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Epoxy Primer Coverage Over a Profiled Slab Calculator

Derate an epoxy primer's data sheet coverage for the concrete surface profile it goes onto, because that rate was measured on a smooth slab.

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  • Every formula cited
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Imperial · sales tax
The net area taking primer, plinths and upstands included.

Measure what gets coated rather than the room. Plinths, upstands and the coved edge at the wall are all primed surface and all easy to leave out; equipment bases that stay in place come off it. On a floor with heavy detailing the difference runs to several per cent, which is more than the rounding on a kit.

The rate on the data sheet, which is measured on a smooth slab.

Published coverage is a laboratory figure taken on a steel-trowelled or otherwise smooth substrate. It is not wrong; it simply describes a surface nobody lays epoxy on, because every epoxy floor starts with the slab being opened up. That gap is what this page exists to close.

How rough the prepared slab is, on the scale a specification names.

ICRI publishes CSP 1 to 10 as moulded replicas you hold against the floor, and a specification names one of them. Each step up adds true surface area and open pore for the primer to disappear into. The factors behind these options are rules of thumb rather than published coefficients, which is why the first bay is the real measurement.

An addition for a dry, old or unusually porous slab, over and above the profile.

Profile and porosity are two different things: a freshly ground slab of dense, well-cured concrete has an open profile and little absorption, while an old, dry, lean slab drinks primer through its body regardless of how it was prepared. Leave this at zero unless the slab is visibly thirsty — a splash of water vanishing in seconds is the field test — and step it up rather than guessing high.

The mixed volume of one kit as your supplier sells it.

Enter the volume of resin and hardener TOGETHER, because that is what goes on the floor. Two-part primers cannot be split, so a kit is the real ordering unit and the rounding up at the end is not waste you can avoid — it is the smallest amount you are able to buy.

Primer needed

4.55 gal

Medium confidence

The arithmetic is exact; the profile factor behind it is a rule of thumb rather than a published coefficient, because ICRI defines the surface profiles and attaches no coverage figure to any of them. Prime one bay, measure what it actually took, and order the rest on that.

Kits to order
2 kits
Effective coverage on this profile
142.86 ft²/gal
What the data sheet rate alone would have ordered
3.25 gal
Extra the profile and absorbency account for
1.3 gal
Then change the inputs to see how far the answer moves.

Show calculation logic

How this was calculated

Formula source(s)

  • ICRI Guideline 310.2R, Selecting and Specifying Concrete Surface Preparation — defines concrete surface profiles CSP 1 to 10 as physical replicas of increasing roughness, and is how a specification names the profile this calculation asks for
  • Effective coverage = published rate ÷ profile factor; volume = area ÷ effective rate × (1 + absorbency allowance). The profile factors offered here are rules of thumb, NOT published coefficients — ICRI defines the profiles and does not attach a coverage number to any of them

Inputs used

Floor Area Being Primed
650 sq ft
Published Coverage Rate for the Primer
200 ft²/gal
Concrete Surface Profile (ICRI CSP)
CSP 4–5 — an ordinary grind or medium shotblast
Extra for a Thirsty Slab (%)
0
Kit Size Supplied
2.75 gal

Intermediate steps

Kits to order
2 kits
Effective coverage on this profile
142.86 ft²/gal
What the data sheet rate alone would have ordered
3.25 gal
Extra the profile and absorbency account for
1.3 gal
Safety / waste buffer appliedProfile and absorbency allowance (+40%)
Final result4.55 gal

Confidence note: The arithmetic is exact; the profile factor behind it is a rule of thumb rather than a published coefficient, because ICRI defines the surface profiles and attaches no coverage figure to any of them. Prime one bay, measure what it actually took, and order the rest on that.

What this calculation does not cover

  • The profile factors are rules of thumb and the page says so in its own sources. They are the right shape — a rougher profile has more true surface and more open pore to fill — but the honest way to use them is to prime one bay, measure what it actually took, and re-order on that.
  • It does not tell you which profile your specification needs. That follows from the coating system and its thickness, and it is in the manufacturer's literature.
  • It assumes one coat. A slab that drinks the first coat to a matt finish needs a second, and that is a decision made on the floor rather than in advance.
  • It says nothing about moisture. A primer ordered correctly and applied over a slab that is still giving up water fails anyway, and no coverage figure is a substitute for a moisture test.

Estimated cost — your price

This site holds no price list for this material — local prices vary too much to publish honestly. Enter your supplier's price and the result is costed with it.

Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.

Sources checked 2026-09-20 · v1.0.0

Regulatory standards & verification citations2
  1. ICRI Guideline 310.2R, Selecting and Specifying Concrete Surface Preparation — defines concrete surface profiles CSP 1 to 10 as physical replicas of increasing roughness, and is how a specification names the profile this calculation asks for
  2. Effective coverage = published rate ÷ profile factor; volume = area ÷ effective rate × (1 + absorbency allowance). The profile factors offered here are rules of thumb, NOT published coefficients — ICRI defines the profiles and does not attach a coverage number to any of them
Cite this page

Your workspace

Most jobs need more than one number. Add the calculators you need next and they open right here, underneath this one — your figures stay on screen and nothing is lost to a page change.

Protection this work requires

  • Stop and check first. Paint under later coats in older housing can be lead-based, and sanding or heat-stripping it produces lead dust that is especially harmful to children and to anyone pregnant. Test before you disturb it — this is a job for a tested, controlled method, not a better mask.

Tools and safety for this job

To roll and cut in two coats and prepare a surface for paint. Generic types, no brands, no prices.

  • Joint-compound dust is very fine and travels: a P1/FFP1 mask is the minimum, and a damp-sponge finish avoids most of it.
  • A dust mask does nothing about solvent vapour: ventilate through, and use an organic-vapour (A1) cartridge respirator in an enclosed room.
  • Most fatal falls on small jobs are from under three metres: use a tower or a ladder tied at the top, and never work off the top two rungs.
Show the 11 tools this job needs

Essential

  • Brushes

  • Dust sheets and masking

  • Filling knife

  • Roller frame, sleeves and tray

  • Scraper

Recommended

  • Caulking gun

  • Extension pole

  • Pole sander

  • Random orbital sander

  • Step ladder

Optional

  • Dust extractor or vacuum with a fine filter

Also needed as materials: abrasive discs, caulk and sealant cartridges, masking tape, plastic sheeting, roller sleeves, sanding screens or paper.

what each painting tool is for, and the spec that decides which to buy where one does.

Now that you have the number

These guides cover the work this quantity is for.

The data behind it: Production rates by operation

How to calculate epoxy primer coverage over a profiled slab in 6 steps

  1. Floor Area Being PrimedThe net area taking primer, plinths and upstands included.
  2. Published Coverage Rate for the PrimerThe rate on the data sheet, which is measured on a smooth slab.
  3. Concrete Surface Profile (ICRI CSP)How rough the prepared slab is, on the scale a specification names.
  4. Extra for a Thirsty Slab (%)An addition for a dry, old or unusually porous slab, over and above the profile.
  5. Kit Size SuppliedThe mixed volume of one kit as your supplier sells it.
  6. Primer neededThe tool computes the primer needed from those figures and shows the formula, its sources, and a confidence rating alongside it.

Primer needed by floor area being primed

Page defaults, not your figures above.

Floor Area Being PrimedPrimer needed (gal)
400 sq ft2.75
600 sq ft4.12
800 sq ft5.5
1,000 sq ft6.87
1,200 sq ft8.25

Frequently asked questions

Why not just publish a coverage rate for epoxy primer?
Because the rate that matters is a product's, and the thing this page changes is not the product — it is the surface. Two floors primed with the identical material take very different quantities depending on whether the slab was acid-etched or scabbled. Publishing a single figure would mean publishing one that is wrong for most floors, and the data sheet already gives you the right starting number.
Where do the profile factors come from, honestly?
They are rules of thumb, and the sources on this page say so rather than dressing them up. ICRI defines CSP 1 to 10 as replicas and attaches no coverage coefficient to any of them, because the relationship depends on the aggregate, the cut and the primer's viscosity. The factors here follow the shape of the effect — roughly a tenth more at a light etch, about double at a scabbled face — and the first bay you prime is worth more than any of them.
The number came out much higher than the data sheet. Is that right?
On a properly prepared slab, usually yes, and that is the whole point of the page. A 40 per cent uplift on an ordinary grind is not a safety margin; it is the primer filling a profile that the laboratory sample did not have. The failure this prevents is the common one — ordering off the tin, running out two-thirds of the way across, and having to stop with a wet edge in the middle of a floor.
Does the same derating apply to the build coat on top?
No, and applying it there would over-order badly. Primer disappears into the profile; the build coat goes on over a primed, sealed surface and covers at close to its published rate. That is precisely what the primer bought. Use the coverage page for the build coat and this one only for the coat that meets bare concrete.
Preliminary estimate, not certified engineering. This tool produces an indicative quantity calculation for planning purposes only — it is not a certified structural analysis, a guaranteed material takeoff, or a substitute for building department approval. Always verify measurements on-site and have a licensed contractor or structural engineer review any load-bearing, code-sensitive, or safety-critical work before purchasing materials or starting construction. Spotted an arithmetic or standards error? Report it to contact@craftquantities.com with your inputs — a confirmed fix gets a permanent check of its own, so the same mistake cannot come back.