I am laying out a roof for a friend. It is a hip and valley arrangement, all roofs being 6:12 pitch. I have modeled it in 3D software, and made it complete with all birdsmouths, etc. Here are questions for you roof specialists.
1. My software tells me the pitch of valleys and hips is 4 3/4 / 12. Is this right?
2. We have exposed rafter tails but with a horizontal cut so the ends match up to fascia boards nailed to the plumb cuts. Should my dimensioning call out the length (height) of the plumb cut end (and let the framing square or template give the horizontal cut)?
Replies
1
Sounds about right, Your framing carpenter should be able to do this given the ptich of the roof without so many details. If he can't, you need another guy who can. You lay out a valley or hip with the square at 6/17 instead of 6/12. That might compare to what you got.
2
Is this allowing for the heel drop on the hip and valley? Calling that out could be helpfull or could be confusing depending on how your guy figures it. Joe fusco has posted links that explain it well.
oops, I see that this is for a friend and not a pro - do call it all out so he has all the specifics like a paint by numbers set.
.
Excellence is its own reward!
"The first rule is to keep an untroubled spirit.
The second is to look things in the face and know them for what they are."
--Marcus Aurelius
Edited 12/22/2002 7:24:06 PM ET by piffin
Gene,
For a 6/12 pitch Hip/Valley as Piffin said you would set your framing square 6/17.
As for your software, it's not correct at 4-3/4 /12.
It would be 4.24 /12.
Your better off with 6/17, just about every framer I know uses that.
If you had a Construction Master Calculator you can do this:
6 [inch] [pitch]
16.97 [inch] [run]
Press [pitch] = 4.24 (That's where the 4.24/12 comes from)
Press [pitch] =19.47° (Or set this angle on your speedsquare)
For your H.A.P. cut (Heel Stand) as Piffin said, you need to Drop the Hip to plane in with the jack rafters and commons.
6/16.97 x .75 = .265174 or 1/4" (Drop)
So if your H.A.P. cut on your common measures let's say 7-1/4".
You make your H.A.P. cut on your Hip 7"
As far as your horizontal cut on your rafter tails, it all depends on what size fascia your going to use. For example when we use 1x6 fascia we cut the plumbcut 4-1/4" which gives you your horizontal cut.
That gives us enough reveal from the bottom of our finished soffit.
But you have an exposed soffit you can lay it out in the field or on your software to see what's best.
As piffin said who ever is framing it should no all of the above.
Hope this helps.
Joe Carola
Joe
As you know, but others may not, the .75 in your equation is related to the single 2x thickness of the material used for the hip/val. It could be 1.5" or 2.25" (doubles or triples). Worth noting because this crap is confusing enough. Also, Ive lately taken to bevelling the bastards to take the guesswork out of it. So far, so good especially with doubled ones using the Height Above Plate method
Piffin
"sounds about right"? not quite
Ian
"about" means about, not exact.
When I got specific, I gave 6/17. He can work the math from there to transpose the ratio. I don't like to do someone elses work for them..
Excellence is its own reward!
"The first rule is to keep an untroubled spirit.
The second is to look things in the face and know them for what they are."
--Marcus Aurelius
Gene
Like the boys say, 6/17 = 4.24/12. Bad program, no donut.
I would leave a reveal at the facia, either below or above the seatcut of the tail. I've seen a craftsman type 1x4 facia on a 7" plumb cut that looked ok. Depends on the rest of the detailing. If you shoot for them to line up perfectly at the very least the vagaries of the facia will make that nearly impossible, not to mention slightly off cutting, humps in walls, crowns and so on and on and on.
When I can, I do everything by fullsized sketch and template.
Ian
Sorry I threw you all off. I was having a little red wine before I posted last. You all can define or interpret "little." My program gives me a ratio of 4.24 and a bunch of little stupid digits, to twelve, as the pitch. Who knows what I was thinking when I typed 4 3/4. As I read from your posts, the software is giving it to me correctly. Here is my roof frame model, and my detail for one of the valleys, the third valley from the left, as you look at the pic. There is no framing part in place that falls outside the guidelines of "bottom of sheathing equals framing." Ridges and hips are dropped appropriately. Valleys are bedded down so that sheathing line comes to the centerlines. Doubled valleys are beveled at top edges, with king valleys changing bevels above valley junctions. As I am telling my guy, if you get the plates in place per the dimensions on the plan view, when you cut the parts per the drawings, it will all fall in place like a jigsaw puzzle. But, as I asked before, is this the best way to detail the horizontal cut at the eave end?
looks pretty thorough. The only critique i might might make is whether he, as a DIY, can understand the note at the top bevel cut 3/8"off this side. I usually will cut and measure to the long point. Make sure he interprets that right..
Excellence is its own reward!
"The first rule is to keep an untroubled spirit.
The second is to look things in the face and know them for what they are."
--Marcus Aurelius
Gene,
Does this program tell you that the bevel for the valley is 18.43° ?
When it gives you the common length and hip length mesaurements does it automatically deduct for the thickness of the ridge being that you tell the program what thickness the ridge is, or do you have to deduct?
In other words, do you have to tell it what the real effective run is?
Does it show the hip drop amount or show that the two Hap cuts are different?
I'm curious how much this program knows and what you have to put into so that all these measurements are correct and can be cut at what the program says so everything fits together like a puzzle.
Truehaven,
Your right about the .75. I was using a 2x as the hip 1/2 the thickness.
In Gene's case using one 1-3/4" LVL it would be - 6/16.97 x .87 = .307602 or 5/16" (Drop)
You really do bevel your 45° hips?
The only members I was thinking of beveling were the doubled king valleys, but I am rethinking that now and will drop them and only bevel off the top section of the lvl above the dormer gable junctions.
There is nothing automatic about my CAD program, for doing roofs, or anything else. I lay everything out to full scale, defining the plate lines and roof shape above, then pop in framing members, and figure out all the joinery, birdsmouths, etc. I have about six hours work into this roof so far, and another couple hours to do the detail sheets. I am sure a good roof cutter would use a lot less time figuring it out as it goes, but I am doing this for a guy that doesn't have a roof cutter person.
I am comfortable with my CAD package and use it to model and visualize and detail most everything I build, from jigs to furniture to foundations to houses.
P.S. Let me tell you a little about the project. It is a hybrid structure, part timber-frame, with the members all being peeled round logs, and the rest conventional wood framing. The 2x12-framed vaulted roof above the main floor great room is supported by a ridge and purlin arrangement of doubled logs, one sitting atop the other with butt ends swapped, and the second floor structure is one done with log joists, with each log squared at the ends that bear on the 2x6 plates, and flat sawn on the tops to receive the t&g 2x6 decking. This roof arrangement I have done is the top roof, all framed in LVLs and 2x12s
Edited 12/23/2002 4:26:41 PM ET by Gene Davis
Gene,
Sounds like a nice project. I guess I was just curious how detailed these programs were. Just rememeber you drop a hip not a valley. If you were to bevel the valley then you would ADD whatever the hip drop measurement would be to to the common hap cut.
Good Luck, Merry Christmas.
Joe Carola
Yes
The reason being I wanted to see if I could and how it looked when it was done. This was on an irregular doubled valley the first time. Same house, the porch hip roof was vaulted with T+G v-joint ceiling so I bevelled top and bottom. I liked the way they turned out and I found that once I knew how to derive the saw angle it wasn't too time consuming. I figurer that with so much carpentry being subbed to shops, like stairs and trusses, I might as well get my jollies when I can.
I love my construction master.
Ian
Gene, Which program are you using for 3-D
I use Cadkey for Windows, the 1997 release. Similar in most all respects to AutoCad. Full 3D mechanical modeling and rendering, with good tools for speedy drawing production. I have a version of Intergraph's SolidEdge on board, too, which is really cool, but I am more proficient with the one I learned first. Here is a furniture design I did with the SolidEdge package. The cabinet is mostly made, but I have laid aside the project for now.