What is an epoxy mortar floor?

A floor made mostly of graded aggregate, such as sand or quartz, held together by epoxy resin. It is mixed on site, placed over a primed slab, leveled with screed rails or a screed box, and compacted and finished with a hand or power trowel. Because the aggregate carries the load, a mortar is placed at a depth no coating reaches, and it is built for the traffic that wears a coating through: steel wheels, forklifts, dragged pallets and dropped heavy parts. As placed, the surface is open, so it is sealed with a grout coat and then usually topcoated.

What is an epoxy slurry?

A pourable epoxy with a fine filler mixed in, placed thicker than a coating and spread so that it flows out. It often has aggregate broadcast into it for texture and grip, and it is finished with a topcoat. Manufacturers position it as a medium duty system: more body than a coating, less than a troweled mortar, and quicker to install than a mortar because it is spread rather than troweled.

Are coating, slurry and mortar different products?

Often not. Several manufacturers sell a single epoxy binder for all of them, and for the primer and grout coat as well. What separates them is how much filler or aggregate goes into the resin, and how it is placed: rolled or squeegeed as a coating, poured and spread as a slurry, or screeded and troweled as a mortar. That is worth knowing when comparing quotes, because two systems described in very different words can share a resin, and two with similar names can be built very differently.

Why does an epoxy mortar need a grout coat?

Because a troweled mortar is aggregate with just enough resin to bind it, and the surface is left open and porous. A floor like that holds liquid and dirt in its texture and is hard to clean. The grout coat is a resin coat worked into the surface to close those voids without changing the texture much. The topcoat then decides wear, chemical resistance and grip, as on any resin floor. Leaving the grout coat out, or skimping it, is how a mortar floor ends up looking fine and cleaning badly.

Can an epoxy mortar slope a floor to its drains?

Yes. Building falls to drains is one of the jobs mortars are made for, and some manufacturers sell a slope and fill mortar specifically for it. A coating cannot do this, because it follows the slab. A mortar is placed to screed rails set at the finished falls, so it can be thicker at the high side and thinner at the drain, then sealed and topcoated with the rest of the system.

Epoxy Mortar and Slurry Floor Systems

The same epoxy that coats a floor can be loaded with filler and poured as a slurry, or packed with graded aggregate and troweled as a mortar. What changes is not the chemistry. It is how much of the floor is resin, how it goes down, and whether the job is to cover the slab or to rebuild it.

Quick answer

An epoxy slurry is epoxy with a fine filler, poured thicker than a coating and usually topcoated. An epoxy mortar is graded aggregate bound by epoxy, screeded and troweled, then sealed with a grout coat and a topcoat. Both are often the same resin as a coating. A mortar rebuilds a slab rather than covering it, which is why it is chosen for steel wheels, heavy impact and sloping a floor to its drains. Where the floor sees hot water or steam, the choice is urethane cement instead.

One resin, three floors

It is easy to assume a mortar is a different, heavier product from a floor coating. Often it is not. Several manufacturers sell one epoxy binder as the primer, the coating, the slurry, the mortar and the grout coat. What turns it into one floor or another is how much filler or aggregate goes in and how it is placed.

Coating

Resin with little or no filler
Rolled, or squeegeed and back rolled
Follows the slab and protects its surface

Slurry

Resin with a fine filler mixed in
Poured and spread so it flows out, often with aggregate broadcast into it
Medium duty: more body than a coating, quicker to place than a mortar

Mortar

Mostly graded aggregate, with just enough resin to bind it
Screeded to rails and compacted with a hand or power trowel
Rebuilds the wearing surface, and can change its shape

The thick end of the coating family is covered on the high-build epoxy page. This page starts where the resin stops being the floor on its own and starts binding aggregate.

What a mortar does that a coating cannot

Takes the traffic that wears coatings through. Steel wheels, forklifts and pallet trucks running the same lanes, dragged loads and dropped heavy parts. In a mortar the aggregate carries that load, not a film of resin.
Rebuilds a damaged slab. A worn, pitted or spalled floor that a coating would only trace can be resurfaced to a new, sound wearing course.
Builds falls to drains. A coating follows the slab. A mortar is placed to screed rails set at the finished falls, thicker at the high side and thinner at the drain, and some manufacturers sell a slope and fill mortar for exactly this.

A small kit epoxy repair mortar for patching spalls, holes and joint edges before another system goes down is the same idea at a smaller scale. It is packaged and cured for fast patching rather than for placing a whole floor.

The layers of a troweled mortar

Prepared slab. Opened far more heavily than for a coating, because a mortar needs deep mechanical key. The guide to surface profiles explains why build and profile go together, and the data sheet names the profile.
Primer. The mortar is normally placed into the primer while it is still tacky. If the primer has lost its tack before the mortar reaches it, the data sheet will usually call for it to be primed again.
Mortar. Mixed, placed to the screed rails, leveled and compacted, then closed with the trowel.
Grout coat. A resin coat worked into the surface to fill the voids a troweled mortar leaves. It seals the texture without burying it.
Topcoat. Decides wear, chemical resistance, UV stability and grip, as on every resin floor.

A slurry is simpler: primer, the slurry itself, often a broadcast, then a topcoat. It normally needs no grout coat because it flows out to a closed surface rather than being left open by a trowel.

Why the grout coat matters

A mortar is aggregate with only enough resin to bind it, so the surface the trowel leaves is porous. On its own it holds liquid and dirt in the texture and is hard to clean. The grout coat closes those voids. Skip it, or skimp it, and the floor looks right on handover and cleans badly for the rest of its life. It is the step most worth checking on a quote for a mortar floor.

What it demands

A heavily opened slab. This is usually shot blasting or scarifying, not a light grind. The shot blast production calculator plans the time, and the profile chart pairs build with profile.
Keyed edges. A thick resin floor cannot feather out to nothing at a doorway, drain or wall. Every free edge is terminated into a saw cut key so it has something to hold. The urethane cement page describes the same detail, and it applies to an epoxy mortar just as much.
A dry enough slab. An epoxy mortar is still an epoxy, and the moisture limit on its data sheet applies the same way it does to a coating. The concrete moisture calculator reads a test result, and the moisture mitigation system is the build-up for a slab that fails it.
A crew and equipment for troweling. Aggregate is mixed into the resin in a forced action mortar mixer rather than with a paddle, the working time is limited, and the finish depends on how well the mortar was compacted and closed. It is slower and more skilled work than rolling a coating, and the quote should reflect that.

Epoxy mortar or urethane cement

The two families look alike: both come as slurries and troweled mortars, both are placed thick, and both are keyed at the edges. The deciding question is exposure.

Hot water, steam and fast temperature swings point to urethane cement. That is the problem it is built for, and the urethane cement page explains why a rigid epoxy is the wrong answer there.
Heavy loads, impact and abrasion without that thermal cycling are where an epoxy mortar is a common specification.

Many buildings end up with both, for example urethane cement in a wash down area and an epoxy mortar in the warehouse beside it, joined at a keyed edge.

Where it fits

Warehouses, distribution and loading docks, especially forklift lanes, ramps and dock edges.
Manufacturing and mechanical rooms, where heavy parts are dropped and dragged.
Worn or damaged slabs that need a new wearing surface rather than a coat over the old one.
Floors that must fall to drains, where the slab was not built with the falls.
Decorative troweled floors, where a colored quartz mortar is chosen for appearance as much as wear.

Where it is the wrong choice

Hot water, steam and thermal shock, for the reason above.
Light duty floors. A coating or a high-build system does the job for far less material and labor.
Live cracks and moving joints. A mortar is thick but still rigid, and a crack that is still moving comes back through it. The crack telegraphing page explains how to tell a moving crack from a dormant one.
Jobs with no time for a troweled install. Where the floor has to be back in use quickly, a slurry or a coating is faster to place.

What this page does not cover

Figures. Thicknesses, mix ratios, strengths and cure times vary by product and are not pinned on this site for these systems, so they are not printed here. The data sheet is the authority.
Urethane cement. Its own page covers the chemistry, thermal shock and moisture tolerance.
Coves. A troweled floor is often turned up the wall as an integral cove. The cove base linear footage guide covers measuring it.