Building Regs - Minimum periods of fire resistance

[John Williams]

Help - remarkably elusive information needed please..
What is the minimum period of fire resistance which has to be achieved for green oak beams and joists in a new build detached dwellinghouse ?
The house has 3 storeys ie basement, GF and first floor. The basement is 3 metres from its floor to finished floor level (on concrete beam and block ) of GF. The GF is then 2.8 metres from its floor to finished floor of 1st floor top storey. The 1st floor is then 5 metres from its finished floor level up to apex of roof in open vaulted ceiling arrangment.
The green oak beams are part of the load bearing walls on the ground floor and the green oak joists span between those major beams to form the floor for the 1st floor.
There are no other buildings nearby let alone attached etc.
I understand that full structural calculations will be needed but the immediate issue is what is the correct figure for fire resistance allowance for those beams and joists.
Many thanks to anyone who can tell me that figure - cannot approach over zealous Council dept at this stage .

 

[bernardgreen]

You do need to get advice from your local building control officers. They are zealous in ensuring new builds are safe to live in.

Maybe out of date now but for our two storey timber framed house fire resistance was ( I quote ) " Modified Half hour ( 15 minutes ) ". For our exposed beams we had to either have double the thickness or ( as we did ) attach sacrificial timber to delay the fire reaching the beams

The really important timing is to ensure the building remains structurally intact long enough for you, your family and any visitors who are in the building to be evacuated. It may be that evacuation from some rooms cannot happen without assistance from the Fire Brigade, hence their response time has to be part of the equation. Stair case full of smoke is one reason for not using the stairs as the escape route.

 

[tony1851]

Minimum period of fire resistance for elements of structure in a dwelling is 30 mins.
But if you have oak beams, you obviously don't want to cover them in plasterboard. It may be
possible to show that the beam will maintain structural interity by oversizing it, working out the rate of
degredation in a fire, and then checking that what's left is still capable of supporting the load.
(but check there aren't spread-of-flame issues).
Timber elements supporting a roof don't need to have any fire resistance.