Decking attached to fence

[GarethSouthgatesWaistcoat]

Re-posting here for traffic

My not-great neighbours installed decking in their small terraced garden roughly 6mo ago. No issues with height (30cm or less) but I've noticed my fence is starting to lean into my garden and at least one of the posts appears wet/rotten at the base.
The fence is my boundary fence and is a couple of years old. It was installed by a fantastic chap and is (was) really sturdy. I'm almost certain their decking has been attached to my fence leaving no gap for maintenance.

I've never had decking so not clear on the ins and outs. Is it normal to attach it to the neighbour's fence? They know it's my fence as they saw it being installed (it's definitely my boundary to maintain). They had a company install their decking. It's on a base but I'm certain it abutts the fence at either side with no gap.

I've tried googling but I can only find discussion on height of decking which isn't the issue here. I can't find anything definitive about attaching decking to a neighbour's fence without permission/ causing damp problems.

If they were reasonable I'd approach them.

It's been very dry here in the SE since late spring which is also confusing me - why would my fence post/gravelboards be damp? Could the decking be responsible?

Thanks in advance

Sorry I should've added I'm unclear whether it's fixed to my fence or abutting it. There is no gap either way.

It's not standard practice to attach decking frames to fences, but I have seen it done before. The frame should be set on slabs/blocks or fixed to their own posts set into the ground. Ok to build the frame right up to the fence line, that shouldn't cause any problems with damp. Is the post wobbly or firmly wonky if that makes sense ? Have seen 3 inch posts rot at the base in a few years sometimes, depends on the ground conditions clay soil poor drainage etc. Only way to find out for sure is to whip out a fence panel if you can and have a look.

Thanks @Catsingangs!

It feels a bit wobbly (from the damp) but not v much movement, more of a lean at the moment.

I shall investigate. As you say if it's found that their contractor has attached it to my fence it'll be apparent as I get my fence fixed and they'll need to rethink their decking on that basis.

Good to know about fence posts rotting naturally! We're on clay soil, ESE facing and that corner of my garden (to the right of the back door) is the dampest, shadiest zone. But the other side of each fence in that region is SSW facing and really hot and dry

Thank you for the reassurance

No probs Let's hope you don't have a CFDNDN situation (cheeky fucker decking next door neighbour). But regale us with the juicy updates if you do ! Have seen lots of odd things this summer with the hot dry weather - soil shrinkage and fence posts warping. Fingers crossed it's something innocent !