DPC on party wall

pangolin said:

darkhairedlord said:

pangolin said:

rjsterry said:

pangolin said:

My neighbour is asking to do a damp proof course injection along our party wall, and I think then tank and replaster his side.

It's a Victorian terrace, build around 1904. Cavity walls, bricks both sides of the cavity (no blocks). No insulation in the cavity.

Under the floorboards is about 1 foot cavity then bare soil. Mainly clay soil around here.

Air bricks front and back but the pavement has been built up over the years and is now slightly higher than the bottom of the bricks. I'm also aware from our survey when buying that the lead between out two roofs (ours is a couple of inches lower than theirs as the street is on a slight slope) isn't great.

I suppose I suspect they'd be better off sorting these issues than tanking over it if there is damp.

I'm not aware of damp on our party wall. Should I just let him crack on, or is it likely to just cause us issues by forcing it all our way?

A few things to run through. Firstly, are you absolutely sure that your party wall is of cavity construction as this would be extremely unusual for a property of this age? You would normally expect solid brick construction with no cavity, especially for a party wall.

Secondly, the air bricks and the void beneath the ground floor are an important part of the house. The air bricks to the front and rear ensure that there is a constant flow of air beneath the floor, which evaporates away any moisture that wicks up through the brickwork, protecting the wall and the floor structure from damp. If your neighbour's air bricks have been blocked, either by paving, or by a rear extension that doesn't maintain the under-floor void, then this might explain the damp that they are experiencing. That said, they should also rule out other possible sources such as slow leaks from water or heating pipes or disused chimneys which have not been capped off.

It is standard practice when injecting a DPC to hack off existing plaster up to about 1.5m above floor level and replaster with salt retardant render. This render allows the damp wall above the new DPC to dry out, but stops the soluble salts within the wall from precipitating out at the surface and damaging the decoration. When treating what is effectively an internal wall, then ideally both sides of the wall should be hacked off and replastered, but I appreciate this may not be something you fancy doing at the moment. This is also where the type of wall construction becomes important: If it really is a cavity wall, then only their leaf can be treated from their side, but if it is a solid wall, then the injected DPC will provide protection to both sides of the wall. The injected DPC should also ideally be positioned below the existing floor level to protect the floor joists, but this may not be practical without lifting all the floor boards.

Lastly, for this kind fo work to a party wall, your neighbour should have issued you with a formal Party Wall Notice, which gives you the right to 'dissent' to the works and appoint a Party Wall Surveyor to draw up a Party Wall Award to cover the works. This gives some protection should the works cause some damage to your property. If it's a reputable firm carrying out the damp proofing, they should have advised your neighbour of his responsibilities. There's an RICS guide to Party Walls here

https://www.rics.org/globalassets/rics-website/media/upholding-professional-standards/sector-standards/dispute-resolution/rics-party-walls-update-01.pdf

It's written from the point of view of the person carrying out the work, but you should be able to work out what applies to you. Hope that helps and DM me if you need anything more specific.

Thanks RJS.

1. Good point, I only know the front and back are cavity. It's probably solid brick.

2. The air bricks aren't covered completely, perhaps 1/3 at most. Ours are the same. Not ideal but it's pavement outside so limited options there.

3. On our side the front half of that wall is behind the stairs and the back half is the bulk of our kitchen units. Not happening frankly. On the plus side if the worst that happens is some discoloration we won't see it anyway.

4. They have given us a notice yes. It's fairly bare bones but gives us the option to approve, ask them to do a survey, or tell them a surveyor of our choice.

I think I'll have a chat with him about what investigation has left them to think DPC is the way to go.

What you don't want is a dispute with your neighbour, this can have implications if you come to sell up.

How so?

pangolin said:

rjsterry said:

pangolin said:

My neighbour is asking to do a damp proof course injection along our party wall, and I think then tank and replaster his side.

It's a Victorian terrace, build around 1904. Cavity walls, bricks both sides of the cavity (no blocks). No insulation in the cavity.

Under the floorboards is about 1 foot cavity then bare soil. Mainly clay soil around here.

Air bricks front and back but the pavement has been built up over the years and is now slightly higher than the bottom of the bricks. I'm also aware from our survey when buying that the lead between out two roofs (ours is a couple of inches lower than theirs as the street is on a slight slope) isn't great.

I suppose I suspect they'd be better off sorting these issues than tanking over it if there is damp.

I'm not aware of damp on our party wall. Should I just let him crack on, or is it likely to just cause us issues by forcing it all our way?

A few things to run through. Firstly, are you absolutely sure that your party wall is of cavity construction as this would be extremely unusual for a property of this age? You would normally expect solid brick construction with no cavity, especially for a party wall.

Secondly, the air bricks and the void beneath the ground floor are an important part of the house. The air bricks to the front and rear ensure that there is a constant flow of air beneath the floor, which evaporates away any moisture that wicks up through the brickwork, protecting the wall and the floor structure from damp. If your neighbour's air bricks have been blocked, either by paving, or by a rear extension that doesn't maintain the under-floor void, then this might explain the damp that they are experiencing. That said, they should also rule out other possible sources such as slow leaks from water or heating pipes or disused chimneys which have not been capped off.

It is standard practice when injecting a DPC to hack off existing plaster up to about 1.5m above floor level and replaster with salt retardant render. This render allows the damp wall above the new DPC to dry out, but stops the soluble salts within the wall from precipitating out at the surface and damaging the decoration. When treating what is effectively an internal wall, then ideally both sides of the wall should be hacked off and replastered, but I appreciate this may not be something you fancy doing at the moment. This is also where the type of wall construction becomes important: If it really is a cavity wall, then only their leaf can be treated from their side, but if it is a solid wall, then the injected DPC will provide protection to both sides of the wall. The injected DPC should also ideally be positioned below the existing floor level to protect the floor joists, but this may not be practical without lifting all the floor boards.

Lastly, for this kind fo work to a party wall, your neighbour should have issued you with a formal Party Wall Notice, which gives you the right to 'dissent' to the works and appoint a Party Wall Surveyor to draw up a Party Wall Award to cover the works. This gives some protection should the works cause some damage to your property. If it's a reputable firm carrying out the damp proofing, they should have advised your neighbour of his responsibilities. There's an RICS guide to Party Walls here

https://www.rics.org/globalassets/rics-website/media/upholding-professional-standards/sector-standards/dispute-resolution/rics-party-walls-update-01.pdf

It's written from the point of view of the person carrying out the work, but you should be able to work out what applies to you. Hope that helps and DM me if you need anything more specific.

Thanks RJS.

1. Good point, I only know the front and back are cavity. It's probably solid brick.

2. The air bricks aren't covered completely, perhaps 1/3 at most. Ours are the same. Not ideal but it's pavement outside so limited options there.

3. On our side the front half of that wall is behind the stairs and the back half is the bulk of our kitchen units. Not happening frankly. On the plus side if the worst that happens is some discoloration we won't see it anyway.

4. They have given us a notice yes. It's fairly bare bones but gives us the option to approve, ask them to do a survey, or tell them a surveyor of our choice.

I think I'll have a chat with him about what investigation has left them to think DPC is the way to go.