Basement Vapour Barrier Experts Needed

[Bigprairie1]

Ok, guys and gals I need some feedback on basement vapour barriers.
(Specifically as it relates to the floor.)
The issue relates to how to best put a vapour barrier in a concrete basement floor system. I've got the wall system/method nailed so that is not an issue.
Here are the facts as relating to this upcoming floor system:
-My house is an older home with an uninsulated concrete slab floor (not insulated under the slab like newer spec homes)
-The concrete/basement is dry and ready for a floor, but its too uneven to go directly onto it with flooring so a framed subfloor is needed.
-The framed subfloor will be a 2x4 system (layed on the flat) with styrofoam insulation (1-1/2"thk.) between then and then sheathed with 3/4" TG Plywood. I will use shims and the ol' laser level to make sure the framing is level prior to all the sheathing, etc.
NOW....where best to put the vapour barrier? I'm leaning heavily on putting it on the upper side of the framing and insulation directly under the plywood. Although some of the reno book info I've seen shows guys laying it down directly on the concrete first....below the framing and insulation on the 'cold side'???
According to everything I know about vapour barrier it is supposed to always be on the inner/warm side of an insulated surface to minimize and eliminate condensation. What gives with this?
So any takers on this issue are more than welcome.
Many Thanks!!!
BP

 

[v1_0]

Re: Basement Vapour Barrier Experts Needed

Ok, guys and gals I need some feedback on basement vapour barriers.
(Specifically as it relates to the floor.)
The issue relates to how to best put a vapour barrier in a concrete basement floor system. I've got the wall system/method nailed so that is not an issue.
Here are the facts as relating to this upcoming floor system:
-My house is an older home with an uninsulated concrete slab floor (not insulated under the slab like newer spec homes)
-The concrete/basement is dry and ready for a floor, but its too uneven to go directly onto it with flooring so a framed subfloor is needed.
-The framed subfloor will be a 2x4 system (layed on the flat) with styrofoam insulation (1-1/2"thk.) between then and then sheathed with 3/4" TG Plywood. I will use shims and the ol' laser level to make sure the framing is level prior to all the sheathing, etc.
NOW....where best to put the vapour barrier? I'm leaning heavily on putting it on the upper side of the framing and insulation directly under the plywood. Although some of the reno book info I've seen shows guys laying it down directly on the concrete first....below the framing and insulation on the 'cold side'???
According to everything I know about vapour barrier it is supposed to always be on the inner/warm side of an insulated surface to minimize and eliminate condensation. What gives with this?
So any takers on this issue are more than welcome.
Many Thanks!!!
BP

Moisture also 'wicks up' through untreated concrete. Over time, this would cause your wood frame to rot where it contacts the concreate.
There's a test that you can do to see what I'm talking about - get a plastic sheet and lay it down on the concrete. After a couple of days, pick it up - the side that was on the concrete would be damp if you have this issue.

Whenever I did any work in the basements of the houses I own(ed) I would paint the (cinderblock) walls/floors with dryloc before anything else. I think you are also supposed to put a plastic sheet between the wall and the frame, and tuck it under the bottom of the frame to protect that too. Then the drywall dosn't go all the way down either - so it can't wick up any mosture.

I do have some of this sort of issue to deal with - sometime in the future - with the house I currently live in. We have wood floors that have been installed on some osb/fiberboard that has been installed on the top of a concrete slab. I'm sure the fiberboard is nothing but a layer of damp sawdust at this point. I did some research and found a product that has a rubber mat on the one side (with raised 'bumps' so that there are air pockets), and fiberboard/plywood on the other. The wood floor goes ontop of that.

 

[wuttja]

Re: Basement Vapour Barrier Experts Needed

I just want to preface my comment with the simple fact that I know very little about this stuff, but wouldn't it be helpful to first put down a thin layer of that floor leveling compound used for leveling floors when you lay tile? That would seem to at least give you something level to start with and then do the barrier and framing? Like I said, I know very little about this but it seemed like a good idea when it popped in my head and then you wouldn't need a framed sub floor to try and level it.

 

[Bigprairie1]

Re: Basement Vapour Barrier Experts Needed

Moisture also 'wicks up' through untreated concrete. Over time, this would cause your wood frame to rot where it contacts the concreate.
There's a test that you can do to see what I'm talking about - get a plastic sheet and lay it down on the concrete. After a couple of days, pick it up - the side that was on the concrete would be damp if you have this issue.

Whenever I did any work in the basements of the houses I own(ed) I would paint the (cinderblock) walls/floors with dryloc before anything else. I think you are also supposed to put a plastic sheet between the wall and the frame, and tuck it under the bottom of the frame to protect that too. Then the drywall dosn't go all the way down either - so it can't wick up any mosture.

I do have some of this sort of issue to deal with - sometime in the future - with the house I currently live in. We have wood floors that have been installed on some osb/fiberboard that has been installed on the top of a concrete slab. I'm sure the fiberboard is nothing but a layer of damp sawdust at this point. I did some research and found a product that has a rubber mat on the one side (with raised 'bumps' so that there are air pockets), and fiberboard/plywood on the other. The wood floor goes ontop of that.

You're on this too, which is good and many thanks.
A couple of things I should have added in my first thread is that the wood framing I will be using will be all pressure treated stuff with (heavy) 40-60lb building paper on the underside for an extra layer of protection away from the concrete.
As well, I did the test you mentioned with the plastic sheet. Over the space of a couple of weeks I put one directly onto the concrete in at least 1/2 dozen places, checking it regularly, and it came up all good and dry....no moisture (so far). I have done some serious work on the concrete in the past to waterproof it, etc. The product I used was xypex and coupled that up along slab/wall seams with hydraulic cement, caulking, and then 4 coats of blue seal. All of that followed putting in a new perimeter 4" drain line(s) and high performance sump/tank, etc. So far so good.
I appreciate anything more that you have to add or methods you are considering for your project. I'm hoping to post a few pics of things as they progress.
Good feedback, many thanks
BP

 

[captmello]

Re: Basement Vapour Barrier Experts Needed

Conditions for your application vary from home to home which is why the building code for basement vapor barriers is changing to no code at all. Moisture varies bepending on drainage and soil type.

I would do the plastic on the floor test and see what results you find. If you find it damp under the plastic, I would paint it with the dryloc product, lay down framing and insulation and vapor barrier below the subflooring.

If the floor is dry under the plastic then skip the dryloc and proceed the same as above.

You should be using treated lumber for your sleepers.

The self leveling underlayment would cost a fortune to level a large area but would work. Depends how far off the floor is.

Good luck.

 

[Bigprairie1]

Re: Basement Vapour Barrier Experts Needed

The self leveling underlayment would cost a fortune to level a large area but would work. Depends how far off the floor is.

Good luck.

...I agree, man this stuff is expensive. I looked into this and by the time I would be done I'd probably spend $500 or more on bags of this. Even then, when I'm done I still have an un-insulated concrete floor...hmm. Anyhow, what I am going to use are shims to level the 2x4 floor framing and then probably Hilti/Ramset the framework down.
For the shims I will probably use a combo of cedar shims and maybe some rubber ones specifically designed to mount on the underside of this kind of wood application (lucked into them from another project I came across)
I'm finding it hard to get a lot of info around supposed 'code' concerning this kind of thing locally.
BP

 

[Bob_VT]

Re: Basement Vapour Barrier Experts Needed

Use PT 2x4 for the underfloor framing Use plastic or vinyl floor tiles for the shims if you are concerned with rotting...

 

[SuzukiChopper]

Re: Basement Vapour Barrier Experts Needed

FWIW, I've always seen vapor barrier brought down to the concrete and then an acoustic sealant used between the barrier and concrete. Same deal with outside walls on other levels of the house. All joints tuck (not duck ) taped. I would think you could just bring it down to your floor frame as well if you're going to be doing a barrier level over the floor frame and insulation.

 

[Bigprairie1]

Re: Basement Vapour Barrier Experts Needed

Use PT 2x4 for the underfloor framing Use plastic or vinyl floor tiles for the shims if you are concerned with rotting...

I like that...and I've got a bunch of left over tiles that have been in the basement for a few years. Good place to use 'em up, done.
Where I have to shim beyond the tile thickness, I can put those down first then stuff a shim or two on top where needed.
Good idea!!
BP

 

[mscher]

Re: Basement Vapour Barrier Experts Needed

...I agree, man this stuff is expensive. I looked into this and by the time I would be done I'd probably spend $500 or more on bags of this. Even then, when I'm done I still have an un-insulated concrete floor...hmm. Anyhow, what I am going to use are shims to level the 2x4 floor framing and then probably Hilti/Ramset the framework down.
For the shims I will probably use a combo of cedar shims and maybe some rubber ones specifically designed to mount on the underside of this kind of wood application (lucked into them from another project I came across)
I'm finding it hard to get a lot of info around supposed 'code' concerning this kind of thing locally.
BP

To level the floor cheaply, I suggest simply using a premixed sand/concrete mix. It's cheap and can can be set at a very thin thicknesses and will hold well, if using a concrete adhesive. http://www.quikrete.com/ProductLines/ConcreteBondingAdhesive.asp

Set the tile right on top.

IMO, insulating the basement floor won't buy much as the cold comes down from above.

 

[Bass Man Bruce]

Re: Basement Vapour Barrier Experts Needed

I would put the vapor barrier under the sleepers just to keep the potential ground moisture out of your home. I don't like a vapor barrier on top of the sleepers as it prevents gluing the plywood ( OSB around here) floor down.
I would also use a foam that's rated for exterior below grade. (Dow blue board or similar)

If your'e concerned about moisture traveling from warm to cold (from basement room to below the floor) you could try to ventilate the "below" area.

I would also try to follow Kenmyfarms idea and make it a "Pub Room"!!

 

[Lone Duck]

Re: Basement Vapour Barrier Experts Needed

Put your vapor barrier on the concrete first before frame. Your wooden floor has to breathe . You do not want mold to form from moisture coming thru concrete in an abnormal wet season or from accidental spills from above.( the foam from a beer for instance)

 

[Beefer]

Re: Basement Vapour Barrier Experts Needed

I didn't read the replies, but I did see a lot of "on the concrete" as I scrolled down. That is correct. Concrete is made with mostly water, wicks water, and is not water-tight, which will allow water to pass, which in turn would make contact with the wood, and eventually rot it (even PT wood).

If you want a good 'home improvement question answering' forum, check out www.inspectorsjournal.com. It's a sight for home inspectors, and they welcome questions from homeowners.

 

[new_boater]

Re: Basement Vapour Barrier Experts Needed

Have a look at this.
it seemed reasonably priced to me and it is what i will be using in my basement as i sometimes have very minor dampness.
and the air barrier acts as a insulating layer for warmth

http://www.dricore.com/en/faquest.aspx

 

[Bigprairie1]

Re: Basement Vapour Barrier Experts Needed

Bass Man you and Lone Duck like the idea of going under the sleepers rather than on top. That was my original intent but I just couldn't figure out 'technically' why you would not put the vapour barrier plastic close to the inner part of the house....just like in the walls.
I keep thinking that the plastics going to be a collector of moisture in almost either case...although my floor moisture test came up dry over a week.
(......what about none?)
It does makes sense that it would mess up certainly any intent to glue the floor down tho'.
It also makes sense to turn the space into a open pub space rather than a guest room...however, that arrangement has yet to be sold to my lovely wife. ( would even have some room for a pool table!!!)
BP
...as well, I was looking at the dri-core product but it wants a dead level surface to start with which takes me back to doing that highly expensive re-concreting business...unfortunately.

 

[Lone Duck]

Re: Basement Vapour Barrier Experts Needed

Bass Man you and Lone Duck like the idea of going under the sleepers rather than on top. That was my original intent but I just couldn't figure out 'technically' why you would not put the vapour barrier plastic close to the inner part of the house....just like in the walls.
I keep thinking that the plastics going to be a collector of moisture in almost either case...although my floor moisture test came up dry over a week.
(......what about none?)
It does makes sense that it would mess up certainly any intent to glue the floor down tho'.
It also makes sense to turn the space into a open pub space rather than a guest room...however, that arrangement has yet to be sold to my lovely wife. ( would even have some room for a pool table!!!)
BP
...as well, I was looking at the dri-core product but it wants a dead level surface to start with which takes me back to doing that highly expensive re-concreting business...unfortunately.

I think when you put the plastic on the inner side of the wall,the wall will breathe thus drying out any moisture. On your floor , you put your plastic on the concrete first so the wood above will also breathe with your room. Any moisture in the concrete will stay under the plastic hence (vapor barrier). Plastic in the inner side of wall will keep moisture outside of it (vapor barrier ) and outside the wall breathes and dries that is also why you seal around plug inlets etc: Helps keep cold and moist air out.

 

[captmello]

Re: Basement Vapour Barrier Experts Needed

The vapor barrier in the walls is to keep the moist air in the house from going through the walls and into the insulation where it will condence and turn to liquid.

I agree that a vapor barrier is necessary on the floor but Like v1_0 said and I agreed, using the dryloc paint would keep the moisture from breaking the surface of the concrete. Frankly, if it were me I think I'd do the dryloc floor and nothing more. Let the floor system breathe. Just my opinion, as a contractor.