Replacing overhead “shelving”

[digitalmonkey]

I have a garage with a vaulted ceiling and the previous owner has used a heavy old door as a shelf which is resting on two large ceiling joists. Since there is nothing securing this door to the joists, I’m worried about both the extra weight and the lack of secure fastening (next time we have a big earthquake). I do like the idea and simplicity of using the joists to hold up a horizontal platform. Are there any alternative changes I can make to make the shelving more secure and lighter? Attached are photos of my current setup.

 

[kbs2244]

that looks like a hollow core door
if so it is plenty light
if not, replace it with one
a few 4 inch deck screws will hold it in place

 

[Zeke]

Wow, the ceiling looks brand new!

Just a quick mention, those are not joists, they are commonly called rafter ties. They aren't designed to hold much weight so you're wise to ask these questions. The screws mentioned ^^^ will be fine or you could put some small angle brackets on from below (easier).

Yeah, a HC door is light as a feather. Certainly lighter than any plywood that would span that distance.

 

[digitalmonkey]

Thank you - I'll double check if the door is hollow core. I like the idea of using angle brackets.