How to Select the Correct Carpet Underlayment

People prefer carpet for a host of reasons, but mostly because it’s just soft and comfortable. Often, they won’t hesitate to spend a little more to get a softer and thicker carpet when comparing samples in the store. But the cushion—not necessarily the same story. It’s not uncommon that customers will sometimes skimp on the cushion with the mindset “a cushion’s a cushion” and will even purchase the cheapest cushion available to save a few bucks. As an installer, let me tell you, just because you can’t see it doesn’t mean that it’s not important. In fact, it’s very important.

But let’s face it, in most cases, installers have no role in selecting the carpet or the cushion. That decision was made maybe days or weeks earlier between the sales associate and the customer. Even so, if something doesn’t look right to you as an installer, mention it to the retailer before installation. Just as you wouldn’t spread the wrong kind of adhesive for a particular flooring type, you should avoid the wrong type of cushion for the carpet the customer has purchased. Chances are that the carpet’s warranty coverage is dependent on the type of cushion and the thickness and density of the pad underneath. A mismatch has the potential for claims and headaches later.

As a rule of thumb, cushion suitability is determined by two criteria: thickness and density. For most residential installations, look for a cushion that is 3/8” to ½” thick. Commercial installations generally run thinner with ¼” to 3/8” in thickness. This is because most commercial carpets are made for higher traffic areas and a firm, stable surface is more important than a soft, cushiony feel. Cushion density is measured in pounds per cubic foot, so for residential use, the range is usually 6 to 8 pounds per cubic foot, and commercial or other high-traffic areas, consider 8 to 10 pounds per cubic foot. Always consult the manufacturer’s recommendations. The Carpet Cushion Council is also an excellent resource of information.

Matching cushion with carpet type is also a consideration. Plush and high-pile carpets can work with thicker cushions, but too thick can cause issues with stability and wear. Berber and loop carpets work well with thinner, firmer cushions to prevent the loops from collapsing and to provide better support. Commercial carpets use a dense, firm cushion that withstands high foot traffic.

I’m often asked what type of carpet cushion is my favorite. Carpet cushions, like so many accessories in our industry, have undergone tremendous development. It’s hard to keep up with so many variations and added benefits manufacturers have included. My advice to installers is to stay current with this area, so you can better advise your customer on what they should look for.

• Rebond (or Bonded Polyurethane Foam): is what most people think of when they think of carpet installation. It’s usually the least expensive but may not be the best.
• Memory Foam (Prime Polyurethane — like the mattress type) cushioning is more expensive, but still must be matched correctly to the carpet type and use to be effective. It can be cost-effective in the long run by extending the life of the carpet.
• Waffle Rubber: Good cushioning but can degrade faster.
• Frothed Polyurethane Foam: Durable and dense, great for high-traffic areas.
• Fiber Cushion: Durable and resistant to compression, suitable for high-traffic areas like hallways.
• Rubber Padding: Excellent for moisture resistance and durability, ideal for basements or areas prone to spills.

In my years of installing carpet and troubleshooting carpet problems, I’ve seen a lot of cushion issues that can also be due to poor installation. As I mentioned earlier, not following the carpet manufacturer’s recommendations, as well as the cushion thickness and density are sources of concern. But there are several other potential mistakes that can be attributed to cutting corners, or ignorance, or both. Don’t be the guy who commits these errors:

• Poorly prepared subfloors are fundamental to carpet installation failure. Don’t fool yourself into thinking that the carpet cushion will hide the imperfections. They always have a way of telegraphing up. And when you neglect cleaning, leveling and repairing, you can end up with uneven cushion installation and reduced carpet lifespan. Ignoring issues such as cracks in the concrete subfloor or moisture problems that are evident can lead to damage to the cushion and carpet over time.
• Sloppy seaming can result in gaps or overlaps over time that results in uneven surface wear.
• Misaligning the cushion or not securing it correctly can cause the carpet to shift. This will result in unsightly wrinkles and bumps in the surface.
• Failure to secure the cushion properly to the subfloor will cause it to bunch up.
• Sometimes carpet can be installed in moisture-prone areas, like a basement. Installing a cushion without a moisture barrier can lead to mold and mildew growth. Some cushion products come with an antimicrobial treatment.
• Cushioning is just like any flooring material in that it needs room to expand. Without allowing for this, you risk buckling along the baseboards.
• Improper cushion cutting speaks for itself.
• Never overlap cushioning. It will be noticed.
• Well sharpened and maintained tools will avoid imprecise cuts and poor-fitting seams, compromising the installation quality. Something as simple as fresh blades in your utility knife will make all the difference.
• Inadequate tack strips around the edges can create loose carpeting and insecure cushioning placement.

Remember, installing the carpet is not complete without the right cushion. And even though you may not have a vote in the selection of the cushion, it’s up to you to make sure it’s installed the right way.