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.
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.
We recommend that you buy and fit new underlay at the same time as your new flooring. Old underlay can disintegrate as it ages, as well as harbour lots of dust and dirt. It will have compressed over time where you've walked, so reusing old underlay will affect the performance of the new flooring laid on top.
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.
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.
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.
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.
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.
Stairs and hallways
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.
A 3mm underlay is ideal for flooring less than 18mm thick. This thinner option provides sufficient support without adding unnecessary height. For flooring that is 18mm or thicker, you'll need a 5mm underlay. This added thickness ensures better stability and cushioning for heavier or more robust flooring options.
How often should you replace carpet underlay. Although a typical carpet underlay will last somewhere between 10 and 25 years, we would always recommend installing new underlay every time you replace your carpets.
Combination (felt/rubber) underlay is considered the 'best of both worlds because it combines the properties of two materials: the felt brings warmth and comfort, and the recycled rubber brings durability and sound reduction.
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.
For added strength and stability, a double-layer subfloor is often recommended. In this configuration, two layers of plywood are installed, with the top layer offset from the seams of the bottom layer. By staggering the seams, the subfloor's overall strength is enhanced, reducing the risk of deflection or squeaks.
FibreBoard underlay is designed to eliminate uneven floors, thanks to it's lightweight yet strong construction. Offering stable support which helps to guard against wear and helps to reduce high impact damage, while smoothing out the most uneven areas.
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. So go thicker if you can afford it!
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.
Good quality underlay will prevent premature wearing and keep your floor looking new for longer. As the underlay acts as a shock absorber, your flooring or carpet will sit better and take more wear.
Start in the corner of the room, taking care to leave a 10mm gap between the fibreboard and the wall. Once the first piece has been positioned correctly, move along the row – leaving an expansion gap of approximately 2mm between each sheet – until you reach the other side of the room.
You can have the softest carpet in the world, but if you lay it directly on top of a solid stone or concrete floor, then it will feel much harder than it could. Underlay provides a soft cushion for the carpet to be placed on, thus it is softer underfoot.
In short, if you're looking for longevity, luxury feel and want your carpet to last, always ensure your carpet is fitted with a quality, new underlay underneath – carpets fitted without underlay may also invalidate your guarantee or warranty, so it's a wise investment long-term.
The underlay should be laid foil side down (essential to ensure maximum resistance to moisture from the subfloor) allowing a 5cm excess of underlay to run up the perimeter wall. Each roll of underlay should be closely butted-up.
The reason they probably want you to use their 1.5mm thick underlay, is because their planks may only be stable on something 1.5mm thick or under. You have potential of voiding your warranty by using anything else. The 3mm pad may be too much give for the floor and cause failures.
The strip should overlap the new underlayment on the replacement plane and be inserted between the shingles and existing underlayment on the adjacent roof plane. The overlap should extend at least 4” (102 mm) to 6” (152 mm) on both planes.
Before you put down your new floors, underlayment is a great way to ensure your subfloor will be level.