents? Obviously, since there will be a door I can’t make it totally air-tight.

I’ll have de-humidifiers running in the basement during the damp months. Should I put a smaller one in this room with a drain to the sink on the outside?

What else am I not thinking of?

posted by bondcliff to home & garden (7 comments total)

I think you might be overthinking it, actually. No need for any of the vapor barriers. If your basement is reasonably well sealed a dehumidifier should do you just fine. As for the drywall, the main advantage is that it's pretty cheap and relatively fireproof. OSB/plywood is much tougher though. Probably no need for the sleepers/plywood floor either, unless you see yourself putting in an actual floor someday.
posted by electroboy at 9:26 AM on October 7, 2008

I think you'll really only need to put vapor barriers on the walls if you plan on furring out the basement walls and then adding insulation, which probably isn't necessary for just a storage space. The reason for that would be more to protect the walls from moisture generated *inside* the space condensing in the wall space than from moisture travelling from outside, which may not be much of an issue anyway. If you want to go ultra-super bombproof on everything though, you might as well do it.

Typically, wood floors installed over concrete slabs on sleepers as you're thinking of doing will have a barrier between the sleepers and the plywood, and a concrete slab will just about always have a vapor barrier underneath it. So I'd probably do that one.

It sounds like, as you say, the mold issue was caused by moisture coming from within the space instead of infiltration from outside. If you're putting up "finished" walls and that moisture is a big enough concern for you, you may want to go ahead on put a barrier on the interior side of your walls as well.
posted by LionIndex at 9:46 AM on October 7, 2008

Probably no need for the sleepers/plywood floor either, unless you see yourself putting in an actual floor someday.

The reason I would do this would be to keep boxes or furniture off the concrete.

And I probably am overthinking it. I do that with everything, even plates of beans.
posted by bondcliff at 9:59 AM on October 7, 2008

Not much more money than sleepers but much easier are floor systems like Dricore. Plus you gain an inch or so of head room over sleepers. Despite the vapour barrier under the floor you should check for humidity from that source as practically all the under slab vapour barriers have punctures. The test is easy: Duct tape a 1 meter/yard square to the floor and wait a week or two. If you notice moisture under the plastic then you need to deal with the moisture in some way. If you don't then a simple sealed/painted floor will be easier to keep clean and free of dust by sweeping than raw concrete.

Drywall is preferred over OSB because it finishes better and easier. If you don't care about nice smooth walls or you don't mind the 70s wood panelling look then OSB is cheaper.

On the exterior concrete walls, assuming you are still in Boston, I'd use foam safe construction adhesive to first attach 1/2" extruded polystyrene insulation (blue/pink board) to the concrete then use it again to attach the OSB/gyproc to the foam. It's thin, goes up crazy quick, provides a vapour barrier, and isolates the concrete from the room reducing possible condensation in the spring. Also the foam gives you a chase space if you ever want to run a receptical/light in the future.

"the walls are waterproofed and insulated on the outside"
Waterproofing only extends to grade usually, you should have a vapour barrier on the warm side of the wall before applying a finish on the exterior walls if any part of the concrete is above grade. Vapour barrier isn't required on interior partitions unless you are trying to isolate noise.

I'd let air circulate rather than sealing things up tight unless you are going to provide HVAC with it's own control to the storage room.
posted by Mitheral at 10:45 AM on October 7, 2008

Well, if you still want to do the floor with sleepers, you can use OSB subfloor. That's about half the cost of plywood subfloor. $10-12/sheet vs. $20-25 for plywood. Definitely do the moisture test suggested above though. Even if it's negative, you still may want to lay down plastic sheeting (overlapped and taped) before putting down your sleepers.

Drywall and OSB should actually be about the same price (standard drywall vs. OSB sheathing). The big difference being that there's no taping/mudding with OSB. It does, however, look like hell, even painted.

Was the foundation poured with insulated forms or was it stuck on afterwards? Was it waterproofed using a tar-like spray on coating or something similar?

One more thing to keep in mind is that fresh concrete can release a lot of moisture. That could be the source of your earlier problems. Still, it sounds like you don't have any problems that can't be solved by dehumidifiers if the basement is built as described.
posted by electroboy at 11:42 AM on October 7, 2008

Re: Drycore. I've looked into it but the cost is more per sq foot and in talking to a contractor he felt sleepers/plywood would be all I need. I've done this before in another house and it was easy enough.

Re: insulation. No need to insulate this room as it'll be storage. When I finish off the rest of the basement (an office and home theater room is planned) I'll insulate that part. I may insulate the wall between the storage area and the future finished area, though that part will be mostly just a door. The long wall will abut the unfinished shop area.

Was the foundation poured with insulated forms or was it stuck on afterwards? Was it waterproofed using a tar-like spray on coating or something similar?

Insulation was added below grade after the fact. The waterproofing was sprayed on. I wasn't there when they did it but this is what I was told by the contractor.

I don't really care how any of this looks inside so I'm leaning toward cheap and easy materials over pretty. The fireproof aspect of drywall is something I hadn't thought of, but I think it might damage too easily what with throwing things on and off the shelves.

This is all very helpful. Please, keep the tips coming.
posted by bondcliff at 12:00 PM on October 7, 2008

Update: I’m almost finished with the project. I used T&G OSB for the subfloor, “Home Advantage”, which I assume is the Home Depot version of Advantech. This was laid on top of 1x4 pressure treated sleepers w/ a vapor barrier between the OSB and sleepers.

Walls are OSB, which does sort of look like crap but the crappy part will only be visible from the crappy unfinished side of the basement, so it’s all good.

I borrowed my brother’s pneumatic nailer to do the framing, which is pretty much the greatest thing ever invented.

Thanks to all for the advice.
posted by bondcliff at 6:44 AM on October 15, 2008