First things first: in case you don’t already know what underlayment is, it’s the material laid on top of the sub-floor, before the bamboo floor is installed (the subfloor is pretty much the raw floor of your house, whether it’s a concrete slab or plywood resting on floor joists).
The long and short of it is that you do need underlayment if you are nailing down or floating a bamboo floor, however you do not need underlayment when gluing down a bamboo floor. Using underlayment under your bamboo floor can provide soundproofing, moisture protection and stability, and reduce wood on wood squeaking. Bamboo flooring and an underlayment/vapor barrier can be installed on any existing floor including concrete, wood flooring, vinyl tile, linoleum, tile, etc., as long as the floor is flat and solid.
What type of underlayment is best with bamboo flooring?
If you’re nailing down a floor – use 15 lb felt paper
The most common underlayments used when nailing a floor down are 15 lb felt paper (i.e. roofing paper) and red rosin paper. Most installers prefer 15 lb felt paper, as red rosin paper tends to leave behind red dust that can stain walls and clothing and is hard to remove.
There is a common misconception that 15 lb felt paper is a vapor barrier – it is not! While it does help to wick away moisture from the bottom of the flooring planks, it is not meant to serve as a vapor seal. Therefore when installing over wet crawl spaces or basements, you need to seal them first as 15 lb felt paper will not protect your floor from sub-floor moisture. Another advantage of installing 15 lb felt paper is it reduces wood on wood squeaking.
People often ask if they can use 3 in 1 foam/rubber underlayment under nail down floors and the answer is that it is not recommended as these underlayments compress slightly when walked on, and the vertical flexion can result in loose nails and squeaky sounds over time.
If you’re floating a floor – use a 3 in 1 underlayment
While bamboo flooring is extremely durable, like all hardwoods it is vulnerable to moisture. When floating a floor, a 3 in 1 underlayment is a must especially if there is excessive moisture emitted by the sub-floor, such as a concrete slab or crawl space. Even if you live in a relatively dry climate, there’s no guarantee that your subfloor won’t have moisture issues. That’s why it’s essential to choose an underlayment with a built-in vapor barrier. The vapor barrier provides complete protection against moisture.
Stability – added benefit of 3 in 1 underlayment
If your subfloor is slightly uneven, underlayment can smooth out small imperfections so that when you lay your bamboo, it lays a little more flat. This benefits more than just your balance — your floor will be less prone to damage and buckling if it’s installed correctly, thereby extending its life!
Sound Absorption – added benefit of 3 in 1 underlayment
A 3 in 1 underlayment prevents a louder, hollow sound and provides a fuller sound when walked on. It also dampens the sound from impact or sound transmission noises. The higher the STC and IIC rating, the more soundproof and sound absorbant it is. (IIC) Impact Isolation Class *ASTM E492/E989 and (STC) Sound Transmission Class ASTM E336/E413 are types of testing for sound traveling through the total floor/ceiling assembly from an upper living area to a lower living area.
Do you like to sleep in, but your significant other is an early riser?
Do you have a new baby that wakes at the slightest sound?
Do you live in a condo or apartment building?
You should definitely look into a 3 in 1 underlayment with the highest STC rating you can find.
Installing over Radiant Heat – always use 3 in 1 underlayment
If you have an underfloor heating system, you need to ensure you use a high quality 3 in 1 underlayment with a minimum thickness of 2mm to insulate and protect your floor. You should only use engineered floating bamboo flooring over radiant heat subsystems as solid woods tend to shrink at a greater rate.
Please note that the color or thickness of the underlay has no relationship to the amount of thermal resistance—this is measured purely by tog ratings.
If you’re still not sure what the best underlayment is for your bamboo floors, get in touch and we’ll match your needs with the right material.