Neighbour's planning application for new build requires underpinning of my wall!

FreeBear

Section62 said: I think the situation may be slightly more complicated than we might be assuming here, as [1] the land is already built on (and their structure (previously?) had some degree of attachment to yours) and [2] it is likely part of your foundations are under the neighbour's land.

The Structural Method Statement appears to assume that the side wall is a shared one. Although the drawings seems to show that a new wall will be constructed in close proximity (touching ?). As things currently stand, one of the documents claims that the existing garage has a ~480mm gap between the OPs wall.

The devil is in the detail, and we really need to see the builder's plans to see exactly what they are intending to do.

ThisIsWeird

https://www.standard.co.uk/homesandproperty/property-news/threestorey-property-sale-walthamstow-narrow-6ft-wide-b1212480.html

Section62

FreeBear said:

Section62 said: I think the situation may be slightly more complicated than we might be assuming here, as [1] the land is already built on (and their structure (previously?) had some degree of attachment to yours) and [2] it is likely part of your foundations are under the neighbour's land.

The Structural Method Statement appears to assume that the side wall is a shared one. Although the drawings seems to show that a new wall will be constructed in close proximity (touching ?). As things currently stand, one of the documents claims that the existing garage has a ~480mm gap between the OPs wall.

The devil is in the detail, and we really need to see the builder's plans to see exactly what they are intending to do.

Unless someone has moved the garage since the 2022 Streetview, the gap looks to be about a brick length so ~225mm.

On the old OS mapping the garage appears to be sited on land which was part of the neighbouring garden (not the OP's) - allowing for OS mapping not always being accurate, and remembering land may have been transferred - it would appear the boundary has probably been the face of the flank wall of the OP's property since it was constructed.

GDB2222

If one flank wall of the OP’s house is underpinned, how does that work with differential movement of the two flank walls and the front and rear walls?

 Islington is mostly built on shrinkable clay, and this terrace has probably survived because the whole terrace has the same foundations, or rather lack of foundations.  If one end is heavily underpinned, how is that blended into the rest of the terrace?

BunnyBurrow

GDB2222 said:

If one flank wall of the OP’s house is underpinned, how does that work with differential movement of the two flank walls and the front and rear walls?

 Islington is mostly built on shrinkable clay, and this terrace has probably survived because the whole terrace has the same foundations, or rather lack of foundations.  If one end is heavily underpinned, how is that blended into the rest of the terrace?

Yes, I think this is where I am coming from really, but you have articulated it better than me

I would rather not be messing around with foundations given the unknown long term consequences. It all feels very uncomfortable.

It's not nimbyism. It's wanting-to-make-sure-I-don't-end-up-with-a-big-crack-in-my-house-ism as that would undoubtedly be a very expensive problem which could happen long after this pair have built their 3-storey shoe box, sold it, made their profit and moved onto their next investment without giving a toss about the long term impact.

Section62

GDB2222 said:

If one flank wall of the OP’s house is underpinned, how does that work with differential movement of the two flank walls and the front and rear walls?

 Islington is mostly built on shrinkable clay, and this terrace has probably survived because the whole terrace has the same foundations, or rather lack of foundations.  If one end is heavily underpinned, how is that blended into the rest of the terrace?

More or less the same way it works when all the thousands of extensions are built in the UK each year, with BC insisting on foundations that are deeper/stronger than the foundations of the rest of the house.  I doubt many homeowners looking forward to having their shiny new extension give too much thought to differential movement.

However, this is where working with the developer and having a PWS onboard is valuable - you can ask the questions and get a SE report you can fall back on if there is a problem in the future.  "The SE, working for me, provided assurance that the underpinning would not lead to differential movement" would be a useful thing to be able to say.

Somewhere in the reports I read that the mass of earth being removed was broadly the same as the mass of the new building, so in terms of total imposed load within the footprint the project would have a neutral effect.  This suggests at least some thought has already been given to the potential effects of the work on the OP's property.

BunnyBurrow

Section62 said:

GDB2222 said:

If one flank wall of the OP’s house is underpinned, how does that work with differential movement of the two flank walls and the front and rear walls?

 Islington is mostly built on shrinkable clay, and this terrace has probably survived because the whole terrace has the same foundations, or rather lack of foundations.  If one end is heavily underpinned, how is that blended into the rest of the terrace?

More or less the same way it works when all the thousands of extensions are built in the UK each year, with BC insisting on foundations that are deeper/stronger than the foundations of the rest of the house.  I doubt many homeowners looking forward to having their shiny new extension give too much thought to differential movement.

However, this is where working with the developer and having a PWS onboard is valuable - you can ask the questions and get a SE report you can fall back on if there is a problem in the future.  "The SE, working for me, provided assurance that the underpinning would not lead to differential movement" would be a useful thing to be able to say.

Somewhere in the reports I read that the mass of earth being removed was broadly the same as the mass of the new building, so in terms of total imposed load within the footprint the project would have a neutral effect.  This suggests at least some thought has already been given to the potential effects of the work on the OP's property.

This is reassuring thank you. I take your point re the PWS etc. Very much appreciate everyone's help with this!

GDB2222

Section62 said:

GDB2222 said:

If one flank wall of the OP’s house is underpinned, how does that work with differential movement of the two flank walls and the front and rear walls?

 Islington is mostly built on shrinkable clay, and this terrace has probably survived because the whole terrace has the same foundations, or rather lack of foundations.  If one end is heavily underpinned, how is that blended into the rest of the terrace?

More or less the same way it works when all the thousands of extensions are built in the UK each year, with BC insisting on foundations that are deeper/stronger than the foundations of the rest of the house.  I doubt many homeowners looking forward to having their shiny new extension give too much thought to differential movement.

However, this is where working with the developer and having a PWS onboard is valuable - you can ask the questions and get a SE report you can fall back on if there is a problem in the future.  "The SE, working for me, provided assurance that the underpinning would not lead to differential movement" would be a useful thing to be able to say.

Somewhere in the reports I read that the mass of earth being removed was broadly the same as the mass of the new building, so in terms of total imposed load within the footprint the project would have a neutral effect.  This suggests at least some thought has already been given to the potential effects of the work on the OP's property.

I don’t know how these extensions do work out, actually? 

https://www.youtube.com/watch?v=-hxTrm34oRI

FreeBear

Section62 said:

FreeBear said:

Section62 said: I think the situation may be slightly more complicated than we might be assuming here, as [1] the land is already built on (and their structure (previously?) had some degree of attachment to yours) and [2] it is likely part of your foundations are under the neighbour's land.

The Structural Method Statement appears to assume that the side wall is a shared one. Although the drawings seems to show that a new wall will be constructed in close proximity (touching ?). As things currently stand, one of the documents claims that the existing garage has a ~480mm gap between the OPs wall.

The devil is in the detail, and we really need to see the builder's plans to see exactly what they are intending to do.

Unless someone has moved the garage since the 2022 Streetview, the gap looks to be about a brick length so ~225mm.

Agreed, streetview does look like the gap is around 250mm. Here is the plan from the SMS -

ThisIsWeird

Bunny's wall appears to be in decent condition. Just curious, but say her wall was in a very poor state, requiring serious remedial work within 5 years. What would happen in such a situation as this, if a new development threatened to cover it, preventing access?