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ARMORTHANE PROTECTING YOUR WORLD

PROTECTING YOUR WORLD

ARMORTHANE PROTECTING YOUR WORLD

Polyurea Thickness:
How Many Mils
Each Job Needs

Typical dry film thickness for floors, roofs, bedliners, tanks and containment, the gallons-per-mil math behind every quote, and how inspectors check the number.
Spec help

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  • Substrate (steel, concrete, foam, wood)
  • Area in square feet
  • Service: traffic, chemicals, water, impact
  • Indoor, outdoor or immersed
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1,604
Sq ft one gallon covers at 1 mil (100% solids)
231 cubic inches per gallon
25.4 µm
One mil, or 0.001 inch
40 mils is about 1 mm
40–80
Mils on most roof, tank and waterproofing jobs
Typical spec range
125+
Mils for heavy wear, containment and impact
About 1/8 inch

Polyurea thickness is the single number that decides how long a lining lasts and what it costs. Spray it too thin and you get pinholes and early wear. Spray it too thick and you pay for material the job never needed.

Quick answer

Most spray polyurea goes on between 40 and 125 mils dry film thickness (about 1 to 3 mm). Floors sit at the thin end, around 10 to 25 mils for the full system. Roofs, tanks and waterproofing usually run 40 to 80 mils. Secondary containment, truck beds and wear liners run 80 to 250 mils. Because polyurea is 100% solids, one gallon covers 1,604 sq ft at 1 mil, so 60 mils covers about 27 sq ft per gallon before overspray.

What's in this guide
  1. 1Thickness by job
  2. 2Gallons and sets calculator
  3. 3Mils, mm and microns
  4. 4How thickness is checked
  5. 5Too thin, too thick
  6. 6Questions
Spec ranges

Polyurea thickness by application

The right mil target comes from what the coating has to resist. Foot traffic wears slowly and evenly. A loader bucket of gravel gouges. Standing water pushes into every pinhole. So the spec climbs as the abuse gets harder, and a written spec should always name a minimum, not just an average.

ApplicationTypical DFT (mils)What drives the number
Garage and shop floors10–25 (full system)Hot tires and dropped tools; usually a polyurea or polyaspartic base with flake and a clear topcoat
Roof over spray foam30–60UV, hail and ponding; an aliphatic topcoat keeps color
Metal or membrane roof restoration40–80Bridging seams and fasteners, thermal movement
Deck, plaza and foundation waterproofing40–80Crack bridging and hydrostatic pressure
Water and wastewater tank lining40–100Immersion, chemistry, pinhole-free film
Pickup truck bedliner60–125Impact, cargo abrasion, texture
Secondary containment and geotextile80–125Chemical hold time and puncture resistance
Dump bodies, hoppers and chutes125–250Sliding abrasion and repeated impact
Blast and ballistic mitigation125–500, engineeredSet by test data for the wall type, not by rule of thumb
Typical industry ranges. The product data sheet and the project spec always win. Tap a column heading to sort.
Read the spec carefullyA spec that says "60 mils" can mean a 60 mil average or a 60 mil minimum. Those are very different jobs. On a minimum spec the sprayer has to aim higher, often 70 to 80 mils average, so no single reading falls short. Price and material counts should follow whichever one the paperwork actually says.
Estimator

How many gallons at your thickness?

Pick a job to load a typical thickness, or type your own. The math uses the 1,604 sq ft per gallon per mil figure for a 100% solids material, then adds your loss allowance for overspray, texture and hose purge.

Material math

Polyurea gallons and sets

Theoretical coverage = 1,604 ÷ mils sq ft per gallon. A standard set is one 55 gallon drum of A side and one of B side, about 110 mixed gallons. Field loss of 10% to 25% is common; rough or vertical work runs higher.

—
Sq ft per gallon, theoretical
—
Gallons, no loss
—
Gallons to order
—
Kits

Pricing a job? Our polyurea coating cost guide turns gallons into dollars, and the polyurea equipment guide covers the rig that sprays them.

Units

Mils, millimeters and microns

A mil is a thousandth of an inch. It is not a millimeter, and mixing the two up is the most expensive typo in coatings: 60 mm would be more than two inches of polyurea. Data sheets from Europe and the Middle East often list microns or millimeters, while US specs almost always use mils.

Imperial

1 mil = 0.001 in

125 mils is 1/8 inch. 250 mils is 1/4 inch. Most US specs, gauges and quotes use mils.

Metric

1 mm ≈ 39.4 mils

A 2 mm lining is about 79 mils. A 3 mm wear liner is about 118 mils.

Micro

1 mil = 25.4 µm

Thin paints are often listed in microns. 500 µm is just under 20 mils.

Wet versus dry matters less with polyurea than with paint. A 100% solids product has no solvent to flash off, so the wet film you spray is very close to the dry film you keep. That is why a gallon of polyurea goes much further than a gallon of a 50% solids roof coating at the same finished thickness.

Quality control

How polyurea thickness is checked

Good applicators do not guess. They check thickness while spraying and again after cure, and they write the readings down. Which tool they use depends on what is underneath the coating.

While spraying

Wet film notch gauge

A notched comb pressed into the fresh film, covered by ASTM D4414. Polyurea gels in seconds, so this only works on the very first pass or on a test panel.

Over steel

Magnetic or eddy current gauge

Nondestructive and fast, per ASTM D7091. SSPC-PA 2 sets how many spot readings to take per area and how far a single reading may fall below spec.

Over concrete or foam

Ultrasonic gauge

Sends a pulse through the coating and times the echo, per ASTM D6132. The gauge must be set for polyurea's sound velocity to read true.

Destructive

Cut or core sample

A small cut or core read under magnification. Accurate on any substrate, but each test spot must be patched afterward.

  1. Spray a test panel first

    Check gun pressure, temperature and pass speed on scrap, then measure it. This sets how many passes reach the target.

  2. Count passes, not seconds

    Most sprayers lay roughly 20 to 40 mils per pass. Crosshatching the passes keeps the film even.

  3. Measure after cure

    Take readings in a grid, with extra checks at edges, corners and welds where film tends to run thin.

  4. Fix low spots the same day

    Inside the recoat window a low area can be built up without sanding. After that it needs prep and a primer.

Getting it wrong

Too thin and too thick

Too thin

What goes wrong

Pinholes over porous concrete, cracks telegraphing through, fast wear in tire paths and loading zones, and early failure in immersion. Low film is the most common cause of warranty claims.

Too thick

What goes wrong

Wasted material and labor, extra weight on roofs and vehicles, and more heat during cure on very heavy passes. On floors, a thick base can look wavy under a clear topcoat.

Thickness also cannot rescue bad prep. A 125 mil liner over a dirty, damp slab will peel the same way a 30 mil one does. Profile, cleanliness and moisture come first; see our guide to surface preparation for coatings.

  • Edges and corners: spray a stripe coat first so outside corners are not left thin.
  • Vertical walls: polyurea will not sag much, but heavy texture can hide low spots. Measure them.
  • Over spray foam: foam texture adds surface area. Plan more material than flat-plane math suggests.
  • Topcoats count: an aliphatic topcoat adds a few mils of UV protection; it is not a substitute for base film.
Spray it to spec

The right mils, measured and recorded.

A certified ArmorThane applicator can quote your job with a written thickness target, the product to hit it and the readings to prove it.

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FAQ

Polyurea thickness questions

How thick should polyurea be?

It depends on the job. Floors use about 10 to 25 mils for the full system, roofs and waterproofing 40 to 80 mils, truck beds 60 to 125 mils, and containment or wear liners 80 to 250 mils. Follow the product data sheet and the project spec.

How many square feet does a gallon of polyurea cover?

At 100% solids, one gallon covers 1,604 sq ft at 1 mil. Divide 1,604 by your target mils: about 27 sq ft at 60 mils, 20 sq ft at 80 mils and 16 sq ft at 100 mils, before overspray and texture loss.

How thick is a spray-in bedliner?

Most pickup bedliners are sprayed at roughly 60 to 125 mils, about 1/16 to 1/8 inch, with extra film on the floor and tailgate where cargo hits hardest. Dump bodies and work trucks often go heavier.

Is 40 mils the same as 1 mm?

Close. One millimeter is about 39.4 mils, so 40 mils is roughly 1.02 mm. Never confuse mils with millimeters on an order; the difference is a factor of about 39.

Can polyurea be sprayed in one thick coat?

Yes, by building several passes within minutes of each other. Polyurea gels in seconds, so a sprayer can reach 60 to 125 mils in one visit, which is a big reason it is chosen over multi-day coating systems.

How do you measure polyurea thickness on concrete?

Use an ultrasonic gauge set up for polyurea, as described in ASTM D6132, or take small cut samples and patch them. Magnetic gauges only work over steel.

AT
Written by the ArmorThane technical team. We have manufactured polyurea, polyurethane and polyaspartic coatings and plural component spray equipment in Springfield, Missouri since 1989. Ranges here are typical; always follow the product data sheet and the project specification.

Sources

  1. ASTM International, D4414 Standard Practice for Measurement of Wet Film Thickness by Notch Gages. astm.org/Standards/D4414.htm
  2. ASTM International, D6132 Nondestructive Measurement of Dry Film Thickness Using an Ultrasonic Coating Thickness Gage. astm.org/Standards/D6132.htm
  3. KTA-Tator, Measuring Dry Film Coating Thickness According to SSPC-PA 2. kta.com/dry-film-coating-thickness-sspc-pa-2
  4. DeFelsko, SSPC-PA 2 measurement mode overview. defelsko.com/coating-thickness/pa2

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