Requirement for two stairs in bulidings over 11m - how old is this

[AnthonyB]

Where the storeys on a building are within those for travel in one direction to a protected route you can have a single stair - but current building regulations overrule this if there are any storeys over 11m from ground.

How far back does this principle go?

I've a nightmare building with deed of easement issues, inadequate construction in the adjoining building, and much more that had it's access to a second stair (via the next building) put on all levels around the 1960's (based on the escape furniture). Would the OSRP 1963's means of escape certificate requirements and Building Regs at the time have required this or would it have been optional & put in on goodwill advice. (Both buildings once had the same owner a long long time ago, but the links are for MoE, not accommodation as several are hatches)

I'm looking at engineering controls to justify a single stair despite height (5 upper floors) as the adjoining building cannot be relied upon.

[nearlythere]

Where the storeys on a building are within those for travel in one direction to a protected route you can have a single stair - but current building regulations overrule this if there are any storeys over 11m from ground.

How far back does this principle go?

I've a nightmare building with deed of easement issues, inadequate construction in the adjoining building, and much more that had it's access to a second stair (via the next building) put on all levels around the 1960's (based on the escape furniture). Would the OSRP 1963's means of escape certificate requirements and Building Regs at the time have required this or would it have been optional & put in on goodwill advice. (Both buildings once had the same owner a long long time ago, but the links are for MoE, not accommodation as several are hatches)

I'm looking at engineering controls to justify a single stair despite height (5 upper floors) as the adjoining building cannot be relied upon.

Can remember from old OSP guidance that the travel distance for MOE also included to a door in a compartment wall. The door had to be at least 1/2 the FR of the wall which at that time I think was minimum 4 hrs. Theory was that when you got through that door you were considered to be in a safe place so the travel distance to a final exit was irrelevant.

[jokar]

AB, the 11m is to finished floor level and not the storey height.  There are a number of buildings around that have 5 storeys and a single staircase.  They normally have lobbies to the staircase and an L2 FA system to ensure early warning and good means of escape.  The travel distances should meet those recommended in whatever guide you use.

[AnthonyB]

How do you estimate building height where it isn't known. Most guides I've come across say as a rule of thumb use 3m per floor to get a rough height.

If what you say is so, why the routes to the next building? I would guess myself it's because AFD was less advanced or used then with most systems manual only or just with rudimentary heats.

I'm going for AFD as compensation, but the problem is that although there are lobbies each floor has a door and office directly off the core and there isn't much room for adding a lobby. It's a totally enclosed stair with lift motor house above via a hatch and thus no simple way of putting in a smoke control as another possible option.

I don't want to use the adjoining building & I doubt they do (it's occupied by Tom Cruises friends). they weren't happy when I went to discuss cooperating over the MoE as I was followed by a SO from the brigade who was arriving to stick the knife in following an inspection, my twisting it further by mentioning I was there over MoE (most hatches were sealed off by them) issues didn't help either

[kurnal]

I have been racking my mind on this one and think that you are right- the hatches may have been installed as a response to OSRA 1963 section 29???

I cant remember any earlier legislation relating to offices and I dont think the Public Health Act 1936 made reference to offices but it may be worth checking.

I wonder if nearlythere is right over the door in the compartment wall having only half the fire resistance? I also recollect something about this but cannot pin it down.

I reckon without any doubt the occupiers would have been instructed by the fire authority under OSRA to either lobby the staircase and install fire doors or an alternative means of escape. I think section 28/29 only empowered fire authorities to enforce means of escape and firefighting equipment, with no mention of fire alarms etc? If so - and remembering technology of the day, detection would not have been an option. I think the lobby aproach was required for all buildings witha single staircase and more than one floor above the ground.

I have looked for the OSRA act but cannot find it online. If you find a link to the full original text  please let me know.

[AnthonyB]

Thanks for this. I don't think I'll need to quote verbatim, but as I'm sometimes asked about how various odd MoE situations arose need to have a pointer.

I think that OSRP 63 affected quite a few buildings of a particular height as I've several that have bypass routes through different occupancies to get to the second stair either through partitions on a floor or in once case out through a window, across a short metal bridge across a light well, through another window into the opposite part of the floor. All were usually 5/6 floors plus, travel distances usually associated with a single direction, some lobbied, some not, all having originally manual alarms.

The problem with the building cited (which although a 5  floor has 'ground' a 2m above street, so total floor heights are over para 4.5 limits) is the reliance on the next building - in theory it shouldn't be an issue, but in practice it often is & I hate these when they crop up.

It's annoying the main compensation possible without a lot of faffing around is only AFD - I've avoided a bypass door having to go into another building having a floor subdivision as it's L1, lobbied stairs and AOV to each lobby on the stair that would be the single route for the new partitioned area, but in this one I'd have to fill doors in or lobby them.