Shelf in old stone wall.

Right, I want to put up a shelf to hold my ridiculously expensive projector.

I was about to buy everything when the shop assistant asks what type of wall it is. I ask my landlord and apparently it's an old stone wall.

The assistant says the old ones are very uneven and no matter what method I use to put up a shelf there will always be a chance of it hitting mortar? and later loosening, and wasting a lot of money for me. If I hit a weak spot or whatever the problem is can I not immediately tell just by trying to push down hard on it or holding my bodyweight? Or can it feel perfectly fine at first and still loosen later. The PJ isnt exactly heavy, but hell I can't risk it falling.

Gentlemen. What should I do ? Am I and indeed the assistant being overly cautious? Thanks, svelte1.

(note: I am not at all svelte)

ceiling mount.

Lol, knowing how dodgy this shared house is, I will run into problems with the ceiling too. I guess I can ask the landlord though.

Unless your projector weighs 200 kg, you won't have any problems screwing into a couple of joists.

If the place is that bad, you can probably see the line of the joists already.

Hello there:
You could perhaps use floor to ceiling stanchions to hold the shelf. That way you would not have to touch the stone wall. There are some very attractive ones out there in struded aluminium, and they can be taken down easily with minimum fuss.

nothing wrong with drilling a stone wall if you use an SDS drill, i do it all the time