Tim Watts wrote:
On 22/05/17 13:34, Bob Minchin wrote:

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

I'm starting to think you're right Bob.

which rules out most tiling systems and you possibly will have to go
with EPDM rubber which is practical but not pretty.
Bob


http://www.ecosystemsdistribution.com/eco-slate/

10 degree pitch. I've had my eye on these for a while...



It's either that or sink the structure into the ground a bit to gain
some extra height - but there's a limit as anything other than a gentle
ramp down isn't a great idea for a workshop.

I've got an awkward corner plot with the house set back to boot - that
gives me two front elevations that I cannot build beyond (PDR) and
forces anything else to be near a boundary.

I am glad the old 5m from house rule was scrapped!

I also have a shared sewer I need to stay clear of (I'm going to sink
footings about 1.5m away and at the same depth or slightly lower and
have about 50cm of overhang on the base (cantilever).


Having thought about it a bit more. You could add a substantial ridge
board and purlins each end of which is supported down through the end
walls. In that way you can get the Gambrel shape without excessive
forces trying to splay the walls as the roof weight is "hung" off the
ridge and purlins
If you can get the purlins just above head height, then it should allow
comfortable movement inside.

Bob