Preparing Aqua4ma & Rigid Shower Trays for Microcement
We always recommend using a rigid shower tray with microcement. The microcement is applied in very thin coats, so it needs to be laid onto a solid surface.
Choose an Aqua4ma shower decks or a rigid shower tray that is suitable for microcement or vinyl floors. And then follow the guidance below to prepare it for the microcement application.
Microcement is applied very thinly at just 3-4mm and it is very much reliant on the substrate for strength and rigidity. Because of this, we only recommend Kudos Aqua4ma Shower Decks or Rigid Shower Trays for Vinyl Floors. This guide explains how to prepare these trays for the application of microcement.
Kudos Aqua4ma Wet Room System
This is the ideal system for wet rooms and shower trays, the panels and trays are completely waterproof and rigid. And the solvent weld bonds the tongue and groove edges of the panels together very well. The solvent weld can also be used to flush out joins between panels & cures within 30 minutes allowing you to sand it flat.
Install the shower deck according to the installation instructions:
https://relentlessmicrocement.com/wp-content/uploads/2025/01/Aqua4ma-Installation-Guide.pdf
Rigid Shower Trays
You can also microcement onto most Shower Tray that are recommended for vinyl floors or microcement. These are rigid shower trays which allow for 3-4mm of product to finished floor height.
Preparing Shower Trays for Microcement
Here are the guidelines for completing the prep work for shower trays and the surrounding surfaces.
Well Consolidated & Completely Flat
Make sure the tray is installed according to the installation instructions. It must be well glued and screwed in place to eliminate any chance of movement. Countersink screw holes.
Check with a Spirit Level
Check the tray with a spirit level to ensure the water will flow correctly towards the waste. Microcement is not generally designed to withstand sitting water, so it’s important that the water will flow correctly.
Around the Waste
Do a dry run with the waste so that you can see how it comes together, and check the levels, bearing in mind the microcement will only add 3-4mm to the surface of the tray.
Ideally, you will have a clearly defined edge to work up to with your microcement – so no water can get underneath it. If you are using an Aqua4ma tray, install the grill retainer, prior to starting the microcement. This will give you a 3mm edge to work up to.
Once the microcement installation is complete, silicone the join between the waste and the microcement so that no water can get behind the microcement.
Around the Shower Tray
If you are microcementing the floor outside of the shower tray, as well as the tray itself, the tray must be flush with the surrounding floor. And there must be no voids between the two surfaces.
Microcement can’t be used to level surfaces/fill large voids. The microcement will follow the contours of the substrate it is going onto so make sure all surfaces are completely flat.
Internal Corners (Between Wall & Floor/Tray)
There must be no voids between the wall & floor. If you are fitting the boards yourself, use an adhesive sealant along the bottom edge of the boards and squash the boards down to the tray/floor. Don’t smear silicone on the surface, instead, let it ooze out and razor scrape off the excess once it is dry.
Use wide, Fibreglass Mesh for Corners to bridge the join in internal corners.
Preparing the Surfaces for Microcement
You have 2 options for achieving a flat surface & bridging the join between the tray and the other boards on the floor. This will depend on which primer you choose. We usually recommend Standard Primer for seamless surfaces, like screeds & Aqua4ma panels, that have been welded. And High Performance Primer for boarded floors, like OSB or Cement Board.
Option 1: Standard Primer
Fill the Joins and Screw holes with Suitable Repair Mortar or Joint Filler.
This is the basic process – it relies on there being no movement at all in the sub-floor. Fill the joins and screw holes so that the surface is completely smooth., as if you were going to paint on it. Microcement is just 3-4mm finished, and ridges
IMPORTANT: Leave until dry, minimum 12 hours. If it isn’t completely dry, the lines & holes may ghost through the microcement and be visible in the finish.
Once the filler is dry you can apply Primer 100 & Fibreglass Mesh.
Option 2: High Performance Primer
This is the more advanced process, which we highly recommend for boarded floors where there is more chance of movement compared to solid surfaces.
This system will reduce the chance of movement transferring through to the surface. It uses an epoxy primer, Impripox, Fibreglass Mesh & Quartz Sand over the entire floor. The Impripox will fill joins and screw holes, up to around 5mm, to level off the floor.
For full application of the high performance primer system visit: https://relentlessmicrocement.com/training/applying-impripox-high-performance-primer/