B3 Internal Fire Spread Structure

[AdamL]

Hi all,

 

I have had recent final inspection notice from Building Control: 

I have 4 topics listed to resolve before April 10th. (Only 3 below, but one was windows to first floor - new windows are to be installed soon) 

 

A few Questions for the forum...

1 ) B3/L1:  Fire resistance/insulation from garage to habitable space (kitchen) : Is there any minimum requirements of fire/insulation (REI30/min. k/m2w) here? or will thermoblock/plasterboard be sufficient. 

2) C2 - I will send pictures of the abutment vents 

3) 100mm PIR was installed. (no photos specifically to this part of the roof) Will need to remove some tiles ...

 

 

Any and all help would be greatly appreciated!

 

 

[Redbeard]

Re garage/habitable space I cannot remember whether there is different treatment for a sheltered (unheated but not external) transition such as this.

 

If it's treated as external then you probably want 0.3W/m2K.

 

Can't answer that one, but can note that 100mm PIR in a vaulted ceiling is unlikely to meet the 0.16W/m2K target. (Was this approved after June(?) 2022? Could be 0.18 if before that date.  100mm won't meet either of those targets. BCOs can offer leeway, but as I understand it they do not have to. If you have not negotiated a waiver before now you may not be in a strong negotiating position. On the other hand they might take the view that you're pretty close and let you leave it as is. Do you really want to take tiles off? Why not cut out say 300mm sq of ceiling (bevel the cuts so you can glue it back) then just take out a core of the insulation big enough for BCO to get their tape measure in. Keep the core to glue back and foam-fill before taping as VCL.

[AdamL]

1 ) B3/L1:  

Quote

 

Re garage/habitable space I cannot remember whether there is different treatment for a sheltered (unheated but not external) transition such as this.

If it's treated as external then you probably want 0.3W/m2K.

 

 

So I will need to insulate more. Rockwool suggests 120mm mineral wool to achieve 0.3W/m2K in this construction to get BCO to sign off.

 

 

3) 100mm PIR was installed. 

Quote

Can't answer that one, but can note that 100mm PIR in a vaulted ceiling is unlikely to meet the 0.16W/m2K target. (Was this approved after June(?) 2022? Could be 0.18 if before that date.  100mm won't meet either of those targets. BCOs can offer leeway, but as I understand it they do not have to. If you have not negotiated a waiver before now you may not be in a strong negotiating position. On the other hand they might take the view that you're pretty close and let you leave it as is. Do you really want to take tiles off? Why not cut out say 300mm sq of ceiling (bevel the cuts so you can glue it back) then just take out a core of the insulation big enough for BCO to get their tape measure in. Keep the core to glue back and foam-fill before taping as VCL.

 

The ceiling has 100mm PIR and also 120mm rock wool: 

My problem is, that I dont have any photos, specifically in the vaulted section (I asked the Mrs to take pictures of this) … and now I am plastered painted/finished core cutting for me could be messy not knowing where the rafters are etc.

I only need photos. 

 

[AdamL]

1 ) B3/L1:  Fire resistance/insulation from garage to habitable space (kitchen) : Is there any minimum requirements of fire/insulation (REI30/min. k/m2w) here? or will thermoblock/plasterboard be sufficient. 
 

With regards to this insulation / fire protection ...

Will the BCO be expecting the insulation/fire protection to be on the "inside" of the property. i.e. to prevent the spread of a fire FROM the garage to the house. or the other way. FROM the house into the garage? 

 

If I do as planned. it would only add protection of a fire in the garage TO the house?

Edited March 16 by AdamL