Need help with a slight roof sag at the ridge beam splice. 4

[bulkman]

I have a 22 by 24 ft garage that has a ridge beam with a slight sag at the splice. The ridge beam is a 2x10 and consist of 1 16ft and 1 8ft The problem is I have a sag of 3/4 to 1 inch at the joint. The rafters and collar ties are in place but the sheathing has yet to be installed. My question is: If I jack up the splice the necessary amount to make the ridge beam straight and apply the sheathing will the ridge beam stay at the corrected straight position once the sheathing is installed and the jack is removed?

Thanks for any help.

Geno

 

[Ron]

bulkman...something seems whacked here.

This is more than a slight sag. Are you sure it isn't misalignment? If it is truly sagging with no load, you'll have a bigger problem after loading. You need to check all your dimensions again. Any chance you have a couple of rafters that slipped out during erection? Are all the collar ties the same length/same elevation? Something doesn't add up.

For the splice, I would use a flitch plate (aluminum, steel or double plywood) bolted through the ridge beam. Splice plate should be at least 2 feet long.

 

[redhead]

What you describe is a ridge board, not a ridge beam. If you only have collar ties and no ceiling joists, your misalignment is caused by the lack of restraint of the rafters at the eave plate. The correct design for this type of structure would be to use a true ridge beam, it would be quite a bit larger than a 2x10. Or the rafters need to be sized correctly for the additonal bending induced below the collar ties, and the collar ties need to be bolted to the rafters to resist the tension forces induced in them.

You need a structural engineer now. Too bad you didn't think to use one to begin with.

 

[LPPE]

bulkman - in answer to your question of wether it will stay when you put the sheathing on - no.
Also, if your collar ties are too far up towards the ridge, they are basically worthless.

 

[JAE]

For a garage, I wouldn't think a ridge BEAM (per redhead's post) would be the best as a beam requires vertical support at each end and one end is most likely a large overhead door opening....requiring an even bigger door lintel.

The ridge board depends upon the collar ties and to some extent the sheathing to resist lateral movement outward of the supporting walls (redhead's "lack of restraint" I think).

This would normally be seen as a gradual sweep in the top of the supporting walls. If you get up on a ladder and peer down the length of the top of the supporting walls, you might see this. But an abrupt movement at the splice doesn't jive with this type of deflection so Ron's concerns (mis-alignment) may be the story.

Check the wall and other alignments to get an understanding of the behavior.