Garry Nutter wrote:

I'm sorry i think i have confused everybody with my terms and what i
want to do.

The Grand Plan Hope Ive explained better this time.

OK, perhaps an ASCII art layout of the beams may help us to visualise
things...

or even something like:

http://www.internode.co.uk/temp/beam-layout.gif

1st get the steel beams in and the joists between,
get some flooring laid in the joists to work off.

You may have difficulty getting flooring in there with all the truss
webbing in place... then again that depends a bit on the type of trusses
you have.

Reinforce the roof rafters
Build the knee wall
Check every things okay

Cut out the old timbers

Oh that is the fun bit... (in fact the most fun I have had with a
chainsaw in ages ;-)

Questions
Looking at Johns site
http://www.internode.co.uk/loft/superstructure.htm 4th picture from the
bottom. John how did you arrive at the size and position for these
timbers which link the roof rafters together?

What, this one?:

http://www.internode.co.uk/loft/images/roofsupport.jpg

Firstly to get some bearings on the shot, you are looking up toward the
ridge of the roof, where the front slope meets the flat roof of the rear
dormer.

The rafters under the slope are spaced at 400mm centres - this was to
match the existing rafters. Some of them are old, some were new where
the original ones were not long enough to meet the extended ridge beam
(remember it used to be a hipped roof). (In the photo you can only see
new ones).

The spacing of the roof joists was also 400mm (chosen deliberately) so
that each one could meet a rafter. Note that this is a slightly non
typical way of doing it. In many cases you would simply stick a steel in
under the ridge to pick up all the rafters. We did not need to do this
however because I was making two rooms that were to have a dividing wall
not far from the ridge position. Hence the dividing wall actually takes
the load of the ridge using the ends of the flat roof joists in
cantileaver.

The size of beam required for the roof joist was calculated in Superbeam
using a uniform loading due to the flat roof of 0.6kN/m (warm deck with
three layers of hot bonded felt - so not that heavy). And a further
point load of 0.48kN per joist exerted by the front roof rafter on the
end of each flat roof joist at a distance of 0.8m from the supporting wall.

So looking at the side :

0.47
| Point load
v
_________________0.6kN / m__________________
/ \ Uniform load

##############################################
##############################################
##############################################
| |
v v
0.67kN downforce on 2.21kN downforce on
read dormer wall partition wall



As i have fink trusses "w" shape made from 4.5 by 1.5 inch timber,

Like the third one down?:

http://www.phillipsbuildingsupply.co...y_designs.html


i plan on screwing or bolting and gluing together a 150*50 timber to
the side of every roof joist.
Do you think this will be strong enough ?

Note that your rafters are already comparable to my 4x2" rafters and are
not as thin and skimpy as the matchstick wood they seem to make some
trusses from. Hence I would expect if you stick a dwarf wall where the
short arm of the W is, and a steel beam under the ridge, you may need no
further strengthening of the rafters.

That should do it for now possible further questions later.

;-)


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/