What is the difference between microcement and macrocement?

Both are cement-based coatings made from cement, fine sand, polymers and pigment. Microcement is thin — applied at around a couple of millimetres — so it follows the shape of whatever is beneath it. Macrocement is the thicker version, laid up to roughly a centimetre, which lets it do more levelling. They share the same underlying property: cement is rigid, so both are vulnerable to cracking if the substrate moves or the preparation is rushed.

Does microcement crack?

It can, and when it does the cause is usually the floor rather than the product. Three things drive it: a substrate that moves (a springy timber floor, or a screed that had not finished drying), rushed preparation, and structural movement joints that were covered over instead of respected. On a solid, stable slab with proper preparation, cement-based finishes perform very well. On a floor that flexes, a rigid finish is a crack waiting for a date.

Is resin better than microcement for a bathroom?

In a wet area resin has a genuine technical advantage, because it is waterproof as a system — the finish and the waterproofing are the same layer. A cement-based finish is not a tanking system, so in a shower or wet room it relies on a separate waterproof layer beneath it: perfectly workable, but one more hidden element that has to be right. Outside the wet zone, on a stable slab, that advantage largely disappears and the cheaper family is a sound choice.

Which seamless floor finish is waterproof?

The resin systems — epoxy-based products built up in coats over a reinforcing mesh — are waterproof in themselves and can be used on floors, walls and inside showers and wet rooms. Cement-based microcement and macrocement are water-resistant surfaces rather than waterproofing systems, so in a wet area they need a separate tanking layer underneath. Whichever you are quoted, ask the supplier directly whether it is waterproof as a system, and get the answer in writing.

Is the cheaper cement-based option ever the right choice?

Frequently. On a solid, stable concrete slab, in a dry area, with proper preparation and enough drying time, cement-based finishes look superb, cost less, and have a mineral depth that many people prefer to the uniformity of resin. Choosing it there is not a compromise — it is the right answer, and the difference is better spent elsewhere in the project. The mistake is not choosing cement-based; it is choosing anything on price without first testing whether the floor is stable enough to carry a rigid finish.

How do I decide if both options are technically possible?

Weigh four things only you can weigh. Your budget — whether the difference buys more here than elsewhere in the project. Your risk — what a redo in two years would genuinely cost you in money and disruption. The look — compare large samples of both in your own light, because plenty of people prefer the cheaper finish. And who you trust to apply it, since both families live or die on preparation you will never see.

Renovation

Microcement, Macrocement or Resin: They Look Identical, and They Are Not the Same

Two families, not three products. Cement-based is rigid and cheaper; resin flexes and is waterproof. Test the floor for span ÷ 360 deflection before you choose.

By Vladimir Castravet·17 August 2026

There are two families, not three products, and the one number that decides between them is span ÷ 360 — the most a floor may deflect before a rigid finish will crack on it. Microcement and macrocement are cement-based: thin, rigid coatings that cost less and perform excellently over a solid base. Resin systems are the other family: more expensive, built up in coats over a reinforcing mesh, so they flex rather than crack and are waterproof in themselves. The estimator will price either against a real scope, and our renovation work and bespoke joinery pages show where these finishes usually land.

That seamless, minimal, no-tiles look everyone wants right now photographs identically whichever product you use. Underneath they are made of completely different things — and that difference decides whether it still looks beautiful in a year.

The two families, honestly

Cement-based — microcement and macrocement. Microcement is a thin cement coating — cement, fine sand, polymers and pigment — applied at only a couple of millimetres. Macrocement is its thicker cousin, laid up to around a centimetre, which lets it take more of a levelling role. Both look stunning and both cost less. The catch is in the material: cement is naturally rigid. It does not want to move. So if the floor underneath it moves — or if the preparation was rushed — it is more likely to hairline-crack.

Resin. Epoxy-based systems, built up in coats over a reinforcing mesh. That construction is the whole point: the mesh and the resin let the finish flex with the floor rather than fracture, it can be matched to a RAL reference with real consistency, and it is waterproof in itself — so it works on floors, walls and inside showers.

You should know we have a foot in one camp: we supply and apply a resin system, so we make money if you choose that family. Weigh what follows with that in mind. Everything in this lesson is checkable against any manufacturer’s data sheet, and I have tried to be as hard on resin as on cement — because a recommendation you cannot verify is worth nothing.

What you are actually choosing between is not a cheap version and an expensive version of the same thing. It is a rigid finish and a flexible one. Almost everything else follows from that single property — including the reasons to pick the cement-based one.

The standards that apply either way

Every figure below has been read out of the Approved Documents or the governing British Standard, with the clause it came from.

| What | The requirement | Source | |---|---|---| | Substrate stiffness | A substrate receiving a rigid finish should deflect no more than span ÷ 360 under imposed load, and span ÷ 720 where natural stone is used. | BS 5385-3 | | Movement joints | Required at perimeters and over structural joints, with intermediate joints on internal floors at the spacings the code gives. A seamless finish must respect the joints in the structure beneath it. | BS 5385-3 | | Screed drying | Allow one day per millimetre for the first 50mm, then roughly two days per millimetre between 50mm and 75mm — confirmed with a surface hygrometer, not the calendar. | BS 8204-1 / BS 8203 | | Moisture from the ground | A floor next to the ground must resist the passage of moisture to the inside. An existing solid floor with no damp-proof membrane will drive moisture into any finish laid on it. | Requirement C2 / AD C | | Waterproofing in wet areas | Where the finish forms part of a shower or wet room, the waterproof layer must be continuous. A cement-based finish is not itself a tanking system; a waterproof resin system is. | Requirement C2 | | Workmanship | Building work must be carried out with adequate and proper materials and in a workmanlike manner — preparation and coat sequence are part of that, not optional extras. | Building Regulations 2010, reg. 7 |

Approved Documents are statutory guidance to the Building Regulations 2010 for England. Compliance is judged against the Requirements in Schedule 1; the Approved Document shows one way of meeting them. Your building control body has the final word on your specific building.

Why the cement-based ones crack — and it is usually not the product

People blame microcement when it cracks. In my experience the product is rarely the culprit on its own. Three things cause it, and all three are decided before a trowel is lifted.

The substrate moves. A timber floor that deflects, a joist span that flexes, a screed that was covered too early and is still shrinking. A rigid coating cannot follow that movement, so it fractures at the point of greatest strain.

The preparation is rushed. Cement-based systems are unforgiving about primer, about mesh or scrim where it is specified, and about the moisture state of the base. Skip a coat, work over a base that has not dried, and the finish carries that defect for its whole life.

Movement joints get ignored. A seamless finish still needs to respect the movement joints in the structure beneath it. Carrying a rigid finish straight over one tells the crack exactly where to appear.

So the honest comparison is not “microcement cracks, resin does not”. It is that a rigid finish demands a stable substrate and perfect preparation, and a flexible finish forgives more. If your floor is a solid, stable slab and the preparation is done properly, cement-based is an excellent, cost-effective choice. If there is doubt about movement — and in an old London house there usually is — the flexible system is buying you insurance.

What resin costs you — the case against the expensive one

Fair is fair. If I am going to be blunt about where cement-based finishes fail, I should be equally blunt about what you give up by choosing resin.

Money. More coats, more material, more labour days. On a large floor that gap is not trivial, and it is money that could go into the joinery, the glazing, or simply into not borrowing.
Time. Five coats with cure time between them is a longer programme than two. If the room is on the critical path, that matters.
Repairability. Both families are hard to patch invisibly, but resin is a chemistry that has to be matched. A localised repair years later may not blend as well as you would like.
The look. This is the one people underrate. Cement-based finishes have a mineral depth and subtle variation that many people prefer — it reads as material rather than coating. Resin is more uniform and more consistent. To some eyes that is cleaner, to others slightly plastic. Neither view is wrong.
Overkill is real. On a dry, stable ground-floor slab, in a room with no water, resin is buying you insurance against a risk you do not have. Paying for flexibility a concrete slab will never need is not prudence, it is waste.

Where cement-based is genuinely the better buy: a sound concrete slab that does not move, a dry area rather than a shower, a properly programmed job with time for preparation and drying, a client who wants the mineral look, and a budget where the difference buys something else you value more. In that situation microcement or macrocement is not the compromise. It is the right answer, and I would tell you so.

A real job in Peckham

Let me give you a real one rather than a principle. On a job in Peckham, the client chose the cheaper, cement-based option. Reasonable decision on the day — same look in the photographs, meaningfully less money.

Within months it cracked. Not one hairline in a corner: several places across the floor. And here is where the maths turns. They do not like it, so it has to be redone. Redoing it does not mean applying more product on top; it means taking the failed finish off, correcting whatever the substrate was doing, and then paying for a finish a second time. Plus the room out of use again, and the disruption again.

Now — the lesson people take from that story is usually the wrong one. It is not “cement-based cracks, so buy resin”. The failure was that nobody tested the floor. Had someone checked the deflection first, one of two things would have happened: the floor would have passed, and the same cheap finish would still be perfect today; or it would have failed, and the client would have had a real choice — stiffen the floor, or spend the difference on a flexible system — made with the facts in front of them.

A finish decision made on price alone is a gamble. A finish decision made on a measured substrate is a choice. The client in Peckham did not get a bad product; they got a decision taken without the one piece of information that mattered.

How to choose — the four questions that decide it

Is the substrate solid and stable, or timber and springy? A concrete slab that does not move puts cement-based genuinely on the table. Suspended timber, a long joist span, anything that flexes underfoot — go flexible, or fix the floor first.
Does it need to be waterproof? A shower, a wet room, a bathroom floor. Resin is waterproof as a system. A cement-based finish in a wet area relies on a separate waterproof layer beneath it, which is one more hidden thing to get right.
How much colour consistency do you need? Over a large open-plan floor, or where floor and wall must read as one surface, RAL-matched resin holds its consistency better than a site-applied cement finish.
What happens if it fails? Not a pessimistic question, a costing one. Redoing a seamless finish means removing the old one first. Price the downside once, honestly, and the right choice usually becomes obvious.

Then weigh the four things only you can weigh: your budget — whether the difference buys more here than somewhere else in the project; your risk — what a redo in two years would genuinely cost you; the finish you actually like, compared as large samples in your own light; and who you trust to apply it, because both families live or die on preparation you will never see. A first-rate applicator with the cheaper system beats an indifferent one with the expensive system, every time.

Where this sits in the build

Seamless finishes fail at design stage more often than at application. The application is rarely the problem; the specification and the substrate decision are.

Concept: the look is agreed — seamless, minimal, no grout lines. This is also where someone should ask what the finish will be laid on, because that answer constrains the family before it constrains the colour.
Technical design: the substrate is surveyed and, if necessary, made good — stiffening a springy timber floor, or programming enough drying time for a new screed. Doing it here costs a fraction of doing it after a failure. The system is then specified by name, with the number of coats, whether a reinforcing mesh is included, the primer, and the movement-joint strategy. “Microcement” on a drawing is not a specification — it is a category.
On site: application, with the substrate moisture verified by hygrometer before the first coat, not assumed from the calendar.
Handover: the system warranty and the cleaning guidance go into the building manual. Seamless finishes are easy to look after and easy to damage with the wrong cleaner.

The London picture

The seamless look sits beautifully in London flats and rear extensions, and that is exactly where the substrate risk is highest. Across the Victorian terraces of south and west London, the floor you are covering is usually one of three things: a suspended timber floor on original joists, a new screed in an extension that may not have finished drying, or an old solid floor of unknown construction.

All three move, for different reasons and on different timescales. Suspended timber flexes under load. A young screed shrinks as it dries — which is why the drying schedule matters so much on a new extension floor. An old solid floor can carry moisture up from below if there is no membrane. A rigid finish laid over any of them without checking is a hairline crack with a date on it.

What to ask before you commit

Test the floor before you choose the finish. Walk and bounce on the middle of the span. Any movement you can feel rules out a rigid cement-based finish until the floor is stiffened.
Ask which family you are being quoted. Cement-based or resin. A quote that just says “seamless floor” has not told you the one thing that matters.
Ask whether there is a reinforcing mesh, and how many coats. The mesh and the coat build-up are what let a system flex.
Ask if it is waterproof as a system. For a shower or wet room, a waterproof resin system is the finish and the tanking in one. A cement-based finish needs a separate waterproof layer — ask what that is and who installs it.
Check the screed has actually dried. Ask for a surface hygrometer reading, not a date.
Ask how movement joints are handled. Structural movement joints do not disappear because the finish is seamless.
Price the downside once. Ask what a repair looks like if it cracks. Knowing that number makes the original choice much easier.

The takeaway

Test the floor before you choose the finish. A stable slab in a dry room makes cement-based the sensible buy; movement, or water, makes resin worth its premium. After that it is genuinely your call — weighed on your budget, what a redo would really cost you, the look you prefer, and who you trust to prepare it. Both families are right somewhere.

Neither is wrong. It is your home, your budget, your call — and a good builder’s job is to make sure you are choosing between two things you understand, then to do properly whichever one you pick.

Get an Itemised Estimate

Get your estimate →

Or call us on 020 8050 8968. We work across Fulham, Chelsea, Battersea, Kensington, Hammersmith and the surrounding boroughs.

Get my price in 60 seconds Full renovations Renovation costs by area Builders in your area

Free Estimate

Get a itemised quotation for your project

Use our instant cost calculator — no calls required, detailed estimate in under 2 minutes.

Get your estimate