-
Ah I can see the issue here, we had an extension on our semi detached. Nextdoor also wanted to build out after us and connect onto our newly built extension. I did refuse and it was built with a step in. My reason was noise related, they were a noisy household and the last thing we wanted to do was add more adjoining walls.
We eventually moved to a detached house but the neighbours house astride the boundary line. We have submitted a plan to step in 600mm for our extension leaving a gap for maintenance and keeping sound from leaking to one property to the other.
Now your situation, I can see it from both sides. We soundproofed the alcoves at great expense and it did nothing as the chimney was the weak spot for noise.
I think your cupboard idea is probably a good one as it will be filled with clothes to hopefully muffle the noise. Fun and games in the world of renovations! It’s a shame we have to step in so much with our extension but I can’t risk building too close to nextdoor as they are also a lively family. At the moment we can’t hear each other and that’s how I wish it to stay.