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Guest Joanne

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We are nearing completion of a new build and have been asked by the building control officer to explain why a fire detection system lower than grade A has been installed.

The system installed by the electrical contractor was an LD2 grade D. The building inspector has seen it earlier in the build and was approving of the fact that we wanted detection in every room and every escape. 


My contractor has confirmed that as no floor area on any level exceeds 200m sq the regs are met by the system. The building control officer disagrees and wants the plant room and hallway leading to the plant room on a different level to be included in the floor area calculation of main level floor area.


It’s a 2.5 storey building - in effect the basements sit between levels so when the floor area calcs have been considered they were seen as a separate level.


I am reluctant to argue as my understanding is limited and I don’t want to upset the inspector and make life too difficult elsewhere unless it’s the right way to go.


My contractor says there is little to argue if this is the stance they take - do I just need to pay him to install a grade A system? 

The inspector has told me that if a ‘specialist’ confirms the regs are met he may accept this statement - that almost sounds like that aren’t sure and it’s a case of interpretation.


Appreciate any guidance

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The basement doesn't count - here is what the Approved Document to the Building Regulations says:

Large dwellinghouses

1.5 A large dwellinghouse has more than one storey, and at least one storey exceeds 200m2 .

1.6 A large dwellinghouse of two storeys (excluding basement storeys) should be fitted with a Grade A Category LD3 fire detection and alarm system, as described in BS 5839-6.

1.7 A large dwellinghouse of three or more storeys (excluding basement storeys) should be fitted with a Grade A Category LD2 fire detection and alarm system as described in BS 5839-6

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Perhaps I’m getting in too deep and should just accept that it’s a pain and further expense. My line of thinking here may just open a can of worms:

the building inspector specifically is in his final inspection notice now asking for a grade A, LD2 system.


from 1.7 this implies that he is classifying this as a 3 storey building. The only way it can be a 3 storey building is if the plant room and hall leading to it (the half storey accessed via 5 steps and that I call basements) are classed as a storey. And if they are a storey he can’t include the floor area in the calculation for the main level.


That means the main level area is under 200msq and that then means the system fitted (Grade D, LD2) does meet the regs defined in 1.1.


Do I seek clarification? What am I asking for clarification on: if it’s a Grade A LD2 or 3 now being asked for or if my argument on floor areas will be considered.


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You can appeal for a relaxation or request a determination https://www.gov.uk/building-regulations-approval/appeals-and-determinations

I don't know the statistics for BCO determinations, but with fire safety enforcement ones the responsible person wins reasonably often so it's not automatically stacked in favour of the state.

I has something similar where the AI included a small entrance hall to flats on a lower level as a storey which necessitated the flat access lobbies off the stair on the floors above having to have a smoke shaft and ventilation added which wouldn't otherwise have been needed!

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Guest Joanne

Thanks for your help Anthony,


We may be getting somewhere.


I employed the services of a fire safety firm to look at the system - they feel it complies so called the AI. 


The AI insisted that the basement had to be included in floor area calculations because there were not enough steps down for it to be considered a separate level.


Document B refers to Storeys not levels. 


The fire engineer quoted the definition of a basement from document B and then asked the AI if he was sure he wanted to ask the customer to remove a Grade D LD1 system that covered every room and every circulation and escape to then fit a Grade A LD2 or 3 system covering just escape/circulation and possible high risk areas over a questionable view of a definition of a basement. 

The completion certificate is not in hand but, it looks like the AI is prepared to consider the knowledge of a specialist in the field….



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  • 2 weeks later...

We don’t have AI’s here but as an erstwhile director responsible for compliance in a building refurbishment company where projects were mostly design and build, have continually found need to question determinations made by Building Control officers. I do so with the utmost respect but also with tenacity with my case founded on well-researched material. I have often been totally wrong but I have also saved my company many thousands of pounds. End of the day we all want compliant, safe and functional buildings. All parties in such disputes should be gracious rather than belligerent, which, unfortunately, can often be the case. 

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