BR distance from boundary and non-combustable roof

[CaptainCaveman289]

G'day folks,

As I understand BR, if you build an outbuilding of 15-30m2 within 1m of of the boundary,
Then you are required to build the structure of primarily non-combustable materials to avoid needing a visit from your local BCO.


Question the first:

What is measured to the boundary to determine the position and it's subsequent effect on construction/BR requirement?
Is it boundary to the wall? To the roof overhang?
To the guttering? (i.e. The closest actual part of the building)

The specifics I understand is that the m2 size is the floorspace within the external walls,
It is straight-forward to make non-combustable walls, i.e. Brick and.block.


Question the second:

How do you make a non-combustable roof?

I think I've read somewhere that to make a conventional timber construction flat-roof considered non-combustable by BR, that it needs inches of crushed limestone - quite extreme construction.
I've also seen a fair few sectional garages with steel structure supporting cement fibre boards - this certainly won't light, is it therefore considered non-combustable?

What about a wooden structure supporting concrete tiles or such? Is that non-combustable?
A wooden structure supporting cement boards?


Question the third:

If a combustable (e.g wood and felt) roof if fitted, and BR involved, do they just check the fire barriers to prevent the roof catching or does the whole building then fall under BR control?


Yours,
Confused from Essex.

(i am confused, but not from Essex)

 

[noseall]

How do you make a non-combustable roof?

There are green mineral felts available that satisfy the spread of fire reg's.

 

[CaptainCaveman289]

How do you make a non-combustable roof?

There are green mineral felts available that satisfy the spread of fire reg's.

Presumably these are those classed as suitable for habitable buildings, which tends to be the 15-25year stuff anyway (don't see the point of 5yr shed felt tissue paper).

Although these meet spread of fire, are these considered substantially non-combustable?
Is everything that meets spread of fire automatically considered to satisfy primarily non-combustable?

I have something of a fundamental mistrust of felt being able to contain a garage fire,
Maybe this is misplaced with regard modern habitable felting.

Also, any perspective on the boundary distance issue? Wall vs eaves vs guttering?

 

[tony1851]

The distance to the boundary is measured from the wall face.

The only exception would be if your eaves projection was so excessive that it could be regarded as a canopy, but that's unlikely for a simple garage.

For the roof, just do it in timber joists, boarding and felt as noseall. If pitched roof, finish in concrete tile.

The rule 'substantially non-combustible' has to be interpreted sensibly by building control (councils differ on how they see this). The greatest fire risk is clearly from and to the wall, so if that is brick or block, there should be no problem.

 

[freddiemercurystwin]

Oh FFS just get on with it.

 

[CaptainCaveman289]

Oh FFS just get on with it.

My workshop is all wood but <15msq, so I can set fire to it as much as I like


This thread is a query off the back of a conversation I had with one of the other petrolheads at work, who getting rid of a crappy old asbestos roofed concrete thing and has previously admired my shed so was asking advice.

The information will also inform my next house purchase as I'm already designing the next, bigger and better workshop

Everybody has been most informative, so thankyou.