DIY Microcement Kit for 100% Waterproof Bathroom Walls

Surface Prep

Before you prime and mesh it’s essential that your surface is completely flat, dry and well consolidated, so that there is no chance of movement.  Use a small amount of the base coat or a suitable filler to flush out joins and counter-sunk screw holes, then sand until the surface is completely flat.  See surface prep for full details of preparing surface for microcement.

Applying Primer 100 & Fibreglass Mesh

Fibreglass mesh adds strength to your microcement and adds strength to the substrate. Cut the mesh to size & then flip it over so that it curls towards the surface. You might find it easier to use Self Adhesive Fibreglass Mesh on corners.

Use a medium pile roller to apply an even coat of primer to the surface and mesh. The primer should help to hold the mesh in place, but you can also use stainless steel staples to hold it down.

Try to get the mesh flat to the surface.  If you do get bubbles in the mesh that you can’t flatten, you might need to move on and deal with them when applying base coats by slashing the bubble with your trowel or utility knife and flattening down at that point. If bubbles in the mesh are still showing through after the 2^nd base coat, sand them out so that you have a completely flat surface before applying top coats.

Primer 100 is a thick, high-quality product.  To get the full consumption out of the bottle, you may need a little water.  Add up to 10% water & shake to get all of the primer out of the container.

Fresh Plaster & Concrete

On freshly laid concrete, screed, self-leveller or fresh plaster use Primer 100 mixed with water at a ratio of 50:50 before applying a neat coat. Similar to a mist coat of paint, this will prevent the primer from sitting on the surface and create a strong bond between surface and microcement. The primer needs to sink into the substrate to take hold, which is where the water comes in.

After around 1 hour it should be dry enough to take a neat coat of Primer 100. If the substrate is very absorbent, you might need to buy more primer to complete this stage.

Leave to Dry

Leave the primer to dry. This should take around 1 hour. Primer 100 will loose it’s tack after 8 hours, so you will need to make sure you apply your base coat within 8 hours or apply another coat of re-prime.

When to Choose High Performance Primer

We highly recommend that you choose this option if you are working on load-bearing horizontal surfaces that have joins e.g. OSB/Ply/MDF/Cement Board flooring or across transitions between shower trays and surrounding floors. It also helps to strengthen concrete surfaces that have cracked, however the cracks should be repaired in advance. It’s also useful for bridging joins between boards in furniture and worktops.

This primer helps to inhibit moisture and stains from transferring through from your substrate.

If you think you need High Performance Primer but haven’t got it in your kit, the products are also available to buy separately.

Mixing 1st Coat of Microne Base without Colour

And it’s not essential that you add colour to the 1st base coat, but you may have enough colour toners to do so if your order requires a tub to be split between the 1st and 2nd base coat.

To loosen the mix, mix thoroughly with a microcement mixer head attachment on a cordless drill.  If it still feels stiff, you can add up to 10% water to loosen & mix further.  That’s a maximum of 1l per 10kg.

Let the mixture rest for a few minutes before applying.

Applying the Microne Base

Using a Microcement Trowel, work your way out from one corner creating a random edge pattern. Keep trowel movements small and random, avoid long sweeping arches – as these will show through to your final finish.

Use the grain in the microcement as your level – if you apply the microcement thicker than the size of the grain, the finish won’t be as strong and will require a lot more sanding. Run the trowel back over each section that you have put down to smooth it out and remove excess product. You should still be able to see the mesh after after applying this coat.

Completely coat each surface without stopping. For complete rooms, start with ceilings, then walls from left to right (or right to left) and then the floor.

Run your finger or a corner trowel along internal corners to push the microcement into the corner and then gently trowel away the excess product.

Mixing 2nd Coat of Microne Base

Add 1 x colour toner for Microne Base to the tub and mix thoroughly.  You can add a small amount of water to the bottle and shake thoroughly to get all of the toner out of the bottle.

Unlike the Top Coats, the colour for Base Coats is not an accurate match to the swatch, it’s just enough to take it in the right direction before Top Coats are applied.

To loosen the mix, mix thoroughly with a microcement mixer head attachment on a cordless drill.  If it still feels stiff, you can add up to 10% water to loosen & mix further.  That’s a maximum of 1l per 10kg.

Let the mixture rest for a few minutes before applying.

Applying the Microne Base

Apply the 2nd Coat of Microne Base in exactly the same way as the 1st coat.

Leave to Dry

This should take around 3 hours but may vary depending on temperature and humidity.

Sand with 40/80 Grit Sand Paper

Once the base coats are dry and before you apply your Top Coats, you need to make sure the Base Coats are completely flat.  You need to use a strong sand paper, like Silicone Carbide, to prevent colour from the disc transfering to your work.

Flatten the Microne Base with a 40 or 80 grit sand paper. An orbital sander is ideal, but, for smaller areas, you can do it by hand.

Use the sand paper to remove ridges and drips that have dried in the microcement.

The top coats are very thin so any ridges or imperfections in the base coats will be visible in the top coats.  Take your time to get it completely flat before moving on to the next step.

Vacuum the surface to remove all dust and debris. Do not wet the microcement.

Microcement Sanding Discs are available from Relentless Microcement.

Mixing Microne Medium

This is pre-mixed with the colour in the tub, all you need to do is give it a mix before you start to loosen it and make sure the colour is evenly distributed.

To do this, mix thoroughly with a microcement mixer head attachment on a cordless drill.  If it still feels stiff, you can add up to 10% water to loosen & mix further.  That’s a maximum of 1l per 10kg.

Let the mixture rest for a few minutes before applying.

Apply 1st Coat Microne Medium

Use the same technique as you did for the base coats. Just remember this coat is thinner, so it needs to be applied thinner too.

It’s important that you go as thin as the grain with Microne Medium – which you’ll see is very thin indeed.

Here’s a reminder of the technique:

Using a Microcement Trowel, work your way out from one corner creating a random edge pattern. Keep trowel movements small and random, avoid long sweeping arches – as these will show through to your final finish.

Use the grain in the microcement as your level – if you apply the microcement thicker than the size of the grain, the finish won’t be as strong and will require a lot more sanding. Run the trowel back over each section that you have put down to smooth it out and remove excess product.

Completely cover each surface without stopping. For complete rooms, start with ceilings, then walls from left to right (or right to left) and then the floor.

Run your finger or a corner trowel along internal corners to push the microcement into the corner and then gently trowel away the excess product.

Leave to dry. This should take around 3 hours but may vary depending on temperature and humidity.

Apply 2nd Coat Microne Medium

After around 3 hours, you can apply your final coat of Microne in exactly the same way as the previous coats.

Be aware that the more you trowel over the microne with a steel trowel, the more it will blacken in high spots. This technique is called “burnishing” and is often used by microcement installers to add depth to their work. You’ll find that Microne Stucco Effect burnishes more readliy than Microne Continuous Effect. This looks great in grey-scale colours but isn’t always desired in lighter or brighter colours. So if you don’t want black marks, then use Continuous and try not to trowel over the same area more than you need to.

Fresh on Fresh Technique

By applying your 2nd top coat within 20 minutes – 1 hour applying your 1st coat, you can achieve a cloudy texture. On floors, you can lay high-density foam boards over the microcement to walk on.

Leave to Dry

Once you have completed your final coat, you’ll need to leave it to dry before sanding and applying sealers. This will take at least 12 hours.

Sand with 220/240 Grit Silicone Carbide Sanding Disc

Once the Microcement is fully dry, gently & evenly sand the surface of the microcement with a 220 or 240 grit paper to remove any rough patches and drips. It should be flat from the trowel so you shouldn’t need to sand it too much at this stage.

Vacuum the surface to remove all dust and debris. Do not wet the microcement.

We stock a range of Microcement Sanding Discs on our website.

Mixing 1st Coat AquaMax Pro Walls

Mix the AquaMax Pro Comp A with the AquaMax Pro Walls Comp B in a mixing jug and stir gently with a paint stirrer for at least a minute.  Do not whisk as it will put too much air in the mix. Leave to rest for a couple of minutes before applying.

For each coat, you will need 500ml AquaMax Pro Comp A + 50ml AquaMax Pro Walls Comp B per 10m2.

The mixing ratio is 10 x AquaMax Pro Comp A : 1 x AquaMax Pro Walls Comp B.

Only mix enough for 1 coat at a time, as the mixture will only last for 45 minutes once combined.

Applying the 1st Coat AquaMax Pro Walls

Use a medium pile roller to apply the AquaMax Pro evenly across the entire area.

Starting in one corner, apply the AquaMax Pro in an area and then go back over it very gently with the roller to remove any excess product, air bubbles and lines.

Work quickly & randomly keeping the edge wet.

Ensure you cover the full area with AquaMax Pro and use the full amount provided (500ml+50ml per 10m2 for each coat).

Leave to Dry

Leave the 1st coat to dry for a minimum of 12 hours before applying the 2nd coat.

Applying the 2nd Coat AquaMax Pro Walls

After 12 hours, you can complete the 2nd coat of AquaMax Pro.  Check the surface for bits of dust and debris that may have settled in it.  You can use a 400 grit sanding disc or razor scraper to remove these before applying your final coat.

Mix and apply the 2nd coat in exactly the same way that you did the 1st one.

Again, you will need 500ml AquaMax Pro Comp A & 50ml AquaMax Pro Walls Comp B to complete 1 coat over 10m2.

Leave to Dry

Leave for at least 48 hours. Light use only for the first 14 days.

IMPORTANT: Like all cementitious products, microcement takes 28 days to full harden. It’s at it’s softest for the first 14 days after laying. During this time it should only be subjected to light use and light foot traffic.

Any heavy work is not recommended, but if it does take place then we recommend that you cover the floor with a breathable material or only cover down whilst working & lift the protection off for the majority of the time. The surface needs to dry out and harden. If airflow is restricted, it will stain & not cure correctly.

Light Use After 48 Hours

You can start to use the microcement surface 48 hours after the final sealer has been applied.  By this time, the microcement is sufficiently waterproof, so you can use showers & taps.

You can also install fittings, but its important that you follow the guidance outlined below, for the first 14 days.

First 14 Days

Like all cementitious products, microcement takes 28 days to full harden. Which means it’s at it’s softest for the first 14 days after laying. It also needs to be kep well ventilated so that air can freely flow from the microcement into the atmosphere as it cures.

During this time it should only be subjected to light use and light foot traffic.  And no part of the microcement should be covered over.  So no leaving bottles in shower areas or rugs on floors.

Heavy work is not recommended during this time, but if it does take place then we recommend covering the floor with a breathable material and only covering down whilst work is taking place.  Protection should lifted off for the majority of the time and certainly through the night. The surface needs to dry out and harden. If airflow is restricted, it could stain permanently & not cure to full strength.

Fixing to Microcement Surfaces

Microcement can be drilled and screwed into using bits that are suitable for the substrate. Any holes or cuts will need protecting from moisture penetration by either putting silicone into screw holes or by surrounding fixtures & fitting entirely with silicone. Use 100% pure silicone for this job, to ensure good adherance to the sealed microcement.

Care must also be taken not to scratch the sealers whilst installing fixtures & fittings.

No Dragging or Dropping

Dragging heavy objects over the surface, or dropping them onto the surface is not recommended at any time, as damage could occur. Lift furniture rather than dragging it, and use lids or felt pads to protect flooring from pressure points or abbrasive surfaces.

Microcement is strong, but due to its limited thickness, it will deform in the event of a strong blow if the support beneath deforms. Generally, abrasion and impact resistance is comparable with hard wood.

Stain Resistance

Chemical resistance depends on the sealer used to protect the product. Our sealers are among the best in the industry for both hardness & strength.

Products containing dyes & acidic or alkaline products like tumeric, vinegar, lemon juice or bleach, may leave slight marks on microcement if left on the surface for prolonged time. If cleaning is done quickly, they shouldn’t stain.

If water stains appear at any time, let the stain dry out & reseal immediately.  Stains may become permanent if not treated quickly.

Prolongued Exposure to Water

If water is trapped against the surface for a prolonged length of time it may stain & potentially cause the microcement to blister. It is not advisable to leave wet towels, plant pots, wet shampoo bottles etc. in direct, prolongued contact with the microcement.

Cleaning

Microcement surfaces can be cleaned with any pH neutral cleaning products.

Do not clean microcement surfaces with aggressive or descaling products, such as those which contain chlorine, bleach and ammonia as they can damage the sealers.

Aftercare

Use Cemher Floor Protect every 2 -3 months to protect you microcement and to help build up the sealers. This specially designed product is formulated to maintain and protect microcement surfaces by waterproofing, reviving, and safeguarding previously sealed areas. It effectively restores minor scratches in floors without the use of wax, ensuring that the surface remains scratch-free when walked on.

To use, simply dilute 100ml of the product in 7 liters of water and apply it with a mop or cloth. For optimal results, repeat the application every 2 to 3 months.