Damp on a solid exterior wall in Victorian house

[Jupiter01]

Thanks for all the responses. Really appreciate it.

Firstly, here are some pics. Sorry for the delay in posting these. All of these were cleaned and painted a few months ago.

Is external wall insulation the same as what @cwhaley has described?

is battening, insulating and dry lining the ultimate solution for this?

if yes, can I have some more detail on this please. Should I use metal studs, a vapour barrier, size of insulation?

Thanks again

 

[IT Minion]

Thanks for all the responses. Really appreciate it.

Firstly, here are some pics. Sorry for the delay in posting these. All of these were cleaned and painted a few months ago.

Is external wall insulation the same as what @cwhaley has described?

is battening, insulating and dry lining the ultimate solution for this?

if yes, can I have some more detail on this please. Should I use metal studs, a vapour barrier, size of insulation?

Thanks again

@cwhaley is describing internal solid wall insulation (ISWI). External solid wall insulation (ESWI) can be similar but is generally done by sticking big slabs of insulation board to the outside walls of your house and then rendering them.

There's a decent primer on them here. https://energysavingtrust.org.uk/home-insulation/solid-wall

ISWI is diy-able, ESWI is also but you need scaffolding and might need to muck about with a lot of pipes and windows so it's more common to see that being done by pros. I prefer External as a concept but internal is much cheaper and easier.

 

[Jupiter01]

Thanks @IT Minion. It's definitely ISWI that I would like further info on please.

 

[IT Minion]

Thanks @IT Minion. It's definitely ISWI that I would like further info on please.

There's been loads of threads on here covering them and some good detailed guides on the web in general. If I were you I'd have a search and a general Google, then pick a solution that you think makes sense and put a link in here for the more experienced people to review.

 

[JP_]

For my 1930s bungalow, 9 inch solid brick walls, i had black mould in the corner of all rooms. I stripped off wallpaper, bleached, stuck on 50mm Kingspan sheets with Everbuild dry fix foam, taped over joins, stuck on plasterboard and boarded. First room was done 2 years ago now, done another 2 rooms since, and all still solid and mould free.

Basically, any relatively cold surface will develop condensation, and then get mouldy. The higher the humidity, the higher the dew point, and cold walls will generally be below dew point at times throughout winter in solid homes. Either heat 24 hours a day or insulate.

 

[endecotp]

For my 1930s bungalow, 9 inch solid brick walls, i had black mould in the corner of all rooms. I stripped off wallpaper, bleached, stuck on 50mm Kingspan sheets with Everbuild dry fix foam, taped over joins, stuck on plasterboard and boarded. First room was done 2 years ago now, done another 2 rooms since, and all still solid and mould free.

I think the time-consuming parts are radiators, sockets and switches, skirting boards, coving, and detailing around windows.

(I have just volunteered to help a friend with a similar project....)

 

[JP_]

I think the time-consuming parts are radiators, sockets and switches, skirting boards, coving, and detailing around windows.

(I have just volunteered to help a friend with a similar project....)

I didn't do the parts of wall with radiators in 2 rooms (2 bay windows wit radiators in the bays) so that was easier. It would have been better to remove radiator and do same, put in larger window sill, but decided against that. I also insulated the floors at the same time, so had all floorboards up. And ripped out the skirting, as rotten in parts (along with some floor and joists, plus woodworm). I ditched the coving. Most sockets and switches were on the internal walls, so that wasn't much of an issue.

 

[Jupiter01]

Thanks for the responses. I’ve been doing some online research too and have some questions please:
- is the batten approach with insulation packed in between battens and plasterboard screwed to the battens advisable? This feels easier...
- what thickness of insulation should I consider for this?
- will this definitely spell an end to these “black marks”?
- do I need to use a vapour barrier sheet in this construction?
- shall I use the moisture resistant boards?

 

[endecotp]

Thanks for the responses. I’ve been doing some online research too and have some questions please:
- is the batten approach with insulation packed in between battens and plasterboard screwed to the battens advisable? This feels easier...

Opinions differ. Wood is less insulating than insulation obviously. If there are heavy things to fix to the wall afterwards, wood makes that easier.

Note that if you choose to glue, for fire safety you should have a couple of mechanical fixings at the top of each sheet of plasterboard through into the wall; in the case of a fire you dlm’t want the walls to literally fall off and block your escape route...

- what thickness of insulation should I consider for this?

For many people it’s a case of how much room can you afford to lose.

50mm of PIR would be a minimum, in my view.

- will this definitely spell an end to these “black marks”?

Good chance, but if there is a source of moisture vapour (shower, drying clothes etc.) it does eventually have to go somewhere....

- do I need to use a vapour barrier sheet in this construction?

I don’t think so; the foil faces of the insulation boards form a barrier. You should probably tape the joins.

- shall I use the moisture resistant boards?

I don’t think so, unless in a bathroom.

 

[Jupiter01]

If choosing to stick insulation directly to the wall without battens, how does plasterboard fix to the insulation boards?

 

[IT Minion]

If choosing to stick insulation directly to the wall without battens, how does plasterboard fix to the insulation boards?

You can glue it with something like gripfix (solvent free probably, easier to work with). That's assuming you don't have battens ,or an entire stud wall on the inside of the insulation.

 

[JP_]

If choosing to stick insulation directly to the wall without battens, how does plasterboard fix to the insulation boards?

Everybuild Dryfix Foam. It's amazing.

I didn't use battens because was worried they would still rot. The kingspan (and other brands) has vapour barrier both sides, so when all taped up with silver insulation tape, moisture cannot pass through it and condense on the wall. With battens, rockwool and plasterboard, moisture could get through and cause damp and rot. Also, even with insulated backed plasterboard, you cannot seal between sheets so condensation is still a risk (plus they're more expensive and harder to work with).

 

[bobasd]

your proposing going in for an large amount of DIY work for a minor problem of condensation.

the ceiling soffit condensation is possibly due to a lack of loft/eaves insulation at that point above the ceiling - it could be difficult to rectify.
how much depth of loft insulation do you have?

why not strip the wallpaper from the affected areas & then clean the plaster - fwiw: the wallpaper is already looking sagging and worn.
the usual drying precautions, as above, and trickle heat and trickle ventilation often succeeds over time.
allow air to circulate against all walls.

 

[Jupiter01]

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

Also, is there any harm in using the green moisture resistant boards?

 

[Johnny Allround]

Good afternoon Gentlemen, I have been reading and catching up with the thread. I have been involved in EWI and IWI for the past 7 years so have a pretty good background in what it will and won’t do. IWI is normally fit to the internal walls only of the exposed walls. The thermal 50mm board were fitted screwed into the existing wall and then plastered and decorated in the normal way. We only ever fit this system on solid wall properties it is not a solution for damp or condensation it’s used for energy savings. EWI is 100mm thermal exterior covering that requires a lot of extras ie extended window cills, guttering, downspouts, extended flues not to mention the right fitting and rendering as well as finishes like coins and sealents , this system again is for energy saving and not a solution for damp or condensation. Damp is normally associated with water or moisture ingression I would strongly suggest there will be a breach somewhere. Condensation is purely an air circulation issue caused by a lack of airflow within the building. Hope this helps.