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'floating' subfloor questions.

madmadscientist's picture

Hello All,


   I need to get started on a subfloor in our 'ground level' guest bedroom.  Its a standard (for CA) 4" thick concrete slab.  This floor is about 1' lower than the exterior ground level and we have extensive exterior drainage in place.  The floor shows no water issues at all.


I am going to use the Delta FL product on the floor under my subfloor.  According to the Delta FL install manual you can lay 3/4" min T&G plywood on top of it and float it completely without any attachments thru to the concrete.


I need to raise the level of the bedroom subfloor up to match the existing levels of the attached bathroom and landing.  If I use 2by4s lain on their side (the 1.5" dimension vertical) as sleepers and 1 1/8" T&G plywood flooring the height would be perfect.  What I don't want to have to do is attach the sleepers to the concrete with about a  million tapcon screws.  The Delta FL folks say that to make a connection thru to the concrete you need to pre-drill each hole then caulk the hole then insert the tapcon....thats a gonna take a while.


What I wanna do is lay down the 2by4s and connect them all toghether some how (pocket screws I have the technology). then glue and screw the 1 1/8" flooring to them and float the floor that way?  Do any of you think that this would work? 


Before you suggest this I have called the Delta FL folk's tech line several times but keep getting voicemail and no callbacks.


 


Daniel Neuman


Oakland CA


Crazy Home Owner

The MadMadScientist

Restoring our second Victorian home this time in Alamdea CA.  Check out the blog http://www.chezneumansky.blogspot.com/ 

Oakland CA 

Crazy Homeowner-Victorian Restorer

(post #65711, reply #1 of 16)

I'd be afraid that the 2x4 sleepers would warp if they weren't attached. You plan on using treated 2x4s in contact with the concrete, right? You don't need a million tapcons. You could just nail them with a powder actuated ramset gun. If you get an occasional nail that doesn't hold, you could put in a tapcon. Use a hammer drill, drill right through the 2x and drive the screw. One fastener each end and every three feet is plenty. Get some instruction with the powder actuated gun if you haven't used one. You can rent the gun and the hammer drill.

Beat it to fit / Paint it to match

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(post #65711, reply #2 of 16)

Hello,


Sorry you misunderstand.  I am going to use the Delta-FL product on the concrete first and then attach the 2by4s to the concrete thru the delta-FL.  For it to keep acting like a vapor barrier you can't just shoot nails thru it.  You have to drill the holes and then caulk the holes before using the tapcon.  If you didn't you would have a bunch of penetrations thru your vapor barrier and it would be useless.


I am planning on running the sleepers around the perimeter and under any partition walls then running them 16" o.c.  Do you have any idea what would be the tapcon attachment schedule in this case?


 


Daniel Neuman


Oakland CA


Crazy Home Owner

The MadMadScientist

Restoring our second Victorian home this time in Alamdea CA.  Check out the blog http://www.chezneumansky.blogspot.com/ 

Oakland CA 

Crazy Homeowner-Victorian Restorer

(post #65711, reply #3 of 16)

In a case like that you aren't using the FL for it's normal puroses. One of which is to allow air under the flooring for insulation.

I would use plain polly for your usage.

. William the Geezer, the sequel to Billy the Kid - Shoe

(post #65711, reply #4 of 16)

Hi Bill,


  No I think I am still using the FL for the same purpose which is a barrier to water vapor moving vertically.  I just need the height of the subfloor to be higher to match existing. Unless I am really confused which is totally possible.


 


Daniel Neuman


Oakland CA


Crazy Home Owner

The MadMadScientist

Restoring our second Victorian home this time in Alamdea CA.  Check out the blog http://www.chezneumansky.blogspot.com/ 

Oakland CA 

Crazy Homeowner-Victorian Restorer

(post #65711, reply #5 of 16)

Isn't the delta FL supposed to allow the water vapor to escape to the inside anyway. They even recommend you leave a 1/4 gap at the wall specifically for this purpose? What difference is it going to make if you fasten the T&G with the tap con screws then. I don't understand why you would have to patch and seal the holes you make.

I'm looking at something similar (at least the Delta-FL, I don't need to raise the floor however) but am not sure what is supposed to happen to the water vapor it is supposed to trap.

(post #65711, reply #6 of 16)

Hello Ribs,


  It is my understanding that you have to patch the holes you make to keep the water vapor from coming thru them.  I think about it like this. The water vapor comes up thru the concrete hits the delta-fl then moves horizontally until it encounters the gap with the wall where it is vented to the room.  Earlier I was able to talk to their tech support.  They said that the delta-fl should come to 1/8" from the finished wall and then the 3/4" T&G should come to 1/4" from the finished wall.  If you are using the (at least) 3/4" T&G you can float the entire thing with no tapcons.  I need to raise my floor up a bit so I have to install the 2by4 sleepers. I still plan on installing the sleepers with the correct gaps wrt the wall.  I'm just trying to figure out how many tapcons-if any I have to use on the sleepers. Once the sleepers are down I will glue/screw the T&G to the sleepers only, not penatrating the Delta-FL.  Where the tapcons penetrate the Delta-FL they will block the flow but thats going to be so small compared to the rest of the area that the vapor can flow in.


 


 


Daniel Neuman


Oakland CA


Crazy Home Owner

The MadMadScientist

Restoring our second Victorian home this time in Alamdea CA.  Check out the blog http://www.chezneumansky.blogspot.com/ 

Oakland CA 

Crazy Homeowner-Victorian Restorer

(post #65711, reply #8 of 16)

Hey Dan,

Still a bit fuzzy on the delta Fl wall interface. If the 3/4 T&G is a 1/4 inch from the finished wall (are we talking about the base of the suds or the actual drywall)how do you finish off this gap. I assume you can't cover it with the dry wall or baseboard otherwise there is no venting. Do you pull the baseboard another 1/4 off the floor (I'd think that would look a bit odd). Do you just have this funny gap?

This may sound stupid but was the stud wall supposed to be built on top of the Delta-FL (hope not as those are already up)

Thanks

Sorry to hijack your thread a bit.

(post #65711, reply #9 of 16)

Hi Ribs,


I was confused also so I asked the tech guy the same question. He said that the subfloor has to be 1/4" shy of the finished surface all around. I didn't ask them how to finish it.  I was planning on having the carpet installed first making sure the tack strips and carpet did not close off the gap. Then I was just going to attach baseboard to the wall in a thickness slightly greater than 1/4" to hide the gap-spacing the base just above the carpet (hopefully no noticable gap) to let the moisture vent.  I do not know if the bottom of the base needs to be 1/4" above the carpet..that would look weird.


I do not believe that you are supposed to install the stud walls on top of the Delta-FL.  Partition walls yes (on top of the subfloor) but not load bearing walls.  This product is meant mostly for basements with conrete walls that are already existing.


At least thats my understanding.


 


Daniel Neuman


Oakland CA


Crazy Home Owner

The MadMadScientist

Restoring our second Victorian home this time in Alamdea CA.  Check out the blog http://www.chezneumansky.blogspot.com/ 

Oakland CA 

Crazy Homeowner-Victorian Restorer

(post #65711, reply #13 of 16)

Hey Dan,

I seem to have gotten a different response from them than you did.

Here are my questions, pretty much what I was asking you.

Couple quick question. Your web site says a ¼ inch gap is left at the wall for any water vapor to escape and allow the floor to breath. If this is the case how do you finish that edge along the wall? The T&G ends, does the drywall of the surrounding walls cover the ¼ opening? Can a baseboard molding go over the top? If either of these is done it would seem there would be no place for the floor to vent to? Can you put baseboard molding but simply leave a ¼ inch gap there as well? Also is the T&G fastened down or floated? If you fasten it aren't you in effect puncturing the vapor barrier? Perhaps this doesn't matter as the plan is to let the vapor escape to the inside anyway?

Also does the basement floor have to be sealed in any way? It would seem not as long as there are no major leaks? Is this correct?

Thanks

Tom

And their response

Tom:

There is no need to provide a 1/4" space along the perimeter of the DELTA FL installation since we are trying to achieve "vapor pressure equalization" to slow down the vapor moisture transmission through concrete slabs in contact with the ground, which would be difficult to achieve with ventilated spaces.

Keep the DELTA FL as tight as possible to the wall. The baseboard can be installed as usual, on the finish floor surface.

As for the screws used to anchor down the DELTA FL, you can dip the screws into a tar based caulking prior to installing them, and the threads will deposit the caulking around the penetration as it is installed to seal off this area. Usually the screw fills the pre-drilled hole anyway, and wicking of vapor moisture is limited.

We trust this provides you with the necessary information with which to install the DELTA FL.

Respectfully,
COSELLA-DORKEN PRODUCTS INC.

D. Walker A.Sc.(Eng.), C.E.T., NSPE
Engineering Dept. Representative

(post #65711, reply #14 of 16)

There is no need to provide a 1/4" space along the perimeter of the DELTA FL installation since we are trying to achieve "vapor pressure equalization" to slow down the vapor moisture transmission through concrete slabs in contact with the ground, which would be difficult to achieve with ventilated spaces.
Ribs,


   I don't know what to tell you.  That bit of advice (about the gap) goes against their own online instructions and the advice I got when I called their tech support folks. It also seems to go against what I thought the whole point of this product was...


There is no need to provide a 1/4" space along the perimeter of the DELTA FL installation since we are trying to achieve "vapor pressure equalization" to slow down the vapor moisture transmission through concrete slabs in contact with the ground, which would be difficult to achieve with ventilated spaces.


I've read that paragraph like ten times and it still does not make any sense to me!?!!?!? Seriously, WTF is he talking about.  Now it sounds like he's saying that the Delta-FL is being used as a serious vapor barrier and he does not want you to let the water vapor escape at all? Where will it go then? Damn I guess I'm going to have to call them again and see if I can get ahold of a real live person....Arrrgh.


 


Daniel Neuman


Oakland CA


Crazy Home Owner

The MadMadScientist

Restoring our second Victorian home this time in Alamdea CA.  Check out the blog http://www.chezneumansky.blogspot.com/ 

Oakland CA 

Crazy Homeowner-Victorian Restorer

(post #65711, reply #15 of 16)

I sent them another email regarding this and he responded right away. Here is that response. My take and kind of always has been is they create a place for the vapor to breathe and evaporate and equalize with the floor rather than direct the water to a source for removal. I saw this on one of their pamphlets somewhere.

my email

Thank you for your recommendations but they leave me a bit confused. They kind of go against you installation brochures on the web which recommend the spacing at the edges. http://www.deltams.com/brochuresonline/documents/DELTAFLInstallation.pdf

Also does the T&G even need to be fastened down I was under the impression you could float the floor? Is fastening it preferred? Again the brochures only recommends fixing the floor when it is not tongue and groove. I also wasn't aware the Delta FL was fastened down at all, I thought it was simply rolled out?

His response

We have changed our position and future literature to eliminate the 1/4" gap to increase the effectiveness of the "vapor pressure equalization".

You don't need to anchor the T & G down if you are only installing carpet or other non-movement sensitive finishes on the flooring, you can float the system. I would suggest that you glue the T & G joints together to create a complete diaphram effect and stiffer floor. You can apply "H" clips on the 4 ft ends of the 4' X 8' panels to support them for deflection that might happen between sheets due to differential surface elevations in the concrete slab.

Any further questions please let me know.

Regards,

D. Walker

and his email in case you're interested
Jkinnear@cosella-doerken.com

(post #65711, reply #16 of 16)

We have changed our position and future literature to eliminate the 1/4" gap to increase the effectiveness of the "vapor pressure equalization".


Well Ribs now I am even more confused.  I sent him a long winded email but I have not heard back yet.  It now sounds to me like they want the FL to completely seal the slab?  Where would the inevitable water vapor go? The folks at the Building Science Center don't like that idea at all.


This product used to make sense to me...I thought of it as acting like a 100% vapor barrier in the vertical direction. The air spaces created by the FL would allow the water vapor in the slab to come out and be vented to the edges, made perfect sense to me.  It seemed to me that this system would vent the water vapor more readily than what Andys dry basement article suggested.


I wonder if the Dri-Core people are changing their tune also?


Daniel Neuman


Oakland CA


Crazy Home Owner

The MadMadScientist

Restoring our second Victorian home this time in Alamdea CA.  Check out the blog http://www.chezneumansky.blogspot.com/ 

Oakland CA 

Crazy Homeowner-Victorian Restorer

(post #65711, reply #11 of 16)

Would it be possible to lay your FL, then the floating T and G ply, then attach your sleepers to the ply (without tapcons)? Then you've made a big sandwich that should float as one unit over the delta-FL.

(post #65711, reply #7 of 16)

I get it now. You are using the roll out membrane on the concrete and will fasten sleepers through that to the concrete. Attaching the sleepers will be just like fastening the bottom plates of partitions. There are several ways to use the FL product. In your case you are looking to gain floor height. When a subfloor product is fastened directly through the membrane, they recommend either the sealant or their proprietary Delta fasteners. This is to prevent moisture wicking directly to the subfloor and perhaps contaminating the carpet. With your application, I don't think that will be a concern. As long as the nail or screw is in the hole and a subfloor is on top of that, wicking won't be an issue. The product is designed to breathe to the perimeter, it's not quite the same as a vapor barrier. If you are concerned, then go ahead and caulk the screws, they'll go in a little easier.

You could get by with 19.2" centers on the sleepers if you are using a 3/4" T&G subfloor. I think you could fasten the the sleepers every three feet or so, staggering from edge to edge. This will be dependant on how well the screws or nails seem to be grabbing and holding. They do allow the use of nails on bottom plates. Tapcons are fairly expensive but if the pilot holes are done correctly, they hold well. Powder driven nails are not always as reliable and may not drive all the way. This is one of those things that you have to determine on site as you progress.

You are not using a "floating floor" in this application. You can use the floating finished floor products directly over the Delta membrane without subflooring. Products like Pergo and the snap together types. I would not float a subfloor directly on the product without using fasteners. Gluing the T&G together will allow less fasteners but this is not even a concern with your application. Most folks are trying not to lose headroom. You will have a nice solid base to attach your subfloor to. There isn't any reason to float it.

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(post #65711, reply #10 of 16)

Hi Hammer,


 Heck if I only have to install the tapcons on 3' centers that won't be a problem.  I was thinking that they had to be on like 12" centers and that would be a heck of a lot of tapcons.  I am also planning on using 1 1/8" T&G flooring on top of the sleepers so doing the sleepers every 2' should be okay? I do want a nice sturdy feeling-warm floor for this room.


When I was talking about 'floating' the floor I meant that I wanted to attach all the sleepers together somehow then attach the 1 1/8" subfloor to the sleepers without having any penetrations thru to the concrete. The Delta-FL literature says that you can lay 3/4" T&G right on top of the FL and not have to attach it to the floor.  They say its fine to 'float' the subfloor in this way.


Thanks for the reply.


 


Daniel Neuman


Oakland CA


Crazy Home Owner

The MadMadScientist

Restoring our second Victorian home this time in Alamdea CA.  Check out the blog http://www.chezneumansky.blogspot.com/ 

Oakland CA 

Crazy Homeowner-Victorian Restorer

(post #65711, reply #12 of 16)

Dan,
You may find this site interesting. There is a video of a standard installation, not what you have in mind but it shows them using the Delta fasteners.
http://www.deltams.com/deltafl/index.html

Beat it to fit / Paint it to match

Beat it to fit / Paint it to match