Corner Hip roof over radius wall

[pemsitcman]

Gentlemen:

I’ve been asked to build a room small addition onto an existing house to solve a water problem. Sometime after the house was built, a concrete patio was poured on the inside corner of two exterior brick veneer walls. Whoever poured the concrete did not put any slope on the pad and the result is water collects in the corner at point B. (A photo and sketch are attached for reference). The patio has a radius on one side (shown in the sketch) along the curved line CD. The dimensions of the patio are:14 ft -11 inches x 11 ft-5 inches excluding the 13-inch projection. Bold line AB/BC depict the existing exterior brick veneer walls.

Given the two roof lines which intersect above the patio, it seem the only practical roof for this addition is a corner hip such as the sketch above. The overhangs on the house are 12 inches so I’d like to match this addition to the rest of the house.

The roof lines of the exiting house above walls AB and BC are on a 12/12 pitch. At points A and C , returns from the exiting roof lines extend over the patio by 12-inches. The distance from the concrete patio surface to the bottom of the returns at A and C is 8 ft-10 ½ inches. The distance from the concrete surface at point B is well over 20-feet….ample height to construct a good pitched roof. I have attached a photo which shows the area where this roof is to be added.

I have not decided on what pitch to use other than I’d like it not to look so odd compared to the exiting roof lines above. I’m guessing 8/12 or greater.

Here’s my problem: the unequal length rafters (bastard hip) and the added issue of the radius wall. I see this job has all the makings of a framing/rafter challenge that’s above my pay grade. However, with some guidance and expert advice I’m confident it can be done. I would greatly appreciate any advice, assistance or information how to generate an accurate cut list for lengths, angles and drops for the rafters/hip/sheathing to insure a quality job. Is there any readily available software that will help or generate such a cut list?

I’ll take any advice you can offer. If you need any other information please let me know.

Jim
Greensboro, NC

[TSJHD1]

I’ll take any advice you can offer. If you need any other information please let me know.

Jim
Greensboro, NC

Well Jim,
It sounds like you've got a nice challenging little framing project there. The first thing I would encourage you to do, is to give us all some info about yourself. Why not start by filling out your profile? Not everyone here agrees with this, but many do, I can assure you. Show us that you are a professional as opposed to perhaps a very well-informed homeowner, since it is a requirement for posting on this site, and you'll surely gets tons of help.
And while you're at it, do you want the fascia lines to all remain level, as opposed to the curved fascia having a radius in elevation as well as in plan?

Tom

[Unforgiven]

In order for you to maintain the same OH and have a flat roof plane the portion that curves outward would hang lower than the rest of the eaves. While a challenge can be fun, I don't think the finished product would look good. How about a picture of the two rooflines you would be joining? From what I can see here you may be ahead to ignore the curve on the slab and build a regular hip. If the quick math fits you could maintain the same pitch as existing, simply frame a wall (or beam) with same plate height as existing, bring the top of your hip king in ~3'6" from point B>A. I attached a sketch.

[Baptista-Inc]

hip cant be in the corner, or use two diff. pithces. you will also have different heights in birdsmouth on radius. I've done alot of cupolas and bell shaped roofs on radius walls, I use plywood and cut a template. Yours isn't too complicated. Good luck

[Joe Fusco]

Jim,

I don't know what your skill level is or the folks you might employ, but this is always an option: http://www.josephfusco.com/Junk_Drawer/Roof_1.gif

[gregoryj]

Are the customers set on constraining you to the curved shape of a faulty patio? Once you explained that you have to remove the patio to put in a proper foundation did they understand that the curve was entirely optional and would add cost rather than save money?

[pemsitcman]

Thanks for the input. The sketch Joe Fusco did is exactly what I had in mind but the rafters over the radius wall is what concerns me. Hey, this isn't some job that's going to break the bank even if I cut every one of the bloomin' rafters wrong. But, I just like doing it right the first time. Too, I like learning new tricks.

After reading my post again, I noticed I omitted some important info. I learned today the GG who poured the patio did pour a continuous footer around the outside perimeter so no issue in supporting a roof load. Also, the top course of the brick perimeter foundation are bull nose and this adds a nice touch along with the radius. I'd hate to tear out the who patio just to make the job a little easier.

Also omitted is the distance from the top of the pad to the bottom of the return: The distance is 106-1/2 inches. I have considered all along the new roof line should run below the existing returns. This 106-1/2 will allow the use of 93-inch studs for the walls. Given the longest rafter span I'll need to check the span tables and maybe work with rafters on 12" centers in order to meet code and still maintain a HAP (height above plate) below the 106-1/2 limitation.

Someone also asked for another photo showing the adjoing roof lines. Photo is attached. Again, any and all suggestions are very welcome.

I believe Baptista mentioned the use of a plywood template. Will you elaborate a little on your suggestion please.


Jim
Greensboro
Lic. GC since 1984