Correct way to install carpet in the basement

12 years ago

I've just finished sealing up all the walls with XPS foam and would like to tackle the floors next (well, actually that's one of my questions):

1. Is it acceptable to install the subfloor over concrete, then frame on top of that or should I frame on the concrete (separating the baseplates from the concrete with XPS) and run the floor up to the framing?

2. My basement was partially tiled by the previous owner, leaving the tiled portion roughly 3/8" higher than the untiled concrete. I like the idea of a Dricore subfloor, but is it possible to find only the corrugated plastic membrane? My thought is to use that to bring the untiled portion up to level, then lay ply/OSB over everything.

3. If the above option doesn't work, can I simply put down 6 mil plastic over the concrete and lay ply/OSB over that as the subfloor?

Thanks for the help with this.

Sort by:Oldest

Comments (9)

worthy
12 years ago

Source: Basement Insulation Systems, Yost & Lstiburek, Building Science Corp.

is it possible to find only the corrugated plastic

Yes. Delta FL. This foregoes the insulation, but saves you some headroom if that's important.

can I simply put down 6 mil plastic over the concrete and lay ply/OSB over that as the subfloor?

This will trap moisture under the poly--at least until it finds its way through the nail/screw holes etc into the layers above it.

******
This is not a recommended method. But in many of the new homes I have built, I have glued down synthetic low pile carpet directly on the concrete without an underpad and have not experienced mildew/mould problems. But this was over 6" of freeflowing gravel and 4"-5"concrete. And I keep a dehumidifier (or two) running year-round.
zayd
Original Author
12 years ago
Thanks, Worthy.

From reading previous posts and topics, you mentioned your preference for framing before the flooring. The diagram you posted seems to suggest the opposite. The way I see it, the two options are these (forgive the crude drawings):

Option 1: Frame on the subfloor

Option 2: Frame on concrete

I like option 1 because I think it offers any vapors under the Delta FL a place to go (conceivably -- if the vapors can actually condense and travel down into the French drain).

I like option 2 because it makes changing the subfloor possible in the future if that's ever needed. The downside with option 2 is that I have to provide a perimeter for venting, which will require me to get creative with carpeting.

So is my rationale sound for preferring option 1? Thanks again for all the help.

Zayd
Related Discussions
Installing a basement subfloor
Q
Comments (10)
The moisture problem is a "normal" amount of humidity from the concrete slab coming up. these older slabs did not have a poly sheet put under the slab at construction time and just have sand underneath. they also have no rebar in them at all. The rigid foam technique I am using is from Building Science and can manage that small natural amount. If the vinyl tile & glue was not there, the small amount of moisture might not even be noticed and the concrete would seem dry as it does in the rest of the garage. The concrete footing: not quite like an "h" bump out - the footing is trapezoidal in shape and flares out a bit more at the very bottom where it contacts the concrete floor. I know about putting drywall on the outside of this footing - my interest is "how" have people in the past "attached" a covering to the concrete footing as it is concrete. You can't just glue the drywall on the outside of the concrete footing because then it will still look trapezoidal and they want the shape to look more like a boxed out rectangle. I have a method in mind but it is tedious and I am looking for techniques as people must have houses like this and may have an easier technique. You can't box it the same way you box a soffit for a duct for example since it is concrete and trapazoidal. something needs to be put at the upper part of the footing to bring it out so a short straight vertical wall can be put in the front of the footing and a small say 6" level horizontal shelf on top of the footing to put things on. I might not even use drywall to cover the footing but a nice smooth grade plywood that we can paint white. the problem is how to box it out so it is not a trapezoid and how best to attach the plywood to the front face. The top face is easy - I could even just PL glue the top piece of plywood on. Only thing I can think of is put a 2"x4" horizontally along the top front of the footing to shim it out. Add more furring strips if necessary to bump it out to match the bottom. Add one furring horizontally along the bottom front side. Use Tapcon screws to attach all of this wood to the concrete (tedious). Then once everything is leveled out - put a piece of plywood on the front and then a small piece on top to make a little shelf.
...See More
Basement bathroom tub install
Q
Comments (2)
I'm a DIY engineer, not a plumber, here's what I know: You can install air chambers in the lines (hot / cold) before the faucet. If you are going to get this inspected, make sure that the faucet is legal in your city. Some locales specify the brass in the faucet must be low lead brass. I don't know about two handled faucets - here again everything is going towards anti-scald, one handled faucets. Maybe it's OK for tubs only. I would check it out. You could put poly on the studs, and then install 2' cement board. I would use glue for vinyl flooring.
...See More
Basement Cold In Summer - Ideas To Correct?
Q
Comments (11)
Your goal of 70 degrees for all areas is not realistic due to the design of your HVAC system and architectural design of the home. The thermostat on first level is torn between 'attempting' to keeping the 2nd floor bearable without making the basement too cold. Problem is cool air falls and hot air rises. So trying to keep the 2nd floor bearable without making basement too chilly is a recipe for disappointment. The best way to accomplish what you want is called a HVAC ducted zone system. However, this solution may not be practical and if not done properly could create other problems. Often times people are shocked what it takes to rectify problems of this nature. Certainly there are those out there who will sell you anything, then slam in in any old way. This method of slam jam may work 20% of the time, until temperature extremes come. Remember it's not just about getting this to work when it's warm out, it's also about getting it to work when it's very hot out as well as when it's really cold. With that said, to do this you would need 3 zones minimum. 1 for basement, 1 for first level, 1 for 2nd floor. Each zone would have it's own thermostat with control of the equipment. By doing it this way you probably wouldn't have to keep first floor as cool as 70 degrees, which would reduce the amount of cool air to the basement due to the cool air falls principle. If the basement is open to the 1st floor, there can be spillover to the basement especially when operating in cooling mode. The basement is naturally cooler and so without heating it / it's possible the temp down there will be less than the desired 70 degrees. The other design flaw you may be up against is return air problems. If the 2nd floor doesn't have a dedicated return to the equipment this can trap heat on that floor which can cause operational problems or hurdles for the system to over come. It would be best design wise if each level has a dedicated return in which a zone system is implemented. But realize there is much more than this to properly design a HVAC zone system.
...See More
install - correct way to transition between 2 tile surfaces
Q
Comments (5)
I'm not fond of a wood transition between two tile floors. Of course it is an easy install...ahem...easy on the installer that is. The Schluter system is correct. It has been used hundreds of thousands of times (should I say millions of times...who's to say the number but it is A LOT!). If a slab that has concerns with cracking/movement (and they all have SOME sort of movement whether it be a little or a lot....so be aware) should have a decoupling membrane. And just to be clear carpet HIDES some HORRIBLE substrates. I mean *GASP* SPUTTER* HORROR* type concrete. Why you ask? Because BUILDERS know that carpet hides HORRIBLE workmanship. Ergo a carpeted slab will be MUCH uglier than a slab prepared for tile. Here's what you are looking for in a tiling professional: https://www.tile-assn.com/ You want to WRITE OUT the contract so that it states: "To be installed per NTCA Specifications AND per tile manufacturer's instructions." And a 1 year labour warranty is standard stuff in the building industry. You are looking at a substantial installation (if we estimate the labour alone will be $10-$12/sf and the tile/materials will be EXTRA) somewhere in the range of 500sf - 600sf (or so)??? Your quote MAY NOT include "subfloor preparation". If it DOES....please ask for the guestimate they have provided for the subfloor. If they have estimated $0.50/sf for concrete work, then they are too low. If they have estimated a MAXIMUM of $4/sf (not to exceed this amount without your written approval) then they are more in keeping with reality. I would stick with the person who is well acquainted with the NTCA guidelines, if not a member, the person who INCLUDES the cost of a decoupling membrane, who INCLUDES the high-priced estimate for slab prep as part and parcel of his quote....and then the person who includes the Schluter system as part of the transition between floors. Please notice how the transition is FAR down the list. Right. There are some more important things that need to be dealt with other than the final look. And Schluter has DOZENS of transition options which work with floors AND/OR wall settings. The appropriate option will be looked at before anything is laid.
...See More
worthy
12 years ago
That BSC diagram shows the wall framing on top the plywood floor. But I've never seen any technical reason for that sequence.

Delta's installation instructions specify that the material should be as tight as possible to the walls and then sealed with foam. BSC also calls for a tight fit. Both the XPS and the Delta have sufficient permeance to permit vapour to pass through.

The BSC diagram illustrates an Enka drain, but no gap. Your first post doesn't mention a pre-existing French drain. These are usually put in to handle exterior water leakage or water under the slab, as in the BSC diagram.
zayd
Original Author
12 years ago
Got it -- thanks.

Does my rationale for Option 1 make sense? I do like the fact that the vapors can go somewhere. And the Platon material I plan to use claims impermeability to vapor, so it seems this would be important.
worthy
12 years ago
the Platon material I plan to use claims impermeability to vapor, so it seems this would be important.

As I mentioned in my earlier post, the Platon is not impermeable. From the Delta website linked above:

"Though the air in the living space is completely isolated from the system, DELTA-FL is designed to allow small amounts of water vapor into the room to maintain a healthy humidity level."

The pic below from Building Science Corp. Digest 103 Understanding Basement, shows the wall framing in place before the floor.
zayd
Original Author
12 years ago
Thanks.

One last open question as I think through this. The finished floor, and therefore the Platon/subfloor, will butt against an interior block wall along one side of the finished area. Since there will be no French drain along that wall, I don't want to let the Platon vent into that area. Should I seal off that side somehow at the Platon? If I don't, the Platon will vent behind the stud wall that will be I front of that block wall.
worthy
12 years ago
The Delta FL should be sealed tightly with silicone or low expansion foam wherever it's butting up to other material.

Here is a link that might be useful: Delta FL Installation
zayd
Original Author
12 years ago
Thanks.

One last open question as I think through this. The finished floor, and therefore the Platon/subfloor, will butt against an interior block wall along one side of the finished area. Since there will be no French drain along that wall, I don't want to let the Platon vent into that area. Should I seal off that side somehow at the Platon? If I don't, the Platon will vent behind the stud wall that will be I front of that block wall.
zayd
Original Author
12 years ago
Thanks, Worthy. Your advice here is truly appreciated.

I'll follow up with after pictures once I'm all done (not sure if I took before pictures!)

Correct way to install carpet in the basement

Comments (9)

worthy

zayd
Original Author

Related Discussions

worthy

zayd
Original Author

worthy

zayd
Original Author

worthy

zayd
Original Author

zayd
Original Author

COMPANY

BUSINESS SERVICES

GET HELP

CONNECT WITH US

Correct way to install carpet in the basement

Comments (9)

worthy

zaydOriginal Author

Related Discussions

worthy

zaydOriginal Author

worthy

zaydOriginal Author

worthy

zaydOriginal Author

zaydOriginal Author

COMPANY

BUSINESS SERVICES

GET HELP

CONNECT WITH US

zayd
Original Author

zayd
Original Author

zayd
Original Author

zayd
Original Author

zayd
Original Author