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:

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

I just noticed that you superficially said *loft* floors there, and my
comments that followed were more generally about "floors" in general -
my fault for not reading carefully.

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

There is a general drive to cut down air currents through void spaces in
direct contact with heated surfaces. If you have a penetration through a
wall, then air will flow through it. Even if that never discharges
directly into the living space, it lowers the thermal performance of the
building.

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.

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.



--
Cheers,

John.

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