Neighbour plans on loft extension using our loft extension wall

silvercar

I just wanted to check if this made sense.

Son has just completed on a terraced house with a loft conversion completed about 10 years ago. Neighbours have lawful development certificate to do a loft conversion. They have now said they intend building next year and will arrange a PWA and appoint a surveyor. Looking at their approved plans they intend for their loft conversion to join on to son's existing house. They said they will need to remove the outer tiles on the side of his extension. The extensions will then meet and as they are the same height, this will look better and also prevent an 'impossible to maintain' gap in the middle.
I can see this makes sense and wouldn't want to be difficult for the sake of it, but is this the correct way of doing things? The one thing that makes me concerned is that son's extension only goes as far (towards the neighbours') as the edge of the ridge tiles. So the neighbours new extension will encroach over the boundary by a few inches. Is this the correct way of building?

silvercar

 picture here.

Sarahspangles

silvercar said:

The one thing that makes me concerned is that son's extension only goes as far (towards the neighbours') as the edge of the ridge tiles. So the neighbours new extension will encroach over the boundary by a few inches. Is this the correct way of building?

The previous owners had the option of building their extension straddling the boundary, but didn’t choose that option. The second extension therefore has to work with an asymmetric boundary party wall or create a permanent maintenance problem. 

Section62

Sarahspangles said:

silvercar said:

The one thing that makes me concerned is that son's extension only goes as far (towards the neighbours') as the edge of the ridge tiles. So the neighbours new extension will encroach over the boundary by a few inches. Is this the correct way of building?

The previous owners had the option of building their extension straddling the boundary, but didn’t choose that option. The second extension therefore has to work with an asymmetric boundary party wall or create a permanent maintenance problem. 

The new building work doesn't have to affect the legal boundary line - the builders can put whatever structure is required on silvercar's son's side of the boundary to connect the two extensions, but maintain the boundary line on the legal boundary.

The PWA can sort this detail out, so long as the PWS is reasonably competent.  It would be advisable for the son to have their own PWS, or make sure they are fully involved in selecting the joint one - i.e. that the PWS isn't a mate or contact of the neighbour.

silvercar

I wasn't sure whether they should build their extension independently and have some sort of bonding gutter between the 2 roofs. Or even, given that son's roof is already in existence, they should be leaving a gap of 1m to allow access to both for maintenance. (Though the latter seems churlish, given that the house is joined on the lower floors in any case).

Doozergirl

It looks like the neighbours are actually proposing to build up the party wall.   In their nature, a party wall 'encroaches' across both boundaries because a boundary has no dimensions but bricks do.  

It would have been sensible for whoever did your son's dormer to have done the same but they took the cheaper option.  

I'd be much happier with what they are proposing than a gap next to a tiled wall. 

Sounds like a positive to me.  

Chickereeeee

It strikes me as a good way to have extra insulation (sound, heat) between the two extensions in that area.

kimwp

I think I'd request that the middle bit was filled in to reduce sound transfer.

ThisIsWeird

I agree with what is said above - you do not want a gap left between the two structures. That might, however, leave concerns about boundary encroachment, but - other than emotive - this shouldn't cause any practical issues at all (aIui).
So that Silvercar - and other folk in similar situations, as this is a regular question on here - is fully informed, what are the various options available, coupled with their pros and cons? I'm guessing:
a) Leave a gap. Pros - can't think of any, other than 'emotive' over boundaries. Cons - hard/impossible to maintain. Will make construction for the neighb very difficult, and will likely lead to bad relations. It will look daft. 
b) build up to existing construction and make it a Party Wall, the same as the house below, with matching external finish. Ie, tiles match, and continue as one. Pros - sensible option. No visual/emotive 'encroachment'. Cons - neighb's might reasonably not want the same finish - eg new neighb wants cladding, or even render to match rest of house. Which leads to...
c) ditto as (b), but with a visual boundary separator/ marker to clearly differentiate the two constructions - there must be options there? Pros - removes any even emotive concern over 'encroachment'. Emphasises the separateness of the two. Prevents any awkward-looking transition betwixt two contrasting finishes. Cons - small additional complexity.
d) ?
Corrections/additions to the above?

silvercar

ThisIsWeird said:

I agree with what is said above - you do not want a gap left between the two structures. That might, however, leave concerns about boundary encroachment, but - other than emotive - this shouldn't cause any practical issues at all (aIui).
So that Silvercar - and other folk in similar situations, as this is a regular question on here - is fully informed, what are the various options available, coupled with their pros and cons? I'm guessing:
a) Leave a gap. Pros - can't think of any, other than 'emotive' over boundaries. Cons - hard/impossible to maintain. Will make construction for the neighb very difficult, and will likely lead to bad relations. It will look daft. 
b) build up to existing construction and make it a Party Wall, the same as the house below, with matching external finish. Ie, tiles match, and continue as one. Pros - sensible option. No visual/emotive 'encroachment'. Cons - neighb's might reasonably not want the same finish - eg new neighb wants cladding, or even render to match rest of house. Which leads to...
c) ditto as (b), but with a visual boundary separator/ marker to clearly differentiate the two constructions - there must be options there? Pros - removes any even emotive concern over 'encroachment'. Emphasises the separateness of the two. Prevents any awkward-looking transition betwixt two contrasting finishes. Cons - small additional complexity.
d) ?
Corrections/additions to the above?

d) Google seems to suggest a bonding gutter between the 2.

My main concern is that of structural integrity if they just use the existing outside wall as their internal wall ie they don't build up a new wall, but take the current wall and plaster it. Would that then mean they have encroached over the boundary and this could cause issues on sale?
Obviously, it won't make a difference to the current room size so has no impact in that regard.

ComicGeek

The side wall of the existing former is probably fairly thin timber framed construction, so will very likely need beefing up to create a compliant party wall. They shouldn't just be taking off the tiles and plasterboarding - likely they will need to build a second timber frame with acoustic insulation and then boarding. So by the time they've built this the internal face of their dormer will be further across.

A good party wall surveyor will deal with all of this.