Insulation for bathroom in 1895 stone built house?

RoyMi6

RoyMi6

RoyMi6

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Redoing the downstairs bathroom.

I know old houses need to breath so wondering about the right insulation to use.

We've removed all the old lath and plaster from the bathroom walls and I'm left with an empty carcus at the moment.

I'll be using bathroom suitable plasterboard on the inside, but the other side of each was is:
- one outside stone wall
- 3 inside lath and plaster walls
- a ceiling that is the joists and floorboards of the floor above.
- 28mm wooden floorboards sitting on wooden joists on stone foundations with about 15cm between the bottom of the joists and the ground.

I have space of about 4cm on each wall for insulation but I know the stone and plaster will benefit from having breathing room to disapaite the moisture.

So what kind of insulation would be suitable? I was thinking cheap rock wool would be find between the joists under the floor? Would sheeps wool be ok in all the walls/ceiling?
 
In a bathroom you want an extractor fan to take all the moist air out, you don't want the walls to be transferring any moisture at all - is it just a single leaf of stone to the outside?
What's the finish on the stone? Is there evidence of water ingress?
 
I generally wouldn't put insulation in the wall cavities in an old house, but I'm no expert.

I'd check there's good airflow and humidity under the floor too.
 
the_r_sole said:
In a bathroom you want an extractor fan to take all the moist air out, you don't want the walls to be transferring any moisture at all - is it just a single leaf of stone to the outside?
What's the finish on the stone? Is there evidence of water ingress?
Click to expand...

Oh yeah, 100% agree but problem is that it's about 18inch stone wall id need to go through for the fan! :D

I'll probably put an extractor in the window at some point but it's a secondary downstairs shower room so not going to get used for showers much (only for the odd guest when time's an issue)

Ehhh no finish to the stone. Just irregular large stones... No current water ingress. I've always leant towards no insualtion so far (unless there's a massive void) but just wanting the bathroom to be kept warmer than most other rooms.
 
Thermal insulated plasterboard (foam or styro backed) then tiles or polished plaster.
 
RoyMi6 said:
Oh yeah, 100% agree but problem is that it's about 18inch stone wall id need to go through for the fan! :D

Done this for a combi flue in our house of the same age, no fun at all 18 inches of stone with scalping's in the cavity which need to be propped up.

I'll probably put an extractor in the window at some point but it's a secondary downstairs shower room so not going to get used for showers much (only for the odd guest when time's an issue)

Ehhh no finish to the stone. Just irregular large stones... No current water ingress. I've always leant towards no insualtion so far (unless there's a massive void) but just wanting the bathroom to be kept warmer than most other rooms.
Click to expand...

Condensation is a big issue in our house on the cold walls, we're going to be redoing a few rooms soon and the initial plan was to dot and dab 22mm insulated plasterboard to the external walls but having had some advice we're now going to frame the walls add celotex and plasterboard with normal 12mm as the cold can transfer through the dot and dab and we'll still be left with cold spots and condensation.
 
I'm no builder but I have read up on this because I'm in exactly the same position. Unless you can prevent cold bridging and ensure vapour barrier tightness with synthetic foam type insulation you can expect to get condensation, the risk is it will actually increase in areas like joists. Doing this well is going to be difficult in a rough stone wall. English Heritage have suggested breathing wool type insulations but I don't know much I fancy that. Personally I have accepted the insulation limitation and have bought a portable dehumidifier that I keep on the landing and run all day (in the winter) to bring the humidity back down. So whilst I get peaks of humidity briefly into the 70s I can keep it in the low 50s most of the time and if the air keeps moving condensation is not an issue in the bathroom. I have bigger issues in the kitchen with high vapour generation and stagnant areas under or behind cupboards.
 
PlacidCasual said:
I'm no builder but I have read up on this because I'm in exactly the same position. Unless you can prevent cold bridging and ensure vapour barrier tightness with synthetic foam type insulation you can expect to get condensation, the risk is it will actually increase in areas like joists. Doing this well is going to be difficult in a rough stone wall. English Heritage have suggested breathing wool type insulations but I don't know much I fancy that. Personally I have accepted the insulation limitation and have bought a portable dehumidifier that I keep on the landing and run all day (in the winter) to bring the humidity back down. So whilst I get peaks of humidity briefly into the 70s I can keep it in the low 50s most of the time and if the air keeps moving condensation is not an issue in the bathroom. I have bigger issues in the kitchen with high vapour generation and stagnant areas under or behind cupboards.
Click to expand...

Do you have extractor fans in kitchen and bathroom? These should reduce the humidity (I'm sure you're probably aware!)
 
I use an extractor in the kitchen which makes a big affect but the neighbouring dining room stays stubbornly high so I use the dehumidifier in there. No extractor in bathroom and nearly 2 foot thick undressed rock walls. So in the winter when the wall temperature can drop below or close to dew point at higher humidity I use the dehumidifier to drop the humidity and consequently the dew point.
 
Maybe not a possibility but in our old 1885 house it was less complicated to build an extension onto it for a modern bathroom than deal with the potential issues :s
 
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