Damp Single Brick Solid wall

[arc5]

Hi, my house is 1900 Victoria terrace with a ground floor passage ginnel on one side.
I have a tiny single brick room on the second floor. The brick is old stock I think and is very soft. The mortar is lime and the original plaster was lime. Someone has skimmed over the plaster with a cement based plaster. The room is very cold and the walls feel damp.

Is there any way to better insulate the room and reduce damp without loosing internal space? I was wondering if I could get the external face of the wall rendered or insulated? My understanding is that cement based plasters are bad for this type of brick and won't let them breath? If I removed plaster and redid with lime plaster would the added breathability reduce the damp level significantly?

Downstairs there is a similar situation but I have space to insulate internally. The walls have again been skimmed with cement based blaster. The damp is especially bad along the ginnel side. The wall is solid single brick and has been rendered on the outside (inside the ginnel). What would be the best solution downstairs keeping in mind that the brick is soft and a lime plaster was originally used? Do you think replastering with lime plaster would add back enough breathability and therefore solve the damp? If I plasterboard on the inside would I still need to use a lime based plaster skim to maintain breathability? I've read a foam backed plasterboard might be an option...?

 

[oldbutnotdead]

Yes you can get external wall insulation fitted- problem may come at gutter level if the roof doesn't project much past the walls (older houses don't tend to have the wide soffits that modern builds do). Downstairs you might do OK drylining the wall (hack off to bare brick, batten the wall, fix vapour barrier, fix insulation, fix plasterboard with really long screws). Or you can try EWI in the ginnel. As a matter of interest, how's the ground level in the ginnel relative to internal floor level? Ideally the outside level would be at least 6" below internal floors....

 

[arc5]

@oldbutnotdead thanks for your reply, much appreciated. Unfortunately you're right, there's no roof overhang. There isn't any insulating waterproof render that could be put on the external wall instead of having to put up sheet insulation?

Unfortunately the internal floor downstairs is lower than the outside ground level . It is concrete and has a damp proof course underneath. My plaster used his surface damp meter to identify lots of damp in the bottom meter of the wall. He told me it was rising damp but have read that this might be a myth. I'm thinking could it be that cold air in ginnel is casing the bottom of the wall to be v.cood and therefore condensation to take place on the inside face, with cement based plaster stoping breathability and making things worse? To be on the safe side.I injected a damp course cream around the bottom wall above ground level. I had to rip off bottom 1.5 meters of plaster to do this. It might be my imagination but I think the walls started to dry once free of the cement plaster. I'm also wondering if I insulate / reinforce the gate at either end of the ginnel whether this would warm it up a bit and stop internal condensation? Thanks in advance!

 

[^woody^]

Damp or condensation?

 

[arc5]

@^woody^ I'm not sure. The damp meter reported high moisture levels on surface of plaster. When I removed plaster it felt wet on the inner surface and the bricks behind felt damp to touch. The mortar came out mostly dry when drilled apart from near the gimmel entrance where it came out wet. There is a slope from the gimmel entrance down to the road and there isn't any water entering the gimmel. Thanks

 

[^woody^]

The damp meter reported high moisture levels on surface of plaster.

Thats the worst thing you can do unless you know how to properly interpret the readings. According to my meter, my desk here is soaking for instance, but I have not spilt my coffee and it is certainly not damp.

Meters are cailbrated for timber, so unless you carry out a full spot survey of the whole wall, and interpret those readings, then you will always find that the meter says your walls are damp.

You can have high moisture levels on the surface of walls purely due to normal humidity. That does not mean the walls are damp. Paint, paste and paper can confuse surface probes.

If you have damp, you will have pools of water, brown or yellow stains, or white salt line. Do you have these?

 

[arc5]

Thats the worst thing you can do unless you know how to properly interpret the readings. According to my meter, my desk here is soaking for instance, but I have not spilt my coffee and it is certainly not damp.

Meters are cailbrated for timber, so unless you carry out a full spot survey of the whole wall, and interpret those readings, then you will always find that the meter says your walls are damp.

You can have high moisture levels on the surface of walls purely due to normal humidity. That does not mean the walls are damp. Paint, paste and paper can confuse surface probes.

If you have damp, you will have pools of water, brown or yellow stains, or white salt line. Do you have these?

The plasterer who also does damp services said that he thought there were salts showing and that his meter was a very good one and reported high damp levels. He tested spots all over the wall and it was definitely flagging up damp on the bottom meter of the wall. Towards the top of the wall things appeared ok. However, as you say, these meters can be very unreliable and pick up moisture everywhere.

The walls had been lime plastered, cement skimmed and then papered and papered over and painted several times over the last 100 years. However I had stripped back to plaster before the meter was used. I don't remember noticing any yellow brown damp spots as I removed the layers.

Thanks!

 

[oldbutnotdead]

Main problem with that ginnel wall (or rather an issue that will plague you) is the outside ground level. Is the ginnel all yours or is it shared? Actually either way I'd be digging it out and relaying it a foot lower (and the front and back yards if they're above floor level) or putting a French drain type trench in next to the house wall if there's anywhere convenient for it to drain to.

Problem with reducing the airflow in the ginnel is you'll end up with stagnant air and water in there, unless it is heated then it'll still be outside in terms of air temperature and humidity. Again, if it is exclusively yours then EWI in there will improve the internal wall temperature (and upstairs floor temperature) which will reduce the dampness in the wall. Re the EWI in general- might be worth getting an EPC done, along with your scores you'll get info on what you can get grants/deferred payment terms on. If the roof is getting on it may be worth looking at getting the slates/tile removed, add firring strips & relay felt, battens, whatever to give you sufficient overhang for EWI to work- not necessarily an massively expensive job, depends a lot on access, roof size, roof pitch, roof cover, rafter condition.

 

[arc5]

@oldbutnotdad the plans show it as being included in my property boundary. However the neighbours bedroom runs across half of it and meets my bedroom in the middle of the ginnel, if that makes sense. What's odd is the boundary of my garden runs in line with the neighbours house rather than half way between the two houses suggesting it is mine. So I think from the legal text, plans and boundary arrangement it's my land but I have to allow access to the neighbour. I really need to go t the solicitor to clear it up....maybe a different diynot post. If it's not all mine i guess I'd prob have to send party wall docs to neighbour before EWI all of it...maybe I could EWI just my half?

That's interesting what you say about airflow, I did wonder about this. Maybe I should try to increase air flow through the passage rather than reduce it....

The upstairs room is an ongoing gripe of mine. It is single skin, tiny and has a slanting roof so you have to kneel at the far end. If I were to replace the roof I'd really like to raise the roof and put a proper pitch on it like the neighbours. However this probs involves at least another diynot post or getting an architect involved as I'm not sure whether you can build up a room at one end and put a pitched roof on especially as single brick all the way down to ground level. If I did create an overhang at least I could EWI the bedroom and kitchen below.

Thanks for your EPC suggestion I'll definitely look into this!

Cheers, Andy

 

[oldbutnotdead]

Ahh, the joys of a flying freehold (your ginnel)- can be contentious. Not sure if EWI counts as structural alteration (probably does)- have a chat with your neighbour, see if their box room over the ginnel is cold as well & are they interested in improving the thermal efficiency.

A halfbrick gable end isn't ideal but there are plenty around so don't get too worried, an extra couple of courses isn't going to change the loading by much. Architects do look and feel, structural engineer is your man for 'can I actually do this'.