Hang item from top chord of 2x6 roof trusses?

Question

The roof truss in question is part of a standalone shed structure in the back yard. Each truss is 2x6, and is composed of 3 planks - each side of the triangle, no center braces or anything. The width is about 10-12 feet. Is it possible to hang two large eye bolts from two separate trusses about 10 feet apart and permanently suspend something between 250-300 lbs between the two of the bolts? I can re-enforce or cross brace any of the beams as necessary, though I'm not sure what would be effective. Here's a shot of the interior with a drawing of what I'd like to do (x2). I know the cable will be against the bottom cord, but no direct weight. Most links I've searched recommend against this, but I'm really really hoping this can be feasible.

What I'm thinking:

Is it feasible? Thanks!

Answer 1

This is dangerous and should be calculated.

1) The top chord of the truss is in compression. By putting a load between web joints, you are putting the top chord in what is called "double bending". What this does is puts an additional amount of compression load on the top half (about) of the 2x6 top chord. This could easily over stress the member (the piece of the top chord spanning from web joint to web joint) and snap the chord. We've repaired these and its expensive.

You must live in a high snow load area, because you have 2x6 top and bottom truss chords for such a small span. (Where I live, we'd use 2x4 because we have minimal snow loads.) So, the truss manufacturer has determined that a 2x6 is required due to the snow load. Maybe it's over designed, but I'd ask the truss manufacturer. Give your local lumberyard a sketch of the size (span) of your trusses and tell them you're adding 300 lbs. and where. They can run the calcs and tell you exactly how and what to use. The calcs are free. (There are specific methods to connecting to chords and webs. ).

2) You show an eyelet type screw into the bottom of the top chord. I'd advise against that for two reasons. (A.) I'd ask the manufacturer, but I'd bet they'll recommend a thru-bolt or clip nailed to cross members...probably 3 trusses. You do not want to over drill the size of hole for a thru-bolt. When we mount roof top equipment or equipment hung in attics, we suspend from rod bolted THROUGH top chord. (B.) A screw type fastener into the top chord will damage the integrity of the top chord (cause the 2x6 to split). The chord will dry out over time and split. Then, you'll loose all holding resistance.

The code requires roofs to be designed with a 15% factor of safety. Verify this with truss manufacturer.

Answer 2

I assume that the span of each top chord is about 6 feet, and that the trusses are well-built, with adequate gusset strength and fasteners. Given that, I see no problem hanging 300 lbs. from two trusses, distributed evenly. It's possible that you'll notice minor sagging if left for several years, but it won't damage the overall structure.

To be extra cautious, fasten a 2x6 or 2x8 crosswise in that location and extending an additional two trusses, in order to further distribute the load. Use at least 2 3" gold screws at each truss, or use a 5/16" by 3" lag screw at each truss.

Answer 3

No problem at all here. For such a small span, snow load isn't even a factor. The same trusses can be used in high snow areas as in low snow areas. As spans increase the difference in plate sizes increase quickly. Cut it in half per load point and you're only dealing with 150 pounds.

It's hard to see in the picture but I don't even think that this is a truss roof. It looks like cut rafters with a ceiling joist. If that's the case, add some nails at the heel or make sure that there's adequate nailing from rafter to ceiling joist to prevent any spread.