On Monday, 22 May 2017 13:35:27 UTC+1, Bob Minchin wrote:
Tim Watts wrote:
Very hypothetical...

http://www.wikihow.com/Build-a-Gambrel-Roof

How strong is that? There must be some not insignificant spreading
forces going through those gusset plates.



I am wondering - as I am musing plans for my workshop, long term project
as the house is nearly done (yea!).

Going for 15m2 to use permitted development (near 2 boundary fences,
wooden, so limited to 15m2 and 2.5m roof height).


I have always thought a gambrel roof would look pretty - but this has to
take some load: snow load, tiles (synthetic, so not as bad as
concrete/clay) and hanging/storing stuff in it.

It's not as easy to visualise the strength as a simple pitched roof with
tie beams.
I reckon this is a non starter for 2.5m ridge height. Note that the wiki
article shows a flat deck on which the beams bear. this is critical to
the strength as it will be in tension to support the roof weight. Even
if you replaced this with horizontal joists they would end up around
chest height.
If you want to stay within PDR then there is little option but to have a
very very low pitch roof which rules out most tiling systems and you
possibly will have to go with EPDM rubber which is practical but not pretty.
Bob

You can use tiles at a very low pitch if you fit asbestos or similar first. Joints must overlap.


NT