"dg" wrote in message
oups.com...

Chris Styles wrote:
All,

I've decided that getting my plans past the BCO would be easy compare to
getting them approved by the missus, but I still have a big loft space
that
is being wasted, and I do need the storage.

So, the new plan is to fit proper load bearing floor into the loft
(2"x10"
for the 16' span, raise them an extra 1" off the wallplate to stop them
interfering with the plasterboard ceiling below when they deflect). I
plan
to leave access via the loft hatch exactly as before, so that is not
extra
"livingspace", just a loft with a decent load bearing floor. At a later
date, I'll come back and put the staircase in, insulate the roof, fire
alarms, electrics, plumbing etc and make it a proper conversion.

Can anyone see any snags with this? Obviously I want to do the load
bearing
floor such that when I do the loft conversion for real, it is suitable,
so
any suggestions appreciated.

Cheers

Chris

A 250mm deep joist 25mm up off the wallplate is [potentially] going to
need a significant chamfer at the ends to stop them protruding throught
the roof. The BCO may well not approve this unless the joist is
strengthend at the bearing or calculated to prove it is OK.

How would I go about strengthening them? Do you mean like bolting an extra
bit of 250mm joint (say) 1m long with the same profile, so that it is
thicker for a little bit leading up to the chamfer

Any purlins to be removed?

Nope, the house is 3 years old, and the roof comprises of the finest 2"x3"
trusses you can buy (for ~£10 each)

The main reason I dont want to board the loft as I did at my last house is
that the trusses have a 16' span, about 10' at the apex, but the only
internal tie goes from the apex to the mid point of the joist. The trusses
at the last house had a larger span, but had internal ties in a "W"
formation, so it look quite substantial.

I'm going to have to get a structural engineer in to work out how to remove
these when I come to do a conversion. I had wondered if I'd be able to put a
16' steel parallel to the joists, put a vertical steel off of that at the
mid point, then run a third steel from the gable to the top of the vertical
steel, running along under the apex to take the weight. Given the the only
tie inside the joist is a direct vrtical to the midpoint of the bottom of
the truss, it would seem that it is only a vertical load that needs to be
taken.

Maybe I should take a picture, so you can all see what I mean (and then all
breathe in sharply through your teeth... "Oooohhh, tricky...." :-)

Cheers

Chris