Fire Resistance for different purpose groups

[Paul B]

Hi

Is the minimum compartmentation between different purpose groups under the control of single occupier (eg. office and factory floor) sixty minutes?

Thanks

[AnthonyB]

Parts of a building occupied mainly for different purposes should be separated from one another by compartment walls and/or compartment floors. Compartmentation is not needed if one of the different purposes is ancillary to the other:

Building uses are classified within different purpose groups, which represent different levels of hazard. A purpose group can apply to a whole building or to a compartment within the building, and should relate to the main use of the building or compartment.

Where a building or compartment has more than one use, it is appropriate to assign each different use to its own purpose group in the following situations.
a. If the ancillary use is a flat.
b. If both of the following apply.
    i. The building or compartment has an area of more than 280m2 .
    ii. The ancillary use relates to an area that is more than one-fifth of the total floor area of the building or compartment.
c. In ‘shop and commercial’ (purpose group 4) buildings or compartments, if the ancillary use is storage and both of the following apply.
    i. The building or compartment has an area of more than 280m2 .
    ii. The storage area comprises more than one-third of the total floor area of the building or compartment.

 

Where there are multiple main uses that are not ancillary to one another (for example, shops with independent offices above), each use should be assigned to a purpose group in its own right. Where there is doubt as to which purpose group is appropriate, the more onerous guidance should be applied.

 

Fire resistance for compartment walls and floors usually starts at 60 minutes and rises based on building height and use, but can in some circumstances be lowered to 30 minutes, usually where sprinklers are provided.

[Paul B]

Hi Anthony B

Thanks for the advice... as I am looking at purpose group 6 (Factory) with purpose group 4 (ancillary offices) with both of the following applying;
    i. The building or compartment has an area of more than 280m2 .
    ii. The ancillary use relates to an area that is more than one-fifth of the total floor area of the building or compartment.

I would be looking at 60 minute compartmenatation?

[AnthonyB]

It reads that way it seems, yes

[Guest Dominic]

a few questions based on this: - imagine a 200 sqm shop with 100 sqm warehouse in 1 compartment, separated by a non fire rated partition

1) A single compartment can have 2 or more purpose groups? (without fire rated walls between the groups)

2) if yes to Q1, then can escape distances etc be applied separately to each Groups area (e.g. shop and warehouse)

3) if yes to Q1, then can occupancies be applied separately for purpose group, or does the more onerous occupancy apply to the whole compartment? 

[Mike North]

A single compartment can have different purpose groups its called ancillary use

Approved Document B Vol 2 2019 Amendment 2020  

0.21

Where a building or compartment has more than one use, it is appropriate to assign each different use to its own purpose group in the following situations.

a.      If the ancillary use is a flat.

b.      If both of the following apply.

i.            The building or compartment has an area of more than 280m2.

ii.           The ancillary use relates to an area that is more than one-fifth of the total floor area of the building or compartment.

c.      In ‘shop and commercial’ (purpose group 4) buildings or compartments, if the ancillary use is storage and both of the following apply.

i.            The building or compartment has an area of more than 280m2.

ii.           The storage area comprises more than one-third of the total floor area of the building or compartment.

 

So given that the total area of the building 300m² and the storage is 100m², the storage area is 1/3 of the total area then Yes.

Each room should have its own occupancy limit based on the space factor for the purpose group