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

Christian Corson christianpcorson at gmail.com
Thu Aug 14 16:40:18 MDT 2014


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
ecocor.us
o. 207-342-2085
c. 207-930-5088





On Thu, Aug 14, 2014 at 6:08 PM, RT <ArchiLogic at yahoo.ca> wrote:

> On Thu, 14 Aug 2014 16:49:07 -0400, Clarke Olsen <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 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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