Party wall or exchange of letters for same footprint building work

Catbells

I;m having two downstairs rooms knocked into one kitchen space using the exact same footprint as currently exists.  The current wall's proximity to my neighbour means we will need to have an agreement - party wall or exchange of letters -  to protect the neighbours should it be required.  Its not a massive building project and I am hoping we can have the lesser of the two expensive choices - ie an exchange of letters but am not sure how this differs from the party wall award or agreement.  Does anyone know?  Thanks

Doozergirl

Why do you need a party wall agreement?  Are you not leaving a pier for the steel to sit on? 

If the PWA applies then whether it's letters or something drawn up by a PWS, they are still party wall agreements. 

Most knock throughs don't need PWAs because the steel needs more than just a bit of a party wall to sit on.  Part of the wall being removed is left behind to take the steel.  

Catbells

Its not so much the steel beams (two needed)
 but the foundations.  Current foundations (for conservatory) aren't deep enough.

Doozergirl

So you're extending?   Or underpinning the conservatory? 

So within 3 metres of your neighbours wall?  Are the foundations intended to be deeper than theirs?  How old is their house/extensions?