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Check out this roof truss bottom chord. It has a strong tie splice in the middle connecting two beams. I'm not entirely sure how the forces worse here - how strong is this tie weight placed on it from above?

Given that this chord is spliced, should I expect this beam to be able to hold significant weight? Should I be able to float a board on top of it and use the area above as storage? Or should I expect this is just to provide strength to prevent the walls bowing outwards with the weight of the roof? (Strong in tension along the beam? Not strong in compression from above?)

Thanks in advance.

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    Probably not made for weight bearing. Can step on them but jumping not recommended(hold my beer, darwin award type). Weight holding will depend, some Christmas lights/trees and some clothes okay, empty bathtubs not so much.
    – crip659
    Commented Jun 2, 2023 at 22:03

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That splice is typical of an engineered truss splice. It will meet the specs for the bottom chord.

Personally I have seen that type of splice applied. They are incredibly hard to remove and very effective. As well as being guarantied by the truss manufacturer.

You may apply the same weight as the truss design allows for the bottom chord.

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The lower chord splice in the truss structure is designed primarily to provide strength in the horizontal tension direction in line with the axis of the lower chord. You should consult with the truss manufacturer to get specific data as to how much vertical loading the truss design in your building is rated for.

Some loading is possible but obviously not unlimited.

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  • Hmmm.... with a 50 year old house, I don't think contacting the manufacturer will be possible. I am curious about this through. Downward forces on this joint will translate into tension forces forces in the splice. I wonder if there are some reliable engineering rule of thumb guides here.
    – user48956
    Commented Jun 5, 2023 at 18:41
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    Any truss consultant or manufacturer worth their salt should be able to take your detailed photos and your careful measurements of the truss construction and offer some analysis.
    – Michael Karas ♦
    Commented Jun 8, 2023 at 2:17
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Too much vertical loading on the bottom chord wouldn't be recommended because the risk of the members splitting in the horizontal direction could occur. This is because vertical loading will cause the upper half of both the spliced members to start bearing on each other creating a compressive force. And this could cause a disruption in the flow of forces in the upper half and bottom half of the member. Which could lead to splitting over time.

In all, it's not really recommended to put extra loading on structural members. Although if that's a risk you're willing to take to save some space.

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