John Rumm wrote:

DOB wrote:

The problem part is the headroom,at present there is 2m to the bottom
of the rafters which are 150mm,thus I should be able to fit the
required insulation and get a 50mm ventilation gap,so hopefully the
only extra space taken up at the top will be that which the plaster
board occupies.

You may want some insulation under the rafter to combat the thermal
bridging effect of the timber...

What I am interested to know is,as I haven't got access to software to
calculate necessary sizes,is it possible to span an 18 1/2 foot gap
with timber ? - if so what would the dimensions need to be,I'd prefer
to work in timber or possibly construct a flitch beam

Gut feel says fairly substantial at that span (i.e. 250mm) (I would go
do the sums, but I just killed the computer with the software on it!) -
you can download the demo version of Superbeam from Tony's site:
www.sda.co.uk

You have the added complication that you may need the new floor to carry
some roof load via your purlins (or more likely a dwarf wall).

I only intend on putting one room up there with a dormer at the back
and a velux at the front.The stairs will access directly under the
apex,flush with the wall so will have 2m head room,if the present floor
height remained unchanged.

Seems unlikely, unless you go for a steel floor - even then I would
anticipate some gain in floor height.

Is there a minimum requirement for headroom within the room,it wouldn't
be a problem for me as I'm 5'8",but obviously the world is generally
full of taller people than me.

Only over the stairs. However I would have though anything less than
about 6'6" would make for a very "close" feeling room even if you could
stand up in it.

Also - do the fire regs regarding escape route from bottom of stairs to
nearest door to outside apply to bungalows too,ie that any door opening
onto said route is solid.

Don't think so.


--
Cheers,

John.

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Thanks for quick response

Regarding thermal bridging - what depth of insulation is advisable
under/over the rafters?