Damp on a solid exterior wall in Victorian house

[noseall]

Condensation is purely an air circulation issue caused by a lack of airflow within the building

Nonsense. You could not be more wrong.


To the OP..

Yes you can foam fix insulation boards and foam fix plasterboards. Or you can mechanically fix or even mix it up. Or you can fix battens or even a stud wall. Up to you how you want to lose/use the space.

You can use insulated plasterboard but I recommend fitting in separates. The pre-insulated stuff I've seen is rarely flat and rarely top performing insulation.

50mm Celotex insulation board at a minimum.

Green moisture board is not necessary unless in a bathroom etc.

Your symptoms (black spot mould) are typical of condensation related moisture. It occurs in poorly ventilated and poorly insulated areas subject to cold bridging. They work hand in hand so need to be remedied accordingly. Ventilation alone will not work.

Boba and Jonny have given you well meaning but conflicting advice.

 

[Johnny Allround]

Sorry Noseall, what I meant to say was the way to get rid of condensation is to increase airflow through the property. We are obsessed with thermally insulating everything at the moment that a lot of properties just can’t breath.

 

[cdbe]

Buy them a vented tumble dryer and make them use it, replace/clean/overhaul/increase overrun on bathroom extractor fan, make sure bathroom door kept closed, get rid of any "airing" cupboard. Kitchen - overhaul extractor/cooker hood and leave on for 15 minutes after cooking, check it vents to outside. Discourage boiling food in big open pans. Don't put furniture against external walls. Open windows.
When I worked for a housing provider we politely called it "lifestyle" - we had dozens of identical houses with a high turnover of occupants - it was always them (notwithstanding leaks, faulty extractor/ventilation and heating system problems) - mouldy houses became unmouldy houses and vice-versa with a change of occupants.

 

[bobasd]

Whats "conflicting" about my post?

We sometimes do work for housing assn's or large landlords - say 40 flats or 20 terraced pre-1914 houses that, along with other works, show small patches of condensation, similar to what the OP reports.
And the idea that their RICS surveyors will allow what you propose when dealing with a small amount of condensation wont fly.
We have to keep it simple and cheap - in other words, appropriate, and it works.

 

[endecotp]

Can I glue the insulation boards to the wall and then fix the plasterboards to these insulation boards using everybuild Dryfix foam?

Yes, but you should also have a couple of mechanical fixings per board through to the wall at the top (e.g. frame fixings). This is for fire safety; you don’t want the walls literally falling apart in a fire.

 

[Jupiter01]

Hi guys,

a couple of questions with the app each of glueing and mechanically fixing insulation boards and plasterboards to the walls.

- will this be able to handle a radiator hanging in it?
- what do I do around the window reveals? How should this be finished?

Thanks in advance

 

[endecotp]

Radiators need to screw into wood or through into the brickwork.

Ideally, insulate the window reveals too.

 

[Jupiter01]

There was a suggestion not to use wood as this can rot and pass moisture through to the surface. I suppose this doesn’t matter if the radiator is screwed onto the timber?

On window reveals, I definitely don’t have 50mm plus plasterboard thickness available. How should this be handled please?

 

[Mr Chibs]

20mm celotex or thicker for window reveals if you can.

For walls, I've got wooden battens, and 50mm on top, and all is well two years down the road.

I had a room that looked like yours, black mould.
Windows don't have trickle vents, but I open the windows an inch to breath for a couple of hours each day.

 

[Jupiter01]

For walls, I've got wooden battens, and 50mm on top, and all is well two years down the road.

Are these battens designed to hold the insulation away from the wall? To be clear, you haven't fitted the insulation between the battens?

 

[Mr Chibs]

Correct they are away from the wall.
I was recommended this way by Celotex.

flat to wall seems more popular, and If I was to do it again, I’d probably do it that way, as fixing shelves/poles to the wall Takes a bit of thought.

The batten method does allow a service gap for cabling though.

 

[Jupiter01]

In that case, I will fix my insulation boards directly to the existing wall and then fix plasterboard onto the insulation boards.
Q. Do I make any special provision for where the radiator will be fixed?

 

[Jupiter01]

Also, I have a vent in this wall. Should I block this off as part of this project or retain?

 

[Mr Chibs]

If you use something like 50mm you can just use longer screws for radiators.

If you fix insulation to wall, you can either bond plasterboard Directly to insulation Or use a batten on top of insulation to keep it to the wall, these batten can they be used for wiring and will give you something to screw the PB into.

I would suggest the air vent is of little use now, I would fill it in. I did mine.

look up insulation washers, as they are handy, cheap in a big bag from ‘thebay’

 

[Jupiter01]

I would suggest the air vent is of little use now, I would fill it in. I did mine.

Can I just leave the vent and stick the insulation board in front of it?

Thanks for your help.