Advice on impact of neighbour's extension

Kai77

My downstair's neighbour is getting an extension done directly beneath my flat. We have a party wall agreement for removal of two chimney breasts at their level but the two surveyors involved agreed no other PWA was needed.

Separately, one of my windows that is in a room directly above where they're extending their kitchen into the garden, is no longer fully shutting. The handle won't close properly and it won't lock either. I've also seen some minor cracks around the frame.

I was assured the back wall wasn't being knocked down, they were just removing the double garden doors so no major work to that wall but they have done a lot of drilling in the ground so I'm not sure if that's created movement?

The surveyors took photos before the work but what else should I be doing now? And was this likely preventable?

ThisIsWeird

Do you have sight of the plans? If so, you should know exactly what was planned, and can compare this with actual. 
Did this require Planning? It almost certainly needed Build Control oversight regardless, in which case the plans may be on the LA's Planning Portal (but your surveyor will surely have a copy if you don't).
So, ask your surveyor to investigate the work being done, and to explain your issues.
The agreed remit of the PWA surveyors is a new one to me - I didn't realise they seemingly 'agreed' what's covered when they take the job! Seems strange to me; "Whoops - that wall is crumbling! But, not my remit - the chimney looks fine..."
If this movement is being caused by the work below, then they need to sort it. Should it have been preventable? Essentially 'yes', certainly to the degree of it causing windows to not close. But sometimes very minor 'hairlines' are pretty much unavoidable with large works, but they still need to sort it.
From what you describe, the 'intention' was to simply remove the double doors and leave an opening into the new extension? In which case, as you clearly understand, this should have had no structural impact on the building, as the existing lintel should have continued to do its job. So obvious Q's for your surveyor include; have they widened the opening, and are there any issues with the existing lintel?
See what your surveyor says.

Kai77

Thanks this is really helpful. I'll take a look at the plans again and my independent surveyor is doing the same. 

Yes as you say it was supposed to just be a new opening via the old doors with the extension added so they agreed no PWA was needed for that particular work. They did however take photos and inspect the whole home so that will help.

I'm wondering if they've gone further than their original plans e.g. knocked walls and not told us and/or the extensive drilling and groundwork has shifted something.  It's a Victorian building so not sure if this makes a difference.

They got planning permission for the extension, not sure about building control involvement now but will call them after I speak to my surveyor.

ThisIsWeird

Building Control will almost certainly be required/involved, so I suggest they will be your contact point if you have any remaining concerns.
Please keep us updated.  

Kai77

Thank you. Will see what they say.

Kai77

Quick update. Surveyor visited and inspected. They've actually made the door opening downstairs smaller, not bigger so it should have more support but in the process of adding a lintel (which I didn't realise was being put in) there may have been some movement.

Surveyor isn't concerned and said it sometimes happens. They'll adjust the window and repair the cracks (once building has settled a bit). 

Kai77

Thanks for your help too!