Loft boarding and joists in my single garage

[GeorgeGeorge]

Hi there

I'm thinking of boarding out part of my single garage (3 metres wide) loft to create storage space and could do with some advice please, to check my research.

The existing ceiling joists look very flimsy so my initial plan is to install new joists just above, but separate to, the existing joists. My thinking is that this leaves the existing joists alone to continue to support the garage roof, with the new joists taking the weight of the loft boards and any stored items.

My plan is to fix 50mm x 135mm truss hangers directly onto the vertical face of the garage walls using four 6x60mm concrete screwbolts for each hanger. Then to hang C16 95mm x 45mm joists from the hangers every 600mm across the 3 metre width of the garage. Then I'd fix 22mm thick R5 rated tongue and grove loft boards (perpendicular to the new joists) to create a storage area about 2.4 metres deep by the 3.0 metres width of the garage.

Some questions please:

1. Is this broadly the right approach? I know some people lay boards onto existing joists but I'm happy to spend a few quid to get something robust and long lasting. I don't want to take any chances with my garage roof

2. Can I drill into the brick walls to fit the truss hangers or do they have to be fitted onto breeze blocks? Is a single skin brick wall strong enough to hold up the loft boards?

3. Is 95mm tall enough for the C16 joists spanning the 3 metres garage width?

4. Anything else I need to change or think about?

Really appreciate any advice given. Thanks in advance for your time.

 

[John D v2.0]

Sounds very prudent, normally 4 by 2s would only do around 2m at 400 centres but youryo not going to take a piano up there!
If you're using hangers your risk is the joists falling out or twisting. You won't be able to do effective struts on such slim joists at such a wide spacing so you should do solid blocking near the end and in the middle. Alternative is bolt a wall plate to the blocks and hang the joists off that with decent hangers and plenty of screws. Then you don't need end blocking.

Are you going to have a plasterboard ceiling below, or store anything heavy (library or engine blocks?) If not that size will be fine for strength for light storage, just the deflection will be relatively high. If you can go to 125 or 150 depth you'll see a big improvement

To be honest for light storage the trusses will. Be sized enough for it, but fair play designing something independent.