wrote:

First may I congratulate you on a very well put together posting and
synopsis! Makes it so much simpler to work out what is going on.

OK, cheers again for the replies. I spent another day in there
clearing crap out over the weekend (is 28kg of lead piping worth
anything? :-) ). Having hoovered out 11 bags of dust in the area of

Only if you take it to a scrap yard yourself... and then not that much.

For starters, here's a scale plan and elevation of the loft (Visio is
really starting to do my head in for this sort of stuff - can anyone
recommend a more 'appropriate' package for plans, elevations and (if
pos) 3D views?):-

I often ask myself that - there must be a package that is more oriented
toward building plans and layouts without going to full blown CAD. When
you find it let me know!

The main beams spanning the full loft are indeed bolted together in two
places, as can be seen he-
http://www.pciq.co.uk/pics/joistbeam.jpg

OK - the previous deduction regarding trusses seems like it is about
right then. The two trusses hold the two big beams, they carry the ceiling.

...and the ceiling joists nailed into the main beam:-
http://www.pciq.co.uk/pics/joistbeam2.jpg

Lath and plaster ceiling - will reduce noise transmission a bit more
than plasterboard, but less likely to have acceptable fire performance
if doing a conversion. Not a big problem though.

So, by my understanding the ceiling joists are simply nailed into the
walls and beams in 6-7' sections, like this:-
http://www.pciq.co.uk/pics/joistevelwl.gif
http://www.pciq.co.uk/pics/joistelevbm.gif

...and if this is the case, no matter how sturdy it currently feels,
there's no way on earth I'm putting any weight on the existing ceiling
joists. New floor it is then! :-)

The truss design and beams it carries do indeed look strong. If they are
upto carrying a complete floor however is another matter. The ceiling
beams however look far less sturdy.

I was planning on using joist hangers mortared into the brickwork as
opposed to the 'bolt in' type since I've tried drilling these bricks
and they're like solid steel. Anything to avoid drilling 80 x 10mm (or
whatever) holes would be a bonus! Anyone have any experience of using
these? I was planning on using the Catnic 50x150 ones from Screwfix,

The "mortar in" types are really designed to be built into the wall
rather than added afterwards. Treat yourself to a nice SDS drill and the
bricks will loose any abilty to fight back!

although (as yet) I have no real clue of how many joists I'm putting
in, how far they'll be apart or how big they'll be...

Usual spacing for a floor is 400mm centre to centre.

The trickey bit is that you have no central supporting wall (hence the
unusual design of the roof). So the spans in either direction are rather
long. I would expect the simplest way would be one substantial beam
(probably a RSJ) right through the middle of the loft to which you can
then attach new floor beams (ther other end resting on the wall plate).

So in plan you get:-

##################### - back wall
| | | | | | |
| | | | | | |
| | | | | | | - new floor beams
| | | | | | |
| | | | | | |
*===================* - new RSJ
| | | | | | |
| | | | | | |
| | | | | | | - new floor beams
| | | | | | |
| | | | | | |
##################### - front wall


If you wanted to clear the space in the loft you would need to do away
with those king posts. The existing ceiling could be supported from the
new floor if required, and the large rafters could probably be left in
place since they mutually support each other. The struts that run from
the rafters to the base of the king beam could be replaced with a pair
of dwarf walls toward the front and back of the loft which would sit on
the new floor - or you may find thay are not actually required at all if
you remove the king post.

1) Simply install the joists in 2 x 3.6m sections bolted together in
the middle (suspended above the existing beams) - spanning the 6.3m
width, that would give a 0.9m overlap for bolting...

That would rely on the existing stucture to carry the load. You would
need your structural engineer to do some calcs to see if it is up to it.
It also depends a little on wether we are talking about adding storage
space, or actually doing a complete "floor" that would be suitable for a
loft conversion.

Option 1 would obviously be better for noise since the loft floor would
be totally isolated from the ceiling, however it would add quite a bit
of height to the floor.

You look like you have a fair bit of height available. If converting
(and say adding a rear dormer) that would make for a decent ceiling
height even with the raised floor level.

A structural engineer is kindly popping 'round to check the situation
out in a couple of hours, so doubtless I'll come back with a whole
different plan... :-)

Let us know what he says - it will be interesting to get his take on it.

--
Cheers,

John.

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