What are Subfloors and Underlayments?

What’s an underlayment? Do we have a subfloor? Are joists important? We often talk of hardwood floors, ceramic tile, natural stone, carpet, and so on–but what about what’s under the floor? When you’re renovating your home with updated flooring, you might be tempted to ignore what lies beneath your shiny new floors, but your choice of materials under the floor has a huge impact on how the floor feels under your feet and contributes to the overall structural integrity (and market value) of your home.

Types of Subfloors

In construction, the subfloor is the continuous base layer on which the underlayment and finish materials (hardwood, carpet, tile, etc.) are installed. The two main types of subfloors are wood-frame and concrete slab. Wood-frame floors are built using sheets of plywood which are fastened to wooden joists to provide foundational support and a continuous surface on which finish materials may be installed.

Concrete slab subfloors, often found in basements, provide a smooth and durable surface for finish flooring installation, but concrete’s coldness, hardness, and its tendency to wick moisture up from the ground make it anything but comfortable, which is why installing an underlayment between your subfloor and top floor makes a significant improvement.

In either case, whether you have a wood-frame or concrete subfloor, your choice of underlayment plays an important part in determining the warmth, springiness and moisture resistance of whatever flooring material is installed on top of it.

What is underlayment?

Underlayment is confusing because depending on the type of flooring you install, you might have a plywood underlayment, a foam pad, or none at all. For example, if you’re installing hardwood in wood-frame construction, your layering would be:

  • Hardwood (finish layer – top)
  • Plywood (subfloor – middle)
  • Lumber joists (bottom)

In flooring, the underlayment is the layer between the subfloor and finish layer that fills in rough spots in the subfloor with a smooth, even surface, protects against moisture, reduces the sounds of footsteps, and provides insulation from the cold.

The best underlayment for your floor depends on your choice of finish material:

  • Hardwood – most underlayment can be used with hardwood floors without problems, but plywood is the most common.
  • Tile – a weak subfloor and underlayment can cause tiles and grout to crack, so we recommend installing a concrete subfloor or cement-reinforced backing to provide adequate structural support before laying down tile.
  • Laminate, LVP, or Vinyl – these popular and cost-effective substitutes for natural hardwood and stone often require a foam underlay to perform their best. Foam underlays are available in standard and “upgraded” varieties. Both options provide cushioning and moisture resistance, but the “upgraded” underlay is thicker for extra padding and acoustic isolation between floors.
  • Carpet – depending on your intended use, carpet is compatible with a wide variety of underlays, with foam and rubber being the most common for water resistance and sound absorption. 

At Dan’s Wholesale Carpet & Flooring we’ve got you covered from subfloor to ceiling with top-quality name brands in flooring, countertops, cabinetry, and roofing for your whole home.

We’re stocked everyday with incredible wholesale pricing on the hardwood, tile, LVP and vinyl flooring, carpet, lighting fixtures, and everything else you need to finish your home renovation. Stop by any of our four northeast Ohio locations, give us a call, or click the button on this page to schedule your free in-home shopping appointment today!