Bathroom installation in period homes

[Melrose]

I’m hoping some experienced members can ease some of my anxieties about this subject!

We’re adding an en suite to a room which has previously contained no bathroom / plumbing. One wall will be external facing, and is currently stripped back to red brick. The floor is suspended timber (first floor level).

Our plan was to use insulating plaster to the external walls (calcea), and the internal dividing studs will just be standard dry wall.

The dilemma occurs when planning the internal finishes... tiling, wet room design etc. Some form of waterproof ‘tanking’ is almost always specified, in the shower area in particular. These are of course not breathable, and our shower area will be in contact with the external wall. Surely applying non brethable layers to the insulating lime plaster is counter intuitive? Would interstitial condensation not occur behind the tanking layer? In that case, would you create a stud wall that will hold the tiles with a cavity between it and the external wall?

Alternatively, I know Tadelakt and microcement are thought to be breathable.... can these be applied directly to the external facing, lime plastered walls?

Any advice on adding en suites to old buildings would be much appreciated!

 

[malcolm]

I think it would be good to use some good waterproofing in a shower. The wall will need to breathe to somewhere if it is to stay dry. Letting water evaporate to the outside works well.

Interstitial condensation would be more of a problem if you added studwork. In a solid wall with insulation it might well occur in the bricks if water gets in from the shower but if the outside is breathable the water will be able to find it's way out as the wind dries the outside of the wall which sucks more water to the surface. I haven't noticed any damp problems in the walls I've insulated or the garden wall that I leave outside in the rain. Though I'm brick built in Bedford which makes this sort of thing very easy.

 

[Melrose]

Thanks Malcolm. I’m less concerned about water getting from the shower out, it’s more so water getting in through the exterior bricks and then being trapped by the waterproof layer?

 

[a twig]

I’ve gone for the stud wall with a cavity approach in the past personally - kept everything away from the (in our case stone) walls and made running services really easy.

Just as belt and braces I installed the biggest extractor fan I could find so that any damp air was vented asap, never had a problem with it

 

[CliffordPope]

I installed the biggest extractor fan I could find so that any damp air was vented asap, never had a problem with it

I've found there is an inherent contradiction between having a powerful extractor fan drawing air in from close to the shower enclosure, and the roaring draught it creates while I am in the shower.
To delay turning on the extractor until out of the shower, or suffer the draught for the sake of clearing the damp air asap?

 

[Cubist]

Hi Melrose and Welcome,

Seeing your earlier reply to Malcolm I suspect that the subject of your worries is not a great one. Yes, by say tiling the bathroom interior wall this will inhibit the flow of air over and through its surface and therefore, in my opinion, would reduce the overall performance of the exterior wall to expel rainwater that may have been absorbed into the brickwork. Would such water be permanently trapped? No, I don't think so, as prevailing external airflow would do much to remove it. Could any trapped water not removed by external convection currents become sufficient to threaten damage to the house? Personally, I think that's highly unlikely even if the wall is fully exposed to prevailing and heavy rainfall for much of the year.

Bluntly, unless you're planning to cover a very large area of an external wall I would not be too concerned if I were you.

Hope this helps.

Cheers,
Cubist

 

[Melrose]

Hi Melrose and Welcome,

Seeing your earlier reply to Malcolm I suspect that the subject of your worries is not a great one. Yes, by say tiling the bathroom interior wall this will inhibit the flow of air over and through its surface and therefore, in my opinion, would reduce the overall performance of the exterior wall to expel rainwater that may have been absorbed into the brickwork. Would such water be permanently trapped? No, I don't think so, as prevailing external airflow would do much to remove it. Could any trapped water not removed by external convection currents become sufficient to threaten damage to the house? Personally, I think that's highly unlikely even if the wall is fully exposed to prevailing and heavy rainfall for much of the year.

Bluntly, unless you're planning to cover a very large area of an external wall I would not be too concerned if I were you.

Hope this helps.

Cheers,
Cubist

Thank you, that is quite helpful! I did fear I’m overthinking. It stemmed from an adjacent room that had foil backed insulation board attached directly to the lime plaster wall, and condensation had formed on the back of these boards leading to a pretty terrible mould situation within the wall. Although I know tile may not create such a cold interface compared to thick foam board, i thought maybe the same issue with condensation might arise!

 

[a twig]

I've found there is an inherent contradiction between having a powerful extractor fan drawing air in from close to the shower enclosure, and the roaring draught it creates while I am in the shower.
To delay turning on the extractor until out of the shower, or suffer the draught for the sake of clearing the damp air asap?

It’s the velocity of the draught that dictates how much you feel it, so using a larger inlet reduces the velocity in the room so you feel the draft less. We used one of these with an egg crate grille above our shower

Plastic Back Box (Plenum Boxes) Top Entry

Manufactured from black recycled thermoplastic.

www.efans.co.uk

Really effective and no chills at all while showering as the air “speeds up” inside the box rather than in the room.

In comparison we installed a “normal” one in our ensuite and it’s proved ineffective and uncomfortable in comparison so on my list to upgrade

 

[CliffordPope]

Thanks for the suggestion. I'd wondered about spreading the draught a bit to make it "thinner", and had perhaps been too much influenced by the advice to mount the inlet as close to the shower head as possible to try and capture the moist air before it could spread out into the room.
I'd thought that perhaps the ideal would be a gentle setting while in the shower, and only turn it to "hurricane" setting for a few minutes once finished.

I suppose it also depends on where the replacement air comes from. Warm air from a warm area of the house would be nice but inefficient, whereas in our house it's cold air sucked in from the lobby by the back door.

 

[malcolm]

It stemmed from an adjacent room that had foil backed insulation board attached directly to the lime plaster wall, and condensation had formed on the back of these boards leading to a pretty terrible mould situation within the wall.

A foil backed insulation board will behave just the same as any other impermeable barrier so there is a fair chance my advice was poor. Unless the foil backed insulation wasn't completely airtight to the room and water got sucked to the colder wall behind. I wasn't thinking about water coming in from outside. It doesn't do that in Bedfordshire when you have exposed bricks on the outside with lime mortar and pointing.

Studding might well be better as it would allow water vapour to go where it can rather than trap it against a membrane.

 

[Bpm]

So shower enclosures must now be fully sealed... Essentially that means tanking, or something like a sealed panel. I'm more worried about leaks from the shower and my timber frame. As a complete alternative, how about a glass shower wall against your outside wall. Gets over the tanking, let's the wall breathe, and just need to consider how to give it a clean from time to time. You can also admire your lime plaster when in the shower!

 

[Cubist]

As a complete alternative, how about a glass shower wall against your outside wall. Gets over the tanking, let's the wall breathe,

Presumably you would also ensure that you could easily remove that large and very heavy safety glass panel so that you could occasionaly clean behind it, maintain the wall, and decorate it as and when needed or dictated by the other half?

 

[Easrow]

We have also fitted an ensuite to a room which never had one. We used roofing batten to bring the plasterboard and tiles off the wall and left the gap behind open to the roof above and the floor joists below so there is at least some circulation of air behind. There is no loft above at that point just the roof. We also have an extractor fan above the shower head at the highest part of the room to get rid of condensation quickly. As it is higher than the shower screen you feel no draught, until you open the shower door at least.
It's has been 5 years so gar and no issues yet and it is used almost daily with Mrs E having the shower at tea making temperature!

 

[Feltwell]

I've just ripped out & replaced our en-suite, which was in a room that would originally have been a store room. I ripped out a lot of soggy plasterboard from internal stud walls! Plasterboard, even moisture resistant plasterboard, just should not be used in bathrooms on walls.

I highly recommend Abacus "Elements" board, there are other similar products out there - a light, but very strong board with a closed cell foam middle that is totally impervious to water, insulates, is very easy to cut and gives an excellent surface to tile or plaster onto - a lot better than the cement based boards. Buy the kit with the joint sealing system and it should last forever. The "No more leaks" kit is good for shower tray and bath sealing under tiles as well, much better than just relying on tube sealant. Have a look at this video from about 7 minutes onwards for the Elements board, though the whole thing is worth watching.

I had 1 external wall that was already gypsum plastered - not ideal but it showed no signs of damp so I left it as is.

I keep meaning to put up a post about the bathroom refit, as folks seem to like these things. Not very "period" but it's a room that had to be modern in our case, no room for anythng else.

 

[WetWales]

hi guys, I appreciate the link above and am planning to use the elements board so thank you for posting that link!! really appreciate that!
what would you guys do with this ceiling...

CEILING!
its T&G cladding, with an extractor right above the shower cubicle and another one the flat ceiling higher up.. the shower cubicle will be on the left of the window, left of the photos. with water pipes routed in the stud wall, our lime plasterer suggested we build a stud on the external wall to give a flat surface but the stone should breathe outward too

but now I am wondering the T&G is going to be ok...
I was thinking just in this one spot on the bathroom ceiling I would try to seal the timber instead of using a breathable paint on it as in the rest of the bedroom ceilings, but now im thinking should we take it down altogether and just lime it, would that be more mould resistant?!
or put the elements board, and then the cladding back up?
behind the cladding JUST on the slopes is silver foil insulation, but the flat ceilings areas are wood fibre insulation so breathable.

not sure if the cladding will just go super mouldy or any steam that gets thru the cladding will hit the foil and condense and have no way out

pic1 bathroom roof with hold for extractor fan,
pic2 same corner
pic 3 foil of bedroom as example. its the same
pic4 bathroom roof


is it also a good idea to build a small stuff against the stone wall to tile onto? you've all talked about it before and no ones had major problems..?

thanks!