Thanks for the reply - please see comments below:-

I see a series of issues here.

Firstly the floor structure will presumably be covered by the party
wall act, so if your neighbour doesnt want any work doing that will
add a couple of grand of legal costs, plus dictate how you do the
work, which can again add costs.

Without getting into the technicalities of the Party Wall Act, I'm kind of
hoping the neighbour doesn't object since the impact will be negligible. I
will be serving notice under the act but, by my understanding anyway, the
Act is more biased towards the owner doing the building work as opposed to
the objector - i.e. even if they do object there's not a lot they can do
about it without getting an injunction... I could be TOTALLY wrong here
though so please, anyone, don't take this as gospel! :-)


Secondly I dont like your propsed beam extensions at all. The wood
thats there is sized for the half run, significantly bigger would be
wanted for double the run. Also how you propose to tie the 2 might
weaken the structure.

As mentioned in the OP, the current joists are 65 x 175mm (2.5" x 7") - the
same size as all the joists in the house, some of which span 3 or 4 times
the width proposed. I'll probably eat my words, but I really don't see it
as being much of a problem. Especially since there's currently a bath,
toilet and sink resting on said joists and, following the building work,
there will be nothing resting on said joists.


Rather than try to extend the beams, which would certainly result in
the ceiling breaking up...

Erm... 'it would certainly result in the ceiling breaking up'... are you
sure about this? Since posting this I've had building control and a
structural engineer look over my plans and they can't see any problems with
them!


...my first thought would be to remove joist B
entirely (using temp support of course) and put new joists running
full width alongside the old ones, without removing the old ones, and
attach old and new securely together. BUT do not do this unless you
consult a struc eng who says its ok in your particular case to do it,
as it might not be.

Good idea, although I do think this is overkill for the particular scenario.
In reality the worst that could happen is that the downstairs ceiling cracks
a bit - and this *is* pretty unlikely. I can't see there being sufficient
deflection to cause catastrophic failure of the ceiling.


There is one more issue: I dont know what size the joists are now, nor
what build regs says about you doing this, but you might possibly find
that to conform to BRs you'd need to put bigger wood in that is there
presently. If you should get caught in this trap, theres always
steelwork, flitch beams, hardwood, etc.

I'm no structural engineer, but I'm pretty certain 7" joists are sufficient
to span a 2.3m gap. :-)

Cheers for all the info though - much appreciated.

Andy