damp in understairs cupboard & on internal wall

[Ponders]

Our terraced house doesn't have a through hall - it stops at the stairs where the door opens into the rear room, & the door into the understairs cupboard is at the other end of the rear room

Our row goes hall-living room-hall-living room, so our understairs cupboard adjoins next door's rear room. The halls & understairs cupboards have solid floors, & none of the houses have DPCs. Our house was built later than the adjoining one. Our understairs was always a bit musty, but nothing major, & occasional use of a dehumidifer kept it under control.

(with me so far? )

Now to the nitty-gritty. Next door's rear room, which adjoins our understairs cupboard, used to have a boarded floor, but 20+ years ago somebody decided that taking that up & installing a solid asphalt floor would be a better idea. They subsequently had rising damp around that floor, but managed to sell the house on without the buyers getting a survey.

Those buyers stayed there for several years but recently moved out & sold on at a loss. The new buyers are gutting the house (it's unoccupied) & have had a proper DPC installed throughout.

Since then, especially with the wet weather this year, our damp problem - especially on the wall between our understairs cupboard & rear room - is getting much worse. I assume the damp that used to rise up their wall is now rising up ours instead.

What I need to know initially is whether it's possible to damp-proof internal walls without hacking off all the plaster? Anybody?

not successfully

Also, from what you say, I would be very suspicious that there is a leaking water-pipe under the floor.

Are the kitchens at the back of the house? Is the water-meter in the pavement at the front? Before the stop cock was covered over and forgotten about, it was probably just inside the boundary next to where the front gate used to be.

Is the incoming water service pipe steel, lead, copper or plastic? how about the neighbours?

that's not likely, unfortunately, PJ (I wish it were that simple!)

a modern copper water pipe comes in by the front door & goes straight upstairs. We had that installed not long after moving in; the stop cock is under the pavement outside the front gate. the original lead one came in under the kitchen sink at the back, & also went straight upstairs. that is now capped off outside

there is a central heating pipe under the solid cupboard floor. the boiler is upstairs & 2 large pipes come down into the cupboard to feed the downstairs radiators. we're already thinking we will need to have the cupboard floor dug up...

these houses were not built particularly well, & we had half the downstairs joists replaced 25 years ago because of wet rot - the ones in line with the rear extension, hence out of range of the airflow between front & rear air bricks

also, a short length of our hall wall adjoins next door's asphalted room, & that feels damp too

the roof needs re-slating & the original gutters need replacing - we've been planning for several years to have everything done at once, but not until there are fewer people & less stuff in the house.

Unfortunately the kids keep coming back & bringing piles of stuff with them

might be the neighbour's pipe.

the neighbour has ripped out everything to start from scratch

they now have a nice new water pipe coming in at the front as well, & their front door, hall & kitchen are on the far side of the house from us

I kind of wish we could rip out everything & start from scratch again...not enough time or money though, & too much family & Stuff