Unequal Pitch Roof Framing - Building & Construction - DIY Chatroom Home Improvement Forum

 DIY Chatroom Home Improvement Forum Unequal Pitch Roof Framing
 Register Blogs Articles Rewards Search Today's Posts Mark Forums Read

08-30-2009, 08:02 AM   #1
Newbie

Join Date: Aug 2009
Posts: 5
Rewards Points: 10

## Unequal Pitch Roof Framing

Is there anyone with some input on framing an intersecting unequal pitch roof. I want to have both ridges pretty much in line with each other. The major roof is a 5/12 with a total run of 14'-3 5/8" and a total rise of 5'-11 1/2". The minor roof will have a total run of 9'-2 1/4". Thanks.

08-30-2009, 09:39 PM   #2
Framing Contractor

Join Date: Apr 2006
Location: Caldwell, NJ
Posts: 1,758
Rewards Points: 1,000

Quote:
 Originally Posted by ranhuc Is there anyone with some input on framing an intersecting unequal pitch roof. I want to have both ridges pretty much in line with each other. The major roof is a 5/12 with a total run of 14'-3 5/8" and a total rise of 5'-11 1/2". The minor roof will have a total run of 9'-2 1/4". Thanks.
What size rafters and ridge are you using?

What is the overhang length?

Are the walls 2x4 or 2x6?

Do both roofs have ceiling joists or either one cathedral ceilings?

__________________
Joe Carola

 08-30-2009, 10:45 PM #3 Apprentice     Join Date: Dec 2008 Location: Stoughton, MASS Posts: 68 Rewards Points: 75 You can have the same pitch for both roofs. The only thing different would be the LCR of the 2 roofs, I know the LCR formula is rise squared, run squared then get get the square root. In your case: 5 squared plus 12 squared is 169. And the LCR is 13. then take 13 and multiply it by the run which is 9.1875. And the theoretical LCR would be 109.4375''. But then you need the O.H(over hang) you want to add it to the LCR. Which is O.H divided by 12, multiplied by the LCR. The 2 roofs should be the same pitch. The rafters just change size. Eeek, it says you have two different slopes. Sorry, the information I just wrote doesnt have to do with anything. I read the topic different. Sorry.. __________________ >>SooN<<
 08-30-2009, 11:54 PM #4 Registered User   Join Date: Mar 2009 Posts: 11,423 Rewards Points: 4,912 Your new rise per ft. is 7-13/16". Be safe, G Last edited by Gary in WA; 08-31-2009 at 01:20 AM.
 08-31-2009, 05:32 AM #5 Newbie   Join Date: Aug 2009 Posts: 5 Rewards Points: 10 [quote=Joe Carola;321540]What size rafters and ridge are you using? What is the overhang length? Are the walls 2x4 or 2x6? Do both roofs have ceiling joists or either one cathedral ceilings? Thanks for your reply. Main roof will have 2 x 8 rafters with 2 x 10 ridge and will bear on 2 x 4 plate on ceiling joists on existing 2 x 4 walls. Minor roof (which is an addition) will have 2 x 6 rafters with 2 x 8 ridge bearing on 2 x 4 plate on top of ceiling joists on 2 x 6 walls. Projection will be 16" including the shingles (The dimensions given include my overhang.) To the best of my knowledge, I need to raise the addition wall height 3 3/4 " more than existing walls to have fascia and shingles line up. If I use the same total rise for the minor roof' where does that actually put my minor ridge in relation to the major ridge? It shouldn't be 3 3/4" higher? This is the part I'm having trouble visualizing.
08-31-2009, 09:35 AM   #6
Framing Contractor

Join Date: Apr 2006
Location: Caldwell, NJ
Posts: 1,758
Rewards Points: 1,000

[quote=ranhuc;321635]
Quote:
 Originally Posted by Joe Carola Projection will be 16" including the shingles (The dimensions given include my overhang.)
What is the exact measurement of the overhang from the outside of the 2x4 wall to the outside of the fascia, not shingles?
__________________
Joe Carola

08-31-2009, 06:19 PM   #7
Newbie

Join Date: Aug 2009
Posts: 5
Rewards Points: 10

[quote=Joe Carola;321694]
Quote:
 Originally Posted by ranhuc What is the exact measurement of the overhang from the outside of the 2x4 wall to the outside of the fascia, not shingles?
15 1/4 " will be the projection.

08-31-2009, 07:00 PM   #8
Framing Contractor

Join Date: Apr 2006
Location: Caldwell, NJ
Posts: 1,758
Rewards Points: 1,000

[quote=ranhuc;321948]
Quote:
 Originally Posted by Joe Carola 15 1/4 " will be the projection.
The pitch using a 2x6 for the minor roof is 7-7/16:12 and the plate height difference is 5-1/2".

I will post drawing later showing you two views.
__________________
Joe Carola

 08-31-2009, 07:36 PM #9 Framing Contractor   Join Date: Apr 2006 Location: Caldwell, NJ Posts: 1,758 Rewards Points: 1,000 Here are the trwo drawings. One is the cross section of the two roofs showing the relationship between the ridge height with both ruins and the outside pint of the 15-1/4" overhang. You always figure the length of the overhang to get the exact pitch and exact rise. Notice that doing this creates a triangle giving you the run and rise of both pitches. The second drawing is a close-up of the outside points at the fascia where the two pitches meet perfect. The overhang run and rise shows you at the plate-line the difference in plate heights using a 2x6 and 2x8 with a full 3-1/2" seatcut. Attached Thumbnails     __________________ Joe Carola
09-01-2009, 06:52 AM   #10
Newbie

Join Date: Aug 2009
Posts: 5
Rewards Points: 10

Quote:
 Originally Posted by Joe Carola Here are the trwo drawings. One is the cross section of the two roofs showing the relationship between the ridge height with both ruins and the outside pint of the 15-1/4" overhang. You always figure the length of the overhang to get the exact pitch and exact rise. Notice that doing this creates a triangle giving you the run and rise of both pitches. The second drawing is a close-up of the outside points at the fascia where the two pitches meet perfect. The overhang run and rise shows you at the plate-line the difference in plate heights using a 2x6 and 2x8 with a full 3-1/2" seatcut.
OK, this makes it clear now. One thing though...given your dimensions on your drawing, it seems I need to clarify myself. The dimensions I gave were the total run including the projection of 15 1/4" to outside of fascia and 3/4" for the shingle projection past the fascia. So I come up with a total rise of 5' 11 1/2". I see you took my total run dimensions to the end of the wall and calculated a different total rise. My difference in wall heights of 3 3/4" was calculated accordingly:

total projection/total run of common (minor) x total rise
SUBTRACT
total projection/total run of common (major) x total rise

16"/110.25" x 71.508" = 10.37757823
SUBTRACT
16"/171.625" x 71.508" = 6.666441369
= 3.711136861 or 3 11/16"

09-01-2009, 05:53 PM   #11
Framing Contractor

Join Date: Apr 2006
Location: Caldwell, NJ
Posts: 1,758
Rewards Points: 1,000

Quote:
 Originally Posted by ranhuc OK, this makes it clear now. One thing though...given your dimensions on your drawing, it seems I need to clarify myself. The dimensions I gave were the total run including the projection of 15 1/4" to outside of fascia and 3/4" for the shingle projection past the fascia. So I come up with a total rise of 5' 11 1/2". I see you took my total run dimensions to the end of the wall and calculated a different total rise. My difference in wall heights of 3 3/4" was calculated accordingly: total projection/total run of common (minor) x total rise SUBTRACT total projection/total run of common (major) x total rise 16"/110.25" x 71.508" = 10.37757823 SUBTRACT 16"/171.625" x 71.508" = 6.666441369 = 3.711136861 or 3 11/16" Please tell me your take on this, I'd appreciate it.
The 3-11/16" plate height difference will work if you use the same size rafters as the main roof, but you said your using 2x6's. That will give you 6-1/16" difference.

The pitch since you cleared the riun up for me will be 7-13/16:12. In the drawing of the close-up of the overhang and plate height hjsing a 2x6 in blue you will see how you will have 6-1/16". The other drawing I drew a 2x8 in yell next to the blue 2x6. You will now see how you will get your 3-11/16" that you are correctly coming up with, but that would be using 2x8's for both rafters.
Attached Thumbnails

__________________
Joe Carola

09-02-2009, 06:11 AM   #12
Newbie

Join Date: Aug 2009
Posts: 5
Rewards Points: 10

Quote:
 Originally Posted by Joe Carola The 3-11/16" plate height difference will work if you use the same size rafters as the main roof, but you said your using 2x6's. That will give you 6-1/16" difference. The pitch since you cleared the riun up for me will be 7-13/16:12. In the drawing of the close-up of the overhang and plate height hjsing a 2x6 in blue you will see how you will have 6-1/16". The other drawing I drew a 2x8 in yell next to the blue 2x6. You will now see how you will get your 3-11/16" that you are correctly coming up with, but that would be using 2x8's for both rafters.
Alright then, you just cleared this all up for me. I'll change up to 2 x 8 on the minor roof. Thanks a heap for your input.
Also. is there an ideal "drop" for collar ties based on my dimensions? What would be adequate material and how far apart would they be needed?

 Thread Tools Display Modes Linear Mode

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are Off Pingbacks are Off Refbacks are Off Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post Canufixit Roofing/Siding 9 02-05-2009 08:33 PM JerryH Roofing/Siding 18 11-07-2008 05:08 PM Thomas O Roofing/Siding 7 03-05-2008 10:51 PM

Top of Page | View New Posts