What thickness underlayment should I use?

Author: Bernard Ward  |  Last update: Thursday, July 24, 2025

With that being said, most underlayments are 2-3mm thick, but are sometimes thicker for carpet or to smooth out an uneven subfloor. It's often advertised that 6mm underlayment offers double the sound absorption as 3mm underlayment.

What is the best thickness for underlayment?

Generally, there are five thicknesses in the following thickness categories: 1/4, 11/32, 15/32, 19/32 and 23/32. The thinner panels are often used for an underlayment under resilient flooring products in conjunction with a thicker subfloor, while thicker panels are used for hardwood and tile flooring.

Should I use 15 or 30 underlayment?

If your roof does not have a steep pitch, you can use #15. This weight of felt is a good economic choice if you have a standard roof. But if your roof has a steep pitch, #30 is a better option because it is thicker and tears less during installation. With #30 you get a thicker layer of underlayment and protection.

What thickness underlay should I get?

A thick underlay, between 11 and 12mm, will give your carpet a cushioned, soft feel. However, a thinner underlay on the stairs may be easier to install. 9mm is ideal.

Can underlayment be too thick?

Choosing a thick (10mm+) underlay for your stairs is not a good idea as it can pose a trip hazard. Moreover, thicker carpet underlays tend to compress slightly with heavy use, which can lead to irregular wear and unsightly lumps, particularly in frequently trodden areas.

Why You Need Underlayment For Your Floors

Does underlayment have to be perfectly flat?

No subfloor is perfectly level, but any signs of unevenness and high or low spots must be remedied. Please follow these requirements: Subfloor unevenness cannot be greater than 3/16 of an inch over a 10-foot span or 1/8 inch over a 6-foot span. Subfloors must not slope more than ½ inch per 6 feet (25 mm per 1.8 m)

Does thick underlay make a room warmer?

Ball & Young supply underlay from 3mm all the way through to 11mm; the thicker the product, the more travel of compression there is, which makes the product feel more comfortable and gives better heat insulation.

How do I choose the right underlayment?

Choosing the right floor underlayment is critical, so we've outlined the top seven things to keep in mind during your research.
  1. Thickness. ...
  2. Compression Resistance. ...
  3. Noise Barrier. ...
  4. Moisture Wicking. ...
  5. Installation Process. ...
  6. Budget Considerations. ...
  7. Underfoot Feeling.

Should I buy an expensive underlay?

If you buy a more expensive carpet, for example wool, that is designed to be durable and last for many years, then you should try to invest in a higher quality underlay. Of course, that's if the budget allows.

Is higher density underlay better?

Density plays a role in both comfort and durability. Higher-density underlay tends to be more resilient and durable, as it can better withstand the pressure and weight placed on the flooring surface. It offers improved support and helps prevent premature wear and tear of the floor covering.

Which is better, 30 lb felt or synthetic underlayment?

It comes in two different weights: 15- and 30-pound, with 30-pound being the more durable, heavy option. Synthetic roofing underlayment is typically made from durable polymers that are created to be water-resistant and easy to work with. Many roofing contractors prefer to use synthetic roofing underlayment over felt.

How much should underlayment overlap?

So, underlayment on low-slope roofs should overlap 19 inches. Remember that underlayment on steep-slope roofs should overlap 2 inches. Also, remember that asphalt shingles should never be installed on roofs having a slope of less that 2:12. The difference is easy to see, once the underlayment is installed.

How long does underlayment last?

In most cases, traditional felt underlayment is rated to last between 12 and 20 years. In other words, in a little over a decade, the underlayment beneath your roof's surface may start to deteriorate. The roof will become more prone to leaks as this added layer of protection breaks down.

Can you have too much underlayment?

More is not always better, and with underlayment, too much can compromise the integrity of your floor's locking system. Adding additional underlayment under vinyl with an attached pad can create too much cushioning, which causes the floor to come apart through use over time.

What is the code for subfloor thickness?

The code requires 1 1/4" floor thickness (overall) unless it is tongue and groove plywood in which case 3/4" is adequate. Will 1/4” plywood over 1x10 plank subfloor be thick enough t ...

How do I choose floor thickness?

A thicker board will absorb sound better than a thinner board, so footsteps will be quieter. For those who really want to ensure quietness, a thicker board will also reduce the echo within the room. Thicker laminate flooring will feel more like hardwood underneath your feet.

Is thicker underlayment better?

Thickness

But as a general rule, the thicker it is, the better. Those around the 3-5mm mark are a great budget-friendly option and they will make a difference to the look and feel of your laminate. But they don't offer the same performance as a thicker underlay.

How much should I pay for underlay?

What is the average price of underlay? The price of carpet underlay is calculated per m2 and – dependent on the supplier and the quality of the product – you can expect to pay anywhere between £2-£8. The more luxurious the underlay, and the better its overall performance, the more it will cost.

How many years does underlay last?

Underlay can last anywhere between 5 and 20 years. Foam and Felt underlay can last up to 8-12 years. However, if foam underlay isn't properly installed or maintained, it lasts only 5 years. Acoustic and rubber underlay have the longest lifespan, lasting 10-20 years.

How thick is typical underlayment?

Underlayment. Underneath the top flooring layer is often (though not always) an underlayment. It comprises padding materials and is typically about 1/4 to 1/2 inch in thickness. The purpose of the underlayment is to provide a sturdy yet comfortable layer for your outer flooring to sit on.

What thickness underlay should I use?

So generally speaking 7mm is about as thin as you want to go unless you have a specialist need for something thinner, but 8-12mm is the band most manufacturers produce carpet underlay with and its perfect for any room and any carpet.

Is expensive underlayment worth it?

The high cost of synthetic underlayment is due to its superior material strength and long lifespan compared to felt or asphalt paper underlayment. While the initial investment may be higher, synthetic underlayment can save you money in the long run by lasting longer and requiring fewer repairs or replacements.

Which type of underlay is best?

Sponge rubber underlay combines the best of durability and comfort. Sponge rubber underlay is made from synthetic rubber, and this gives comfort and durability meaning it can last for years and years underneath your carpet.

What is the downside to laminate flooring?

Not moisture-proof

Being made of wood, laminate flooring is not impervious to the effects of moisture. Therefore, it's not suitable as a hard flooring for bathrooms and should be used with caution in kitchens or laundries. Light surface water for cleaning shouldn't cause issues, but saturation must be avoided.

What is the best underlayment for insulation?

Rubber is one of the best choices for underlayment because it is super versatile. It protects your floor from mold and mildew and protects your ears from hollow sounding floors. In fact, it is one of the most sound absorbing and insulating underlayments out there.

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