Hardwood Floor Underlayment [Full Guide]
I used to think hardwood didn’t need underlayment. Pad was just for carpet.
But this isn’t the case. Many times it’s not optional–you have to have underlayment. But even when it’s not required, there are plenty of good reasons you might want it.
Here are the goals of this article and what we’ll cover in order:
- Decide if you need underlayment for your hardwood
- Decide what underlayment you should choose
- Answer any final questions: pricing, radiant heat, etc (can leave any questions in the comments)
Is underlayment necessary for hardwood floors
The short answer: usually.
If you already have a plywood subfloor, and the subfloor is smooth and level, then you may not need an underlayment beneath the hardwood floor. Plywood has some moisture resistance already compared to solid wood, and it mostly gives a smooth surface.
So plywood likely means you aren’t required to have underlayment, but it still can provide other benefits.
The 5 benefits of underlayment with hardwood
There are two reasons it helps to know why you might benefit from underlayment:
- So you can decide if you want it in cases where it’s not necessary.
- So you know what you’re paying for, and what features to look for.
What I mean by point 2 is, if you don’t know what benefits underlayment can provide, than you won’t know why you should spend more or less. Or why it even matters what underlayment you choose.
Let’s take a look at all the benefits:
One of the most important reasons to use underlayment is to protect your hardwood floor against moisture damage. You can often find underlayment with an added vapor barrier which helps to keep your wood floors safe from water damage.
You will often see this recommended for floating floors, but when it comes to keeping water and moisture away from your hardwood floors, every bit helps. No matter how well installed or maintained, any gap between the planks can let water seep under your floor. Once the water has soaked into the floors from beneath, you can be facing expensive damages once the boards warp or break.
Captain’s warning! You should avoid nailing through some types of waterproof underlayment, as the punctures will keep them from working correctly. Always check the underlayment warnings to see if it can be used with a nail-down installation. If not, your installer should take precautions, such as installing another plywood layer on top of the underlayment, to keep from damaging it.
An even subfloor is one of the first requirements for any hardwood flooring installation. When you nail or glue wood floor onto an uneven surface, the finished wood floor will also be uneven. Not only does this pose a tripping hazard, it also leaves your beautiful wood floor looking less than perfect.
Major flaws should always be repaired before installing hardwood floors, but minor dips and cracks do not necessarily require a complete overhaul. If you can find an underlayment thick enough to compensate for small, uneven areas, it would be less expensive and faster to use that than to tear apart the whole subfloor.
Put simply, a busy household on wood floors can produce a lot of noise. From kids and pets running and playing in the living room to the background noise of voices, televisions, and general household ambiance, the sounds can quickly add up.
You can find underlayment that helps absorb sound from the air and keep the sound waves from bouncing quite so vigorously around the room. Other types of underlayment muffle sounds made on the floor itself, which is especially helpful for upper stories of your home if you do not want to hear every footfall from lower levels.
Another drawback of wood flooring is that it’s a solid, sometimes cold, surface and not especially pleasant to walk or stand on for long periods of time. If you have chosen a harder wood floor, known for its durability and longevity, this may be even more noticeable.
So in these cases, underlayment will be an added investment that you will thank yourself for on chilled winter nights and any time you walk on areas not covered by rugs. Underlayment cushions your feet when you walk on the hardwood floor and insulates it from intense temperature change.
Stabilizing floating floors
If you have installed engineered hardwood as a floating floor, then underlayment will be very important. Floating floors are not attached to the subfloor so they can easily expand and contract when exposed to the moisture and heat in the air. Moisture can also pool up in the gap between the subfloor and the floating engineered hardwood, which will eventually damage or warp even the best-engineered hardwood flooring.
Best type of underlayment for hardwood
There aren’t many decisions when choosing an underlayment for your hardwood floor. Choose the best material for your job, and you’ll be happy with your purchase.
Let’s cover the characteristics and pros and cons of hardwood underlayments:
This is the most popular hardwood underlayment.
If you are not using a floating floor, and most of the time with hardwood you won’t be, then one of the best types of underlay is heavy, black felt. These help keep moisture from coming up through the subfloor even when you nail directly through it, and can be stapled to the subfloor so they stay in place.
Black felt underlayment looks a lot like roofing underlay but does not have any asphalt or tar. It is odorless and safe to install in confined areas of the home.
Felt underlayment provides protection, but it lacks in bells and whistles. It’s thin and won’t give you much cushion underfoot or sound-dampening. If these are high on your priority list, you might want to move on to another material.
Cork isn’t quite as popular as felt, but it makes a great underlayment.
Cork is natural and renewable so it fits in well with a “green” home remodel.
Cork underlayment has excellent sound-reduction properties. It is even used in music studios to keep out background chatter from finished recordings. The best sound-dampening will come with 6mm cork underlayment, but you can also buy cork underlayment with 3mm thickness if you need a narrower underlay.
If you are trying to even out minor subfloor imperfections, cork is flexible and will fit evenly between the subfloor and the hardwood floor. It also helps to insulate against cold and heat and is water resistant. It’s not waterproof, but you can buy cork with a moisture barrier.
One last benefit of cork is for those suffering allergies: it has anti-microbial and anti-fungal properties.
Rubber is easy to install, provides an excellent moisture barrier, and does a good job reducing sound.
So why is it the third most popular hardwood underlayment?
Mostly due to cost. It’s not way more expensive, but expect to pay around $1.50 for rubber underlayment.
The other benefit of rubber underlayment is it’s easy to DIY. Most underlayments are, but sometimes you have to glue down the others where rubber you just cut and set it down.
Cost of hardwood underlayment
Like anything in flooring, this varies a lot on quality, but expect to pay between $0.50 and $1.50 for underlayment. Cheap cork or felt could be lower, and you can pay more for special features but many of these will be marketing hype. Usually, you can stay in this range and get anything you need for your hardwood.
Radiant heating and wood underlayment
If you have radiant heating with your hardwood floors you can still use an underlayment, but you should pick one with a low R-value. A low R-value easily allows the heat to travel through the underlayment to the floor surface compared to a high R-value, which will actually work against the radiant heat by providing too much insulation.
Captain’s parting words!
An underlayment is very helpful when installing your hardwood floors. The slight addition of cost and time pays off in the long run by giving your floor some protection against moisture, reducing noise, increasing your comfort, and evening out any minor subfloor flaws without a major redo.
There are a few types of subfloor you can choose from. You should always check with the floor and underlayment manufacturers to make sure you are choosing products and installation methods that work well together. With that bit of preparation, you will be able to improve performance for both long after the floor is installed.
Next step? If you haven’t already, I’d check out our unbiased hardwood guide. It covers everything from the type of wood for durability to design choices.
Any questions I didn’t cover on hardwood underlayment? Let me know in the comments below.