Underlayment Options - What goes under the flooring?

Foam: Foam underlayment smooths subfloor imperfections, cushions the floor for comfort, protects against moisture, and offers some sound insulation. Many types include a built-in vapor barrier. While foam underlayment is required for engineered hardwood and laminate (unless the underlayment is already built in), it’s also sometimes used under vinyl plank flooring, but not always necessary.​

Moisture barrier: A moisture barrier is used under wood flooring, laminate, and vinyl planks when installing floors or walls in areas prone to dampness or excess moisture, such as basements, ceilings, or crawl spaces where a foam underlayment is not installed.

Roof felt: Felt underlayment is a solid option when it comes to hardwood flooring. Most are 1/8" to ¼" thick and come in rolls, providing crucial benefits like soundproofing, water protection, and a flat, smooth, even surface. ​

Plywood/Luan: The preferred underlayment for sheet vinyl flooring is 1/4″ plywood or luan. Some installers will lay vinyl over existing OSB or plywood subflooring if it is in excellent condition. Plywood or luan is available in 4’x8’ sheets.​

Plywood can also be used to make up the difference in pre-existing and new vinyl plank/hard   surface flooring.  ​

Cement board / Hardibacker: 
Cement board consists of cement material and fibers made from wood or cellulose. The fibers reinforce the cement and also give it a certain amount of flexibility that allows for movement without cracking the cement. (Not required on cement subfloors.)​

Carpet Pad: Required for all carpet installations that are not glued directly to the subfloor, they can be made of foam or rubber depending upon where the carpet would be installed.The type of carpet pad you choose is up to you! New padding is clean, odor-free, and extends your carpet's life. Lowe's offers different types of carpet pad:

• ​6 LB Carpet Pad: (6-lb density, 11.11-mm) 100% recycled construction. Will have a lighter, softer feel under your feet. it is not built to withstand heavy foot traffic.

• Select Carpet Pad: (8-lb density, 11.11-mm) 100% recycled bonded foam core with a breathable moisture barrier, approved for high-traffic areas.

• OdorBan Carpet Pad: (8-lb density, 11.11-mm) 100% recycled construction rebond carpet padding with antimicrobial moisture barrier to repel spills and inhibit the growth of mold, mildew, and odor-causing bacteria. Perfect for Frieze, Textures, Fashion Forward, and Berber carpets.
• Memory Foam Carpet Pad: (11.94-mm) This pad features high-performance memory foam for added softness and responsiveness in low-traffic areas. It includes a breathable moisture barrier to block spills and allow vapor to escape, plus Fresh Dimension® treatment to resist mold and mildew in the pad.
• Elite Foam Carpet Pad: (13-mm) Offers top insulation for energy efficiency. Features activated carbon for odor control, DuraPlush® foam for superior cushioning and durability, and a textured design for comfort. The breathable moisture barrier blocks spills while allowing vapor to escape. Fresh Dimension® treatment resists mold and mildew.

Some manufacturers have recommendations for certain cushions, such as firm cushions no thicker than 7/16 inch for cut pile carpets, and very firm cushions no thicker than 3/8 inch for Berber and most commercial carpets. A Lowe's sales specialist can help you pick the best pad based on your carpet type.