Probably overpanicking but - any structural engineers out there for advice please?

[NotMondayAgain]

We had a dormer loft conversion completed in the winter. Our structural engineer did the assessment before building started and said no additional underpinning was needed.

Around Feb this year we had fitted wardrobes out in. I just noticed there is a gap now between the ceiling and the wardrobes. I think this has come on quite quickly as the wardrobes face the bed and I just noticed the problem this morning so almost like it's happened overnight. The wardrobe is still touching the ceiling in the corners but not in the centre and the gap is about 1cm. Is there any chance our floor is caving in the middle of us it more likely the wardrobe has just been affected by hot weather? I can't see any cracks in the walls in the room underneath.
Thanks

With photos..first one shows it still joined in the corner, second one shows the gap

I am not a Structural Engineer but DH is. It’s unlikely altering the roof to add windows will rarely affect foundations so that’s not an issue. You underpin failed foundations due to subsidence. It’s ground conditions (dry) and insufficient foundations that cause subsidence.

If there are no internal cracks below, that’s good but what about external cracks? Can you see anything? If there is nothing, then it’s not subsidence.

It could be heave. This is where the ground pushes up (the opposite of subsidence really) and pushes the walls outwards. You would typically see a gap appearing beteeen the walls and the ceilings. This would appear on the ground floor as well as the first floor. Can you see anything elsewhere in the house that might suggest the walls have moved outwards?

Lastly, the wardrobe structure might have shrunk. Can you still open the doors ok? Is the floor still level? As the wardrobe cornice has moved slightly out of true, are the doors affected too? If it’s just the cornice, it’s probably just shrunk (like my front door at the moment!)

Unless you find any cracks, gaps, and sloping floors, you probably have nothing to worry about. Other than what to do the the gap.

Most likely that it's the weight of the wardrobe causing the floor to deflect a bit. And it has probably been like that for a while without you noticing (it's funny how easily it is to not notice things like this). I wouldn't be overly worried - floors do deflect and wardrobes are pretty heavy when full of stuff.

An easy way to tell would be to hold a piece of string taught on the floor alongside the wardrobe. If there's a gap in the middle then you know it's the floor deflecting.

Floors shouldn’t deflect with a built in wardrobe unless the joists are under sized. A wardrobe is a normal addition to a bedroom. The end panels of the wardrobe take the wright of the clothes and the rails themselves. The wardrobe itself shouldn’t normally cause a problem. It would be unusual. Was the floor a bit bouncy before the wardrobes were installed?

Weight of the clothes...

Depends on the arrangement of the wardrobe, and whether the wall it is against is a supporting wall. Pretty much all structural elements deflect to some extent. It is only a problem if the deflection is such that it causes things to crack, is unsightly etc. In this case it is made more noticeable because you have a flat edge (the ceiling) adjacent to a varying gap which draws your eye and makes the gap seem bigger. Joists are normally sized to have a maximum deflection of 14mm (depending on the overall span), so even if the floor had deflected 10mm it is still within typical limits. Anyway, it is a very easy thing to check as I described.

Not a structural engineer - but have lived with significant subsidence

The types of things which started to happen to us - which are of concern are:

Window struggling to open
zig zag style crack
Door frame moving and door not fitting properly
skirting board coming off wall

As I said not an expert - but I would say your situation (probably) is nothing to be very concerned with. I think your wood has shrunk in the wardrobes