Blisters in Microcement Surfaces

What Causes Blisters to Occur in Microcement Surfaces?

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.

Blisters occur when water is trapped under the surface of the microcement.

Most often water gets behind the microcement through open edges around the boundaries of the microcement or around the shower waste.

But it could also be caused by leaking pipes, moisture in the substrate or rising damp.

Traditional Microcements Need to Breathe

Traditional Microcements, like Microdur need to breathe. If a wet item, is left on the surface for prolonged periods of time, the trapped moisture can cause darkness or blisters to occur. Often, once the item is removed, the microcement surface will slowly recover over time, so don’t be in a hurry to start repair work in this case.

How Can I Repair Blisters in Microcement?

First, the source of the water needs to be identified and eliminated so that the microcement can dry out.

Check around the shower waste and along the edges of the microcement surface to see if there’s anywhere that water could be getting behind it. Before you do any repair work, you need to let the surface dry out fully, so keep the area dry and leave any gaps exposed so the air can get to it.

Removing Small Blisters in Microcement

To minimise the damage to the microcement, you can prick each blister with a pin, and gently push on them to release the moisture.

Then wait until the microcement is completely dry, we’d expect this to take at least 48 hours, depending on heating & ventilation, but you may be able to speed this up by using a hair dryer on a medium heat.

Once dry, if the blisters will push flat, and you are happy with the visual appearance, you can apply 2 coats of sealer over the pinholes.

If the microcement has delaminated from the substrate, you can inject a small amount of Impripox under the surface to stick it down, then seal

Follow this guide on Resealing Microcement Surfaces.

Removing Larger Areas of Water Damage

For big blisters, where a lot of water has got underneath the microcement, it may be better to sand the surface back and let it dry out fully.  The microcement must be fully dried out before you apply anything on top of it.

Once dry, check that the surface is strong & well consolidated, it may need sanding more to achieve this. You’ll need to recoat the entire surface that the damage is on as microcement is notoriously difficult to patch seamlessly.

Recoating 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: https://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: https://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: https://relentlessmicrocement.com/training/touching-up-microcement/

Silicone All Open Edges

Before you allow water to touch the surface again, make sure you’ve fixed the source of the problem, by applying silicone along any open edges & resealing the surface.