Space Seperation

[GB]

I have a timber clad building 1m from the boundary with 30mins FR walls however building is clad with timber cladding. Not many windows or doors.

Does the external wall surface need to be Class O being 1m from boundary?
I am interpreting ADB V2 Diagram 40 suggests that if I am 1mm under 1m, I need to be Class O, if I am 1mm over 1m there is no provision and I can use untreated timber cladding. Am I correctly interpreting this?

There is a strong resistance to using flame retardent application to the external face of the timber therefore am looking for an alternative approach if just under the 1m.

[Phoenix]

I think you're reading it correctly, more or less.  If it's not a multi-storey assembly building and if it is 1000mm from the boundary then it needs no special protection.  If it is 999mm though, it will need to be class 0.  Yes, it's only one millimetre but a line has to be drawn somewhere. 

If there is no boundary fencing and if, perhaps, vegetation is growning next to the walls or, worse still, someone has thought it a good idea to fix a litter bin on the wall, then I think a risk assessment would tell you that the external face of the wall should be class 0 (and preferably incombustible), even if it is 1000mm or more.

If, on the other hand, it is only 500mm from the boundary but there is a six foot brick wall at the boundary then you might deem it safe to leave it untreated.  There is room for manoeuvre here.

Stu

[Phoenix]

Also, would flame retarding treatments be able to make the surface class 0?  Seems unlikely, certainly for the long term.

Stu

[GB]

Many thanks Stu - glad to see there is someone else either as daft as me and working at this time of night...or watching the Super Bowl