If your planks already have a pad-attached underlayment, you most likely won't need an underlayment. However, if your flooring manufacturers installation instructions allow for an extra underlayment, adding an extra underlayment will provide improved sound reduction, insulation, and moisture protection.
Luxury vinyl plank manufacturers mention only vapor barrier in their installations. They recommend this due to not allowing (concrete subfloor) getting moisture or alkalinity to your flooring choice. This will eliminate any potential for claims or damages to the manufacturers flooring.
If you're laying the LVP over an existing cushion-backed vinyl floor or a below-grade tile floor, you won't need to use an underlayment. However, you'll want to use one in every other application, including covering existing hardwood floors, uncushioned vinyl flooring, and concrete floors.
Engineered vinyl plank (EVP) flooring (also known as rigid core luxury vinyl flooring) can be made with three different cores: stone-plastic composite (SPC), wood-plastic composite (WPC), and pure vinyl. SPC floors aren't as comfortable, so they pair best with soft underlayments made from foam, felt, and cork.
You may know luxury vinyl plank flooring can be installed directly over your existing flooring. This is where you determine whether you need underlayment or not. If installing your luxury vinyl plank flooring over an existing vinyl floor or tile then you won't need an underlayment.
When you install your vinyl on a wood subfloor, the top plywood should be a minimum of 1/4″ thick. For most subfloors, you will need to add an extra layer of wood. To do this, measure and cut the plywood to fit your room.
Concrete Subfloor
For floating floors, like loose-lay vinyl sheet or rigid vinyl planks, a vinyl flooring underlayment may be required as a vapor barrier and can also add much-needed cushion and warmth underfoot. You may also want to look for an underlayment designed for moisture mitigation and insulation.
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) Subfloors must be structurally sound.
Without underlayment to add a layer between these damp subfloors and the surface flooring, your laminate can quickly become wet, warped, and mildewy, harming its overall integrity. Moisture over time can also break down floor adhesive which causes the floor to start warping.
Your vinyl planks will be placed parallel to the focal wall or the longest wall in the room. Measure out the length and width of the room, and divide the width of the room by the width of the planks. Plan for ¼” gap along the walls to allow for expansion.
Before doing the installation, you must ensure that the floor beneath is swept clean. Sheet Vinyl flooring works best with plywood because it is easy to install and has an impressive level of water resistance. Also, plywood will help you save money in the long run because you won't have to do repair time and again.
“Welded joints to vinyl are waterproof, therefore the whole flooring is a waterproof thing.” “Commercial grade vinyl doesn't require waterproofing.”
How to lay vinyl flooring on concrete. As you don't have to install underlay for Vinyl Flooring or LVT, this can go directly onto the concrete subfloor. However, allow 24 hours for your flooring to acclimatise by leaving it out of its packaging.
Vapor barriers should fully cover any ground and overlap at least 6”. Create a conditioned crawl space. Conditioned crawl spaces can prevent vapor drive and moisture build up and provide the added benefit of increased energy efficiency while still capturing the cost savings of building over a crawl space.
When you're installing a vinyl plank floor or any rigid type of new flooring, it's important for the underlying layer to be both level and flat. If you're installing vinyl planks on top of a concrete floor, the standard tolerance required is for the floor to be level to 3/16” within a 10' radius.
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).
When you have a bump or dip in your subfloor, the uneven surface can cause vinyl planks click-lock-systems to become uneven. This will cause creaking or “popping” every time you walk over the floor. An underlayment can help fill in subfloor imperfections and leave your flooring a smooth surface to lay on.
Moreover, if your floor is just slightly uneven, keep in mind that a vinyl plank over uneven floor can provide it with full coverage, as well as other sturdy materials. Not only do these types of materials give the floor the illusion of being more even than it really is, but they're also easy DIY flooring options.
Yes, provided it meets the specifications required for subfloor preparation.