Rising damp & other issues

[saffron77]

Advice on damp/condensation
Would really appreciate advice on how to address damp issues in ground floor Victorian flat. It seems to have become worse in recent years - we have had a few rising damp surveys & an independent survey (which was much more thorough & helpful) . We had the flat rented for 8 or so years & prior to this carpets, walls & kitchen were all updated. We have a large patch of damp above skirting in hallway on party wall - up to about a metre high. It fits the description of rising damp & all rising damp specialists have picked up on it. Independent guy has not ruled it out but said also check leaks (water mains, neighbors etc). Under floor seems all joists were replaced many years ago & all look fine. Obv there was a reason for that work. Could the original dpc have been affected by the joist work? Would the dpc injections be the only solution? I know neighbor on other side had decorated but has possibly used a water resistant plaster & paint - looked glossy. One suggestion has been this has pushed damp through more on our side. We have air bricks but unf the patio to the rear is too high so we have advice to deal with that.
we are just getting v confused with various advice & warnings about dpc not being the answer. We are quite near a river & foundations are deep - a little damp looking in parts but no pools of water. Any advice grateful received . I can dig out photos if helpful - thanks & sorry for long post!

Is that wallpaper on the wall? It looks like it's coming away. I'd be tempted to pull it off and see what's happening behind there.

I assume it has modern gypsum plaster on it? You could try stripping off the plaster back to brick to let it dry out. If it dries out over the course of a few months then replacing the modern plaster with lime plaster will allow the wall to breath and the moisture will come out into the air inside the house and will disperse without causing a problem as long as the house is reasonably well ventilated.

Thanks - I’ve now peeled it off & put a dehumidifier on - see pic

Not sure type of plaster. I’ve also had a suggestion of using Oldroyd? System with plaster over the top to allow the wall to breathe . We are quite confused about what’s going on. Also have been advised that party wall work needs neighbours approval. We want to sort out issues in a reasonable amount of time - rising mortgage & no rent . Obv don’t want anyone having to live with unrepaired damp

Rising damp is a myth and dpc injections are a con, I suggest you join the traditional and listing building advice group on Facebook

Geneticsbunny · Today 11:20

I assume it has modern gypsum plaster on it? You could try stripping off the plaster back to brick to let it dry out. If it dries out over the course of a few months then replacing the modern plaster with lime plaster will allow the wall to breath and the moisture will come out into the air inside the house and will disperse without causing a problem as long as the house is reasonably well ventilated.
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ChickpeaPie · Today 14:31

Rising damp is a myth

No it isn't.

Lime plaster. The leading brand is limelight. Re-plastering (up to a height of about 3 feet) is a messy job, but worked for me.

IMPORTANT...when you repaint the walls, use 'clay based paint' ('Earthborn is a leading brand). If you use normal emulsion paint such as Dulux, it will flake off the wall - which at least proves that the wall is 'breathing' and moisture is emitting from the wall. 'Clay based' paints allow the moisture to pass through the paint.

That picture looks a bit like the wall has been painted with gloss paint? That definitely won't be helping if it is gloss

First stop, Heritage House website. Lots about damp on there. Never, ever, let any 'damp specialist company' touch your house unless you have read what's on there first.

Absolutely second getting lime plaster, plus the earthborn.

I am not sure - it’s a fine layer of what I thought might be glue for lining paper

Thanks for suggestions
I was initially very hesitant to go straight for a new dpc but independent surveyor said could not be completely ruled out - possible original dpc had broken down or been affected by joist works (done prior to us moving in). We are also concerned there is high humidity in the flat - dehumidifier has been on for 3 days & needs more. There is a critical missing air brick under front door which we are trying to rectify but air bricks to the opposite side of this damp party wall area seem to be sufficient (the replaced joists are all dry & look new although installed many years ago)
tenants who recently moved out constantly dried washing in the flat & told me they saved money by heating one room at night….the carpet seems to be holding a musty smell which we were not sure has absorbed condensation or just bc of the damp. We just need to put it right before redecorating to rent out

If the building is Victorian, the dpc will probably be slate. This won't degrade but could possibly have been damaged by the joist work. If you look outside, you should be able to see where the row of slates is. Then you can follow the level inside the building to see if it corresponds with where the new joists were put in under the floor.

If they have damaged the dpc, under the floor level then I am not sure how you could repair that? Hopefully someone else might have some advice.

Either way, taking the new gypsum plaster (pink) off of the wet wall will help dry the wall out and will help work out what the underlying issue is. Once gypsum plaster gets wet, it is pretty much ruined and Salts and stuff leak out, so it will have to come off regardless of what you do next.

If you want to check if the plaster is gypsum or lime you can chip off a small peice and put it in vinegar. If is fizzes it is lime.

thanks for advice - will try the vinegar :). suspect it's gypsum . I expected a bubbling salt like appearance to come through the wall and the skirting to get wet - but it's fine...

We looked for row of slate but can not see any - its mid terrace and the back of flat has a high ish render (with what looks like previous dpc drill holes in the middle of the render)..... We looked 15 - 20 cm under the floorboards beneath damp patch and all we see is a thicker mortar area which we've been told could be the slate area... I guess the main issue is the big patch of damp above skirting needs sorting out - strange though, under floor boards looks dry but maybe this is normal and the damp is inside ??- party wall neighbour avoiding discussions and obviously this can't drag on because we need it repaired & rented & we've been told the only other option without neighbour approval would be tanking?? Does this make sense...we are getting even more frustrated & confused!

I assume the external wall is dry on the inside? If the render is over the dpc then it will be breaching it and allowing water to move up the wall. If it's dry then it can be ignored for the time being but worth noting in case there are problems in future.

Is the damp wall anywhere near a chimney breast? If the wall is dry underneath the floor and the underfloor space is well ventilated then the damp can only be coming from a pipe leak somewhere or running down a chimney.

Taking the wet plaster off is still the best first step. If the wall dries out with the plaster off then it will be fine to put lime plaster on and leave it like that. It can take months for a wet wall to dry out though. The quicker you take it off the better and you might be able to speed it up by having the heating on and ventilating the flat.