Define protected staircase

[Lagosman]

I recently visited a multi occupancy  office building built in the sixties or seventies, it comprises basement, ground and 4 upper floors. The basement is a carpark. The main staircase serves all floors including basement.

Some years ago an additional escape staircase was provided to provide secondary MOE for the offices; the FR doors that enclosed the main staircase have been removed including the doors at basement level. The offices at ground and upper levels are provided with 30 min FR doors with SC devices and lead to the unenclosed staircase via a short corridor approx 4-5m in length.

Clearly the basement should have the FR doors to the main staircase reinstated. The short corridors are protected, would you define the staircase as enclosed in FR construction and therefore protected?

Comments and observations please guys.

[William 29]

You seem to be describing an accomodation internal stair i.e. unprotected and an external escape??

[AnthonyB]

I wouldn't class it as a protected stair if all the doors off it to the central corridor have gone.

The old fire certificate plans would show FD30 doors off each stair landing and depending on the size of the floors either a non protected central corridor or a protected corridor and possible (again size dependant) cross corridor protection.

The layout contravenes benchmark guidance and would take some justifying, put the stair doors back on is the easiest option.

[CivvyFSO]

I think I know what you mean, and provided that all the risks are on the other side of fire resisting construction you could certainly treat it as a protected stair. However, I would be looking carefully at any false ceilings, and the line of fire resistance continuing right up to the floor above on the corridors. (More than simply cavity barriers) You are 100% right that the basement needs sorting out.

Whereas with no alternative escape route the stair might have needed lobbies in order to comply with the normal recommendations, the creation of a suitable second escape route would the negate the need for these lobbies which might explain the removal of the main doors, but is no excuse for the basement issues.

[Revol]

Re: the comment above, i.e. the corridor becomes part of the protected stair enclosure. Not sure if I like this! ... there is a B Regs determination on a related topic ref 45/3/164 

[wee brian]

well spotted Jon

Multiple doors leading into the enclosure of a protected stairway can result in an increased risk of doors becoming propped open etc. thats why ADB says dont do it.