# Delta-FL on floor and XPS on walls. Should I install the flooring or the walls first?



## Jackofall1 (Dec 5, 2010)

http://www.cosella-dorken.com/bvf-ca-en/pdf/install_instructions/DELTA-FL_install_inst.pdf

By the looks of these instructions, you would build you wall system first and then run the Delta-FL up to it and then seal it.

Mark


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## yotaman (Jan 31, 2011)

Jackofall1 said:


> http://www.cosella-dorken.com/bvf-ca-en/pdf/install_instructions/DELTA-FL_install_inst.pdf
> 
> By the looks of these instructions, you would build you wall system first and then run the Delta-FL up to it and then seal it.
> 
> Mark


Thanks. I have that PDF printed. It doesn't talk about using 2" XPS. I planned to build the walls on top of the Delta-FL.


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## Jackofall1 (Dec 5, 2010)

If you build the walls on top, how will you ever fasten the lower horizontal member of the wall framing.

THere is a picture of the installer, sealing the floor to the bottom plate of the wall, just imagine there was 2" XPS behind it.

Mark


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## yotaman (Jan 31, 2011)

Jackofall1 said:


> If you build the walls on top, how will you ever fasten the lower horizontal member of the wall framing.
> 
> THere is a picture of the installer, sealing the floor to the bottom plate of the wall, just imagine there was 2" XPS behind it.
> 
> Mark


I plan to tapcon it to the concrete. 

This is a quote from the instructions that gave me the idea of building the walls on top of the Delta-FL.

"For applications without stud walls already in place, non-load bearing stud walls may be constructed on top of DELTA®-FL."


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## JoeyJoeJoe (Mar 3, 2011)

I have the same question for our new house. I plan to use Delta-Fl with 3/4" T&G plywood with the wall framed directly on top of the subfloor. I'm only throwing up 1/2" XPS directly on the poured concrete wall though and then insulating the framed 2x4 wall with the insulation blankets that came with the house. By framing directly on the subfloor you will prevent the need for a treated base plate for the wall since it will no longer be in contact with the bare concrete floor. I'll either use long tapcons to secure the wall through the subfloor or do something like nail the base plate to the subfloor and then tapcon the subfloor down directly. Be sure to caulk any tapcon holes before driving them in to maintain the vapor barrier. 

Before connecting the walls to the subfloor, however, I plan to somehow run a plastic vapor barrier connected to the face of the XPS down under the plywood portion of the subfloor. So it will essentially be taped to the XPS and then run down and lay directly on the Delta-Fl. This should effectively cut off any contact with any wood (subfloor or walls) to vapor/humidity. It will then be sandwiched between the Delta-Fl and plywood. Make sense? This is kind of what they show in their pictures for already framed walls. I don't think a roll of 6 - 10 mil plastic is too expensive. Depending on the size of your basement and how far you want it to stretch out from the wall, one roll will probably be adequate.

I'm still on the fence for needing to tapcon the subfloor down everywhere else though. We have a very flat floor and the T&G plywood should help keep things relatively secure. Something else to note is laying down some landscaping fabric under the Delta-Fl to prevent any annoying plastic-to-concrete noises. Although I doubt that would be a real problem if you tapcon every piece down. For an extra $100 or so for the fabric, I'm willing to take the chance.


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## duffywaldorf (Mar 25, 2011)

*Wow, good to hear it*

JoeyJoe-- What you just explained about delta, 3/4 inch sub, XPS on the walls, poly taped to the XPS...etc.etc....is EXACTLY what I have been thinking about doing. The exact same set up and means/method. I fail to see how this could give you any problems when and if a little water finds its way in. Now, a flood is a whole sep issue, but this would allow any water in the concrete floor (through cracks) or any poured wall leaks to have the water run down the XPS/poured wall, and under the framed wall, under the dimples of the delta fl and there it sits. A guy at Lowes today said that he recommended cutting in vent holes in the subfloor and the delta fl, much like a HVAC vent duct/vent cover. He said to cut one along each wall, so that if moisture were to get under the delta....that it would have a way to air out and actually dry out. The way we have thought to do this woudl infact trap any and all water and not allow it dry out. I struggle with that piece. Otherwise, I like where you head's at. Today is 3-25. Did you finish your's yet?


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## Gary in WA (Mar 11, 2009)

Welcome to the forum, duffywaldorf! Joe,J,J hasn't posted since that once. I would set the p.t. plate on a sill sealer for a thermal/capillary break, run the FL next to it leaving required gap. You don't want the basement/Fl air getting to the foam board, to the concrete wall and condensing. Use the ADA with drywall, also for that purpose; http://www.buildingscience.com/docu...rs/air-barriers2014airtight-drywall-approach/

Don't use any faced f.g. in the cavities, and make sure the foam is more than 1/2" thick, for most locations.

Gary


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## leungw (Apr 20, 2009)

I did the same thing in my basement. I did 2" XPS, then 2x4 walls in front of the XPS, then Delta-FL on the floor.

I failed my inspection. Inspector said I could not leave wall cavities empty because XPS is combustible. I initially thought that drywalls would be considered thermal barrier. But he said that a fire could start in an electrical box and could spread in the wall cavities, so the thermal barrier has to be right up against the XPS. He said he would be okay if the wall cavities were stuffed with unfaced fiberglass and that's what I eventually did.


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## duffywaldorf (Mar 25, 2011)

GBR in WA-- thanks for the heads up. 
Here's what I wanted to do....Seal every joint of the XPS with both sealant and also tape the joints....every seam AND to the concrete floor and near the joists. Basically, make the XPS wall air tight. I worry about that as if a crack in the foundation walls cause a good amount of water intrusion, then that water is trapped between XPS and Concrete wall.....and has nowhere to run but up the wall and fill that space....ugg. 

I thought it would be good to leave 1/2 inch between XPS and concrete floor/slab. That way, water could fall down to the floor. So I then thought to lay Delta FL, with thin layer of XPS over it. Then seal wall XPS to floor XPS with caulk and tape. So air, water stay under the xps both on the wall and under the subfloor. Creating a thermal and vapor barrier. water or air could rundown and trickle under the Delta FL, but since XPS is on walls and over the Delta FL, then it's thermal and vapor tight. Then build framed walls on top of delta/XPS/TandG OSB....tight to XPS walls. Then fiberglass in between studs, drywall, etc. follow?


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## Gary in WA (Mar 11, 2009)

I wouldn't leave a gap to the concrete floor. The whole idea is keeping the basement air from the wall. I have a site (somewhere) stating to glue the foam in 6" cross-grids against the wall to prevent any air leaks from traveling, as would other glue configurations, causing condensation. Then sill seal the p.t. bottom plate for a thermal/capillary/air break. Run the FL up to the frame wall leaving the gap, per directions. http://www.greenbuildingadvisor.com...ressure-treated-sill-plates-and-building-code Just my 2 cents, it *is* your basement..... We have done extensive comments on basement insulation- fire-stop required every 10' lineally, at wall/ceiling intersections, etc. That is one I never heard of, leungw.....

Gary


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## duffywaldorf (Mar 25, 2011)

GBR--- Gotcha. I understand the logic now. Thanks. So you are saying to buy a roll of sill sealer foam and lay that down before anchoring the PT base plate with tapcon screws. I think that's a great idea. SO after walls are done....with sill sealer....why would I need to leave a gap between delta and PT base plate? I don't get that part. If you go to delta's website, and download the PDF instructions, I don't see where it says that.


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