Hot Topics: Installing Carpet on Concrete

Carpet installation.

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This DIYer wants to install carpet on a basement floor, but he doesn't quite know where to start. And is the moisture in basements a hazardous environment for carpet? The forum weighs in.

Original Post: Installing carpet on concrete?

Charlie2 Member

I'm considering installing carpet in my new home myself. What are some things I should consider? Should I nail the tack strip to the concrete, drill a hole, and use aluminum/nylon anchor, or is polyurethane adhesive good enough? Since it's for a basement floor, is underlay all that I need between the concrete and carpet?

marksr Forum Topic Moderator

I'm not a carpet installer, but I've painted 100s of new construction homes built on slabs and they always use a tack strip (except for glue-down carpet). While the tack strip looks the same as the kind used over plywood it has different nails so they can go into the concrete.

Are you sure the basement stays dry? Preform a moisture test on the concrete.

Bud9051 Member

Also not a carpet pro, but want to point out that a basement concrete floor is far different from a slab-on-grade concrete floor. Slab-on-grade has taken measures to reduce/eliminate moisture passing up through that floor whereas most basement floors have not. I'm not talking liquid water, but moisture vapor which passes right through concrete. If blocked by a vapor barrier, the moisture slowly accumulates and becomes the water you dread.

Building a basement that is dry is an expensive process rarely used. Without those extreme measures, you are left to manage the moisture to prevent related problems.

Pilot Dane Group Moderator

Basement floors are a tough place for carpet. It can be done, but you need to make absolutely sure that the floor stays dry, especially if you plan on using padding underneath the carpet. Carpet without a pad can tolerate more moisture vapor as it can easily pass through the carpet, but padding can act as a barrier and cause mildew in and under the pad.

Notice that I've been saying water vapor—not liquid water. Even if the basement appears dry, water vapor can pass through the slab if the slab does not have a vapor barrier. One test is to get a square of plastic sheeting. Lay it flat on the floor and continuously tape down the edges so it's totally sealed to the floor. If you used clear plastic you can see water condense, but if you used opaque plastic you'll have to periodically pull up the plastic to look underneath. Make sure you check in different seasons. Just because it's dry during the dry season doesn't mean you won't have a problem when the weather is more wet.

sam floor Forum Topic Moderator

Having installed thousands of yards of carpet in basements, it's rare to find one with a moisture problem. But if you do, it can be a mess. The plastic sheet on the floor is a guesstimate. Have it checked with a moisture meter to be sure. If you just have a little moisture, it will usually evaporate through the carpet and pad. Under no circumstances should you put a plastic moisture barrier on that floor. It will just lead to mold growth under it. A little moisture is normal. You will get some condensation on all concrete with temperature changes.

Charlie2 Member

Thank you so much for all the responses. I have not checked out the moisture in the basement yet. Even if I use a moisture meter, I don't think it will tell the whole story. As many have said, it may not have moisture in the dry season, but it's hard to tell when seasons change.

Okay, so the process is tack strip, underlay, and carpet. No plastic moisture barrier between concrete and underlay, correct?

If I don't use carpet, besides letting the concrete look bare, what other options do I have so the floor looks nice?

stickshift Group Moderator

Ceramic tile is a great choice on a slab.

Personally, I don't have a problem with carpet on a basement slab as long as you know there are many things that can happen, which would lead to you pulling it back up and potentially replacing the pad and even the carpet.

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