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DPC on party wall

pangolinpangolin Posts: 4,032
edited 21 March in The cake stop
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?
Genesis Croix de Fer
Cube Attain

Posts

  • ProssPross Posts: 29,958
    Paging RJS!
  • Harry182Harry182 Posts: 1,159
    A party wall agreement is in order before the work begins. It's your neighbor's obligation to pay for it and your right to appoint your own surveyor. Make sure the survey includes a damp survey.
  • rjsterryrjsterry Posts: 21,019
    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.
    1985 Mercian King of Mercia - work in progress (Hah! Who am I kidding?)
    Pinnacle Monzonite

    Liberal metropolitan, remoaner, traitor, "sympathiser", etc.
  • oxomanoxoman Posts: 9,868
    If single brick between you and your neighbour you can get staining your side. Tanking is a way of ensuring it doesn't happen again. Alot of cellar / basement apartments are tanked. Suspect the mortgage lender will have insisted something done about it.
    Too many bikes according to Mrs O.
  • darkhairedlorddarkhairedlord Posts: 7,111
    I'm no expert ;) but you should not need dpc on a party wall. If there is a damp problem caused by raising the pavement then the pavement needs dropping.
  • pangolinpangolin Posts: 4,032
    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.
    Genesis Croix de Fer
    Cube Attain
  • pangolinpangolin Posts: 4,032
    oxoman said:

    If single brick between you and your neighbour you can get staining your side. Tanking is a way of ensuring it doesn't happen again. Alot of cellar / basement apartments are tanked. Suspect the mortgage lender will have insisted something done about it.

    I think they bought a year or so before us, so about 3 years ago.
    Genesis Croix de Fer
    Cube Attain
  • darkhairedlorddarkhairedlord Posts: 7,111
    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.
  • pangolinpangolin Posts: 4,032

    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?
    Genesis Croix de Fer
    Cube Attain
  • orraloonorraloon Posts: 9,148
    Perhaps irrelevant. A previous house of mine was built in 1870 of std brick. Had been 2 semis but previous owner had bought out the other side and then botched up the conversion before stopping 1/2 way through then the couple split.... Anyways...

    The party wall between the 2 halves was built with a small cavity space between 2 verticals of brick laid the 'wrong' way up, i.e. on edge. I suspect the outside walls were similar but over the years had been rendered so couldn't see that. May just have been a way of using less brick, saving money.
  • darkhairedlorddarkhairedlord Posts: 7,111
    pangolin 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?
    When you sell you make a declaration in the contract about prior disputes. If you fail to declare you could face legal action from the new owner.
  • pangolinpangolin Posts: 4,032

    pangolin 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?
    When you sell you make a declaration in the contract about prior disputes. If you fail to declare you could face legal action from the new owner.
    I see, thanks
    Genesis Croix de Fer
    Cube Attain
  • rjsterryrjsterry Posts: 21,019
    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.
    Good to hear you've had a proper notice from next door. Usually the notice gives you the option to consent or dissent to the works, triggering the need for a party wall award. If you feel dissenting is a bit confrontational, most party wall surveyors will agree to just prepare a 'schedule of condition' - usually a photographic record of the state of the wall on both sides before the work was carried out - rather than a full award. This saves your neighbour a bit of money but still gives both parties some reassurance.

    Yes, definitely worth finding out a bit more about why he's doing the work.
    1985 Mercian King of Mercia - work in progress (Hah! Who am I kidding?)
    Pinnacle Monzonite

    Liberal metropolitan, remoaner, traitor, "sympathiser", etc.
  • rjsterryrjsterry Posts: 21,019
    orraloon said:

    Perhaps irrelevant. A previous house of mine was built in 1870 of std brick. Had been 2 semis but previous owner had bought out the other side and then botched up the conversion before stopping 1/2 way through then the couple split.... Anyways...

    The party wall between the 2 halves was built with a small cavity space between 2 verticals of brick laid the 'wrong' way up, i.e. on edge. I suspect the outside walls were similar but over the years had been rendered so couldn't see that. May just have been a way of using less brick, saving money.

    😬 I've seen brick on edge used for infill of internal partition walls but not for a party wall. Mind you, dodgy builders are certainly not a new thing. I've seen a front facade with nice yellow stocks on the outside and commons on the inside - fair enough; no point wasting more expensive bricks where they aren't going to be seen - only to save a bit more, all the headers were actually only half bricks. So what looked like a 9" wall was actually two skins of 4 1/2" with nothing holding them together and the outer leaf peeling away towards the street. The whole thing had to be stitched back together with metal rods and epoxy.
    1985 Mercian King of Mercia - work in progress (Hah! Who am I kidding?)
    Pinnacle Monzonite

    Liberal metropolitan, remoaner, traitor, "sympathiser", etc.
  • orraloonorraloon Posts: 9,148
    😊 Cowboy builders ain't a new thing. I don't live there anymore... not my problem...
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