On Sunday, October 21, 2012 4:07:53 PM UTC+1, John Rumm wrote:
On 21/10/2012 00:37, wrote:
On Saturday, October 20, 2012 10:33:20 PM UTC+1, John Rumm wrote:
On 20/10/2012 20:33, wrote:
On Saturday, October 20, 2012 4:42:00 PM UTC+1, John Rumm wrote:
On 20/10/2012 01:49, wrote:
On Friday, October 19, 2012 3:53:36 PM UTC+1, John Rumm
wrote:
On 19/10/2012 13:38, wrote:


Also building regs are not retrospective. So if a floor
was designed as a floor, and was compliant with the
standards of the time, you would be able to use as the
basis of your room in the roof, it even if the standards
applying had changed since it was built.

There's no way a BCO will accept a loft conversion in a 1924
house on its original 3" loft floor joists.

I doubt a loft with 3" joists would not have been deemed
acceptable as a proper floor for a habitable space - even in
1924. However, my point was, that if you upgrade something now
to the current standards of a floor in a habitable room, then
there would be no need to upgrade it further if one later made
the space habitable - even if the standards for a floor have
changed by then.

3x3 was the smallest standard habitable flooring joist size in
Victorian houses. It was much used for short spans, such as
across corridors & landings.

And it still might be acceptable now (for short lengths)

IIRC the 1924 BR didn't specify joist sizes, so 3x3 would still
be compliant for habitation then. It could be used in loft floors
above corridors, where the span was short.

A loft floor is not a floor in the accepted sense though - its not
expected to carry significant load.

I challenge you to find any BCO that would accept that in a loft
conversion today.

A BCO would be happy with a loft using 3x2 - its a good deal better
than many a lofts built with modern trusses. However that is a very
different thing from a loft floor which going to be used for a
habitable room. If you are converting the loft, then the same spec
as would apply to any other floor in the building will kick in. Out
of interest I had an experiment with superbeam to see what you can
get away with on a 3x2 (well 72x47mm) and a typical floor load
(uniformly distributed 0.8kN/m on each joist). 1.3m seems to be
about the limit - so you could probably still do a landing with it
and comply with modern building regs. (having said that, its
generally simpler to use one depth all over to save having to buy
lots of timber sizes)

For clarity, lets take it a step further. Say the loft got 2x2s in 4'
spans in 1924, hopelessly unsuitable for habitable rooms, but still
compliant for them in 1924.
I don't think 2x2 would have been used for the floor of a habitable room
in 1924 or at any other time.
Its seems to are engaging in a little reductio ad absurdum.

That's exactly the point. All Victorian loft floor joists were compliant for habitable use at time of building, but no BCO is going to accept them in a conversion today.


NT

So it was built in compliance with BR
standards for habitation at the time, and you can indeed walk on
them, just about. But no BCO in their right mind would accept a
conversion to habitable now on 2x2s.