[Greenbuilding] Roof slopes (was Re: Glass roofing)

Vadurro, Rob, EMNRD rob.vadurro at state.nm.us
Thu Aug 14 16:43:41 MDT 2014

Or algebra:

a/b= b/a+b

Rob Vadurro, AIA
Park Architect
New Mexico State Parks
1220 South Saint Francis Drive
Santa Fe, NM 87505
505-476-3361 fax

From: Greenbuilding [mailto:greenbuilding-bounces at lists.bioenergylists.org] On Behalf Of Christian Corson
Sent: Thursday, August 14, 2014 4:40 PM
To: archilogic at chaffyahoo.ca; Green Building
Subject: Re: [Greenbuilding] Roof slopes (was Re: Glass roofing)

For what it is worth a 7/12 is 30.25 degrees. 4/12 - 8/12 are all non even angles. An 9/12 pitch is 37 degrees, 10/12 40 and 12/12 45 degrees.
I am curious.........how is it that a 7.5/12 at 31.whatever degrees represents a ratio that is similar to a golden rectangle? That ratio is represented in a x/y axis at 1.6ish/1 they are right angles and they are 90 degrees.
Am I missing something?

Christian Corson
Technical Director
Ecocor  LLC.
chris at ecocor.us<mailto:chris at ecocor.us>
o. 207-342-2085
c. 207-930-5088

On Thu, Aug 14, 2014 at 6:08 PM, RT <ArchiLogic at yahoo.ca<mailto:ArchiLogic at yahoo.ca>> wrote:
On Thu, 14 Aug 2014 16:49:07 -0400, Clarke Olsen <colsen at fairpoint.net<mailto:colsen at fairpoint.net>> wrote:
True, the temples are shallower, but the diagonal of a golden rectangle (10 to 16.14....) is an ancient proportion used for
roofs in New England.

On Aug 14, 2014, at 3:28 PM, candtcampbell at juno.com<mailto:candtcampbell at juno.com> wrote:
I could have sworn that the pitch of a Greek pediment was something like 5.2 in 12.
My favorite pitch is 7.5/12, aka 10 in 16.

"7.5/12" and 10/16 are both Murrican (ie based on Imperial units) approximations of the diagonal of the Golden Rectangle -- close, but not perfect, Perfection being that which the Golden Mean is supposed to represent, derived by geometry rather than arithmetic.

Me ? I like 7/12 for roofs. 30 degrees. Easy to set up for cuts and joints. Not so steep that you slide off when walking around on it but steep enough that snow and rain don't accumulate on the outside and the inhabited roof volume is an interesting space  -- human scaled as opposed to slopes 12/12 or more which are better suited the Divine where much of the "soaring" space (or as one typo in a realtor's ad called it "sorrowing 20 foot ceilings") of the interior roof volume cannot be practically utilised.

Enginoids also like 30 degrees for roof slopes. Steeper than 30 degrees and live loading due to wind becomes a governing factor in the structural design --shallower than 30 degrees, gravity loads govern -- 30 degrees is the sweet spot between the two and is structurally very efficient.

=== * ===
Rob Tom  .  .  . T60BOM
Kanata, Ontario, Canada

A r c h i L o g i c  at  Y a h o o  dot C A
(manually winnow the chaff from my edress if you hit "reply")

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