Trouble Shooting

It may be that the microcement has been applied too thickly, which is why it’s starting to crack. Microcement needs to be applied in very thin coats – no thicker than the grain size.

Click here for an explanation of why this has happened & how to resolve it: relentlessmicrocement.com/training/how-to-avoid-cracks-in-microcement

There are 2 scenarios where cracks appear in the corners. Either there is movement between the 2 surfaces, or the microcement is applied too thickly in the corner.

If there is movement, it will need to be eliminated & the microcement sanded, then another coat applied. Use your finger or a corner trowel to really squash the product into the crack to fill it.

If there is a build-up of product in the corner, you'll need to sand off the excess & apply another coat. This video shows the best technique for applying microcement into internal corners: relentlessmicrocement.com/training/how-to-avoid-cracks-in-microcement

When floors crack in straight lines, it’s usually because there has been some movement in the screed, below the microcement, that has caused the floor to crack. Usually the floor cracks at weak points in the floor, like between corners and doorways.

This guide tells you everything you need to know about why straight line cracks appear & how to repair them: relentlessmicrocement.com/training/movement-cracks-after-microcement-installation

We use standard consumption rates to calculate the quantity of each product that goes into a kit. But it’s not an exact science & occasionally people use more or less than the quantities provided.

Just to put your mind at rest, we haven’t charged you more than you would have paid for the individual products that you received.

We sell the products in Xm2 kits to try to make it easier for customers to get the products that they need. But we feel it’s important to note that this should not be understood as a commitment by us to provide additional products if the stated no. m2 is not met. Hope this makes sense & you understand, it just isn’t sustainable for us to make such a commitment.

For Primer 100, if the surface is very absorbent it may absorb more than 1l Primer 100. On fresh plaster & cement based products, dilute the 1st coat with 50% water & follow with a neat coat. In this case, more Primer may need to be purchased on top of the kit.

And don't feel like you have to use more Primer to stick the mesh down completely, it might just help you to hold it in place, if it's not sticking well then use a staple gun to hold the mesh instead.

For Microcements (excluding Terrazzo/Sparkle), make sure you're using the grain as a level and never apply it any thicker than that. You should apply it as thinly as you possibly can, so that you hear the scraping of the trowel against the previous coat. The 1st base coat will just fill the gaps between the mesh but not cover it.

If you do need to buy any additional products then you can do that online or by getting in touch. relentlessmicrocement.com/get-in-touch

Don't feel like you have to use more Primer to stick the mesh down completely. That’s just a handy tip to help you to hold the mesh in place, if it's not sticking well then use a staple gun, with stainless steel staples, to hold the mesh instead.

Once you apply the 1st Base Coat, that will hold the mesh in place securely.

If the scratches are in the sealer, then you can give the surface a gentle sand with a 220 grit sanding disc & apply an additional coat of sealer. This should fill the scratches & add more protection to the surface.

Visit this guide for more information on resealing the surface: relentlessmicrocement.com/training/resealing-microcement-surfaces

If the scratch has gone deeper into the microcement surface, then you will need to repair the microcement too. This guide explains the best approach for touching up microcement surfaces: relentlessmicrocement.com/training/touching-up-microcement

Microcement is notoriously difficult to patch, and almost impossible to do seamlessly. Touch ups are intended to take your eye off an imperfection, but don’t expect a seamless repair, as that is very difficult to achieve.

Here's a guide to touching up the microcement: relentlessmicrocement.com/training/touching-up-microcement

Because Microne, the product that we recommend for bathrooms, is 100% waterproof, it won’t allow any water to penetrate through it. Which is absolutely necessary in bathrooms, wet rooms and showers.

If water gets to the underside of the microcement, however, it will become trapped under the surface & if the water pressure builds up, it could result in a blister of water forming under the surface.

This guide explains more about how to prevent blisters from forming & how to repair surfaces where blistering has occurred: relentlessmicrocement.com/training/blisters-in-microcement-surfaces

This happens when the surface has been trowelled a lot of times with a lot of pressure on the trowel. As the steel of the trowel is rubbed over the surface, it causes the surface to blacken in areas.

The areas that blacken more tend to be raised slightly more than the rest of the surface. So the blackening might highlight trowel marks left in the previous coat or imperfections in the substrate.

This guide explains more about why they happen & how to control the appearance of the microcement: relentlessmicrocement.com/training/dark-marks-after-trowelling

If you have noticed black, yellow or orange marks appearing slowly over time on the microcement surface, it may be mould that is slowly forming on the surface.

Most of the time these can be wiped away easily & controlled with regular cleaning, but if left unnoticed they can becme more stubborn.

This guide explains the best way to deal with mould patches that have developed on the microcement surface: relentlessmicrocement.com/training/mould-patches-on-the-microcement

If you do discover stains on the surface, then try scrubbing cleaning product into the stain with a white scouring sponge. To see if that starts shifting it.

If that doesn’t work, try scrubbing it with bleach. Make sure the bleach is washed away with water so that the surface is neutralised within 15 minutes, in order to prevent damage to the sealer.

And as an absolute last resort, you can use a 220 or 120 grit sanding disc to sand back the surface to remove the stain and then apply another coat of sealer, to replace any that you have sanded off.

Here's a useful guide which explains further: relentlessmicrocement.com/training/stains-on-the-microcement-surface

If you have discovered yellow patches or a yellow film on the surface of the microcement after applying a solvent based sealer, like MaxiPur, it may be that there was some on site contamination or the rollers used were not suitable for use with solvents.

This guide explains more about why this happens & how to resolve it: relentlessmicrocement.com/training/yellowing-following-application-of-solvent-based-sealer

Microcement base coat & joint filler don't have the body to be used to build up surfaces or fill gaps more than around 2 or 3mm, if it's applied too thickly, it will eggshell & be weak in those areas.

To build up surfaces, use a product that is suitable for use with the substrate, will set hard & is intended to be applied at the depth required.

Generally, concrete repair mortars are good for building up cement-based products, like cement board & screeds, but always check with the manufacturer of the product that you’re thinking of using to be sure that it’s suitable & if any accompanying product or prep work is required, like primers.

You can also use a cement-based repair mortar on top of microcement base coat, as long as the surface hasn’t been sealed. Again follow the manufacturers guidance on application.

You could also consider boarding over the surface or using a self-leveller to get to the right level.

Just make sure whatever you do, you respect the falls towards the shower waste.

Black plastic shavings in the mix are normally caused when the microcement is mixed too aggressively in the black Cemher tubs that the microcement is delivered in.

Here are some tips that will help you to avoid mixing too aggressively & explain how to recover your mortar: relentlessmicrocement.com/training/black-plastic-shavings-in-the-microcement-mortar

You need to use silicone carbide sanding discs with microcement. You can buy them on our website: relentlessmicrocement.com/product/cemher-microcement-sanding-discs

Some of the less strong ones, like Aluminium Oxide, can leave their colour on the surface as the cement wears them down instead. This should just be dust so you can hopefully dust it off.

This guide explains more about why this happens & how to fix it: relentlessmicrocement.com/training/dark-or-red-marks-after-sanding

If you find the silicone carbide disc that you are using is wearing down too quickly, then try a lower grit.

Grout lines should be dry before the microcement is applied. If the grout lines still contain moisture when the microcement is applied, the moisture gets trapped under the surface & can change the colour of the microcement along the grout lines, causing them to be visible in the surface of the microcement.

If the grout lines aren’t sufficiently flushed out, so that the surface isn’t completely flat, the grout lines may also be visible.

This guide explains more about why you might be seeing grout lines & describes the best way to resolve the problem: relentlessmicrocement.com/training/grout-lines-visible-in-microcement-finish

The microcement that we recommend for floors is very hard, at around 28-50N/mm2, depending on the spec. It has a higher compressive strength than most concretes.

To put those figures into some context, this means that 1m2 of the microcement can hold 2.8 – 5 tonnes of weight without deforming.

If your microcement flooring isn’t proving to be as strong as this, then there is most likely a problem with the microcement application or the substrate it was applied to.

This guide outlines the most common reasons for weaknesses in microcement floors: relentlessmicrocement.com/training/microcement-floor-isnt-strong-enough

Microcement is very strong, but it is dependent on the surface that it is being applied to for support.

If you’ve discovered straight line cracks in your boarded, microcement floor after the microcement has been installed, it’s most likely because there has been some movement between the boards below the microcement.

This guide tells you everything you need to know about why they might have appeared and what you can do to fix them: relentlessmicrocement.com/training/movement-cracks-after-microcement-installation-boarded-floors

There may be a very simple explanation for the colour not appearing to be a good match, this guide explains some of the different reasons why this may be the case: relentlessmicrocement.com/training/my-colour-doesnt-look-right

We always recommend that surfaces are clean & dry before microcement is applied. This can sometimes be difficult to achieve, particularly on older floors, where unknown spills have become ingrained in the surface. Or where a lot of spills have occurred previously on site.

If you can see that the floor is stained before you start, or you have suspicions that oil-based products may have been spilled on the surfaces in the past, it’s best to use High-Performance Primer. This is an option on all microcement kit pages.

This guide explains more about how to block persistent stains from appearing in your microcement surface: relentlessmicrocement.com/training/blocking-persistent-stains-during-application

Our microcement sealers are highly resistant to staining from the majority of household products and chemicals. And most of the time they will wipe away easily.

From time to time we do get contacted about stains that are more difficult to remove. Here’s our guide on dealing with stubborn stains in microcement surfaces: relentlessmicrocement.com/training/stains-on-the-microcement-surface

We don’t recommend patch repairs generally, because it’s very difficult to do them seamlessly. Repairing, then recoating the entire surface is the only way to achieve a seamless repair.

This guide explains the best process for repairing microcement surfaces: relentlessmicrocement.com/training/repairs-to-microcement-surfaces

Whilst we don’t recommend patching, and can almost guarantee it can’t be done seamlessly, we understand you may want to give it a go, so have written a guide explaining the best approach for minimising visibility of patch repairs: relentlessmicrocement.com/training/microcement-patch-repairs

And here's our guide to touching up the microcement in very small areas, like chips, and into corners: relentlessmicrocement.com/training/touching-up-microcement

From time to time, we hear of problems when applying microcement over plywood, this is due to a fault in the manufacturing process of the ply.

This guide tells you everything that you need to know about why it happens & how to resolve it: relentlessmicrocement.com/training/stains-in-microcement-installed-over-plywood

Water is very good at finding its way through any open or unsealed gaps.

If you’re adding fixtures & fittings to microcement surfaces, it’s important to apply silicone along open edges & around fixtures & fittings to avoid problems with water ingress.

If any open edges or fittings have been missed in wet areas, or if the silicone has failed over time, it is possible that water could find its way behind the microcement.

This guide explains how to repair microcement surfaces where water has got behind the surface to the substrate: relentlessmicrocement.com/training/water-ingress-on-microcement-surfaces

The microcement that we recommend for bathrooms, wet rooms & showers is completely waterproof, but if water is left sitting on the surface for prolonged time periods, it can start to leave a watermark over time.

This is because there is an element of breathability to the sealers, they are not intended to be fully submersed for several hours.

When the surface is dried out, the water mark should disappear.

Here’s our guide to repairing surfaces where water has pooled: relentlessmicrocement.com/training/water-marks-caused-by-pools-of-water

Historically, porous micocements like Microdur, mixed with water, were the only option available to installers. And it was the Hydroprimer that soaked into the surface to saturate it, followed by AquaMax or MaxiPur, adding a hard surface protection, that made the system waterproof.

This system works well, but only if there is sufficient sealer across the entire area. Even a single pinhole, caused by an air bubble, in the microcement, or the sealer, can allow water to penetrate through to the microcement & cause a water mark.

Usually, the surface will darken where water has penetrated through to the microcement, but it should dry out & return to a normal colour once the area has been left to dry.

It’s important that you act quickly to avoid the water mark becoming a permanent stain.

This guide explains more about how to resolve water marks in the surface of a traditional microcement floor: relentlessmicrocement.com/training/water-marks-in-microdur-other-traditional-microcements

Sometimes, things don’t exactly go to plan & with other trades & building materials on site during & after microcement installations, it’s not unheard of for building materials and other chemicals to be spilled on the surface of the microcement.

Likewise, you may find certain stains take more than your average cleaning product to remove.

This guide explains more about using chemicals on the microcement surface: relentlessmicrocement.com/training/what-chemicals-can-i-use-on-microcement-surfaces

It’s best only to use the non-burnishing plastic trowels for top coats, as the base coats will wear them down quite quickly.

If the edge has become uneven, so that it’s dragging through the microcement, sand the edge of the trowel to get it flat & sharp again.

Drying times depend on the specific products used, as well as the site conditions, like temperature & ventilation, and the thickness of the product.

If the microcement has been applied thicker than the grain in the product, it will take longer than expected for it to dry.

This guide demonstrates the correct technique for applying microcement:

relentlessmicrocement.com/training/correct-application-of-microcement

If it is taking longer to dry than expected, you will need to wait until it has dried full before moving to the next stage.

Generally, good ventilation and a relatively warm environment will encourage the microcement to dry quicker. So, if you can get a fan in the room & turn the heating on, that will help to speed up the drying process.

Adding a “Hint of Colour” to the 2nd base coat ensures that the colour will remain consistent, even if the top coats are sanded back too far.

If the hint of colour hasn’t been added, the impact that will have does depend on the colour that you are working with.

For very dark colours, there is more risk of the white in the base coat showing through when you sand the surface. So you may want to add a 3rd base coat with colour, or take extra care when sanding not to sand the top coat back too far.

For lighter colours, it’s less of an issue, as the base coats don’t need to be a perfect match with the top coat, just not too contrasting.

If you do want to purchase additional colours, you can buy them separately here: relentlessmicrocement.com/product-category/microcement-products/microcement-colour-toners

And to purchase additional microcement mortars, click here: relentlessmicrocement.com/product-category/microcement-products/microcement-mortars

There may be just a very small amount of thick colour toner in the bottom of the bottle. Which may look like its dried up.

This is because the colour toners are measured out to suit the colour & product that they are being added to. Sometimes, it only requires a very small amount of toner to get it to the right colour. And the colour toners themselves are very concentrated.

To get all of the colour out of the bottle, add a small amount of water & shake it well, this will dilute the colour so that you can mix it in to the tub.