Reinforcing Attic Roof Trusses for Flooring and Storage

[antivenom]

I'm converting the attic above my garage for light storage by adding flooring and a folding aluminum attic ladder. Also, I have an electric hoist I plan to install to haul storage items up there so I don't have to awkwardly carry them up the ladder. The attic area is about 20x20. The trusses are a fink with a raised heel(I think that's the correct terminology), 24" OC. They are designed for 10psf on the bottom cord and 20psf live load on the bottom cord in the center between the two tallest webs. I've attached the truss specs.
For the flooring I'm using 3/4 OSB T&G ([URL unfurl="true"]https://www.lowes.com/pd/23-32-CAT-PS2-10-Tongue-and-Groove-OSB-Subfloor-Application-as-4-x-8/1000065715[/url]). I've had to cut it into ~2' wide strips to get it up there easier.
Should I strengthen the trusses?
Specifically around where the attic ladder is installed and where I'll put the hoist. I haven't really figured out the best way to permanently mount the hoist yet. The attic ladder is ~50lbs. Link to attic ladder Link to hoist The hoist capacity is way over what I will ever lift up there. I don't plan to lift anything over ~75lbs.
Will sistering 2x4's the length of the bottom cord on each side of the attic ladder add any strength or will that just add weight?
Should I add gusset plates to any of the joints?
Also, I have discovered that one of the trusses has a split in the W5 web at the bottom, what would be the best way to repair it?
I can take some pics of that later if it would be helpful.
Thanks in advance!

 

[BAretired]

The tape measure covers part of the truss plate, but the part we can see indicates that there are not many teeth carrying 467# tension and some of them are very close to the end of the member or the crack, rendering their contribution nebulous.

Under uniform snow load, W4 and W5 are tension members, whereas W3 and W6 are compression members. A stress reversal can occur with unbalanced snow load or unbalanced storage load, or both. Mounting a hoist to the underside of those trusses is not a good idea in its present condition.

BA

 

[r13]

Don't park your BMW under it!

 

[antivenom]

I’m waiting on the truss manufacturer to get back to me regarding the repair to the split web. I’ll seek out a local structural engineer next week as well to get an independent opinion on the situation. It sounds like the trusses are not designed well anyway, so who knows what the quality of the recommended repair will be.

Thanks for the advice and information!

 

[BAretired]

Offhand, the addition of plywood gussets each side of truss at nodes I and K (and perhaps other nodes) sounds like a practical solution, but this is something your local structural engineer needs to determine after inspection.

BA

 

[antivenom]

So I finally talked to the truss manufacturer, someone in the engineering dept. They recommended that I repair the split web member with an 18" 2x4 scab, attached with 2 rows 16d nails, 4" OC to support the damaged member.
Does that sound reasonable or should I get a second opinion?

 

[BAretired]

I would not be happy with that.

BA

 

[jayrod12]

Agreed, unacceptable repair. That possibly might replace the lost 2x4 capacity, but honestly not really since the 18" piece will barely cover the cracked length. You want to develop the two members (original and reinforcing) on either side of the damage to ensure the load is picked up by the repair.

And, as indicated previously, the bite of that metal plate does not appear to be enough in that cracked diagonal, and their repair detail does nothing to address that.