On 06/11/2012 15:06, David WE Roberts wrote:
"John Rumm" wrote in message
o.uk...
On 06/11/2012 11:50, David WE Roberts wrote:
We are building a veranda across the back of the new extension, and a
car port up the side of the house to link with the veranda and provide a
covered walkway from the front to the back of the house.
The main veranda and car port are pretty straightforward but the corner
where the two meet requires a bit more thought.
The solution appears to be a hip, joining the two roofs sloping in
different directions.
The triangle calculator suggests the hip will be 5.3m long.
Working from
http://www.bsw.co.uk/uploads/files/b..._4pp240810.pdf
seems to suggest that 72*220 (3*9) C16 might do the job.
However this is for floor joist sizes on a ground floor.
You have missed the one bit of information that would be needed to
make sense of this - the type of roof you are expecting them to carry...
Ooops - 10mm polycarbonate using glazing bars supported by wood.
That makes it a tad simpler ;-)
The roof itself will weigh practically nothing (i.e. 100N/m^2) in the
grand scheme of things. So the biggest forces you need deal with are
snow loading (about 0.6kN/m^2), wind uplift (depends on where you are -
but could account for another 0.4kN/m^2), and access (i.e. it needs to
be strong enough to support the weight of someone building it).
A 5.3 m hip suggests about 3.7m rafter span.... What were you planning
on using for those? What is holding up the far end?
I would have thought 5x2 would be fairly conservative. Then the hips
could be a tad deeper say 6x2 (or deeper and slimmer 7x1.5).
It will also depend a bit on what rafter spacing you go for. The poly
sheets are available in a range of widths.
--
Cheers,
John.
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