Roof cricket
Roger_S39
| Posted in General Questions on
Hi all,
Looking for advice/best practice for how to get the details/construction right for a roof cricket for the following scenario, please.
Single story hip roof butts up against a future vertical brick wall of the second story, of a new construction home in the framing stage.
Without the cricket, the base of the sheathing would create a horizontal edge/line about 8-12 ft against the adjacent wall.
Important considerations:
-Flashing
-Water proofing
-Slope
-Location valley – how far back from adjacent wall
-Prevention leaves/debris
-Additional input
Thank you.
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Replies
Simple. Don't do that. Having a roof slope back towards a vertical wall is just bad design. You can still get much of the hip roof look by doing the hip on three sides, but continue a ridge from the peak to the vertical wall. Your cricket is now the full height of the peak.
With any sort of cricket in this area, you are going to concentrate the water flow at the front and back corners, immediately against the vertical wall. This is always difficult to detail and with brick it's even harder. The odds of failure are very high. While it is possible to get this right, I've never seen it done during original construction, only after a failure when a really goo waterproofer/mason comes in and builds very intricate kickout and through-wall flashings for the brick. These are very expensive details and still very high-risk.
I strongly recommend doing everything you can to avoid this detail.
I agree. Crickets are a remedial solution, not something you plan in new construction. We carefully avoid putting chimneys near roof valleys. That's exactly what you get with a cricket.
One way to mitigate the risk might be to oversize the cricket, and build it more as a gabled dormer with the valleys landing well clear of the wall. How all that comes together I'm not sure.
No one can really help you without a picture or a roofplan or elevations.
Is this is a framing scenario after a truss set where you have some flexibility in field framing? Field framed valley?
Would appreciate any constructive responses/thoughts.
Thank you.
That's not really a cricket. You need to frame from the peak of the offening hip to the outside corner of the 2nd story creating a shallow valley. Flashing will depend on the resulting pitch. Try to frame the valley past the corner of the 2nd story to keep water in the valley from hitting the 2nd floor wall.
Like this
Could you expand on: that's not really a cricket", please?
Would your suggestion require pulling lumber down or adding to what's present?
If the later, is it better to add or start that section again?
Trying to understand the situation to avoid future leaks down the road 5-10+ years etc.
Roger,
What T. Carlson has drawn will work with the caveat he added about keeping the bottom of valley away from the corner of the wall. The steeper the slope the better it will work and shed any debris. 4/12 would be a safe minimum.
I've got to add that seeing something like that on a new build represents a real design flaw.
Thanks Malcolm,
For the purpose of learning, what could of been a different way to have designed the roof.. given the first floor is wider/larger than the second floor?
If the layout stays the same with no second floor above this section of first floor, how could the roof have been framed differently?
Appreciate the opportunity to learn/hear ideas from you and others.
Thank you.
Roger,
Architecture, like the design of most objects (computers, furniture, cups, cars), is a three dimensional iterative process. You go back and forth between the plans and their implications on the sections and elevations. Experience helps you build a skillset of things that work, and those that cause problems - like bump outs on two floors sharing an exterior wall - and avoiding them.
Like anything else, in general the more you do it the better the results. My advice to people who want to design their own house, or draw their own construction drawings, is to run the results past someone with design and construction experience, so these types of things are addressed way before the framing starts.
If you look at the questions here on GBA, a fair proportion of them involve people who have dug themselves a hole by not thinking through the implications of their designs on their insulation strategy, roofing materials, or other facets of the construction. They were almost all avoidable with a bit more planning early on.
For ease we usually sheet off that dead roof and then frame on top. That should have been noted on the truss blueprint.
The roof is framed on site with 2x6 stick framing/rafters - yes/no.
Given as is, is your above red line suggestion still the best way forward, or something more substantial with removal of existing roof framing and beginning again?
Thank you.
You'd have to evaluate the load being built onto the roof that's framed. It's been so long since I have done a complete stick frame and I don't know your roof codes so I can't advise you on framing member selection. It can be done as proposed if the framing can take the applied load.
The way to avoid it would have been to slide that second story over to let that hip drain off but that would have made a narrow collection point for snow and potentially a lot of rainwater.
Another solution, although it may not fit in architecturally, would be to replace the lower hipped roof with a shed one.
Thats a great suggestion.
If he's willing to rip it off. Would definitely be more robust and flexible.
I like the shed roof in that scenario with standing seam on it to set it off.
"with standing seam on it to set it off"
I've seen that on a couple of houses around here recently. It's a combination I wouldn't have thought of, but is a really nice look.
Two follow - up questions:
1) If the shed roof is done, how does it look where there needs to be roof over the part of the lower floor that extends past the adjacent wall? Also, how does it look where the shed roof meets the roof to the rear ( opposite end to where the back wall is)?
2). If the existing roof is kept and #5 and #6 are utilized, would the usual 30 lb felt, ice and water shield in the valley, asphalt shingles with the California cut be ok or would this area need special attention with the entire area of roof decking needing a peel and stick membrane and other materials such as a valley with the W metal flashing piece etc.?
Thank you.
That would be an example of a shed dormer.
If you wanted to frame the valley or cricket, looking at your pictures and elevation it looks like a 12/12 roof, you might have a 14-16’ run with a rise at least 6’ puts your new valley roof plane at a 4” + pitch, probably more. So it might look alright and is enough to shed water. I have seen them shallower and it looks terrible, 4” pitch might look a bit out of place, 6 or 8 should look fine. It can be roofed like normal.
Cut valley make sure the hipped bump out is roofed first and the new valley plane or “cricket” as you call it is shingled over so water doesn't run into the cut.
This complex of a house and your questions is concerning. Is this your house or someone elses?
Thank you for the reply.
Will be the future home owner.