Party Wall Damp from Neighbour's Garden

[Seb101]

The rear wall of our outbuilding forms part of the boundary of our property. Recently there has been a lot of damp coming through the walls inside the building at a low level, it's rotted the wood battens and the plasterboard completely. When I stripped the plasterboard back, after a heavy rain there was actual flowing water trickling into the building through the party wall.

I asked the neighbour to let me inspect it from their side and they agreed. What I've discovered is that the ground level on their side of the wall is about a foot higher than our side, so their lawn and flowerbed is right up against the wall. I've no idea if it's always been like this or if they've done some landscaping over the years (they claim it was always like this).

I am unsure what to do here. The only real fix would be to dig out their garden, re-point the wall and create a soak-away between the earth and the wall, but I can already tell they are not going to like that.

What alternatives do I have, if any?

 

[freddiemercurystwin]

One of the dimpled waterproofing membranes + a drainage channel from the likes of Newlath or Permagard or similar sounds like it could be made to work here. If it's literally only the bit of wall that's below your neighbours ground level then you could stop the membrane say 300mm above that level. The drain is then gravity fed into a handy land drain if that can be made to work or otherwise into a sump from where it's pumped away. Ordinarily these systems assume you'll be employing a floor membrane too but you could use polystyrene for your insulation and then just lay some plywood or similar on top of the membrane or actually just a dpm would work OK here.

 

[Seb101]

One of the dimpled waterproofing membranes + a drainage channel from the likes of Newlath or Permagard or similar sounds like it could be made to work here. If it's literally only the bit of wall that's below your neighbours ground level then you could stop the membrane say 300mm above that level. The drain is then gravity fed into a handy land drain if that can be made to work or otherwise into a sump from where it's pumped away. Ordinarily these systems assume you'll be employing a floor membrane too but you could use polystyrene for your insulation and then just lay some plywood or similar on top of the membrane or actually just a dpm would work OK here.

Nice. Could this somehow drain into waste water drain? Unsure how that connection would work, in terms of smell prevention!

 

[freddiemercurystwin]

Nice. Could this somehow drain into waste water drain? Unsure how that connection would work, in terms of smell prevention!

Yes that's the whole point of the gravity train method, at the end of the drain is a pipe you connect to a gully or similar, smells will be prevented if that land drain has a trap on it which it ought to.

 

[JohnD]

What is the floor of your outbuilding made of?

What us the soil like under the floor?

Where do your roof and gutter drain to?

 

[foxhole]

The rear wall of our outbuilding forms part of the boundary of our property. Recently there has been a lot of damp coming through the walls inside the building at a low level, it's rotted the wood battens and the plasterboard completely. When I stripped the plasterboard back, after a heavy rain there was actual flowing water trickling into the building through the party wall.

I asked the neighbour to let me inspect it from their side and they agreed. What I've discovered is that the ground level on their side of the wall is about a foot higher than our side, so their lawn and flowerbed is right up against the wall. I've no idea if it's always been like this or if they've done some landscaping over the years (they claim it was always like this).

I am unsure what to do here. The only real fix would be to dig out their garden, re-point the wall and create a soak-away between the earth and the wall, but I can already tell they are not going to like that.

What alternatives do I have, if any?

How can there lawn be against a party wall , which means a shared wall.

 

[^woody^]

but I can already tell they are not going to like that.

Does not matter. It's their responsibility to prevent your property becoming damp from their land.

You could get your local council involved by using their powers under environmental health law, and the neighbours could be required to sort it out permanently within 21 days.

That's your bargaining point for starters.

 

[JohnD]

Unless you are on a hill, and rainwater is trickling down the hill until it meets your building, there may be a source of water such as a gutter or downpipe. Hence my question.

It might be possible to block the water from inside. Hence my other question.