Timber frame fire resistance

[Handy1971]

When is the introduction of a cement board required exteranlly on a timber framed extension? It is single skin, in its own grounds and no boundaries to consider.
The rain screen is either render board or plastic cladding, no descision on that as yet, although if plastic cladding it will add an element of combustibilty to the external make up. Does a 140mm stud,9mm OSB, breather membrane,vertical batten and either a render carrier or possibly plastic cladding give you the required 30mins resistance? This isnt a dormer where perhaps some unprotected areas are allowed, but a ground floor extension with only OSB as fire protection.(The Architect hasnt specified any cement board) Thanks in advance.

 

[^woody^]

Have the plans been approved?

Perhaps the plasterboard will provide the necessary fire resistance.

 

[Handy1971]

Building notice and permitted development. I'm pricing it up, perhaps I'll have a word with BC. Cheers

 

[gonch69]

Think the external fire protection part only comes into play when 1m from boundary

 

[gonch69]

But you will need fire socks in the cavity

 

[Handy1971]

No cavity, single timber frame.

 

[gonch69]

If you have cladding or render board it will be on batterns which forms a cavity

 

[gonch69]

With some timber frames they use cement board instead of osb to get around the fire requirements