On Friday, October 19, 2012 3:53:36 PM UTC+1, John Rumm wrote:
On 19/10/2012 13:38, wrote:
On Friday, October 19, 2012 1:26:36 AM UTC+1, John Rumm wrote:
On 18/10/2012 23:56, meow2222 wrote:
On Thursday, October 18, 2012 1:49:59 PM UTC+1, John Rumm wrote:
On 18/10/2012 13:11, meow2222 wrote:
On Wednesday, October 17, 2012 9:07:08 PM UTC+1, GMM wrote:
On Wednesday, October 17, 2012 8:56:57 PM UTC+1, (unknown)
wrote:


However, its not just about safety, but also producing an adequate
quality of building, where the floors don't bounce up and down, and
all the joints crack in the plaster because there is too much
movement.

No, its not. Millions of old houses have timber a fraction the size
of the current requirements and don't suffer any of those problems.

True, so long as the fraction you have in mind is say 7/8ths...
Many places in the past would have used say 7x2 where these days 8x2
would be deemed adequate.
There are places which use significantly shallower timbers, but then
tend to have more frequent cross members and hence shorter effective spans.

I'm talking about 3, 4 & 5" timber where new builds would use double to triple the size


However it is true that what was acceptable in the past would no
longer meet current standards. That is partly a reflection on more
stringent requirements for air tightness of properties,

I've never known a Victorian ceiling/loft floor be draughty

Modern buildings are in general very much less draughty than Victorian
places. There have been many changes in building practices to achieve
this. One example being joist support. It is no longer common to set
joist ends into openings in walls since (among other things) it also
creates a potential air gap. The switch to joist hangers also frees you
from the limitation of needing to use joist sizes that match a brick
height multiple in height.

But one place draughts don't come in is through Victorian ceilings


The OP can use lighter timbers than those that would be required to
meet the standard of a floor if he wants, although if there was a
suggestion that at some point in the future it was upgraded to a
habitable room it would be sensible to build it to the required
standards now obviously.

Standards change, so its not obvious, its just an option

Indeed, but they rarely reduce, so its fairly obvious (to me at least).
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.


NT