Top ten most common mistakes

1. The approved documents are not mandatory

The Building Regulations are a set of minimum standards that a building must meet by law. They should ensure that it is structurally sound, safe for occupants in case of a fire, meets energy efficiency targets and so on. How these standards should be achieved is not stipulated. However, because the Building Regulations are printed at the front of their “approved documents”, the optional guidance is often mistaken for the mandatory regulations. If you wish to demonstrate that the means of escape for a building are indeed adequate by using fire engineering principles, the British Standards series 5588, or even a well-founded argument that is accepted by your chosen building control body, then the requirements of the Building Regulations have been met.

2. Not all corridors need fire protection

The requirements for fire protection to internal corridors (approved document B, paragraph 4.21) are often overestimated. In fact, there are only two common situations where 30 minutes of fire protection is needed in a corridor – first, where bedrooms are accessed from the corridor, and second, where the corridor is a dead end.

3. Separating doors in corridors

It is often quoted as a regulation that all corridors that are more than 12 m long need to have sub-dividing fire doors at 12 m intervals. This is incorrect on two counts: first, the guidance (approved document B, paragraph 4.23) applies only to corridors that connect two or more storey exits; and second, if the corridor exceeds 12 m in length it only needs one sub-dividing door positioned centrally in the corridor. The guidance aims to prevent smoke from a single fire passing the length of a corridor and making two or more storey exits impassable.

4. How much better is an L1 fire escape system?

There are many instances where the means of escape strategy does not meet the guidance in approved document B and the compensating factor offered to the building control body is the fact that the automatic fire detection system has been upgraded to an L1 standard – which means it covers the entire building. But does this make a difference?

When considering means of escape, the total escape time is made up of two critical time periods: pre-movement and movement. If the escape travel distances are excessive, then the movement times will be increased; conversely the pre-movement time must be decreased to compensate.

When you consider that an L3 system should be “designed to give a warning of fire at an early enough stage to enable all occupants, other than possibly those in the room of fire origin, to escape safely, before the escape routes are impassable” (paragraph 5.1.3), and that an L2 system has additional detection in areas with a high risk of fire, the installation of an L1 system will provide little benefit to pre-movement time or means of escape as a whole if an L3 system is sufficient to get everyone out of the building.

5. The DDA is not Part M and vice versa

In essence, Part M of the Building Regulations requires reasonable provision to be made for people to access and use a new building or extension and its facilities. The Disability Discrimination Act on the other hand consists of several pieces of civil law that enable disabled people who feel they have been discriminated against to take action for damages against organisations or individuals.

The difference is that Part M prescribes a mandatory minimum level of compliance for a building, whereas the DDA is specific to the individual and their interaction with a given environment – which includes the provision of services, employment and the general principle that to treat someone less favourably is unlawful. For example, if a person with Downs Syndrome were treated inappropriately by a shop assistant, they could take action under the DDA, even if the building itself complied with Part M. A corollary is that it is impossible for a building to be DDA-compliant as the act is not a standard, it is a legal vehicle.

6. Use and misuse of cavity barriers

Cavity barriers are provided to restrict the spread of fire or smoke within a concealed space, from ceiling voids to cavity walls. However, if there is no source of ignition and a limited fire load within that cavity, the requirements of approved document B, section 10 are relaxed. Here are some simple guidelines:

• Cavity barriers should be provided within cavity walls at the intersection of fire-resisting construction, such as compartment walls and floors. They should also be provided every 20 m unless the cavity is adequately closed at the top and around openings, the wall is brick or block, or the wall needs to have fire resistance only because it is load bearing. If the wall does not have a boundary condition it probably does not need the additional barriers.
• Within a suspended ceiling over a subdivided area, cavity barriers should be provided every 20 m.
• Within a suspended ceiling over an open-plan area, cavity barriers should be provided every 40m.
• Where an open plan area exceeds 40 m, cavity barriers above a suspended ceiling can be omitted altogether if the void is class 0, the building has automatic fire detection and the area is divided from the rest of the storey.

7. What you have to fit in a stair well

There are four types of stairs within approved document B and each is quite specific.

• If you have sufficient protected means of escape stairs elsewhere in your building, you can do what you want with any extra staircases. This is because an accommodation stair is not considered when calculating a means of escape strategy, so there are few restrictions on it.
• A protected stair is relied upon in the means of escape strategy and will need to be surrounded by material with at least 30 minutes of fire resistance. Within the protected stairwell you are allowed to have a reception that is less than 10 m2 in area, fire resisting storerooms, lifts and sanitary accommodation.
• If the protected stair passes through a compartment floor, it must be upgraded to a protected shaft. The only things that a protected shaft can contain are sanitary accommodation and the staircase.
• The final stair is a fire-fighting shaft and should have nothing in it except that required under BS 5588: Part 5 for fire fighting purposes. Strictly speaking it should not even provide a means of escape for occupants, as a crew of six fire fighters would struggle to make headway against 100 evacuating residents.

8. Disabled refuges

About 99% of all new buildings provide wheelchair access to an upper floor. They also have to have an adequate level of escape for wheelchair users. The present guidance requires a disabled refuge on each storey landing of escape stairs. This is to allow the wheelchair user to remain in the protected refuge, which should have a means of communication to raise the alarm, without delaying other occupants. This is less than ideal as it relies on assisted escape and leaves some occupants behind. However, this solution is the best available and provides a satisfactory level of compliance for means of escape for wheelchair users.

9. Which disabled WC, when and where?

The provision of disabled toilet facilities has become a lot more complicated recently. But here are some basic rules:

• If you are providing WC facilities, at least one needs to be the fully compliant wheelchair-accessible type (approved document M, diagram 18).
• If this WC is the only one in the building it has to be 0.5 m wider and include an additional hand basin (paragraph 10.5d).
• The door should preferably open outwards, but that does not mean it has to.
• The wheelchair-accessible WC should not be used for baby-changing.
• A wheelchair-accessible WC should be available where general sanitary facilities are located and there should be a minimum of one every other storey with a horizontal travel distance between wheelchair-accessible WCs of no more than 40 m.
• Where you have separate sex WC blocks in addition to the unisex wheelchair-accessible WC, at least one cubicle per block needs to be a smaller ambulant cubicle. This can have an inward opening door, needs a 450 mm diameter turning circle and grab rails (diagram 21, paragraph 5.11).
• Where the WC block has four or more cubicles the ambulant cubicle needs to be the larger variety, fully compliant with diagram 21 and have an outward opening door (paragraph 5.12)
• Finally, fire alarms in WCs must be visual as well as audible (paragraph 5.4g).

10. Ancillary use – when not to use compartmentation

The Building Regulations generally accept that different purpose groups – office, residential, assembly and so on – need to be separated from each other by a 60-minute fire resistant compartment wall. However, there are some cases where this is not required (approved document B, appendix D, paragraph 3). Where a particular purpose group makes up less than a fifth of the total floor area of the whole building or compartment, there is no need for fire separation. This threshold is raised to a third for storage areas in retail buildings. This is most often used for small offices in industrial and storage buildings.