Loft conversion Dormer on party wall line

8 Jan 2014
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United Kingdom

Imagine this issue comes up often enough. Did search and read one or two postings but not entirely clear of the answers.

Next door have an application for lawful development for their loft conversion.

They have not yet discussed with us but I want to be informed, so when it is discussed, we can ensure this happens smoothly and fairly to both parties in both properties.

The property is semi detached so only affects one other property (ours).

The plans simply show the dormer on the party wall line with no detail for roof / tile / guttering overhang. The dormer has a flat roof - that is clear - material is not detailed in the elevation notes.

Isn't it likely roof detailing would extend the footprint of the dormer and be likely to trespass?

If so how is this normally and practically designed and built knowing the existence of this issue?

Is the dormer wall stepped back from the party wall slightly? I haven't had party wall notice yet, so unsure how they intend on building the wall of the dormer. Timber studwork / extension of brick party wall or other....

We will also probably consider something for the loft in the future so definitely don't want to be unreasonable but also don't want to end up in a disadvantaged situation because their build was first, if that makes sense?


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If the plans/elevations simply show the party wall effectively being extended up to form the dormer side (cheek) then yes they will be encroaching and it seems you're aware they have no right to overstep the boundary which is normally the centre of the PW. If their plan drawer (I hesitate to say designer) was any good he'd have stepped the cheek in away from the PW a bit to avoid this issue. It also looks better IMO and it also allows for long term maintainence if the adjoining owner (you obviously) to come along later and do a dormer yourself. The cheek can easily be supported on a double rafter, that's just standard joinery. It maybe that your neighbour is blissfully unaware of this issue so you need to pop round and find out with a softly softly approach at this stage and find out what the score is. So begs the question do you get on well with this neighbour?
Wow, that was quick, thanks.

Yes, we do get on quite well with them and as said I do want to be reasonable but at the same time don't want to disadvantage our intention to do same also....

The other thing, in terms of discussion, they are not that tuned to practical matters or construction thinking. They are very likely to just come back with something like the builders know what they are doing so they will sort it!!! I just need to think about how to politely counter that....

The designer or drawer, was the third party that their loft conversion company obviously use / engage. On the elevations, there is nothing to tell me the method of construction of the dormer wall except there is a party wall drawn that slices through the elevation and the side of the dormer is on that - no step back shown.

There is also a floor plan for the loft space but does not seem to show dormer wall construction - not that I can see anyway.

Edit: The side elevation facing our side is also shown with hung tiles if that makes any difference. If it was an extension of the party wall wouldn't it be brickwork?

Just thinking further on, even if they did step back slightly and we did the same how would either property maintain sides of the dormer - can't see it working even with a slight step back?

They haven't yet served party wall notice nor told us of the lawful development app, although they had mentioned the intended loft conversion. I suppose the best time is to wait until they want to discuss the party wall notice.....
The set-back needs to be enough to allow access so like 400mm so that if you set yours back the same amount you'd have a gap of 800mm. In theory they could build just inside the boundary and so could you, leaving no room, it happens, people can be pig headed. BTW they don't legally have to serve a PW notice so don't bank on that. Don't wait for that, as it may never happen, address it now. If it's a 'loft conversion specialist' they can be notorious for cutting corners unfortunately.
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When you come round to discussing the loft conversion just tell them you are thinking of doing the same and if it is on the boundary you will just attach your dormer to theirs.
Or that's another option. But if the neighbour builds over the boundary and then the OP decides not to convert their loft that could lead to a sticky situation down the line. If the neighbour does not breach the boundary then that would leave the option open, if the neighbour agrees.
BTW they don't legally have to serve a PW notice so don't bank on that.

They might if any main beams/trimmers bear onto the party wall.

But if it's a loft conversion 'specialist', they won't bother the client with little technicalities like that because it will hold the job up. They might not even get a Building Control body in. They will want to be in and out quick.
Right. Thanks people . Seems like there are options how to approach rather than one right way but it is preferable not to have encroachment.

I think there will be steelwork going into the party wall. My understanding is this would mean they "should " serve party wall notice and if building up the party wall.

To be fair the specialist loft company website mentions, planning permission, permitted development, building regs approvals and party wall agreements with neighbours.

It would be really difficult and potdntially dangerous if they build something in loft space without and possibly not to building regs standards. It would introduce dangers and risks to my property......I hope it doesn't come to that as it would affect value and saleability of their own property....
As far as full width extensions are concerned, I find it staggering that present policy allows the following in terraces...

Instead, I think it should be a requirement that the Party Wall is raised to the full height of the extension...

Is the bottom pic showing the front elevation of a house? (looks that way with the fancy windows). If so, surely they must have had p.p.for that?
Ah - yes - I understand your point.

Problem with our LPA is that if we build off the party wall, they refuse to accept it as pd, because they say that it is not 'development within the curtilage', ie the dormer goes over the boundary.

Probably could be appealed, but few clients are prepared to hold up the work
for the sake of a few extra inches on the width.
I'm not sure that you do understand my point. Both dormers are exactly the same width (internally). The difference is simply the treatment at the party wall.

Your LPA is sharper than most. Around here, they wouldn't even notice.

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