Underlays

If I'm laying carpet on a concrete floor do I need to lay anything other than underlay down first?

Public Comments

1. Is the concrete laying against the ground? If so, you would want to know if the slab had a moisture membrane laid between it and the dirt. If not, moisture CAN seep up through the concrete and ruin the carpet. Putting a membrane down between the carpet and the concrete surface would do nothing but trap the moisture between the concrete and the membrane, still ruining the installation.
2. The answer to your actual question is no, you do not need to lay anything other than the carpet. This is often done in houses that have carpet on a slab with in-slab heating through it. As the first answer said though, you would want to ensure that your slab has a moisture vapour barrier (plastic type sheeting) under the slab if the slab is on the ground. If it is suspended or first floor or higher then this won't be a problem. If you don't have a moisture vapour barrier, you could look at applying a liquid tanking membrane over the slab first.