Hello again….I attempted to post this message earlier today, but it seems to be lost in cyberspace.
I`m helping a buddy frame an addition on his home, but I`m having trouble with the rafter cuts. I`ve done a few small simple roofs in the past, but I`m really hung up on this one.
It`s a simple gable framed roof, so there`s nothing more than common rafters, but I`m stuck.
My outside measurements of the span come to 25′ 3/4″ which I`m dividing in half to get 12′ 6 3/8″……My ridge height needs to be 10′ 7 1/2″, to reach the same ht. as existing roof. The roofs are offset, so the exact same ht. may not be necessary, but I want to be close. For the life of me I can`t figure out the ridge cut and rafter lengths.
Any help would be greatly apreciated.
Thanks in advance for your time and attention.
Replies
pitch cut 10-1/4"
diag 16'4-9/16"
if your ridge board is a two by
Sombody else check me out here for confirmation.
Excellence is its own reward!
Edited 9/9/2003 3:25:59 PM ET by piffin
Your correct, I used a construction calculator and got almost the same measurements. Pitch 10-3/16" rafter length with 3/4" subtracted for half of ridge 16'-4 3/8".
Mike
I'm thinking that you might be going about this from the wrong angle.
I really hate to use the word "wrong", so please don't take offence, because none is intended.
If your new roof is a continuation of the existing roof then you will need to match the length and pitch of the existing rafters. The HAP will have to be the same, too.
If it doesn't continue the existing roof, then you should,IMHO, match the HAP and pitch and let the ridge fall where it may.
The figures the guys gave you are also what I came up with, but the HAP needs to be taken into account and we don't know what you are using for rafters which changes the HAP.
If you are using 2x6 rafter and the HAP is 4-1/4" (for a 10/12) this will add to your overall height....
Then I think you are looking at 16' 1-11/16" rafter that is 9-3/4 to 12.
If you are using a 2x8......
the HAP is more like 6-1/4
16' 1" rafter and the pitch is still about 9-3/4" to 12
Jeez, I just reread what I have written, I hope it helps.
And hey guys if I'm wrong fix it, but be nice, K?
I think you are right and I would be trying to match HAP and pitch of the old regardless whether offset or aligning, then let the ridge fall where it will. I was only responding to the math Q without following thru on design issues. Too many variables there from here......
Excellence is its own reward!
My initial post was so much more thorough.....when I realized it hadn`t materialized later in the day, I was in a bit of a hurry when reposting this version. Sorry for the missing information.
The new roof is offset from the original, so nothing needs to line up directly. The pitch will not be the same, but this is intentional as the architect is attempting to "soften" the height of the building visually. Were we to match the existing roof pitch, the new ridge would sit a few feet higher than the existing.
My ridge is a 2 x 12.....the rafters are 2 x 10 sitting on 2 x 6 wall plates with 5/8" sheathing.
I`m a remodeler by trade with limited framing experience.....I can`t determine what you all are refering to by H.A.P. (Height Above Plate?)
You guys are the best....I truly apreciate your assistance!
EDIT: So as not to confuse...Dave (Rocker) was unable to access the website using his screen name on my computer last evening....hence, this and several other posts under my screen name. Think you`re confused? Imagine logging on this morning with Email responses to posts you never made! LOL!
J. D. Reynolds
Home Improvements
"DO IT RIGHT, DO IT ONCE"
Edited 9/10/2003 9:09:44 AM ET by JAYBIRD
probably the easiest for you , since you already know what the height of the ridge board is, is to just go ahead and set the ridge board at the height you want it. A 2x4 underneath it at either end, with two short blocks sandwiching the ridge and 2x4 prop. Center the ridge... either w/ a plumb bob or drive a nail on the top of the board, hook two tape measures, one each going to each exterior wall. You want the same dimension. Simply hold one of your uncut rafters in place, on the gable end, and scribe the cut-marks on the rafter with your pencil. Once at the ridge for your plumb cut, once at the wall for your birdsmouth cuts.
That was going to be my last resort....I`ve done it that way before...thought it might be time to try it like a pro.
Thanks for the input, much apreciated.J. D. Reynolds
Home Improvements
"DO IT RIGHT, DO IT ONCE"
Rocker,
Giving you straight numbers is only going to help you this time, but I guess that’s what you need.
For openers I’m using a CM4 to give you this numbers simply because it’s quick.
The first thing you said is you have a total ridge height of 10’ 7-1/2”, but you didn’t say from where it’s measured from. If you measured it from the top of the plate then it’s OK if you measured it from the deck then it’s to big by the amount of the plate thickness. One 2 by would be 1-1/2” Two 2 by’s would be 3” and so on.
Let’s just say it’s from the top of the plate. Now as bee pointed out will have to make an allowance for the H.A.P of the width rafter you use whether they be a 2 x 6, 8 or 10. You would need to subtract the HAP from the total height, in the case if I use bee’s example of a 2 x 6 on a 10 pitch roof the HAP would be 4-1/4”. You subtract that from the total height and now get 10’ 3-1/4”
If your ridge is a 1 by then you would subtract ¾ from your run and that would now be 12’ 5-5/8”. If you plug these numbers in to a CM4 you get:
A pitch of 9-15/16” in 12”
And a rafter length of 16’ 1-7/8” from the ridge to the birdsmouth’s plumb cut.
Well thought and well taught...
Where did the old Joe go? You're acting, well, resurrected.
;).
Excellence is its own reward!
Yes, the ridge height is taken from the tops of wall plates....another peice of info that didn`t make it this time around.
Thanks so much for your expertise!J. D. Reynolds
Home Improvements
"DO IT RIGHT, DO IT ONCE"
Jay,
The picture to the right describes the H.A.P
View Image
For a more in depth look at the H.A.P. and with HAP chart and some was to calculate it try this link. View Image
Rocker,
2x10 rafters Yuck!
9-5/8 to 12 plumb cut.
Length from ridge to plumb cut of birds mouth 15' 11-7/8"
H.A.P 7-1/4" this will give you a 5-1/2" seat cut
Cut em, hump em, nail em, admire em.
I would like to see a photo when you get done. I normally don't like mixing pitches, so I'd like to see how it turned out, K?
Rocker wanted me to pass along his thanks too all of you....unfortunately, he still didn`t quite get it, so I ended up doing exactly what I was trying to avoid....jumping in on one of his projects.
Here`s a pic of the new roof line against the existing....it varies slightly, but nothing that should draw too much attention.J. D. Reynolds
Home Improvements
"DO IT RIGHT, DO IT ONCE"
nice.. exposed rafter tails with double sheathing to hide the roofing nails ... and show the boards ?
olde remodeler's trick ....Mike Smith Rhode Island : Design / Build / Repair / Restore
You got it....nice eye....I know its there and I have trouble pickin` it up in the pic.
As much as I didn`t want to get involved, we actually had much fun popping that frame up. I gotta give him one more day as there`s an 18" overhang with the rakes.J. D. Reynolds
Home Improvements
"DO IT RIGHT, DO IT ONCE"
Hey, that is the exact solution I was looking for to create a more refined appearance on the underside of a roof deck overhang with exposed rafter tails.
I thought about just infilling between the rafters with tongue and groove but the OSB deck wouldn't be much of a nailing surface. I really didn't have a lot of confidence that all that cutting and trimming would end up tight enough to the rafters to be convincing either.
Thanks to Jaybird for posting that shot and to you for pointing it out. Kevin Halliburton
"I believe that architecture is a pragmatic art. To become art it must be built on a foundation of necessity." - I.M. Pei -
we always do that with exposed rafter tails.. usually 1x6 beadboard with a 5/8 plywood overlay... we've also used 5/8 T 1-11 with a 5/8 cdx overlay..
here's a shed roof with the 1x6 and 5/8 overlay...
Mike Smith Rhode Island : Design / Build / Repair / Restore
here's the side view..
Mike Smith Rhode Island : Design / Build / Repair / Restore
Thanks for sharing that old trick with this new dog. I'm over-running the double 2x6 splines on my SIP roof 2'-0" long on the rake to create the needed overhang and was looking for a nice way to finish them. Was starting to resign myself to closing in the soffits. The exposed rafter tails would work so much better with the house as a whole. Ah-Pree-Shate-Cha!!Kevin Halliburton
"I believe that architecture is a pragmatic art. To become art it must be built on a foundation of necessity." - I.M. Pei -
Ya primed the rafter tails before hand...good man....tried to convince Rocker to do likewise...I`ll find out tomorow if he heeded my advice.J. D. Reynolds
Home Improvements
"DO IT RIGHT, DO IT ONCE"