Yes, you can apply microcement over a tanking (waterproofing) system, and doing so is the correct way to build a microcement wetroom. Microcement bonds securely to a properly applied tanking membrane, so you waterproof first and then apply the finish on top. The key is using a compatible tanking system, letting it cure fully, and then applying your microcement directly on top in thin, even coats. You do not need a primer over tanking: the microcement bonds straight to the cured membrane. This guide walks through the whole process for both walls and floors, so your shower, bathroom or full wetroom ends up seamless, water-resistant and built to last.
If you have ever worried that microcement "won't stick" to a waterproofed surface, this is the post for you. It is one of the most common questions we get, and the short answer is: it sticks, as long as you prepare it correctly.
What is tanking, and why do you need it under microcement?
Tanking is a waterproofing layer applied to walls and floors before the decorative finish goes on. In a shower or wetroom it is what stops water reaching the substrate behind your microcement, protecting the wall boards, floor and structure from long-term damp.
Microcement itself, once sealed, is highly water-resistant and perfect for wet areas. But microcement is a finish, not a waterproofing membrane on its own. In a shower or wetroom you want a dedicated tanking layer underneath doing the waterproofing, and the microcement on top delivering the seamless concrete look. The two work together: tanking keeps water out, microcement makes it beautiful.
Can microcement go over a tanking or waterproofing system?
Yes. Microcement adheres well to a correctly applied and fully cured tanking membrane, and you apply it directly onto the tanking with no primer needed. The main mistake to avoid is applying microcement onto tanking that is still green (not fully cured). Let it cure fully and you get a solid, reliable bond.
Here is the order of work at a glance:
| Step | What you do | Why it matters |
|---|---|---|
| 1. Prepare the substrate | Fix and seal boards, tape and treat all joints and corners | A stable, sound base is essential for any finish |
| 2. Tank it | Apply your tanking system (two coats, like a thick paint) | This is the waterproofing layer |
| 3. Let it cure | Allow the tanking to fully dry and cure | Microcement will not bond to uncured tanking |
| 4. Apply microcement | Build up thin coats directly onto the cured tanking, then sand and seal | The finish and its water resistance (no primer needed over tanking) |
Which tanking system should you use?
We recommend a compatible tanking system such as Dukkaboard Aqua77. Its tanking liquid goes on like a thick paint in two coats, and our microcement bonds to it reliably once it has cured. Systems like this use a thin fleece tape at the joints and internal corners, which keeps the build-up flat, and that matters because a bulky tape can telegraph through a thin microcement finish.
Whatever system you choose, the principles are the same: waterproof every joint, internal corner, and floor-to-wall junction, apply the recommended number of coats, and let it cure fully before you go anywhere near it with microcement.
How to apply microcement over tanking on walls
With every Concrete Lab kit, each coat uses the same microcement (there is no separate base coat and top coat). For a tanked wetroom wall (tanked cement board), use our Wall Kit, which is a two-coat system. If you are instead going over existing tiles, use the Wall Tile Kit, which is a three-coat system with reinforcing mesh set into the first coat to bridge the grout lines. Either way you apply straight onto the cured tanking, with no primer needed:
- First coat. Apply the first coat of microcement directly onto the cured tanking. If you are using the Wall Tile Kit over tiles, press the reinforcing mesh into this first coat.
- Remaining coat(s). Once dry, apply the next coat of the same microcement: a second coat with the Wall Kit, or a second and third coat with the Wall Tile Kit, to build and smooth the surface and bring out the colour.
- Sand. Lightly sand for a smooth surface, removing any high spots or trowel marks.
- Seal. Apply our two-part polyurethane sealer in the recommended coats. This is what makes the finished microcement water-resistant and wipe-clean.
How to apply microcement over tanking on a wetroom floor
A wetroom floor follows a slightly different order, because the floor has to be level, sloped to the drain, and reinforced before it is waterproofed:
- Level and reinforce the floor first. Before tanking, apply a self-levelling compound with reinforcing mesh to create a flat, sloped-to-drain, reinforced base. In a wetroom, the floor reinforcement happens at this stage, below the waterproofing. The self-levelling compound is sourced separately and is not supplied in our kits.
- Tank the floor. Apply your tanking system over the levelled floor, including around the drain and the floor-to-wall junction, and let it cure fully.
- Apply two coats of microcement. Our Floor Kit is a two-coat system. Apply both coats of the same microcement directly onto the cured tanking, no primer needed.
- Sand and seal. Sand smooth, then seal thoroughly. Floors benefit from careful, even sealing because they see standing water and foot traffic.
Good news on product choice: you use the same microcement on both the walls and the floor. Concrete Lab uses one deliberately strong formulation rather than separate wall and floor grades, which makes it stronger, simpler and quicker to apply, and means your walls and floor colour-match perfectly.
How do you blend the floor-to-wall junction seamlessly?
This is the detail that makes a wetroom look professional. Because you are using the same microcement everywhere, the walls and floor already match. At the junction, reinforce and blend the two surfaces so there is no hard line or visible join, carrying the finish continuously from floor to wall. Take your time here: a smooth, continuous corner is what separates a seamless wetroom from a patchy one.
Common mistakes to avoid
- Applying onto uncured tanking. The number one cause of adhesion problems. Wait for a full cure.
- Coats too thick. Microcement is built in thin layers. Thick coats crack and dry unevenly.
- Ignoring movement. A flexing or unstable substrate will telegraph through any thin finish. Make the base solid first.
- Rushing the seal. The sealer is what makes the surface water-resistant. In a wetroom, seal thoroughly and let it cure fully before use.
What you will need
- A compatible tanking system (for example Dukkaboard Aqua77) to waterproof first
- Microcement Wall Kit (2 coats) for tanked walls, or the Wall Tile Kit (3 coats, mesh in the first coat) if going over tiles
- Microcement Floor Kit (2 coats) for the microcement finish
- A self-levelling compound with reinforcing mesh to level and reinforce a wetroom floor before tanking (sourced separately, not supplied in our kits)
- Concrete Lab Sealer (included in every kit; buy extra if you need more coverage)
Each kit includes primer (for non-tanked substrates such as MDF, plywood or cement board), the microcement (two or three coats depending on the kit) and sealer. You will not need the primer over tanking, but you will use it if you are also microcementing non-tanked surfaces in the same project.
FAQs
Does microcement stick to tanking?
Yes. Microcement bonds well to a properly applied, fully cured tanking membrane, and you apply it directly onto the tanking with no primer needed.
Do I still need to waterproof if I am using microcement in a shower?
Yes. Microcement is water-resistant once sealed, but in a shower or wetroom you should always tank (waterproof) underneath it. Tanking does the waterproofing; microcement provides the finish.
Can I use microcement on a wetroom floor and walls?
Yes, and it is the same product for both. Using one microcement across walls and floor means they colour-match and blend seamlessly at the junction.
How soon can I use the shower after applying microcement?
Wait until the sealer has fully cured before exposing the surface to water. Follow the cure time given in your kit instructions.
What tanking system do you recommend?
A compatible system such as Dukkaboard Aqua77, applied in two coats and left to cure, gives a reliable base for microcement.
Ready to build your wetroom? Start with a Wall Kit and Floor Kit, or get in touch and we will help you plan your project and quantities.
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