Neighbour's path breaches DPC

[davista]

Hi, I'm looking for some advice on a penetrating damp situation in a single (not cavity) wall in our (actually my GF's) house. The bottom of the wall and around 50cm of the solid concrete floor are damp (10 to 30% on a moisture meter).

We have recently discovered that the neighbours paved path is a few cm above our DPC. There is a gully between their path and our wall, filled with gravel - presumably to act as a French drain. However, the top of the gravel is around 8cm above our DPC rather than the often-quoted 150mm below it. I have uploaded a photo showing this.

Our neighbour is lovely and it was the previous owners who must have installed the path, so we're keen to explore the simplest and most cost effective solution. I had wondered whether I could install chemical DPC rods on the next level up, but then I thought that this may be too high and the damp would continue to come through the wall below it.

So today I drilled an exploratory hole through the mortar in the brick course above the existing DPC and found that the DPC is around 7cm above the internal floor. This was never a problem until the path was laid bridging the DPC, but I don't think creating another higher DPC would achieve anything as damp isn't rising far up the wall anyway and it's mostly the bottom and skirting that are the most damp.

I would very much welcome any suggestions that would avoid lowering the path or perhaps even digging a much deeper gully - which the neighbour isn't keen on as she feels it might be a hazard, as well as being a big job. I've read that one possible solution might be to dig down to a couple of courses below the DPC, clear the soil from the wall and then install a membrane against the wall (perhaps flashing or a roll of DPC standing up as a baffle) and then backfill with gravel. Does this sound like a good idea or a terrible one?

Obviously, any better suggestions would be greatly appreciated

Many thanks

 

[JohnD]

. I had wondered whether I could install chemical DPC rods on the next level up,

Useless.

Dig out the channel.

To prevent you falling into it, you can put random cobbles or large pebbles, with large gaps between them and no dirt, earth, sand or fine material. Water will not rise up large irregular gaps by capillarity, and it will drain well.

Landscape fabric will prevent mud washing into it.

Pebbles can look quite ornamental

Even gravel can hold damp.

Look out for any source of water such as a downpipe or broken drain, and correct it.

 

[davista]

Hi @JohnD

Many thanks for your thoughts. Yeah, as I feared, it really needs to be dug out to do a proper job - as you quite rightly say. It looks like the trench wasn't dug deeply enough as it's no lower than the DPC, and then a thin topping of gravel was laid in top.

I think what you're suggesting with the stones is a French drain and it's interesting about the capillary action, which I reckon may be happening with the gravel - especially with soil mixed up with it. Good tip about covering with landscape fabric to keep the soil and mud out, maybe with some decorative stones on top.

I think it's just rainwater runoff from the path, but I'll check for other sources like a blocked drain or leaking downpipe too

 

[Ivor Windybottom]

The gap between the paving and house isn't full of gravel, it's full of mud with a bit of gravel on top.

Not that it really matters, it all needs to be lower. Digging out the gap between paving and wall wouldn't be sufficient, the path needs lowering.

Have they raised the level over the years? E.g. slapped paving on top of old concrete?

Check all paving slabs with a spirit level, if they're tipping water towards the wall or just level then that's even worse. Drainage needs to be designed in, if there's nowhere for it to go on the other side of the path then it needs actual drainage, e.g. an Aco drain or similar.

Any botch job involving waterproofing is as likely to keep water in as keep it out, it just won't work.

It's not your problem and needs to be resolved. Don't accept the poverty card. They need to fix it.

 

[davista]

Thanks Ivor. Yes, it's clear to me now that the gravel is no use as a drain and was just a top dressing for the mud in the shallow trench between their path and our wall. I don't know whether the paving was laid on top of an existing path.

It's my GF's house and she was renting it out when the previous owners of the house next door laid the new path, so had no idea of what had been done and that it had lead to a nasty damp problem. In fact she had been previously told that it was rising damp, which made no sense as she'd lived here for a couple of decades with no problem whatsoever.

We only recently discovered that the neighbours path had breached the DPC, which lead to me trying to find out more and what needs to be done to fix it. I take your point about it being our neighbours responsibility and everyone has confirmed this, but we feel sorry for her as she's inherited the problem through no fault of her own, especially as she's a lovely person and a good neighbour. I feel sure she'll want to make it right.

 

[davista]

Many thanks for all of you who have kindly replied and generously shared your experience. I'm most grateful for the guidance. We'll be meeting up at the weekend with our neighbour and her retired builder father to discuss a way forward. We have quite a bit of damage inside with plaster falling off (previously hidden behind a cupboard) so there's quite a lot to do internally as well as externally on our neighbour's side to rectify the breach of our DPC. But once the damp stops coming through we can dry it out thoroughly and start repairs and redecoration.

 

[Ivor Windybottom]

Good stuff. Definitely sounds like you have a good positive attitude towards it and they do too. I'd be happy to help them as much as possible, count yourself lucky that you have good neighbours.

We had a similar issue with our previous neighbours. They fixed it, but were extremely grumpy about it.

 

[davista]

Thanks Ivor. Yes, we've been trying to do as much as we can to find out more about what needs to be done to put things right, such as posting on this forum, rather than just leave it to our neighbour to do. She's lovely and we're certainly lucky to have such a good neighbour.