Best Underlayment for Vinyl Plank on Concrete (Pad vs No Pad)

Whether vinyl plank needs underlayment on concrete depends on the plank: bare-backed planks usually need a thin pad with a vapor barrier, while planks with an attached pad usually need no second layer. The wrong pad can void a warranty or weaken the click lock. This guide covers our top pick, attached-pad rules, moisture limits from Shaw and Armstrong, and how to install it.

Best Underlayment for Vinyl Plank on Concrete

Our pick for bare-backed planks is QuietWalk LV. The maker lists it at 1.4 mm thick with an attached vapor barrier, a water vapor transmission rate of 0.12 lb per 1,000 sq ft per 24 hours, a rating of 6 lb per 1,000 sq ft per 24 hours for concrete moisture, and a built-in lip and tape system so the seams need no separate underlayment tape. It is listed for luxury vinyl plank, rigid core vinyl, and wood plastic composite, and carries a limited lifetime warranty. Source: MP Global Products, QuietWalk LV.

At the Amazon price we checked, the 360 square foot roll works out to about 40 cents per square foot, which is the real cost to compare against a roll of 6 mil film plus tape. We have not laid it ourselves, so treat this as a spec-based pick, not a test result.

One more point before you buy: the “best” pad depends on your planks. If the box says the planks have an attached pad, skip to the next section before spending anything.

Attached Pad, Separate Underlayment, or Vapor Barrier Film?

Three setups cover almost every vinyl plank job on a slab. The table shows what each one means in practice, using only what the makers quoted in this guide actually state.

Your planks	What goes on the slab	What the makers say
Bare back, no pad	A thin underlayment with a vapor barrier, or 6 mil poly film	Armstrong recommends 6 mil polyfilm over concrete on or below grade for its rigid core planks. QuietWalk LV is a 1.4 mm pad with an attached vapor barrier.
Pad already attached	Usually nothing extra, or a film if the maker asks for one	Shaw allows a second underlayment under attached-pad products in residential use, up to 3 mm. Shaw also says an extra 6 mil poly layer may be used as added protection.
Any rigid core, concerned about dampness	Test the slab first, then follow the film or barrier the maker specifies	Armstrong says the product alone should not be used as a moisture barrier.

If you are working with plank that is not vinyl, our guides on laminate flooring underlay and underlayment for engineered hardwood cover those materials, since the rules above are for vinyl and rigid core products only.

Why You Should Not Double Pad Vinyl Plank

Stacking a thick foam pad under planks that already have one feels like a comfort upgrade, but it is a common way to loosen a click lock. Shaw’s installation guideline for an attached-pad rigid core product puts the reason in plain words:

“Soft underlayment and soft substrates will compromise the product’s locking ability as well as diminish its indentation resistance.”

Shaw, residential resilient installation guideline for attached-pad products

The same Shaw guideline family allows a second underlayment under products with an attached underlayment in residential installations, as long as it is no more than 3 mm thick. That is why a 1.4 mm pad like QuietWalk LV is within Shaw’s limit while a plush 6 mm foam is not. The 3 mm cap is a Shaw number, so check your own maker. Source: Shaw Floorté WPC installation guidelines.

• Pad already attached: read the guide for an explicit yes or no on a second layer before adding one.
• Stacking two moisture barriers: none of the sources we read describe a benefit, and a poorly sealed second film can trap water, so use one continuous system.
• Cork, rubber, or thick foam under click lock: softness is the issue, not the material, so a maker that specifies a maximum thickness is the safer guide.

Moisture Limits for Vinyl Plank on Concrete Differ by Maker

Many articles quote one number as the universal limit. The makers we read do not agree with each other, and the differences are large enough to change whether you can install at all.

Source	Calcium chloride (MVER)	In-situ RH probe	Barrier it names
Shaw Floorté guideline	8 lb per 1,000 sq ft per 24 hr	90%	6 mil poly, perm rating 0.1 or less, may be added as extra protection
Armstrong Luxe Plank, rigid core guide	5 lb	95%	6 mil polyfilm over concrete on or below grade, 6 in overlap at seams
QuietWalk LV (underlayment maker)	Concrete protection listed at 6 lb per 1,000 sq ft per 24 hr	Not listed	Attached vapor barrier, 0.12 lb WVTR

A pad rating does not replace your floor’s limit. An underlayment listed for 6 lb of vapor emission cannot raise an Armstrong limit of 5 lb, and the reverse is also true: your slab can pass your flooring maker’s test while exceeding what a pad is rated for. Compare the slab test result with both documents. Sources: Shaw and Armstrong.

The 75% RH figure you see online is a general guideline for some products, not the number these two makers print. That is the information most roundups skip: the limit that counts is the one in your plank’s guide, and it can be higher or lower than what a blog states. Hardwood has stricter limits again, as our hardwood guides explain.

Test the Slab Before Buying Any Underlayment

Underlayment is not a repair for a wet slab. Test first, so you know whether you need a film, a pad with a barrier, or a different floor.

1. Pick the method: Shaw names in-situ RH probes (ASTM F2170) and calcium chloride kits (ASTM F1869). Armstrong lists both too and calls the probe method preferred.
2. Test enough spots: Shaw’s guideline describes three RH tests for areas up to 1,000 sq ft and one more per added 1,000 sq ft. Test near exterior walls, too.
3. Record dated readings: a warranty claim may ask for them. Photograph the kit or probe in place.
4. Compare to two numbers: your flooring maker’s limit and any limit printed on the underlayment.
5. If it fails: wait and retest or use the moisture control system the flooring maker specifies; do not simply add more pad.

Our hardwood over concrete guide covers the NWFA moisture tests and limits for wood flooring in detail, and our guide to installing hardwood on concrete covers glue-down and floating methods. Vinyl limits are different, so use the maker numbers above for plank.

How to Install Vinyl Plank Underlayment on Concrete

1. Clean the slab: sweep, then vacuum. Armstrong’s guide calls for concrete that is dry and smooth, free of dirt, paint, wax, oils, and other contaminants.
2. Check flatness: Shaw’s tolerance is 3/16 inch in 10 feet or 1/8 inch in 6 feet. Grind high spots and fill low spots with an appropriate patching compound.
3. Roll out the underlayment: run it in one direction and butt the seams. QuietWalk LV uses a built-in lip and tape system; film products overlap, so follow Armstrong’s 6 inch overlap for polyfilm.
4. Seal seams: for a floating floor over concrete, Shaw’s guideline for attached-pad products says film seams must be taped.
5. Keep it flat at walls: trim the pad at each wall so it does not ride up under the expansion gap or the baseboard.
6. Lay the first row: follow the gap the flooring maker specifies at every wall; our guide on cutting vinyl plank helps with edge pieces.
7. Click planks together: stagger end joints and keep the seams of the pad and the planks from lining up.

Radiant Heat, Noise, and Where Underlayment Does Not Help

Shaw says a radiant system must be on and operational for at least 2 weeks before installation to reduce residual moisture, and that operating temperature should never exceed 85 F. Armstrong’s rigid core guide also caps radiant surface temperature at 85 F. Check that your underlayment maker lists radiant use before choosing a pad.

For noise, QuietWalk LV lists an IIC of 70, STC of 62, and a delta IIC of 28. Treat those as results from the maker’s test assembly, not guarantees for your floor, and ask your building if it requires a specific IIC. A pad also does not fix an uneven slab or a floor that fails the moisture test.

Other Ways to Handle the Moisture Layer

If your planks have no pad and you want the lowest-cost vapor control, a polyethylene film is another route. ROBERTS Moisture Barricade is a 6 mil film listed as a Class 1 moisture barrier for use above, on, and below grade over concrete with vinyl, laminate, SPC, WPC, and engineered wood flooring, and it comes in rolls from 120 to 1,000 sq ft with an adhesive strip to join pieces. Source: QEP, ROBERTS Moisture Barricade. A film does not add cushion or sound reduction, so pair it only with planks that already have a pad.

Option	Thickness	Moisture control	Best use
QuietWalk LV	1.4 mm	Attached vapor barrier	Bare-backed planks that need cushion and sound control
ROBERTS Moisture Barricade	6 mil film	Class 1 moisture barrier	Planks with an attached pad where the maker asks for a film
No extra layer	None	Maker’s own system	Planks whose guide says no underlayment over concrete

Common Mistakes With Vinyl Plank Underlayment on Concrete

• Adding a second pad under planks that already have one.
• Skipping the moisture test because the plank is waterproof.
• Ignoring maker limits and using a number from a blog instead.
• Leaving debris on the slab, then wondering why the floor shows bumps.
• Letting film seams gap or bunch up at walls.
• Using a thick, soft foam under a click-lock floor.

Frequently Asked Questions

Do you need underlayment for vinyl plank flooring on concrete?

Not always. If your planks have a pad attached, most makers want no second pad, or only a thin one. If the planks have no pad, a thin underlayment with a vapor barrier or a 6 mil poly film is the usual choice over concrete. The deciding document is your flooring maker’s installation guide, because that is what a warranty claim is judged against.

Can you put underlayment under vinyl plank that already has a pad attached?

Only if the flooring maker allows it. Shaw’s guideline allows a second underlayment under its attached-pad resilient products in residential installations, capped at 3 mm thick. Shaw also warns that soft underlayment compromises locking and indentation resistance. Other makers may say no second pad at all, so read your own guide first.

Is a vapor barrier required under vinyl plank on concrete?

Not under every product, but Armstrong’s rigid core guide recommends a 6 mil polyfilm moisture barrier over concrete on or below grade and says the product alone should not act as the barrier. Some underlayments, such as QuietWalk LV, have a vapor barrier attached, which can serve the same purpose if your flooring maker accepts it.

What moisture level is too high for vinyl plank on concrete?

It depends on the maker. Shaw’s guideline lists 8 lb on a calcium chloride test and 90% RH on an in-situ probe test. Armstrong’s rigid core guide lists 5 lb and 95% RH. Neither matches the stricter limits used for hardwood, so use the numbers printed for your exact product.

Does waterproof vinyl plank mean I can skip the moisture test?

No. Waterproof describes the plank, not the slab. Excess moisture can still hurt adhesives, trigger mold or mildew under the floor, and void a warranty that requires testing. Both makers quoted here set slab moisture limits even for waterproof rigid core products.

Start with your flooring maker’s guide, test the slab, then choose one moisture system and one thin pad if the planks need it. For related projects, see our guides to putting vinyl over wood floors, laying vinyl plank in a bathroom, and gluing down a floating floor.