Upgrading fire resistance of floors

[jasper]

i have been asked a question regarding upgrading the fire resistance of floors within a building which I don't know the answer - the building is a detached six-storey old mill building with one side if it having concrete floors and the other wood i.e. you can see the floorboards above. I have obviously highlighted this in my FRA but they have asked for the options to upgrade and approximate cost per m2. I know of vermiculite boarding and sprays etc. but the problem I see is that below the ceiling are pipes which could get in the way. Does anyone know what options are available and what the potential costs are per square metre?

[Phoenix]

Sorry if I'm missing the point here but can't you just put up plasterboard ceilings to the appropriate standard?

Stu

[terry martin]

Have to agree with poenix. why not upgrade the ceiling below?

[kurnal]

Do you know the dimensions and nature of the timbers involved?  Oil soaked?

I had similar issues once on one mill then found that the floorboards were 75mm thick! Fine for means of escape but not so great for heritage/ property  protection.

[jasper]

Due to the hight of the building I am sure it needs to be 90 mins fire resistance (used for offices), they are standard floor boards approx 1.5-2cm thick and the aim is to protect from below

[nearlythere]

Due to the hight of the building I am sure it needs to be 90 mins fire resistance (used for offices), they are standard floor boards approx 1.5-2cm thick and the aim is to protect from below

Are the floor joists exposed on the underside jasper and does the pipework or some of it run between the joists? If so do I assume you don't want to enclose the pipework? Obviously there is a problem with just underlining with a fire resisting board or you would not be asking?
Photograph might help.

[jasper]

Hi nearlythere, from the underside you can see the floorboards sat on top of exposed wooden beams with the pipework suspended below the beams, I don't think there is a major problem boarding it, however lighting would be required for the corridors so it is a case of boarding below the pipes, or spraying the underside of the floorboards, or some for of suspended ceiling system that could achieve the required fr

[nearlythere]

however lighting would be required for the corridors so it is a case of boarding below the pipes,

Not quite sure what you mean by this Jasper.

[CivvyFSO]

Due to the hight of the building I am sure it needs to be 90 mins fire resistance (used for offices), they are standard floor boards approx 1.5-2cm thick and the aim is to protect from below

ADB doesn't ask for 90 minutes between floors of offices in a building that height. There is generally no requirement for compartmentation until the building hits 30m for the office purpose group.

[jasper]

Due to the hight of the building I am sure it needs to be 90 mins fire resistance (used for offices), they are standard floor boards approx 1.5-2cm thick and the aim is to protect from below

ADB doesn't ask for 90 minutes between floors of offices in a building that height. There is generally no requirement for compartmentation until the building hits 30m for the office purpose group.

I may be reading it wrong but in ADB elements of structure for floors 'any other floor - including compartment floors' in table A1 states 'see table 2' in table a2 for offices unspinklered at up to 18m in height is 60 mins fire resistance and under 30m is 90 mins - have I got this wrong?

[CivvyFSO]

Yep, you are right. Sorry, got my simple little brain all confused just thinking about compartmentation requirements.

Are they particularly high floors? Is the top floor actually above 18m?

FWIW: BRE digest 208, mentioned in ADB, only gives examples of how to get 1 hour or half an hour.

[Fishy]

BS 5268: Section 4.2: 1990 (Structural use of timber. Fire resistance of timber structures. Recommendations for calculating fire resistance of timber stud walls and joisted floor constructions) would allow you to design an upgraded floor of up to 60 mins fire-resistance.

For more than that you might try the British Gypsum 'White Book'  or similar publications from Knauf.  Google these.  All will require the installation of multiple layers of board on the underside of the joists.

Fire resistance of the floorboards themselves will be limited by the gaps/joints and/or by the structural fire resistance of the joists.  You can calculate the latter, but not the former (with any reliability).

I've never seen a spray system that would give me any confidence in any significant enhancement of fire resistance for a typical timber floor construction.