A poly vapour barrier and the pad bonded to the back of a vinyl plank do different jobs, so the answer for a basement slab depends on the floor you choose and on what the concrete underneath is doing. Swiss Krono, one of the laminate makers we carry, requires a vapour barrier on concrete before the underlay goes down. For floating SPC vinyl, a published SPC installation guideline from Shaw recommends 6 mil poly film over concrete and sets moisture limits the slab has to meet first. Below, we follow that decision from moisture reading to finished floor, with specs and prices from our vinyl plank collection plus one laminate.
The short answer for a basement slab
- An attached pad is not sold as a vapour barrier. The listings for the three SPC planks below talk about comfort and sound (one of the three also mentions moisture protection), and none of them calls the pad a vapour barrier or vapour retarder.
- Swiss Krono laminate on concrete gets a barrier first. Swiss Krono's instructions require a vapour barrier on a mineral subfloor before the impact and sound underlay is laid.
- Floating SPC is decided by the slab test. Shaw's published SPC guideline recommends poly film for floating installs over concrete and sets maximum readings for two ASTM moisture tests.
- A reading over the limit stops the job. The same guideline calls for moisture mitigation on existing concrete when results exceed product limitations, so the barrier question comes second.
If you are planning the whole basement budget rather than one technical detail, our flooring installation cost guide for Toronto sets out how installation is priced by flooring type.
Why the slab reading comes before the barrier
Installation instructions name two ASTM methods for concrete, and each reports a different number. ASTM F2170 determines percent relative humidity inside a concrete floor slab using in situ probes. ASTM F1869, the calcium chloride test, measures the rate of moisture vapour emitted from bare concrete, expressed in pounds of moisture over a 1000 sq ft area during a 24-hour period.
The F2170 standard explains why: excessive moisture in a slab after a floor covering goes down "can cause floor covering system failures such as debonding, peaking and deterioration of finish flooring and coatings". It adds that manufacturers of such systems generally require moisture testing before installation on concrete.
A result is also a snapshot. In the standard's own words, moisture test results indicate the condition of the slab "only at the time of the test and in the specific locations tested", so an old reading says little about the room on install day. Our guide to moisture testing concrete subfloors covers how each test is set up and read.
What each floating floor needs over a basement slab
The four floors below are click-lock floating floors from our catalogue: three SPC vinyl planks with a factory-attached pad and one laminate that takes a separate underlay. Each is sold by the box, and the last column summarises the published slab guidance quoted further down.
| Product | Box price | Coverage per box | Material per sq ft | Total thickness | Wear layer or rating | Attached pad | Published slab guidance |
|---|---|---|---|---|---|---|---|
| Driftwood Mist SPC | $59.00 | 16.55 sq ft | $3.56 | 8mm | 20mil | EVA | Shaw generic SPC guideline (not Riche instructions): poly film recommended |
| Greige Oak SPC | $59.00 | 11.82 sq ft | $4.99 | 10mm | 20mil | EVA | As above (Shaw benchmark) |
| Blonde Sand Oak SPC | $62.93 | 23.64 sq ft | $2.66 | 6mm | 12mil | IXPE | As above (Shaw benchmark) |
| Swiss Krono Grey Oak laminate | $42.83 | 17.22 sq ft | $2.49 | 10mm | AC5 | None listed | Vapour barrier required before the underlay (Swiss Krono) |
Prices checked October 6, 2026. Box prices and coverage come from our current catalogue.
The thickness and wear-layer columns describe the plank, not the slab. Driftwood Mist's listing, for example, splits total thickness into the SPC core plus the attached EVA pad. Neither figure changes what the concrete underneath needs, which is why the last column comes from installation documents.
SPC vinyl with a factory-attached pad
Each of the three SPC planks arrives with its pad bonded at the factory: EVA on Driftwood Mist and Greige Oak, IXPE on Blonde Sand Oak. The Driftwood Mist listing presents its pad as a cushioned feel plus sound reduction, and Blonde Sand Oak's as comfort, thermal insulation and noise reduction. Greige Oak's listing adds moisture protection to cushion and sound absorption. None of the three describes its pad as a vapour barrier or retarder.
For the slab itself, a published benchmark helps. Shaw Industries' generic SPC installation guideline states that installation of 6 mil poly film underlayment "is recommended for floating method over concrete substrates". It treats the film as an extra layer rather than a cure: "For existing concrete substrates with high moisture, moisture mitigation will need to be completed if testing results exceed product limitations."
The same document puts numbers on those limits. Its testing line reads "maximum moisture level per ASTM 1869 CaCl is 8 lbs. and ASTM 2170 In-situ Relative Humidity 90% per 1000 sq.ft. in 24 hours", and it says not to install over concrete with a history of high moisture or hydrostatic conditions. Limits differ between manufacturers, so compare your reading with the instructions for the exact plank you buy; the Shaw figures show how one SPC guideline frames the decision.
Blonde Sand Oak is the lowest of the three SPC options at $2.66 per sq ft, with a 12mil wear layer and 23.64 sq ft per box, and its listing points to the slim 6mm profile for renovations where transition height to the next floor matters. Greige Oak sits at the other end at $4.99 per sq ft for a 10mm plank with a 20mil wear layer.
Whether SPC needs any extra underlayment at all is a separate question; our underlayment guide for SPC vinyl answers that one, so this page can stay on slab moisture.
Laminate over a slab
Swiss Krono, whose laminate we carry, is direct about concrete and screed: "A vapor barrier must be installed on a mineral sub-floor before the impact and room sound underlay is laid." Its vapour barrier page gives the reason: "If laminate flooring is permanently exposed to rising moisture, it swells and causes irreparable damage." That page also recommends a vapour barrier on mineral subfloors such as concrete and screed because these floors release moisture.
Basements get their own conditions in Swiss Krono's planning answers. The slab "must have been poured with a poly sheet underneath it" and must be more than 90 days old so it is adequately cured. If the floor has a drain, or a French drain along the inside of the perimeter, Swiss Krono does not recommend laminate. Its subfloor list sets cement screed at a maximum residual moisture of 2.0 CM%. Our 10mm Grey Oak laminate is AC5 rated and covers 17.22 sq ft per box at $42.83.
When the slab reading is over the limit
A reading above the ceiling in your product's instructions means the floor waits, whichever material you picked. Seasons matter as well: Swiss Krono warns that a subfloor which seems dry in summer might be completely different in winter, so test close to the install date.
Work through it in this order.
- Deal with the water first. Natural Resources Canada describes a simple check: tape a sheet of plastic to the slab and look underneath after a day or two. Condensation under the plastic indicates moisture moving up from the ground, and NRCan says any later renovation will require remediation to deal with the damp conditions, naming concrete sealing or waterproofing and subfloor membranes as examples.
- Price mitigation as its own item. Moisture mitigation and subfloor work are not part of a per-square-foot floor rate; we quote them after seeing the slab.
- Revisit the floor type. If Swiss Krono's basement conditions cannot be met, that laminate is off the list for the room. For vinyl, the limits come from the plank's own installation instructions.
- Check your building's own rules. In a condo or shared building, confirm what is permitted before you order.
Membranes, coatings and combination underlays are a decision for whoever handles the slab work, and they are not products we stock. Our guide to moisture barriers over concrete sets out where each type fits, and the complete guide to basement flooring in Toronto covers the whole room.
How we plan a basement install around slab moisture
To price a basement, we need the room sizes, the building type, the current floor and what you know about the slab: its age, whether a poly sheet sits under it, and any test result with the method named. Levelling, subfloor repair and moisture mitigation are quoted after we have seen the space, because the slab's condition decides how much preparation the job needs.
We supply and install click-lock SPC vinyl and laminate, and the slab question is settled before the floor is ordered. A reading close to a limit calls for a proper test, not a barrier bought on a guess.
Basement vapour barrier FAQ
Do I need poly under vinyl plank on a basement slab?
For floating SPC, the Shaw guideline treats 6 mil poly as recommended on concrete, but the film only helps once the slab is within its moisture limits. Check the instructions for your plank, since limits differ between manufacturers.
Is the attached pad on SPC enough on concrete?
Not as a vapour barrier. The three SPC listings above describe the pad as cushioning and sound control, and Greige Oak's, which mentions moisture protection, still stops short of calling it a vapour retarder. Treat the pad as part of the plank and settle the slab question separately.
Does a waterproof plank keep slab moisture out?
Waterproof describes the plank. Greige Oak's listing says its rigid core "will not swell, warp, or buckle from moisture exposure", and Blonde Sand Oak's says it "will not swell, warp, or buckle when exposed to water", but vapour rising through a slab is a separate matter, and ASTM F1869 notes that all concrete subfloors emit some amount of moisture in vapour form.
How do I know if my basement slab is dry enough for flooring?
Compare a measured result with the limit in your product's instructions. Manufacturers name ASTM F2170, which reports relative humidity as a percentage, and ASTM F1869, which reports pounds of vapour, so use the method your instructions accept. A plastic-sheet check shows moisture moving but gives no number to compare.
My slab has been dry for years. Do I still need a barrier?
For Swiss Krono laminate, yes: the manufacturer requires one on mineral subfloors, and notes that such a film is often advisable even for floors that look dry at first sight. For SPC, let a current test decide rather than the slab's history.
Get a basement flooring quote in Toronto and the GTA
Send us your room sizes, building type and what you know about the slab, and we will price the floor and its installation around it. You can request a basement flooring quote online.
Top Floorings Depot
3781 Victoria Park Avenue, Unit 1, Toronto, ON M1W 3K5
www.topfloorings.com
Call: 416-499-0117
Text: 416-770-8819