Can you put underlay over underlay?

Author: Prof. Orion Zulauf PhD  |  Last update: Friday, July 18, 2025

When it comes to installing flooring, many homeowners wonder whether using two or more layers of underlay will provide better results. The short answer is that doubling up on underlay is not recommended and, in fact, can cause more harm than good.

Can you put new underlay on top of old underlay?

The short answer to this is yes. You just need to select the underlay you would like, lift and remove the old underlay. I would always advise cleaning and sweeping the floor. Also use this opportunity to secure any loose boards. Then lay your underlay and refit your carpet.

Can you put underlay on underlay?

With time and wear, underlay will become compressed and here at Leader Floors, we recommend using new underlay each time you change your flooring. Adding new underlay on top of the old underlay will impact the performance of the new underlay and can be harmful to your new flooring.

Is it okay to overlap underlayment?

In steep-slope conditions -- that is, 4:12 and steeper -- upper courses of felt underlayment should overlap lower courses by at least 2 inches. Here, you can see the difference between the underlayment overlapped 2 inches on the upper roof, and overlapped 19 inches on the lower, less steep roof.

Can you have too much underlay?

Too much padding can make the floor too bouncy, which strains the laminate's locking system. If you are fitting a laminate floor with a pre-attached underlay to concrete though, it's a good idea to install a vapour barrier as well. This will help prevent moisture damage.

Choosing the Best Underlay For Laminate & Wood Flooring

Can you put two layers of underlay?

Impact on Flooring Warranty:

Many flooring manufacturers specifically advise against using more than one layer of underlay, as this can void the product's warranty. The extra cushioning places unnecessary stress on the locking mechanisms and joints of the floor, making it more likely to fail prematurely.

What can I do with excess underlay?

Cut underlay into strips and braid them into tug toys, or create crinkly balls for them to chase. Warm and comfy pet beds: Upcycle larger pieces of underlay into snuggly beds for your pets. Add a layer of soft fabric for extra comfort.

Will underlayment help with uneven floor?

Before you put down your new floors, underlayment is a great way to ensure your subfloor will be level.

Can you put new roof underlayment over old underlayment?

After all, the smallest mistake can cause the biggest mishaps for your roofing system and yourself as the homeowner. With that in mind, when replacing your roof, one of the things that you should make sure will be done is to completely remove and replace the old underlayment.

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.

How thick should underlay be for floating floors?

If you are installing a floating laminate floor or floating engineered timber floor, then you will be required to install prior to the floor being laid a foam or rubber underlay. A minimum of 3mm underlay is recommended by Imperial Flooring Australia.

How do you stick underlay together?

Installation method

Each roll of underlay should be closely butted-up. Tape all joins with single sided waterproof tape and press firmly into place. Once the flooring has been fully laid, trim the underlay to the top of the flooring, fit skirting or quadrant to finish.

How long will 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 often should underlay be replaced?

Underlay should be replaced every 5 to 10 years, but this can vary based on quality and usage.

Should I remove old underlayment?

The truth is, for a variety of reasons, replacing old underlayment is not just recommended; it's crucial for the integrity of your roofing project. As a leading provider of exterior services, BSR explains why a tear-off is ideal during roof replacement and why retaining an old underlayment is not a wise choice.

Should underlay be stapled?

Stick your underlay to your subfloor – use adhesive glue or staples to make sure that your underlay is firmly attached to your subfloor. Lay your carpet on top – Now you can have your carpet fitted on top. Remember that caring for your carpet is the most important way to look after your flooring and your underlay.

What is the life expectancy of roof underlayment?

Underlayment also creates a smooth surface for installing shingles or tiles, guaranteeing a secure and consistent fit. On average, a roof underlayment lasts for 15 to 20 years.

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.

Can underlayment overlap?

Felt underlayment should overlap the edge metal at the eaves and be overlapped by edge metal on the rakes. This is also the case for rubberized asphalt underlayment, but not necessarily for synthetics.

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.

Should you put a vapor barrier between subfloor and underlayment?

Therefore, because concrete is porous, it's a good idea to install a vapor barrier over your concrete subfloor before installing your flooring. This way you can stop the vapor drive of water upward to your floors, protecting them from any damage (source).

What is the best underlay for uneven floors?

If you're wondering what's the best underlay for laminate or wood flooring, Fibreboard is a brilliant choice. It helps smooth uneven floors, reduces noise and acts as an excellent thermal insulator. Not to mention, it's also the number one choice of underlay for laminate and wooden floors.

Can you double layer underlay?

Underlayment is manufactured and meant to be used as only a single layer to allow your floor to be balanced and float properly. If you install any additional underlayment, the base for your flooring will end up being too soft and could jeopardize the integrity of the locking system.

Can you use old underlay?

When Can You Reuse Your Carpet Underlay? There are specific scenarios where reusing your underlay might be suitable: Age of the Underlay: If your underlay is relatively new (around 1-2 years old) and in excellent condition, reusing it can be an option. However, most underlays have a lifespan of around 10 years.

Is it OK to walk on underlay?

In short yes, absolutely. Underlay will help cushion the laminate flooring from shocks and impacts caused by general movement and furniture.

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