Extension & party wall advice

[Afonavon]

Sorry for this rambling post...

We’re having a single storey extension done. We’re at the very start of the process having finally chosen a builder. Our immediate neighbours don’t have extensions, so only a garden wall on one side and a lean-to on the other. Can the new extension wall replace the existing garden wall, therefore remaining in the same place on the boundary? Our builder thinks not, and that we need a 10cm from the current wall, even though neighbours are happy for the extension wall to replace the current section of the garden wall. Other houses along the street seem to have extension walls replacing the garden wall section, but the builder is adamant that it can’t be done. Any advice or experience?

Mine replaced the garden wall, slightly higher actually. If it doesn’t replace it will there be an issue with leaves etc building up in the tiny gap? Is it that the builder doesn’t want to access next door which I think would be needed either way.

It can replace the garden wall but you will need planning permission unless you own all of the land on which the extension would be located. You and your neighbour will need to sign a party wall agreement

My side shed formed part of the garden wall and I demolished it to build an extension. So my house is up to the property line, and the brick wall extends forward to the end of the drive. In the back it's a wood fence from the end of the extension. It did require a party wall agreement (as I think any extension within a meter of neighbours property line). Your builder will need access from your neighbors side and finish it properly on that side.

Yes you absolutely can build up the party garden wall to make the side wall of your extension.

I’d be a bit worried your builder thinks it can’t be done... how much experience does he have?!

You’ll need a party wall agreement, but you’d need one anyway if building foundations within 3m of their house (ie your builder’s solution doesn’t avoid the need for party wall agreement).

Do you have planning permission? My local council insists side extensions are slightly stepped in from the boundary and can't be astride or on the boundary. Could it be the same where you live?

Permitted Development extensions can't go beyond your own boundary, and this includes the foundations. If you get planning permission you can straddle the boundary. It's also possible to build up to the boundary if you have eccentric foundations and no eaves overhang above.

We brought house that had replaced the boundary wall with extension. This was agreed with the neighbours but the neighbours sold their house before we moved in. Omg we had murder with the new neighbours. We had to contact planning department to get the plans. They were going to take us to court.

Is your builder thinking that the footings for the new extension will be on the site of the existing boundary/garden wall. If so, the wall of the extension will be built on these and therfore slightly inside the line of the current garden wall