I should know how to figure this out but I’m coming up blank.
If I know the slope of the commons to be 1.8 degrees, how do I find the slope for the hip ?
I should know how to figure this out but I’m coming up blank.
If I know the slope of the commons to be 1.8 degrees, how do I find the slope for the hip ?
Fine Homebuilding is excited to be the official media partner of the 2024 Building Science Symposium series! This event offers builders, tradesmen, architects, designers and suppliers to discuss topics ranging…
"I have learned so much thanks to the searchable articles on the FHB website. I can confidently say that I expect to be a life-long subscriber." - M.K.
Get home building tips, offers, and expert advice in your inbox
Fine Homebuilding
Get home building tips, offers, and expert advice in your inbox
© 2024 Active Interest Media. All rights reserved.
Get home building tips, offers, and expert advice in your inbox
Become a member and get instant access to thousands of videos, how-tos, tool reviews, and design features.
Start Your Free TrialStart your subscription today and save up to 81%
SubscribeGet complete site access to expert advice, how-to videos, Code Check, and more, plus the print magazine.
Already a member? Log in
Replies
Try this Hip-Valley Roof Framing Calculator.
Select Angle mode in the drop-down menu. Enter the Main and Adjacent Pitch Angles (the Major and Minor Pitch Angles) in the Rise fields. Disregard the Run fields. Enter the plan angle between eaves (the Total Deck Angle). Click on the Framing Angles button.
I'm getting 1.273° for the Hip Pitch Angle; that's assuming the Commons on both spans are equal and your angle between Main and Adjacent eaves is 90°.
The formula is:
Hip-Valley Pitch Angle = arctan (tan Common Pitch Angle × sin Plan Angle)
Hip-Valley Pitch Angle = arctan (tan 1.8° × sin 45°) = 1.273°
If the Commons are expressed in terms of pitch or Rise/Run and we want an answer for the Hip-Valley in terms of the slope or pitch rather than the angle, we can use:
Hip-Valley Pitch = Common Pitch × sin Plan Angle
Am I reading this question correctly? 1.8° seems like a pretty small slope.
Edited 10/4/2005 12:52 pm ET by JoeBartok
Edited 10/4/2005 12:52 pm ET by JoeBartok
Edited 10/4/2005 1:25 pm ET by JoeBartok
A 1.8 degree slope is 3/8" / 12 slope.
Your hip or valley rafter slope will be 3/8" / 17.
Hey joe once again its good to have you out there. With your math we don't need to think about pitch , we can just use the numbers and and calc the angles. Great site for figuring the angles, and thanks for putting up the formulas also.
Joe,
Every pitch based on a 12" run. So if you have a hip running at 45° with the 12" run your hip would be running at 17".
If you have a 12" x 12" square your diagonal would be 16.97056" or 17"
Or 12 x Square Root of 2 = 16.97056"
For your 1.8° roof that pitch would be 3/8" rise for every foot. So for your hip you would have a 3/8" rise for every 17" and you would hold your framing square 3/8/17.
No matter what the pitch is if your hip is running at 45° you set your framing square at ?/17.
How did you arrive at the 3/8" from the 1.8 Framer ?feeling a little dense today ..
"How did you arrive at the 3/8" from the 1.8 Framer ?"You said in your first post that you had 1.8° for a slope. On my calculator I did this:1.8 [Pitch] Returns 3/8"Also this:1.8 [Tan] x 12 = 3.77115" or 3/8"If your given a pitch in degrees all you have to do enter the number in degrees and press the tan button and multiply x 12. 22.62 [Tan] x 12 = 5So that's a 5/12 pitch and your hip would be 5/17.Joe Carola
The better question is how did you come up with 1.8°? Most of us work in rise over run pitch.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
I do too Piff, it's just that this time I'm trying to match the slope of an existing shed roof. The slope didn't look like anything I've seen before so I got up there with my Smart level and measured 1.83 deg. Maybe an Owner-built addition ?I want the corrugated panels of this new patio cover to tuck right up under the existing roofing.Sorry Joe, I did buy a Construction Master but I haven't figured out how to use it yet ! I'm going to have to read over your tutorial again when I'm not feeling dense in case I run into this again ..these images are what I drew after getting the info from Joe, but then I went ahead and re-drew it using a 1:12 pitch where I know how to find the hip.
nice drawings.For a job like that, with such a low slope, I would probably use a riped top to make up the pitch on my hip rafterI'd also be very picky about sealing joints and fasteners against leaks.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!