Framing endwalls for single-slope roof with outlookers
So I’m building a small house with a low pitch, single slope (shed) roof, wood frame construction. In Florida, so strict building code and structural requirements. I can’t quite figure out the best way to handle the detail of the angled top plates of the two end (rake) walls.
I’m obsessing over the need to overlap the double top plates at the corners but this seems impossible because of how the end wall top plate will meet the side walls at an angle – they will just butt up to the side walls and sit on their own corner studs which will obviously be nailed to the eave wall corner stud groups.
The top of the end walls top plates have to match the plane of the bottom of the rafters, because the roof designs calls for a 1′ rake overhangs formed by outlookers. No, I cannot do the overhang with an add-on ladder structure.
It bothers me that top plates can’t overlap at the upper corners, but am I overthinking this?
I attached a cross-section for reference. It’s the short exterior end walls for the loft 2nd floor that I’m talking about. No framing detail in the plans other than the outlookers themselves.
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Replies
Dave,
Forget about lapping the top-plates. The gain - which is the shear strength of the two nails which would connect them - isn’t significant enough to worry about, and can be compensated for with a more aggressive nailing schedule on the sheathing.
I’d suggest one of these two ways of framing the end-walls:
1. Plane the top-plates with the bottom of the rafters. You can then cut notches in the rafter that sits over the wall to accommodate the lookouts.
2. Frame the end-walls with a single top plate planed with the bottom of the rafter, and strap the roof with 2”x4”s @ 24" oc on the flat under the sheathing. This will also improve your roof ventilation, which otherwise is impeded by the lookouts at the last rafter bays. Block between the strapping where it goes over the top plate (effectively forming a second plate).
If you use the second option you can also use solid 2"x material visible from below on all your overhangs, expose the rafter tails, delete the soffits, and vent through the blocking between the rafters.
Thank you Malcom, I appreciate the input!
Re. #1 - my lookouts sit edgewise and pass directly over the end wall top plate, fastened to it with hurricane clips. They're the same size as the rafters (2x12) and span from the first common rafter set 16" in, across the end wall, to the fly rafters. So there isn't a rafter directly over the end walls at all. I do get your point about the outlookers blocking ventilation at the last rafter bay but that seems unavoidable.
2. I can't picture what you mean by "strap the roof with 2x4's on the flat under the sheathing". How does that interact with the rake overhang's lookouts?
Dave,
Re: #1. If your lookouts are also 2"x12"s, I'd cut a 1 1/2" notch (say 12" long) in the top of the lookouts over the last rafter bay for continuous ventilation.
Re #2. The strapping would form the overhangs. You wouldn't need lookouts.
I built the single-story version of what's in your picture but as a shed/shop, 12x20 with a 3/12 pitch. It was a materials and methods test bed for future projects on the house.
Dropped gable wall, outlookers cantilever and tie back to the first rafter, outlookers same depth as rafters, etc. I think my gable overhang is 22 inches over the door, after some AWC research and guidance from a Simpson structural blog article.
I went through the same thought process about the overlapping top plates but didn't lose much sleep over it, as the wall plates get tied together pretty solidly at the top corners with the blocking and the outlookers (and the roof sheathing, and....)
I have an unvented roof though (1.x inches of foam on top, fluffy between the rafters), so I have no concerns with interrupted ventilation across the outlookers.
I do like the method of notching the tops of the outlookers for ventilation. It becomes no different in shear than the unsupported (perpendicular) sheathing seams between all of the other rafters, and the full height outlooker blocking will provide shear along the gable wall line.
If in doubt, you could always consult a local structural engineer to specify a strap, tie, etc., for those corner connections.
Chris,
The only downside to using lookouts the same size as the rafters is you can end up with a very thick fascia.
Definitely agree. I wouldn't have done it if the rafters were any larger; I think mine are only 2x8 because of the short span. They're chunky but acceptable for such a simple building style.
You can always use straps