The Building Code Mistake That’s Failing Resinous Floor Inspections

A resinous floor can be installed correctly, cure on schedule and still fail inspection. Not because the installation was wrong. Because a local building code references ANSI A118.10, a standard written for tile waterproofing membranes, and applies it to a system it was never built to test.

This mismatch is showing up more often as more facilities move from tile to resinous systems in wet and demanding spaces. If you’re dealing with a failed inspection, or want to avoid one on an upcoming project, here’s what ANSI A118.10 actually covers and which standards should be part of the conversation instead.

What ANSI A118.10 Actually Covers

ANSI A118.10 is an ANSI/TCNA waterproof membrane standard, built for the flexible membranes used behind or under tile in wet spaces like showers. It references the TCNA (Tile Council of North America) handbook and is designed around a specific assembly: membrane, thin-set, tile.

A monolithic resinous floor isn’t that assembly. There’s no membrane, no thin-set, no tile transition — just a continuous system troweled or rolled directly onto the substrate.

The friction usually comes down to this:

• Many local codes cite ANSI A118.10 by default for any wet-space waterproofing requirement.
• The code itself doesn’t distinguish between a tile membrane system and a resinous coating.
• The inspector is following the code as written, not making an arbitrary call.

Fixing this requires a conversation about which standard applies, not just proof that the floor performs well.

Is Epoxy Flooring Waterproof?

Yes. A properly installed epoxy or resinous system forms a continuous, non-porous surface with no seams for water to travel through. That’s a different kind of epoxy floor waterproofing than a membrane provides, but it’s real.

Where this matters:

• In commercial restrooms, locker rooms and wash-down areas, a monolithic resinous floor eliminates the grout lines and transitions where water typically gets in.
• In food and beverage production environments, that same continuous surface is what allows daily wash-down without water migrating into the substrate.
• In industrial settings with chemical exposure, waterproofing is only part of the picture — chemical resistance and abrasion resistance matter just as much.

Epoxy flooring is waterproof by design. But “waterproof” isn’t a single pass/fail rating — it’s a performance characteristic that gets measured through specific tests, which is where ASTM D570 comes in.

ASTM D570 Water Absorption of Plastics: The Standard That Should Apply

ASTM D570 is the water absorption of plastics standard, and it measures how much moisture a material absorbs over a set immersion period. For a resinous floor, that’s the test that actually speaks to the water-resistance question codes are trying to address.

Unlike ANSI A118.10, ASTM D570 water absorption testing doesn’t assume a membrane assembly. It tests the material itself, which makes it a direct fit for a coating or resinous system rather than a tile-adjacent product.

If you’re specifying or inspecting a resinous floor and water intrusion is the concern, ASTM D570 data is the documentation to ask for. It answers the actual question a code official should be asking, instead of defaulting to a standard written for a different flooring type.

ASTM D4541 Pull-Off Adhesion Test: Why Bond Strength Matters More Than Membrane Classification

Where resinous floors are much more likely to run into trouble is adhesion, not water intrusion. That’s what the ASTM D4541 standard measures.

Also called the pull-off strength of coatings standard, ASTM D4541 measures the force required to pull a coating away from its substrate. It tells you how well the system is bonded, not whether it technically meets a membrane classification.

In the field, this is the number that predicts real failure:

• A coating with strong pull-off adhesion test results stays bonded through temperature swings, heavy traffic and chemical exposure.
• A coating with weak adhesion is the one that delaminates, regardless of how it performs on a water absorption test.
• Substrate prep, not the presence or absence of a waterproofing membrane, is usually the real variable behind a floor failure.

If an inspector’s underlying concern is long-term floor performance, an ASTM D4541 pull-off adhesion test for coatings addresses that more directly than ANSI A118.10 ever could.

What to Do When an Inspector Cites the Wrong Standard

A few steps can keep a misapplied A118.10 requirement from turning into a drawn-out delay:

• Ask the inspector whether the requirement traces back to the adopted building code, a specific local ordinance or department policy. Request it in writing.
• Have ASTM D570 and ASTM D4541 test data ready before the inspection, not after a failure.
• Loop in whoever specified the system. Architects and specifiers often have more standing to appeal a misapplied code reference than a contractor does alone.
• Document the appeal, even when it’s slow. Codes get revised over multi-year cycles, and a documented pattern helps make the case for change at the state or local level.

This isn’t a workaround. It’s making sure the right standard gets applied to the right flooring system, in writing, before it costs a project time or money.

Frequently Asked Questions

Is epoxy resin flooring waterproof?

Yes, a properly installed epoxy resin system creates a continuous, non-porous surface that resists water penetration. That performance is best measured with ASTM D570, not a tile membrane standard like ANSI A118.10.

What’s the difference between ASTM D570 and ANSI A118.10?

ASTM D570 tests water absorption of the material itself, including resinous coatings. ANSI A118.10 tests waterproofing membranes built for use behind or under tile, which is a different assembly entirely.

What does an ASTM D4541 pull-off adhesion test measure?

It measures the force required to pull a coating away from its substrate, which indicates bond strength. That’s often a better predictor of long-term floor performance than a membrane rating.

Can a building inspector require ANSI A118.10 for a resinous floor?

Some do, usually because local code references A118.10 as a default wet-space requirement without accounting for flooring type. Providing ASTM D570 and ASTM D4541 documentation, along with a written record of where the requirement came from, is the most direct way to address it.

Building codes take time to catch up with how flooring systems are actually built and tested. Until they do, the burden falls on contractors, specifiers and facility owners to have the right documentation on hand.

If you’re specifying or installing a system and want to know more about the standards that speak directly to how a resinous floor actually performs, we can help.