Roof Angle Question

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Roof Angle Question; Need the experts here.
Topic Started: Oct 31 2009, 05:52 PM (95 Views)
Mercman	Oct 31 2009, 05:52 PM Post #1
Bronze Medal Member Posts: 2,708 Group: Members Member #482 Joined: November 25, 2006	What would the degree be of the angle on the roofs pictured below?



old-hermit	Oct 31 2009, 07:23 PM Post #2
Member Posts: 433 Group: Members Member #680 Joined: April 25, 2007	It's calculated by rise (center line verticle to peak) and run (centerline horizontal to edge). The top left gable roof in the picture appears to be 12/12 or 45 degrees. Here are calculators. http://www.webmath.com/rtri.html http://www.blocklayer.com/Roof/ http://www.construction-resource.com/calculators/roof-frame.php



Dan S	Oct 31 2009, 07:38 PM Post #3
Bronze Medal Member Posts: 2,216 Group: Members Member #607 Joined: January 31, 2007	Roofers usually dont speak in angle degrees, but as old hermit mentions, in terms of rise. If the roof rises 3 feet upwards in 12 linear feet (measured level to ground) it's a 3/12; "Three twelve" pitch. An experienced roofer (which I'm not) can usually tell the pitch pretty close just by a quick look at it from the ground.



DamnCranky666	Oct 31 2009, 10:32 PM Post #4
Admin--Chief Crank Posts: 14,957 Group: Admin Member #666 Joined: April 1, 2007	Sorry, buddy, I'm math impaired.



tufftin	Nov 1 2009, 09:45 AM Post #5
Member Posts: 133 Group: Members Member #863 Joined: December 4, 2007	Standard where I came from is 4-12. 4 foot rise to every 12 feet of roof and that would be an easy scale to reproduce in 1/24th. Mike



Mercman	Nov 1 2009, 02:19 PM Post #6
Bronze Medal Member Posts: 2,708 Group: Members Member #482 Joined: November 25, 2006	Thanks guys the one that has my stymied is the Barn in the lower left. Guess I'll have to call my brother as he was a carpenter.



gramps-xrds	Nov 1 2009, 05:18 PM Post #7
Junior Member Posts: 82 Group: Members Member #998 Joined: June 28, 2008	Mecman, the roof in the lower left is a Mansard. The only thing my carpentry book says is that the lower roof should not exceed 70 deg. The top is just a gable. You can make it anywhere from 3/12 to 5/12. Hope this helps some.



chester	Nov 1 2009, 07:09 PM Post #8
Bronze Medal Member Posts: 2,791 Group: Members Member #526 Joined: December 13, 2006	That would be a gambrel roof Gramps. Pitches on gambrels varied from area to area and from era to era. In colonial times, the lower pitch was usually a 12/12 with a very small 6/12 on the upper pitch. But today most gambrels have as much as an 18 lower pitch with a larger (as shown) top pitch of about 4 or 5. In terms of degrees Merc. the lower pitch would be about 70� and the upper about 20� from level (horizontal). These roofs allow for more than just a half story second floor by increasing the amount of head room at the eaves. Much of all of this discussion is speculation since what pitch is used varies greatly at the discretion of the builder and owner. In my almost 40 years as a builder I don't think I've ever built two gambrels the same pitch. Mike, I don't know where you live but here in New England, a 4 pitch roof is asking for trouble with snow loads being what they are. We generally find an 8 pitch to be minimal. Edited by chester, Nov 1 2009, 07:10 PM.



Lou	Nov 1 2009, 07:55 PM Post #9
Bronze Medal Member Posts: 2,798 Group: Members Member #622 Joined: February 15, 2007	The gambrel roof is typically used for barns and the farmers didn't really care that much about degrees. My barn has that style roof in slate. Eyeball the upper roof's angle. The lower angle is real steep. Eyeball that also. The roof on the adjoining drawing appears to be a Swedish barn roof. I'm not sure if it has a name, but that's what we Pennsylvania farmers call it. Edited by Lou, Nov 1 2009, 07:57 PM.



Mercman	Nov 1 2009, 09:05 PM Post #10
Bronze Medal Member Posts: 2,708 Group: Members Member #482 Joined: November 25, 2006	Thanks guys This info helps alot. Like Cranky my brain is doing funny things.



Clayton	Nov 1 2009, 09:35 PM Post #11
Junior Member Posts: 30 Group: Members Member #957 Joined: April 28, 2008	The barn style sheds we build for our Habitat for Humanity houses have a standard 4 piece roof. The angle of the lower section from the vertical is 22.5 degrees and then the next section equals 45 degrees (two 22.5 combined). The center connection at the peak is also 45 degrees, again comprised of two 22.5 degree pieces. Basically all of the joints add up to 90 degrees per side and 180 degrees total. I hope this makes sense. Clayton Edited by Clayton, Nov 1 2009, 09:36 PM.



Lou	Nov 1 2009, 09:51 PM Post #12
Bronze Medal Member Posts: 2,798 Group: Members Member #622 Joined: February 15, 2007	If Virg OK's your angles it passes my approval. But if it all adds up to 180 degrees wouldn't the building be upside down? Oops I think I got it. All included angles must add up to 180 degrees if it is half the included surface of 360 degrees and the perimeter walls measure 90 degrees to the apparent horizontal surface, then the sum of all previous angles must be as you stated. Right Virgil?



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