# subfloor over concrete in basement



## ctkeebler (Nov 8, 2009)

hello can somebody help we with the proper procedure for putting a subfloor down over the concrete floor in my basement. I know I need to put down something and was looking for what would be the minimum wood stringer and plywood to keep as much headroom as possible. Can I use like 1x6 pressure treated with plywood on top? whats the minimum thickness on the plywood and does it have to be tongue and grove?

Should I "cheat" and put the stringers on like 12 inch on center to make the floor more solid or with the 1x6 would 16 still be okay?>

Could I use some composite decking as the stringers or is that not structurely sound enough?

Thanks

Tom


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## Wildie (Jul 23, 2008)

ctkeebler said:


> hello can somebody help we with the proper procedure for putting a subfloor down over the concrete floor in my basement. I know I need to put down something and was looking for what would be the minimum wood stringer and plywood to keep as much headroom as possible. Can I use like 1x6 pressure treated with plywood on top? whats the minimum thickness on the plywood and does it have to be tongue and grove?
> 
> Should I "cheat" and put the stringers on like 12 inch on center to make the floor more solid or with the 1x6 would 16 still be okay?>
> 
> ...


 I am doing the same thing, as you are! 
I plan to use 2'X2' tiles that are constructed from OSB (oriented strand board) on top and vinyl under-neath!
The vinyl is formed in such a manner, so as to allow air circulation underneath.
They just lay in place and can be lifted if required!


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## ctkeebler (Nov 8, 2009)

I already used the dricore but the basement flooded over the dricore and its ruined and needs to be taKen out, also once they are down they don't come out Because they are lockexdtogether


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## Gary in WA (Mar 11, 2009)

http://www.buildingscience.com/documents/insights/bsi-003-concrete-floor-problems?full_view=1

Be safe, Gary


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## Wildie (Jul 23, 2008)

GBR in WA said:


> http://www.buildingscience.com/documents/insights/bsi-003-concrete-floor-problems?full_view=1
> 
> Be safe, Gary


 A very interesting link! Thanks! 

In 1978, I built an attached garage on a concrete slab! At the time it seemed to me, to be a good idea to lay down 6 mil plastic sheeting, immediately under the slab and I have been well pleased with its performance! 
The floor has been perfectly dry and has never cracked, even though the garage is unheated and has experienced temperatures ranging from 0F to 90F.


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## Wildie (Jul 23, 2008)

ctkeebler said:


> I already used the dricore but the basement flooded over the dricore and its ruined and needs to be taKen out, also once they are down they don't come out Because they are lockexdtogether


 If you experience flooding, most floors will be damaged and will have to be removed!
With this in mind, I have considered ceramic tile but someone painted the floor and I'm worried about the tile bonding.


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## stadry (Jun 20, 2009)

EVERYTIME i take the cheap option, it comes back to bite me in the *** either by having to sit/stand/drive by & LOOK at it or watching it break/fail & having to replace it w/what i shouldda done/bought before 

i congratulate you for not having the debilitating character defect i battled often in my ' beginning-homeownership-years ' youth :laughing: also having done my own bsmt once ( or twice as the case may be :furious: ), laying down 6mil is minimal,,, newer product's been developed - 15mm polyesther-reinforced - you can get it at any const supply house,,, i'd use that instead of the vp 6mil stuff.

vapor barrier - 2x4 p/t'd flat sleepers 16"o/c over that - sub-floor of ( MIN ) 3/4" t&g 5-ply's what we found's best for a bounce-free, quiet, comfortable floor :thumbup: finally !


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## ctkeebler (Nov 8, 2009)

Here are some pics where you can see the water wicked (I think) through the seams of the floor. The center are dry but the edges are not. I don't think it will dry enough to be useful as Im concerned about mold and the woood warping.

The problem I see taking it out is I put the drircore down first leaving a gap all the way around the perimeter. Then I put 2 inch foam over the wall and on top of the dricore. Then I build the walls on top of the dricore leaving about 1/2 inch from the wall. The walls screwed into the dricore and every 8 feet the sole plate is power nailed through the sole plate and the dricore into the concrete floor.

There is about 4 inches of dricore I will not be able to remove.


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## ctkeebler (Nov 8, 2009)

itsreallyconc said:


> EVERYTIME i take the cheap option, it comes back to bite me in the *** either by having to sit/stand/drive by & LOOK at it or watching it break/fail & having to replace it w/what i shouldda done/bought before
> 
> i congratulate you for not having the debilitating character defect i battled often in my ' beginning-homeownership-years ' youth :laughing: also having done my own bsmt once ( or twice as the case may be :furious: ), laying down 6mil is minimal,,, newer product's been developed - 15mm polyesther-reinforced - you can get it at any const supply house,,, i'd use that instead of the vp 6mil stuff.
> 
> vapor barrier - 2x4 p/t'd flat sleepers 16"o/c over that - sub-floor of ( MIN ) 3/4" t&g 5-ply's what we found's best for a bounce-free, quiet, comfortable floor :thumbup: finally !



The 15mm polyester reinforced product you are talking about do you have a trade name? Two different local lumber yards didnt know what I meant. Also is there a special way to install this or is the installation similar to the traditional 6mm poly?

I was going to lay down 1x4 with 3/4 tongue grove on top with 16 on center hoping that would be enough for a non bounce floor but still not lose a lot of headroom.

The 2x4 with the 3/4 plywood is over 2 inches and makes the center beam a head hazard and the last stair step would be all goofy.

So Im lost at what to do


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## stadry (Jun 20, 2009)

understand - that's because lumber yards aren't const supply houses,,, they'll all carry a product by now,,, if you've got a headroom issue, 1x4's would be good.

you're not lost - just mis-directed a bit :whistling2: hope you get lots of eggs tomorrow - Happy Easter !


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## Wildie (Jul 23, 2008)

itsreallyconc said:


> EVERYTIME i take the cheap option, it comes back to bite me in the *** either by having to sit/stand/drive by & LOOK at it or watching it break/fail & having to replace it w/what i shouldda done/bought before
> 
> i congratulate you for not having the debilitating character defect i battled often in my ' beginning-homeownership-years ' youth :laughing: also having done my own bsmt once ( or twice as the case may be :furious: ), laying down 6mil is minimal,,, newer product's been developed - 15mm polyesther-reinforced - you can get it at any const supply house,,, i'd use that instead of the vp 6mil stuff.
> 
> vapor barrier - 2x4 p/t'd flat sleepers 16"o/c over that - sub-floor of ( MIN ) 3/4" t&g 5-ply's what we found's best for a bounce-free, quiet, comfortable floor :thumbup: finally !


 Following GBR's link, the article cautions against a non-permeable barrier on the topside of a concrete floor, as it prevents moisture from being released from the concrete.
He also warns against vinyl flooring for this reason!
If moisture from the concrete, condenses on the under-side of the vapor barrier, I would think that this could allow mold to grow!
This fellow seems to have presented some very convincing arguments.


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## ctkeebler (Nov 8, 2009)

So if I understand the article correctly, and Ill admit a lot of it was a foreign language 

I need to put some type of epoxy coating over the concrete floor, then extruded polystryene then the 1x4 sleepers with the plywood on top of that.

Or if I want to use carpet I need to put a plastic dimpled sheet membrane, then the extruded polystryene and the plywood ontop of that (without any sleepers).

I added a picture for the first description, was unable to add the second as it was too big. I hop with proper reference to the author and article it does not violate the copy right. I wanted to add them as a reference so when the expert DIYers answer my question they see what I am talking about.

For documentation here is the reference/footnote.

http://www.buildingscience.com/documents/insights/bsi-003-concrete-floor-problems?full_view=1

*Insight, Concrete Floor Problems*

By Joseph Lstiburek
Building Science Insight 003: last updated 2009/06/29


Page 6


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## ctkeebler (Nov 8, 2009)

Watching Holmes on Holmes today he just put down 1 inch foam and then plywood I think 5/8 on top and tapcon the combination to the floor. Any thoughts on this type of subfloor instead of sleepers and plywood. Im guessing the floor would be hard as the foam can support quite a bit of weight.

Thanks


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## Wildie (Jul 23, 2008)

ctkeebler said:


> Watching Holmes on Holmes today he just put down 1 inch foam and then plywood I think 5/8 on top and tapcon the combination to the floor. Any thoughts on this type of subfloor instead of sleepers and plywood. Im guessing the floor would be hard as the foam can support quite a bit of weight.
> 
> Thanks


 I think that its important that the slab can breathe! So, as long as it can 'vent' via the dimpled plastic, I would agree that the foam, between the plywood and the concrete, would be fine! 
Putting down the sleepers may cause problems, like mold growth or if PT, gassing into the living space!


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## ctkeebler (Nov 8, 2009)

Wildie said:


> I think that its important that the slab can breathe! So, as long as it can 'vent' via the dimpled plastic, I would agree that the foam, between the plywood and the concrete, would be fine!
> Putting down the sleepers may cause problems, like mold growth or if PT, gassing into the living space!



On the show, he put the foam directly on the concrete floor, he didnt use the dimpled plastic. My question was it is recommended here to put the foam directly against the concrete walls, would this recommendation hold true as well for the floor?

1 inch foam laid directly on the concrete floor then 3/4 or 5/8 plywood directly over the foam. Then both screwed into the concrete floor?

Thanks

Tom


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## Wildie (Jul 23, 2008)

ctkeebler said:


> On the show, he put the foam directly on the concrete floor, he didnt use the dimpled plastic. My question was it is recommended here to put the foam directly against the concrete walls, would this recommendation hold true as well for the floor?
> 
> 1 inch foam laid directly on the concrete floor then 3/4 or 5/8 plywood directly over the foam. Then both screwed into the concrete floor?
> 
> ...


 To my mind, I would place the foam and plywood to butt against the bottom wall plate! 
My walls are made from spruce, and I have used PT treated stand-offs (on 24" centre's) to allow the slab to breath. The lower plate is standard, construction grade spruce!


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## ctkeebler (Nov 8, 2009)

I guess my three options for the subfloor are:

(1) Put 1 inch XPS foam directly on the concrete floor then 3/4 or 5/8 plywood on top and tapcon both the wood and foam to the concrete floor.

(2) Put down 6mm vapor barrier and use 1x4 pt sleepers with 3/4 or 5/8 plywood on top and use either 16 or 24 on center spacing for the sleepers. With 24 inch spacing can put 1/2 inch foam between the sleepers but there will be a gap between the foam and the plywood unlike option #1. where the plywood is directly ontop of the foam.

(3) Put down a plastic dimpled membrane and put the plywood directly on top of the dimpled membrane.

I was wondering if there is a preferred way. I read the building science and it looks like the dimpled way was recommended, but Im not sure how hard the floor would be and I dont know anybody that has done that.

Tom


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## acerunner (Dec 16, 2009)

if i'm thinking about the same episode of holmes on homes that you are referring to, the foam padding has dimples as well. He describes it as egg carton for drainage and breathability. Here's a snapshot of it. Is this what you were thinking?


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## Wildie (Jul 23, 2008)

There is option #4! Dimpled plastic, 1" foam and 5/8" t/g subfloor!


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## ctkeebler (Nov 8, 2009)

acerunner said:


> if i'm thinking about the same episode of holmes on homes that you are referring to, the foam padding has dimples as well. He describes it as egg carton for drainage and breathability. Here's a snapshot of it. Is this what you were thinking?


The one I was referring to was in a basement. He put the XPS foam directly on the concrete then the plywood and then screwed it to the floor.



Wildie said:


> There is option #4! Dimpled plastic, 1" foam and 5/8" t/g subfloor!



Do you have a brand name for the dimpled plastic? 

Also do I attach the plastic first to the concrete floor then attach the foam and plywood to the floor through the dimpled plastic?


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## Bob Mariani (Dec 1, 2008)

Wildie said:


> A very interesting link! Thanks!
> 
> In 1978, I built an attached garage on a concrete slab! At the time it seemed to me, to be a good idea to lay down 6 mil plastic sheeting, immediately under the slab and I have been well pleased with its performance!
> The floor has been perfectly dry and has never cracked, even though the garage is unheated and has experienced temperatures ranging from 0F to 90F.


the fact that it is unheated contributes to why it still is working.


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## stadry (Jun 20, 2009)

that range of temperatures indicate random crk'ing should've been expected,,, hi temps cause conc to expend & cold the exact opposite however good jointing patterns usually prevent random crk'ing,,, its just good practice to place vapor barrier under conc for most instances,,, in fact, engineers're spec'ing 15mil more & more.

can't speak to ' foam ' on conc - only miradrain/delta drain/sonnedrain ( generic )


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## Wildie (Jul 23, 2008)

Bob Mariani said:


> the fact that it is unheated contributes to why it still is working.


There is more to the story though! I excavated the perimeter, down 16" and built a retaining form from 2, 2X8's. Inside the form I ran reinforcing and rolled out mesh reinforcing over the whole area!
The attached garage was 16X28 with a heated utility area at one end only!


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## Bob Mariani (Dec 1, 2008)

I was referring more to the fact of moisture problems not as evident in an unheated space. This means the change in temperature is less then pressure difference is less thus less moisture transfer and much less a chance of condensation.


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## Wildie (Jul 23, 2008)

Bob Mariani said:


> I was referring more to the fact of moisture problems not as evident in an unheated space. This means the change in temperature is less then pressure difference is less thus less moisture transfer and much less a chance of condensation.


 Ah so! That makes sense, as it is sitting on a block of ice for 4/5 months!


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## acerunner (Dec 16, 2009)

ctkeebler said:


> The one I was referring to was in a basement. He put the XPS foam directly on the concrete then the plywood and then screwed it to the floor.
> 
> 
> 
> ...


 I did some research. I think that dimpled plastic stuff is called Delta FL (http://www.cosella-dorken.com/bvf-ca-en/products/foundation_residential/floor/products/fl.php). On HoH, he laid it down, taped the overlapping seams, layed down the t&g subfloor, and screwed it all down together with concrete screws. 

Do you remember which episode that was (episode name or #)? I'm curious to see for myself what he did.


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## acerunner (Dec 16, 2009)

Wildie said:


> There is option #4! Dimpled plastic, 1" foam and 5/8" t/g subfloor!


 That's a good idea. The dimple plastic looks like it only provides vapor/moisture barrier, but not insulation. Downside is that the floor will now be just as high as using sleeper floor setup.


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## Wildie (Jul 23, 2008)

acerunner said:


> I did some research. I think that dimpled plastic stuff is called Delta FL (http://www.cosella-dorken.com/bvf-ca-en/products/foundation_residential/floor/products/fl.php). On HoH, he laid it down, taped the overlapping seams, layed down the t&g subfloor, and screwed it all down together with concrete screws.
> 
> Do you remember which episode that was (episode name or #)? I'm curious to see for myself what he did.


 Hey, thats an interesting product! Its distributed here where I live and it may very well be the answer to my situation!
It appears that laminate flooring can be laid directly over it!


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## ctkeebler (Nov 8, 2009)

I am working on solving the water issues, sump pump, gutters draining into 4 inch pipes under ground and pipe running 100 feet away from house. Sealing cracks in floor, looking at drains around the sides of the house.

But also want to do what is the best on the inside of the house. I'm leaning toward the 6ml vapor barrier, maybe put down twice in opposite direction, the 3/4 inch XPS pink rigid foam board them 5/8 plywood over that. Is the 5/8 the thinnest that is recommended?

Water was never an issue before, but I dont want water issue again and just because this was a 100 year storm, doesn't mean its going to wait another 100 years.


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## Scuba_Dave (Jan 16, 2009)

Yeah.....a 100 year flood can happen 2x in a decade.....or not for 150 years again


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## ctkeebler (Nov 8, 2009)

Scuba_Dave said:


> Yeah.....a 100 year flood can happen 2x in a decade.....or not for 150 years again


Scuba, any thoughts on the sub floor dilemma?


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## ctkeebler (Nov 8, 2009)

Just to make sure I understand the insulation rigid board I should use on the floor

Dow 1/2" x 8' x 4' R-3.3 Polyisocyanurate Rigid Foam Insulated Sheathing is not the correct stuff right even though it has moisture resistant facers?


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## Wildie (Jul 23, 2008)

ctkeebler said:


> Just to make sure I understand the insulation rigid board I should use on the floor
> 
> Dow 1/2" x 8' x 4' R-3.3 Polyisocyanurate Rigid Foam Insulated Sheathing is not the correct stuff right even though it has moisture resistant facers?


 Sorry, but I have absolutely no knowledge about any form of rigid foam insulation.
Unless, someone comes forward, you are on your own! 
Then, you will be our resident expert on foam insulation! :huh:


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## Scuba_Dave (Jan 16, 2009)

ctkeebler said:


> Scuba, any thoughts on the sub floor dilemma?


Sorry...haven't done any rigid yet on a floor


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## ctkeebler (Nov 8, 2009)

Scuba_Dave said:


> Sorry...haven't done any rigid yet on a floor


Would you? Do you think its a good idea?
Thanks


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## acerunner (Dec 16, 2009)

just curious if you decided on which method to use? I'll thinking about doing the same thing soon.

not to confuse you more, but here's yet another option. very similar to the delta fl stuff. http://www.superseal.ca/all_in_one_subfloor.html


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## salg (Jan 3, 2011)

acerunner said:


> if i'm thinking about the same episode of holmes on homes that you are referring to, the foam padding has dimples as well. He describes it as egg carton for drainage and breathability. Here's a snapshot of it. Is this what you were thinking?


 
did you ever find out what it was called?


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