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Dormer conversion issue, next to existing neighbour extension

2 replies

Otter1986 · 18/03/2026 10:46

We are house hunting and are struggling to find anything we like... however, a doer upper on a street we love has been sitting on the market and we are considering a viewing and a reasonable offer that reflects the state of the property (currently we don't think it really does reflect that).

Now, we know that the seller might be difficult which is why the house is still on. But we think the real issue could be the ways in which the neighbours have extended. On one side the neighbours have the most enormous side return extension and the wall is insanely high. Overall not that much of an issue though it clearly impacts light into the back reception. But on the other side, the neighbours have done a big L shaped loft conversion which may well be on or over the boundary. We would also want / need to do a conversion (the original house is pretty small), so my question really is whether being second mover on extensions can cause problems? Has anyone run into problems building a dormer loft next to a neighbour who already has one? Will we be left short changed while they basically straddled our house?! Builders have said they can do it but the gap left might need to be bigger etc and it starts to become a bit unattractive. We plan to knock on the door again, to say hey, but they never seem to actually be there!

Any thoughts / experience / recommendations would be helpful.

OP posts:
Rollercoaster1920 · 18/03/2026 11:12

If they have extended on top of the party wall you just use the wall they built and pay them some money for it (half the current rate to build such a wall).
If they have overhung guttering into your property then there is a trespass and it could be tricky.

Determine where the property boundaries are first, and so whether the walls are party or not.
Also there can be practical issues like design of roof and drainage that might restrict what you want to do. You might need to set back from the boundary which can lose space, but also can create an issue with gaps which are unmaintainable and can cause water ingress or damp.

Neighbours probably won't like you building up to their extension (effectively terracing it) too, even when they have built right to the boundary.

bloodredfeaturewall · 18/03/2026 11:20

ask for party wall agreement documentation

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