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Roofing/Roof Calculation and sketch


With reference to the following details for my proposed roof plan  attached, can assist me with sketching and computing the following below for my roof.

Drawn to a scale 1/8"=1' and with an overhang of 3'can you assist me with sketching a hip roof for a 4/12 slope or a 1/6 pitch and computing the following:
1. common rafter length
2. hip rafter length
3. jack rafter length
4. number of galvanize sheets
5. also how much labor and how much/type materials would be required
Any additional info required please let me know


This link will assist you in your calculations. It will also give roof area.
Then you can calculate the number of sheets you need.
Labor costs I have no idea or materials costs since I am in North america.

---------- FOLLOW-UP ----------

Is there a formula for calculating common rafter, hip rafter and jack rafter lengths.
Also what is the difference among the three.

I am not a framer so this terminology is new to me. The lengths will depend on the spacing of the rafters. Could be 16 or 24 inch on centres. Do not know the building requirements where you live.

Check the web like me and find this:

Jack Rafter: a rafter having less than the full length of the roof slope, as one meeting a hip or a valley.

Hip Rafter (angle rafter): The rafter in the corners of a hip roof. The foot of a hip rafter lands on a dragon beam.

check out these link:


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D. John Henderson


My 33 years in the building science business has involved air barriers, waterproofing, and flat & steep slope roofing systems.


My roofing encompasses commercial systems (BUR, mod-bit, single-ply) and residential applications (asphalt shingles, cedar shingles, slate and metal. I am cognizant of code stipulations in regards to FM and UL for commercial roofs.

Attended numerous courses offerd by Roof Consultants Institute, Roofing Industry Educational Institute, Factory Mutual Research Corporation, University of Wisconsin, and BURSI. Lectured for RCI and mentored at a local university for a Building Science Certificate.

Past/Present Clients
Government, commercial businesses such as The GAP, hospitals, school boards as a roof designer.

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