Bit of advice needed for our stand alone, semi detached garage (i.e. half of the garage building belongs to next door) please.

I have boarded part of the ‘upstairs’, but I’m wary of overloading by putting too much stuff up there. How much is too much? Can I reinforce the joists to make sure I don’t cause any bowing? Various pics:

Edit- it’s the side that the joists are hanging from brackets in the wall that I’m thinking about. The other side looks well supported to me.

Ta

If it was me I’d either fit some vertical support under the joists against the wall or middle as needed. Or, a horizontal piece up against the joists screwed into the block wall. Unless you are seriously loading it up and then climbing up there to look at stuff you are probably ok though.

Cool, thanks. Vertical support under the joists against the wall sounds good to me and within my DIY skill range 😉

Depends on the stuff but that is a pretty sturdy fixing. I’d be happy to have general storage up there without any worries. You can add an extra upright if you like, it’s an easy job, but as is it’ll be pretty decent

Could just run a horizontal timber under all the beams. But for what you have there I’m sure it’s fine.

They hold a couple of hundred kilos each from memory

The density of the blocks will determine the safe load on the hangers
The heavier the boarding the lighter the load that you can store, use lighter boarding so that overloading is obvious in the boards before the joists and their fixings
If a loft hatch is designed into your house then you can store 25kg/sq m (that includes any boards and fixings). In an open garage structure it’s anyone’s guess

Those joist hangers will support anything you can physically lift up there! Four houses I have just built have the entire first floor supported on the same ones.

You’ve got a lot less up there than in my garage, and I doubt you’ll have anything heavy due to physical weight of lifting it up there.