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Are Rafter Framed Roofs Passe

chmink's picture

We are building a lakeside house in the Finger Lakes Region of Central NY. The house has a Great Room with a two story Cathedral ceiling perpendicular to the main roof, both simple gables. The lake facing outside wall of the Great Room is all windows, with polygons on top parallel to the roof line.

We recently received plans and elevations from the builder’s design group, and did not like the large margin of siding between the top of the windows and the roof line. This is a result of the builder designing with roof trusses.

We asked for a price difference to have the Cathedral roof rafter framed. The builder balked saying the added expense would be so high he wouldn’t waste his designer’s time to prepare a framing plan, and that he only would do trusses. The roof spans 20’, has an 8/12 pitch, a ridge line to the perpendicular main roof of 17’-8, and has eaves to the main roof of 10’.

I have been using RS Means Residential Cost Data, which for this size roof, gives a labor cost difference of ~+$2.00 per SF of plan area for rafter vs truss roofing. I am not sure how they calculate the plan area for an intersecting roof, but if I conservatively use 20’ x 17.7’ x $2.00 SF, this is only about $700. I found similar SF cost data on the internet.

Of course the builder told me I was crazy. Can anyone shed some light on whether my numbers are way off, or whether this builder doesn’t have the skills to frame an intersecting gable roof with rafters?

Why do you think that (post #216168, reply #1 of 7)

Why do you think that stick-framing a cathedral roof will reduce the need for framing above the windows?

Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

Why do you think that (post #216168, reply #2 of 7)

The trusses are deeper than what at mostis probably a 2x10 rafter.  See attached truss detail.

Roof_Trusses.JPG72.4 KB

Sissors truss (post #216168, reply #3 of 7)

A sissors truss would probably not be as deep at the wall as a 2x10. The difference would be that the ceiling pitch would be somewhat less than the roof pitch. 

2x10 will not give you enough (post #216168, reply #5 of 7)

2x10 will not give you enough space for the required insulation if you are using fiberglass or rockwool. 

Need spray foam to meet the R38 required for ceilings  in your area. 

That will affect your cost more that the labor to stick frame a roof.

2x10 will not give you enough (post #216168, reply #7 of 7)

Thanks,  I was just guessing at the rafter depth.   Certainteed has a Cathedral Ceiing High Performance Batt that is 10 1/4" thick.  Not sure if this is requires 2x10 or 2x12.  Either way, a 12" rafter is still much shallower than a truss.

Trusses are strictly second (post #216168, reply #4 of 7)

Trusses are strictly second class construction in my area.  Everybody that you would want to build your house around here stick frames the roof.  You are just in the wrong place I guess.

In Florida the issue is (post #216168, reply #6 of 7)

In Florida the issue is engineering. If you buy trusses they come with stamped plans. If you are stick framing you need to go get an engineer to stamp your plan. I had a screwed up truss order in a hip and we conventional framed that little piece, If we did not have a good relationship with the inspector I would have been back down at Plan Review and at the engineer. We would have been in the penalty box for a week or two, minimum.