How would you interpret this party wall act agreement?

[buildingextension2023]

We are building an extension, but our neighbours extension is built right up to our boundary so they have signed a party wall act agreement with the below wording:

The work will involve the excavation of a trench adjacent brick party wall to existing extension (103) to a depth not less than existing foundations, cast new concrete foundations and erect a single skin concrete block wall to roof level, voids fill with polystyrene panels approximately 50mm thick with block word secured to existing brickwork with stainless steel starter kit fixed to existing brickwork

how would you interpret the above?

Steve the party wall surveyor here - Interesting, what they want to do is to use your wall to make their wall comply with the building regulations and to avoid building their own independent wall. The party wall act doesn't permit them to do that, although you can reach your own private agreement. The party wall act does let them use a party wall (ie a wall astride the boundary) that you have erected, but it also says they must pay you compensation for that usage. Did you have a party wall surveyor or did they just draft an agreement?

@stevenway1 hi Steve, so their extension is twenty odd years old and was there when they purchased the house. It is right up to the boundary. Therefore, if we left a gap we would lose out on the length we could have by having to come in as their extension is on the boundary. We had an experienced surveyor draw up plans, submit the planning and put together the party wall act. They had copies of everything we said about our extension being connected to theirs including the visual plans.

Can you advise where we stand?

So you want to whose on your neighbors existing wall. The key question is whether it is up to the boundary but entirely on their land, or if it astride the boundary so partly on your land.

If fully on their land then what you propose is really risky and needs a legal agreement to use the neighbour's wall.

If astride the boundary then it's a party wall and what you propose makes sense. But you need to pay half the cost of the wall at today's rates.

@Rollercoaster1920 it’s astride the boundary and we are building our own wall too, but theirs and our wall will be connected. Our houses are semi detached so the extensions too will be connected

@Rollercoaster1920 is correct, section 11 of the party wall act says that you should compensate the neighbour for using a party wall built at their expense. Usually, this is 50% of today's cost of building it (including foundations etc.) but it can vary. A party wall surveyor will be able to help, and your neighbour might insist on one, but if you have an agreement between you anyway, the cost of the surveyor might be more than the compensation. In London, I would expect to use something like half of £275 / sq m enclosed on but it does vary

@stevenway1 its not been built at their expense. As we’re erecting our own wall but it’ll be connected to theirs?

You need to pay them to use their existing wall as part of your structure.

You need to pay them to use their existing wall as part of your structure.

@Rollercoaster1920 hmm okay. I’ll speak with our surveyor who drew up plans and did all the legal/ written agreements. Thank you

@buildingextension2023 the wall you intend to build against theirs is not independent - if their wall didn't exist, you would need to build differently as an external wall to meet building regulations.

@stevenway1 we are building our own wall though? It’s just connected to theirs. It’s an independent wall as it’s our wall. They’ve built on the boundary so if we built not connected to theirs, we would lose out on size?