Roof rafters ON ridge beam or butted to (with hangers)
build_r
| Posted in General Discussion on
I am framing a shop that is 22′ deep and has two 1 3/4×18″x22′ LVLs to span and it’s unclear to me whether the roof rafter can or should be butted or land on top.
From what I’ve seen it sounds like it can go either way depending on the situation, having the beam lower (head room) isn’t an issue. I can’t say I like the idea of notching the plumb cut but understand it just may be done and not adversely impact bearing, though I do prefer top vs side (just a personal preference).
Thoughts?
Thanks,
David
(And apologies is this has been answered here but I didn’t find this specifically)
Replies
Using (2) 1-3/4 x 18" LVLs suggests that it's a ridge BEAM and not a ridge BOARD. I'd go with whatever results in the least effort, even to the point of lapping the rafters over each other on top of the ridge beam. Although with that, you should still notch the bottoms of the rafters to bear completely on top of the ridge beam. Which then suggests that a simple plumb cut and framing the rafters into the side of the ridge beam might be faster.
Other details may come into the discussion.
You did not spell out the span, size, or slope of the rafters.
Will you want a ridge vent at the peak of this roof?
How will you secure against uplift?
a) yes, it is a ridge beam (I am familiar with the difference and specifically said 'beam')
b) rafters are spanned 16oc 12' span with a 560plf adjusted to 690 (x1.25 per mfs specs) (dble 18" 1 3/4 = 700 plf), 3/12 pitch
c) Understandably venting will come into play but that's more a blocking issue, IMO
d) uplift I believe is addressed by straddle-strapping (CHSP)
Let me know any other thoughts and thanks to all.
David
What are you using for rafters?
The reason I mentioned venting, is that your selection of the rafter/beam connection detail may impact available options.
If you run the rafters to the peak, it will let you use widely available ridge vent options.
If you mount the rafters in hangers on the sides, it would mean your ridge vent would have to cover a wider gap. (3.5 inches plus the gaps would mean 5 inches or so) There are, of course, several options for roof venting.
Thanks Mike, understood. Using 'solid sawn' 2x6 16"OC.
I'm curious (by nature) but why you would focus on this because I've done ridge venting both when rafters butt ridge boards or beams and when they're stacked (usually just different blocking details).
And you might think given that experience why am I asking about rafter landing... and it's because although I've done and seen it both ways I want to know more about why and the pros and cons of each decision and given there's a wealth of knowledge here (can't believe Piffin is still around ;)) I wanted to hear from the BrainTrust known as BT/ BreakTime :)
You might catch Piffin and several others here:
https://forums.delphiforums.com/Breaktime_3/messages/?start=Start+Reading+%3E%3E&gid=2119297042
Tell ‘em Calvin sent you and don’t embarrass me.
My opinion, for what it's worth, is that either is fine. Hanging them will cost you $150-200 more than putting them on top, for the hangers, but should go faster than having to cut the birds mouths. I just finished building an uninsulated 24' x 24' outbuilding and chose to put the rafters on top. The only reason was to save the cost of the hangers.
Yeah I just looked at hangers yesterday, $10per and I would need 38... do the math, that's nearly $400 just for the hangers! I appreciate all that the steel/ brackets/ etc. do for safety and such but the price of it isn't cheap necessarily (last big job was appr. $5k for hardware, though it was probably a bit over spec'd). I also like the idea of relying more on gravity (top loading) than an engineered solutions which as you say isn't 'wrong', it's just another way to do it and has tradeoffs (caveats). I like to understand the caveats as it expands my 'toolbox' of options, understanding and knowledge :)
I just looked, 2x6 rafter hangers at Home Depot are $5.16 each, and 10% off for every 10 you buy, so $180 for 38. But still, $180 you don’t have to spend. Simpson LRUZ ZMAX
Thanks Eddo, You are correct! My local HIS (Friedmans) had the LSU26 for $10 and the LRUZ for appr. $9. I'm not a regular of HD but I know Friedmans will price match, HD must be getting volume discount. I am fine spending $ when need be/ justified, where no equivalent carpentry options can create as much integrity (e.g. DTT2Z), but thanks for checking that out.
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