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Discussion Starter #1
Hey folks. I have gone back and read many past posts but wanted to post my own specific situation. I'm in the very first stages of converting an “L†shaped basement room into dedicated home theater. I am hard set on building a 3-inch (approx.) floating floor over the existing floor, which is vinyl over concrete. BUT, I will only be doing so over the longer of the two legs of the L shaped room, which will make up the actual viewing/seating area (dimensions for this area are 17Hx12xWx7H). I will also be padding and carpeting this new raised floor.

The reason I am building the floating floor is because we have a gapping hole in the cement in the far corner of OTHER leg of the room with a sump pump in it. While it has NOT happened in over 15 years, there is always a chance some water could creep up and leak onto the floor. So the raised floor is a cautionary measure for piece of mind. The floor of the shorter leg of the L room, where the sump pump is, will remain as is so I will always be able to visually inspect it (though I plan on enclosing the hole and sump pump in a small closet like structure).

Also, I do not own this house, it belongs to my fiancée’s mother whom we live with (it’s a long story), so my intention is to create SOMETHING that is of great improvement over the existing, unused room, but to do so in as little a "permanent" manner as possible in the extreme off chance I ever have to undo anything. I want to strongly emphasize the extreme unlikelihood of ever having to undo my work, but just for security measures, I don't want to approach this project as if I am building a totally permanent structure in my own home, to withstand a tornado. In other words, I need to cut a few corners as opposed to building this using EVERY single “best†or “right†way of doing things. I will not be able to use the most IDEAL way during construction for every aspect. I know how that sounds but it pretty much sums up how I would like to approach this, and just about anything I do will be an improvement over the existing unused room anyway. I have been given totally free reign so no worries there, but I still wish to approach this with a small amount of caution.

With that in mind, this is my plan, how sound does it seem to you folks, I understand it isn't the IDEAL way of doing it, but would it at least be reasonably acceptable to accomplish this aspect the way I suggest I will do it (I know that sounds subjective, but just looking for general feedback)?

This is a sub-level basement so three walls are currently exposed concrete foundation (about 7ft high) WITH 2x4 furring strips already nailed to the concrete (there was old paneling nailed to the furring which I already tore down). For the floor I plan to build a frame around the perimeter of the 17x12 area that will have the 3-inch or so raised floor. My plan is

1. Cover the entire 17x12 area with 6 mil PLASTIC vapor barrier first, overlapping the edges by a few inches. I will then use construction tape or something to secure the strips together.

2. Lay down the pressure treated 2x4s along the perimeter then every 16in OC. I will screw the perimeter 2x4s to the existing joists that are already nailed to the bottom edge of the concrete foundation. I will NOT use adhesive to secure any 2x4s to the concrete floor, I will be using a large number of Deck screws instead to secure the furring to the existing perimeter 2x4s. I will also be placing additional Nailers in some locations between the 16 inch apart furring (for use with the seams of the plywood floor boards when applied).

3. Lay down 1 inch Polyisocyanurate, rigid foam insulation strips between each floor furring. Will be cut to fit in snug between the 2x4s.

4. Apply a second layer of vapor barrier strips, cut to fit over top of insulation.

5. Lastly, lay single layer of T&G ¾ inch plywood atop the frame. Secure with screws every 12 inches. NO adhesive. Stager seams.


I will be doing the same process for the wall as far as sandwiching the 1-inch insulation between two layers of vapor barrier. Then dry walling. The only thing I anticipate some of you pointing out is, from what I have read, often, you place the insulation directly against the concrete then a single layer of vapor barrier INTERIOR to the insulation. Will 2 layers hurt (I don’t know if this sort of thing could actually act to TRAP moisture between the layers)? Will the empty air pockets below the floor boards/walls cause noticable problems with sound aspects?

So, does this sound at least acceptable way of accomplishing the job or am I missing anything that could actually cause a “problem†if doing it this way? What potential problems do you think could result post construction by doing it this way? Thanks for any and all advice folks, it’s greatly appreciated.

Sorry for lengthy post, I just wanted to be sure to include all pertinent information.


Jim
 

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Two comments:


If your 2x4's on the floor are not firmly in place (glued & anchored) they will very likely warp causing a very eneven floor.


Be sure the foam you choose if proper for the application. I used the Owens pink construction foam for my floor. Which was built similair to what you propose.
 

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Discussion Starter #4
Thanks for the reply Jim, I appreciate it. I decided to go ahead and use the masonry nails to secure the 2x4 sleepers down to the concrete floor after all. I just started the floor frame today and I feel a lot better about using the nails to really lock those 2x4s down, feels nice and solid. Thanks again.


Jim
 

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I used construction adhesive and a Remington power nailer. Actually my kids 16 & 18 at the time did this job while I cut materials.


Jim Mc
 

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I am not an expert by any means, but from what I understand the vapor barrier to do is keep "any" moisture from coming in contact with the sheetrock of a wall. The barrier doesn't keep moisture from forming, it is used just to keep it from touching the interior wall. If I remember my high school physics classes, I think that unless there is a vacuum you can not prevent moisture from forming when there is two different air temperatures coming in contact with one physical surface (condensation). I don't think the first layer of plastic will do anything for you. I hope that I have it right.


Michael
 
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