Flooring over concrete
A slab is never fully dry. The floor on top either tolerates that or fails from underneath.
For the moisture that rises through the slab every day of its life.
Under the floor
For living on a floor that starts as cold, hard concrete.
On top
Test the slab, then choose.
Every manufacturer’s warranty over concrete is conditional on a moisture test, calcium chloride or in-situ probes, and the number a product accepts is printed in its installation guide. The materials below are ranked by how they tolerate a slab that breathes; the ones at the top have nothing in them that takes on water.
Water resistance counts double, then durability and comfort — a slab is hard and cold, so warmth underfoot separates otherwise equal floors — with a small preference for materials mainly sold into homes.
$7.00–$11.00 per sq ft installed
The best living-space floor for a slab: fully waterproof at the core, floating so it needs no adhesive to fight the moisture, and the foam composite core with an attached pad takes the edge off a cold, hard slab in a way SPC does not. Keep the thickness up — 8 mm or more with the pad — so it bridges small slab imperfections.
$6.00–$9.50 per sq ft installed
Waterproof, rigid enough to float over minor slab unevenness without telegraphing it, and it does not care what the slab does. The stone core is denser than WPC and so colder and harder underfoot, which is the only reason it is second. Over radiant heat in a slab it is the better of the two.
$7.50–$11.00 per sq ft installed
Glue-down vinyl tile is what commercial buildings put over slabs for a reason: it is thin, fully bonded, and moves with the concrete. The adhesive is the one thing the moisture test governs — high-moisture adhesives exist and cost more — so it is a professional installation over a tested slab, not a weekend job.
$13.50–$24.00 per sq ft installed
Tile and concrete are the same family of material, and porcelain over a slab is as permanent as a floor gets. The tile itself is impervious; the slab has to be flat within 1/8" over 10 feet or the tile lips, and a crack-isolation membrane over any slab that has already cracked stops the crack from finding its way through. Cold underfoot, which is exactly why slab homes so often pair it with radiant heat.
Same rule as the picks, run over everything that qualifies. Ties go to the cheaper material.
| Material | Moisture from below | Durability | Warmth & feel | Radiant-ready | Installed / sq ft |
|---|---|---|---|---|---|
| 1Luxury Vinyl Plank — WPC (Wood-Plastic Core) | $7.00–$11.00 | ||||
| 2Luxury Vinyl Plank — SPC (Rigid Core) | $6.00–$9.50 | ||||
| 3Luxury Vinyl Tile (LVT) | $7.50–$11.00 | ||||
| 4Porcelain Tile | $13.50–$24.00 | ||||
| 5Triexta (PTT) Carpet | $5.50–$8.00 | ||||
| 6Epoxy & Resinous Coatings | $7.00–$14.50 | ||||
| 7Polyester / PET Carpet | $4.00–$6.50 | ||||
| 8Sheet Vinyl | $4.50–$7.50 | ||||
| 9Luxury Vinyl Plank — Flexible (Glue-Down) | $5.00–$7.50 | ||||
| 10Wool Carpet | $11.50–$18.50 | ||||
| 11Olefin (Polypropylene) Carpet | $3.50–$5.50 | ||||
| 12Laminate | $5.50–$9.00 | ||||
| 13Polished Concrete | $6.00–$10.00 | ||||
| 14Ceramic Tile | $9.00–$15.00 | ||||
| 15Natural Stone | $21.00–$40.50 |
Solid planks are nailed into a wood subfloor. Over concrete that means a sleeper system or a glued-down plywood layer first, and even then most manufacturers exclude below-grade and many restrict on-grade. Engineered hardwood glued directly to a tested slab is the version of this floor that actually works, and it looks the same.
A slab that feels dry to the hand can still emit several pounds of vapor a day. Every flooring failure over concrete — cupped engineered wood, bubbled adhesive, a musty smell under vinyl — traces back to a slab nobody tested. The test costs less than the first repair.
Standard laminate has a wood-fiber core, and vapor from below swells it from underneath without ever showing on the surface until the joints peak. It is allowed over a slab only with a 6-mil poly barrier or a combined underlayment, and the sealed-core tier is the one to buy if the room ever gets wet.
Broadloom over a slab needs a moisture-resistant pad, or the pad becomes the thing that holds moisture and smells. Below grade it should be a synthetic pad specifically; above grade, at least not a rebond pad that wicks.
Slabs are poured to a tolerance that is fine for a house and wrong for a floor. Rigid planks and tile both need a slab flat to within 3/16" over 10 feet (1/8" for large-format tile), and grinding high spots or pouring a self-leveler is where the labor quote goes. A quote that has no line for floor prep over a slab has not looked at the slab.
Engineered hardwood, yes — glued directly to a slab that has passed a moisture test, or floated over a vapor barrier for products that allow it. Solid hardwood needs a wood subfloor between it and the concrete, which means either a sleeper-and-plywood build-up that raises the floor by more than an inch or a glued plywood layer, and most manufacturers still restrict it on or below grade.
For anything with a wood core — laminate, engineered hardwood, bamboo — yes, as a minimum. For vinyl plank and tile the material itself is the barrier, but the adhesive under glue-down products still has a moisture limit. The installation guide for the specific product lists what it wants, and the warranty is conditional on it.
Carpet over a good synthetic pad, then cork, then WPC vinyl plank with an attached pad. If the room is going to be tile or SPC, the warmth comes from an electric radiant mat under it rather than from the floor itself.
Two standard tests. Calcium chloride (ASTM F1869) measures vapor coming off the surface in pounds per 1,000 sq ft per 24 hours; most products accept 3 to 5. In-situ relative humidity probes (ASTM F2170) drill into the slab and read the concrete itself, which is more reliable and is what most manufacturers now specify; the common limits are 75 to 85 percent RH. A flooring installer can run either for a small fee, and the result should be in writing.
Yes, and it is the most common floor over a slab for that reason. Floating rigid-core plank goes down over a clean, flat slab with no adhesive, and the plank is waterproof so vapor does not harm it. A thin underlayment is usually included on the plank; a separate vapor barrier is optional for the plank and worth having for the smell.
They are the same material with a different exposure. A slab-on-grade sits at grade, so it breathes vapor but does not take standing water or the cold of a below-grade room. A basement slab does both. Everything on this page applies to a basement, and the basement page adds the flooding and temperature questions on top.
Each of these ranks every material against one problem, the same way this page does.