POLYZEN Insights

PU Concrete Flooring — When Do You Actually Need It, and at What Thickness?

PU concrete is the answer when a floor faces heat, water and aggressive chemistry together — hot washdown, steam cleaning, cold rooms, organic acids. But “PU flooring” covers everything from a thin coating to a 9 mm trowelled screed, and the thickness is not a finish choice. It decides what temperature and impact the floor can actually survive.

More money is wasted on PU flooring through the wrong thickness than through the wrong product. A specification that says “PU flooring” and nothing else can legitimately be quoted as a 1 mm coating or a 9 mm screed — systems that differ in cost by several times and in capability by far more. This article explains the family, and how the thickness is decided.

What Is PU Concrete, and How Is It Different from a PU Coating?

Cementitious polyurethane — also called PU concrete, urethane cement, PU screed or polyurethane mortar — is polyurethane resin combined with cement and graded aggregate. It is a screed: laid at depth with a trowel, not rolled on as a film.

A PU coating is something else entirely: a thin resin film applied over concrete, with no cement or aggregate body. It gives colour, cleanability and light chemical protection. It does not give thermal shock resistance, because it has no depth in which to absorb differential movement.

The reason PU concrete tolerates heat is physical, not chemical. Because it contains cement, it expands and contracts at a rate close to the concrete slab beneath it. When hot water hits an epoxy or a thin coating, the film moves and the slab does not, and the bond breaks. A cement-based screed moves with the slab — which is why it survives what defeats a coating. The mechanism is the same one described in why epoxy floors peel, bubble or delaminate.

The PU Family — Coating, Self-Levelling and Screed

Four broad build-ups, and they are not interchangeable.

These are the ranges the resin flooring industry works to. The build-up POLYZEN specifies for a given area, and its exact performance values, are confirmed per TDS after a site survey.

Why Does Thickness Decide Almost Everything?

Because a screed resists thermal shock by having body. Heat does not stop at the surface — it travels down. A thicker screed spreads that movement over more material and keeps the stress at the bond line low enough that the floor holds.

Three properties scale with depth:

• Temperature range. Across the industry, thin build-ups are specified for stable or moderate conditions, while the widest temperature ranges — including sub-zero cold rooms and steam cleaning — are quoted at the heavier thicknesses. It is common for manufacturers to state that a screed is stable to steam cleaning at 9 mm, and not to make that claim at lesser depths.
• Impact and load. A 9 mm screed absorbs a dropped tool or a steel-wheeled trolley. A 1 mm coating transmits the impact straight to the concrete and chips.
• Service life. Depth is wear reserve. A textured screed can be worn for years before performance is affected; a thin film cannot.

The practical consequence for buyers: if a quotation promises steam cleaning and thermal shock resistance but does not state a thickness, it has not promised anything measurable. Ask for the thickness in millimetres, per zone.

How Thick Does Your Floor Need to Be?

Thickness follows the conditions, not the budget. As a working guide:

Two conditions almost always push a specification upward: steam and sub-zero. If either is present in the area, a thin build-up is the wrong answer regardless of what else is true.

POLYZEN installs the full range — from PU coating through to 9 mm screed — and specifies the build-up per zone after survey, with values confirmed per TDS.

When Is Epoxy the Better Answer?

Often. PU concrete is not a superior product; it is a different one, and over-specifying it wastes money.

Epoxy is usually the right choice where the floor is dry and thermally stable: packing halls, dry stores, assembly areas, warehouses, showrooms, laboratories. Epoxy gives a harder, glossier, more easily detailed finish, a wider colour and decorative range, and generally costs less to install for the same area.

The switch to PU concrete is triggered by conditions, not by importance:

• Hot water, steam or hot product on the floor
• Rapid temperature swings, including cold rooms
• Continuous wet working with organic acids or caustic sanitation
• Heavy impact combined with wet

Where none of those apply, a well-built epoxy system such as heavy-duty epoxy flooring will serve longer and cost less.

What Gets Missed During Installation?

A correct product at the correct thickness still fails if the detailing is skipped. Three things separate a screed that lasts from one that lifts.

Anchorage grooves. This is the detail most buyers have never heard of and most failures trace back to. Wherever a screed terminates — at edges, doorways, drains, bay joints, upstands and at intervals across large floors — a groove is cut into the concrete and the screed is keyed into it. Industry practice is to cut the groove roughly twice the width and depth of the floor thickness. Without it, the screed has only a flat bond at its most vulnerable line, and thermal movement peels it back from the edge inward.

Surface preparation. Mechanical only — grinding or vacuum-shrouded shot blasting. Acid etching and percussive scabbling are not appropriate: one leaves salts and an unreliable profile, the other bruises the concrete and creates a weak layer just below the surface.

Coving and drain termination. In wet areas the screed should be carried up into a coved junction and terminated into the drain body, not butted against it. Drains and doorways are the wettest, hottest and most abused lines in any plant, which is why they are where failure begins.

How Do You Write a PU Specification That Cannot Be Misread?

Six lines are enough, and each of them closes a gap a vague specification leaves open:

1. Zone — name each area separately. One building often needs three different build-ups.
2. Thickness in millimetres — per zone. This single line prevents most disputes.
3. Temperature range — the highest and lowest the floor will actually see, including cleaning.
4. Cleaning regime — chemicals, concentration, temperature and frequency. Ask the sanitation team, not only the engineers.
5. Detailing — coving height, drain terminations, anchorage grooves, falls to drain.
6. Handover documentation — thickness verification and a written system warranty.

A quotation that answers all six is comparable with another quotation. One that says “PU flooring, per sq ft” is not.

The POLYZEN ZENPU Systems

POLYZEN formulates and applies the full ZENPU range, so the survey, the specification and the installation answer to the same party.

• ZENPU Coat (ZP-100) — UV-stable PU coating for dry, thermally stable and exposed areas.
• ZENPU Level (ZP-200) — flexible PU self-levelling build where a smooth, seamless finish is required. Delivered as PU Self-Levelling Flooring.
• ZENPU Cretescreed (ZP-300) — trowel-applied PU cement screed, the heavy-duty build for steam, thermal shock and impact. Delivered as PU Concrete Flooring, PU Screed Flooring and Food-Grade PU Flooring.
• ZENPU Hybrid (ZP-400) — EPU build for sports and comfort surfaces.

Sector context: Food & Beverage · Pharmaceutical & Life Sciences · all PU flooring systems. For a zone-by-zone view of a food plant, see which flooring is best for food and beverage processing plants.

Thickness, temperature range and chemical resistance are confirmed per TDS for each system and zone.

Which Standards Define PU Concrete Performance?

Four references carry most of the weight in a cementitious polyurethane specification. ASTM C884 assesses thermal compatibility between concrete and a resin overlay — a pass or fail on whether the system survives thermal cycling over a slab, and the single most relevant test where hot washdown or freezing is involved. ASTM C531 measures shrinkage during cure, while ASTM D696 gives the coefficient of thermal expansion that decides how much the surfacing moves relative to the concrete. ASTM C579 covers compressive strength of the hardened surfacing, and ASTM C267 its chemical resistance. Where the floor is walked on wet, slip resistance is measured as DCOF per ANSI A326.3.

The practical consequence of those numbers is thickness. Thinner cementitious PU builds are not rated for severe thermal shock or steam cleaning; heavier builds are specified where that duty is real, which is why a chill room and a blast freezer are not given the same floor. Actual values for any system are stated per TDS. Where the environment runs below freezing, the failure mechanism is set out in why standard epoxy fails below freezing.

Frequently Asked Questions

What is PU concrete flooring?

PU concrete, also called urethane cement, PU screed or polyurethane mortar, combines polyurethane resin with cement and graded aggregate. It is trowel-applied at screed thickness rather than rolled on as a film, and because it contains cement it expands and contracts at a rate close to the concrete slab beneath it.

How thick should PU flooring be?

Thickness follows the conditions. PU coatings are around 1 mm and suit dry, thermally stable areas. Self-levelling builds run around 2 to 4 mm. PU screeds run around 3 to 6 mm for self-smoothing builds and 6 to 9 mm for trowel-applied builds. Steam cleaning and sub-zero conditions normally require the heaviest build.

Can PU flooring withstand steam cleaning?

At sufficient thickness, yes. Across the resin flooring industry, stability to steam cleaning is normally quoted at the heaviest screed build, commonly 9 mm, and is not claimed at thin build-ups. A quotation that promises steam resistance without stating a thickness has not stated a specification.

What is the difference between PU coating and PU screed?

A PU coating is a thin resin film that provides colour, cleanability and light chemical protection but has no depth to absorb thermal movement. A PU screed contains cement and aggregate and is laid at depth, which is what gives it thermal shock resistance, impact strength and wear reserve.

Is PU concrete always better than epoxy?

No. Epoxy is usually the better choice in dry, thermally stable areas such as packing halls, dry stores, warehouses and laboratories, where it offers a harder, glossier finish and lower installed cost. PU concrete is specified when heat, steam, rapid temperature swings or continuous wet working are present.

What are anchorage grooves in PU screed installation?

Anchorage grooves are cuts made into the concrete wherever the screed terminates, such as at edges, doorways, drains, bay joints and upstands, so the screed is keyed into the slab rather than only bonded flat. Industry practice cuts them roughly twice the width and depth of the floor thickness. Omitting them is a common cause of edge failure.

How much does the thickness change the cost?

A great deal, which is exactly why a specification that says only PU flooring is dangerous. The same words can be quoted as a 1 mm coating or a 9 mm screed, and those are not close in price or in capability. CostMyFloor lets you see the difference for your own area before you compare quotations.