Third party wall costs

[LH1]

We converted our loft a few years ago and now our neighbour wants to use our wall to build on for their loft conversion. We have agreed everything re surveyors and agreement apart from how much they should pay us to use the wall. Any ideas anyone?

What is your house worth, how much was the conversation?

Conversion

About £800,000. No idea of cost of loft as done with the rest of the house conversion.

Work out square footage locally how much would they gain using your wall, how much would it cost them to build a wall, how much it devalues yours etc.

Ask the surveyor but I am sure the Act only allows you to ask for half of the cost you paid. I don't think you can pick any figure you like.

Should I take the square footage off their plans? Why would it devalue ours. Sorry I am a bit naive about these things and they want to put the amount in the agreement before the surveyor comes around.