Microcement shower

[SimonD]

I'm just prepping a bathroom for a microcement walk-in shower. I've decided to take a bit of a punt with it to see what it's like and how it works over the long term. I've looked at shower panels and decided against them, and I'm not tiling the place either. I'm doing the whole install myself so will be fully responsible for prep and finish - this also means I'm better able to select the full build-up spec and resins that I use for the waterproof finish.

 

Having done a search I was unable to find anything specific on BH already, so thought I'd  ask if anyone has personal experience of using microcement in a shower and how has it faired for them? 

[Adam2]

hi @SimonD how did you get on? My neighbour has been using microcement  for some tables and a desk - looking really good and doesn't seem very challenging to apply - he was applying to MDF panels. Are you using a waterproof product to build or applying a coating after? I'd be worried about a coating due to possible gaps and then subsequent wear on the surface.

[SimonD]

On 02/12/2021 at 18:42, Adam2 said:

hi @SimonD how did you get on? My neighbour has been using microcement  for some tables and a desk - looking really good and doesn't seem very challenging to apply - he was applying to MDF panels. Are you using a waterproof product to build or applying a coating after? I'd be worried about a coating due to possible gaps and then subsequent wear on the surface.

 

Good to hear some experience. I've not done the install yet, we've been playing with samples to decide on the colour, a task in itself! I've also been talking to suppliers re recommended substrates and like with everything there seems to be rather differing opinions. One supplier of a major Spanish microcement manufacturer has said I can simply use plasterboard with skim as the microcement is waterproof, but I have to say I'm a bit wary of that in a shower enclosure. I'm going to use Knauf Exterior Aquapanel as the substrate instead.

 

The buildup has also been an interesting task in research as different makes have slightly different approaches. Some do use 2-part resin mixed coats and then also waterproof coating, some use one-part base and middle coat with a couple of layers of waterproof coating with different hardeners. Some suggest a reinforcing mesh within the shower walls, some don't. I need a little time to figure this out and make a decision that isn't self-builder overkill yet remains robust.

 

Since there hasn't been any other input, I'll assume it's not got much traction here and will report back once I've taken the plunge, hopefully before Xmas if I'm lucky.

 

[Adam2]

Yes agree re a water resistant panel. Good luck, can't wait to see the results, may inspire me ? Worst case can always put another panel over the top!

[oaros]

It looks like a way to get a Venetian plaster look, but more resilient. I have looked at few websites, seems popular in Spain/Italy.

 

When you say you have been playing with samples, is that applying it to test areas in your bathroom or or looking at finished samples form the manufacturer? 
 

Would building something out of Wedi panels as a base for the microcement work? I like the cement look and am hoping to find an alternative to the Wedi top panels.

 

If you have the time, a build thread with lots of photos would be much appreciated.  ?

 

[SimonD]

I've just started with microcementing a shower now. Decided to use an ensuite for the experiment so if it goes wrong, nobody's really going to notice 

 

Here are photos of 1st stage - boarded with Aquapanel Outdoor as the base because I had 3 panels knocking around, but you can use plaster and skim, plasterboard, and even plywood as the base.

 

At this point I've just filled the countersunk screw wholes, joints and gaps with the microcement base coat. Nothing out of the ordinary just recording the steps for anyone interested. Tomorrow will be sanding it all down and then hopefully applying basecoat and mesh.

 

[Annker]

@SimonD

Happy to have found this thread!

I'm planning finishes for an upcoming build. I really dislike grout/grout lines; visually and practically, so I'm considering ways to avoid having and essentially that means using alternatives to tiling. 

Do you (or any other reader) have plans to use alternatives to tiles for the floor finishes in the bathrooms? 

[jack]

On 04/12/2021 at 13:56, SimonD said:

I need a little time to figure this out and make a decision that isn't self-builder overkill yet remains robust.

 

Having had to remove and replace all of the cracked marble tiles from two showers because the tiler failed to follow some pretty basic principles, I'd go for self-builder overkill every time!

[SimonD]

6 hours ago, Annker said:

Do you (or any other reader) have plans to use alternatives to tiles for the floor finishes in the bathrooms? 

 

I know some people will shudder and say don't do it in a bathroom, but I'm using birch plywood for my floor in this ensuite and the guest bathroom. It's finished with Rubio Monocoat and waiting to go down as soon as I've got the microcementing done. You can use microcement on the floor too.

[SimonD]

5 hours ago, jack said:

 

Having had to remove and replace all of the cracked marble tiles from two showers because the tiler failed to follow some pretty basic principles, I'd go for self-builder overkill every time!

 

Oh no, that's awful! Sorry to hear that. I think I have slipped into self-builder overkill mode again.

[SimonD]

Day 2 of the ensuite now with step 2, 3 and 4 of microcement preparation.

 

Step 2 was to sand down the basecoat used to fill the countersunk screws and joints, but I have to say this was a pain. Next time, I think I'll use the Knauf Aquapanel skim and/or filler as the microcement basecoat has aggregate in it so it's impossible to feather out the edges and it's really hard so destroys the sanding pads on the orbital sander. Took ages to only get a moderately good finish here. I'm hope the minor blemishes will be filled when coating.

 

Step 3 just to apply the primer to the boards.

 

Step 4 to add the reinforcing mesh which basically gets stuck to the primer (kind of - it just holds it in place for the microcement basecoat.

 

Next step is to apply two coats of the basecoat, one uncoloured, the other coloured.

 

Pictures attached of the stages completed today.

[Adsibob]

On 04/12/2021 at 13:56, SimonD said:

One supplier of a major Spanish microcement manufacturer

Is that Topcret?

[Adsibob]

8 hours ago, Annker said:

so I'm considering ways to avoid having and essentially that means using alternatives to tiling. 

Or use giant tiles. We are effectively tiling our whole shower area with three massive tiles. So only grout lines are in the corners.

[Annker]

8 hours ago, Adsibob said:

Or use giant tiles. We are effectively tiling our whole shower area with three massive tiles. So only grout lines are in the corners.

Yes I've thought about that method but personally I worry that large format tiles are more susceptible to telegraphing cracks from movement at substrate level; I have it in my head that grout lines provide some accommodation of horizontal movement, or at least that if there is significant horizontal movement the grout line will crack before the tiles.

 

Also wont you still have grout joints crossing the floor? Although only a couple.

[Adsibob]

51 minutes ago, Annker said:

Also wont you still have grout joints crossing the floor? Although only a couple.

Yes, but I see this as helpful in a shower area as they provide grip.

51 minutes ago, Annker said:

I have it in my head that grout lines provide some accommodation of horizontal movement, or at least that if there is significant horizontal movement the grout line will crack before the tiles.

In theory, you are probably right. But in practice I don’t see why that would be the case. The shower room in my car is on the first floor of the old part of our house. Everything has settled and I’m not expecting any movement.

[SimonD]

10 hours ago, Adsibob said:

Is that Topcret?

 

Cemher

[SimonD]

Okay, so next stage done now with 2 coats of the basecoat.

 

I've some mistakes in that I used the basecoat to fill joints and countersunk screw holes and I used the microcement mesh across all the corners. This meant that I used a bit too much basecoat and ran a bit short on the second coat! I also used the mirocement mesh on both internal and external corners, which was not great. Next time I'll use normal scrim tape on any corners. Having never done this before I may have applied the first coat slightly too thick too. Anyway, not too much of a disaster. All that has happened is the small wall area within the built in shelf will need to be tiled at the back and sides.

 

Applying the basecoat is really quite similar to applying thin coat render on external wall insulation, but it's a lot thinner, with each layer being only approx. 1mm.

 

I'm going to allow this cement to set overnight and tomorrow, first sand down this layer and then apply two more layers of a slightly different cement layer with what looks like a finer aggregate, but is still trowelled on like the basecoat.

 

Overall, I'm quite  happy with how it's turning out.

 

[Adsibob]

It’s looking very nice! Good luck with the next steps.

[SimonD]

Next stage finished and allowed to set for 24 hours. This layer was much easier to apply than the 2 basecoat layers, buttered on nicely and gives a nice texture to the wall - you may not see it in the photos but the white has soft whisps of grey so it's not an entirely uniform white. Now I just need to sand this down lightly and apply what look to be runny types of resin, not quite the same as epoxy resin.

 

The instructions are slightly confusing as with this kit I have 2 types of finishing coat, one durable, one extremely durable. I've been supplied with enough to apply two coats of each but the instructions only suggest one coat of each. If I apply 2 coats of each, I'll have to wait 12 hours between each coat, which obviously extends the finish time by quite a bit, but I'm erring on the side of caution so leaning towards 2 coats of each, just to be thorough.

 

Pics of the second microcement layer:

[Adsibob]

Nice colour; I like it!

[SimonD]

Okay, I've done the shower enclosure now. In total 4 coats of finishing resin since my last post, two coats each of a different type. Each coat sanded with 400 grit paper. I'm ever so slightly worried about the final coat as I was slightly short on hardener for this coat so I hoping it is hardy enough. However, if it isn't I can always get some of the same 2 part resin and re-coat.

 

I've also put in the shower, shower door etc. but just waiting for tiles to put into the back and side of the built-in shelf.

 

I'm very happy with how it's turned out. I like both the look and the colour (Montblanc White). Now we just have to see how it stands up to some abuse and I'll report back over time.

 

Below are final photos where I've added a couple in the hope it shows the colour and texture in close up, but may not work.

 

Hopefully this may help anybody looking at microcement in their shower.

 

 

 

 

[Adsibob]

On 12/01/2022 at 17:24, jack said:

 

Having had to remove and replace all of the cracked marble tiles from two showers because the tiler failed to follow some pretty basic principles, I'd go for self-builder overkill every time!

Hmm, we are about to have a bathroom tiled with marble by a tiler, starting  tomorrow. What mistakes did he/she make?

[Adsibob]

I’m thinking of doing our niche with microcement finish. @SimonD is your noche made of cement  board or something else?

[SimonD]

1 hour ago, Adsibob said:

I’m thinking of doing our niche with microcement finish. @SimonD is your noche made of cement  board or something else?

 

Yes, mine uses Knauf Aquapanel, but you can just as readily use skimmed plasterboard, or even plywood as the base.

Edited January 30, 2022 by SimonD

[jack]

6 hours ago, Adsibob said:

Hmm, we are about to have a bathroom tiled with marble by a tiler, starting  tomorrow. What mistakes did he/she make?

 

I described what happened in this thread: 

 

If you don't fancy reading it all, I'd say the main takeaways are to make sure you use proper fixings (eg, not plasterboard screws if you're using a tile backer board), and lots of them, and don't butt boards up hard against each other.