I have a shallow pitch roof design that involves 225mm timber purlins
supporting 50mm counter-battens, then battens and interlocking concrete
tiles. Span of purlins is 4 metres. (Insulation between purlins based
in knauf insulation examples). Then purlins were to be hung from
masonry using joist hangers.
What could I replace the timber with in order to make the roof thinner
? I have no experience with composite beams etc.
Cheers,
Simon.

On 7 Nov 2005 02:46:13 -0800, wrote:

I have a shallow pitch roof design that involves 225mm timber purlins
supporting 50mm counter-battens, then battens and interlocking concrete
tiles. Span of purlins is 4 metres. (Insulation between purlins based
in knauf insulation examples). Then purlins were to be hung from
masonry using joist hangers.
What could I replace the timber with in order to make the roof thinner
? I have no experience with composite beams etc.
Cheers,
Simon.

Steel

Do you mean purins or rafters ?

Steel must be boxed in. You need to go back to the engineer and ask
him to recaculate. The extra weight may effect him, and he can advise
what size you need. Or simply go back and ask if the roof can be done
thinner.

Rick

Steel
Do you mean purins or rafters ?

I mean purlins. The counter-battens run up the slope at right angle to
the purlins, but are
only 50mm.

Steel must be boxed in. You need to go back to the engineer and ask
him to recaculate. The extra weight may effect him, and he can advise
what size you need. Or simply go back and ask if the roof can be done
thinner.

The ceiling construction will box them in.
What engineer ? This is a DIY group ! I'm doing full plans of course.

I have looked at the multi-beam purlins from kingspan. They are light
for their strength.
The load tables take some figuring out though.

Simon.

wrote:

I have a shallow pitch roof design that involves 225mm timber purlins
supporting 50mm counter-battens, then battens and interlocking concrete
tiles. Span of purlins is 4 metres. (Insulation between purlins based
in knauf insulation examples). Then purlins were to be hung from
masonry using joist hangers.
What could I replace the timber with in order to make the roof thinner
? I have no experience with composite beams etc.

Can we have a little more detail please. I guess you have 225 x 75
purlins, but I can't figure out the jack rafters. What size are the
battens and what is the weight of the tiles/sq M?

Regards
Capitol

wrote:

The ceiling construction will box them in.
What engineer ? This is a DIY group ! I'm doing full plans of course.

If you know the loadings, then get the demo copy of superbeam from the
sda web site and fiddle with some alternatives in that. A flitch beam is
one way of reducing the size a bit while still maintaining most of the
ease of working with wood.

--
Cheers,

John.

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Can we have a little more detail please. I guess you have 225 x 75
purlins, but I can't figure out the jack rafters. What size are the
battens and what is the weight of the tiles/sq M?
Approx roof span - 4m ridge/eves x 5m. Pitch around 13 degrees.
225 x 75 Purlins at spacing 1m, 50x50mm counter battens (or call them
rafters) at 400mm spacing
bearing directly onto the purlins. 25 x38mm battens carrying
interlocking concrete tiles
(redland regent). Tile + fixings load 0.59 kN/m2 (from
www.alpeng.co.uk).
Timber sizes taken from 1992 part A tables for dead load 0.75, imposed
load 0.75.
Simon.

In article ,
Rick wrote:
What could I replace the timber with in order to make the roof thinner
? I have no experience with composite beams etc.

Steel

Do you mean purins or rafters ?

Steel must be boxed in.

That's interesting. I had a loft conversion designed by an architect and
well supervised by the BCO. None of the three steels are boxed in.

--
*Some days you're the dog, some days the hydrant.

Dave Plowman London SW
To e-mail, change noise into sound.