What a building inspector will be looking for when it comes to fire safety

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Understanding the fire regulations need not be complicated when building your own home or converting your loft. In a recent Homebuilding and Renovating article, they explained the key facts and concerns that a building inspector will be looking out for when it comes to fire safety.

Fire safety regulations can cause anguish for many homeowners, particularly those building three-storey homes, but it is vital to get them right, before the building inspector comes calling.

When building a new detached home, there are a few occasions when you will be aware of the Building Regulations. Things are very much tighter for people building attached houses or flats, but for the sake of simplicity here is a breakdown for detached homes.

Fire Safety and the Building Regulations

Fire safety in any new home is not achieved by one single measure. Instead, it is compiled from a collection of several different precautions — read our previous blog on ‘Does your Smoke Alarm positioning meet Building Regulations?’ to find the appropriate government issued documents for your location.

Where to Place Smoke Alarms

For new homes and extensions, at least one mains-powered smoke alarm system with detector/alarms interlinked should be fitted on each floor. (Mains-operated smoke alarms should be fitted with batteries as a back-up.) They should be positioned within 7.5m of bedroom doors and located in landings and hallways. Smoke detectors should also be positioned at least 300mm away from pendant lights and from the interface between the ceilings and walls.

Open plan areas which feature kitchens create an added risk. As such, they require the addition of a heat detector/alarm interlinked to the smoke alarm system. Again, these should be positioned at least 300mm away from pendant lights and from the interface between the ceilings and walls.

Creating a Means of Escape

If the first floor of your home is no higher than 4.5m above the exterior ground level, then you will need to be able to escape the house from the first floor via egress windows to all habitable rooms (i.e. to bedrooms but not bathrooms). Smoke alarms and an egress window are all that are required for fire safety for any habitable room up to 4.5m above ground.

Egress windows should be:

 

  • no higher than 1.1m from the finished floor level
  • …and at least 450mm x 450mm and a third of m2 in area
  • They should be positioned so as to allow rescue by ladder. As such, they can’t be located above features like polycarbonate conservatory roofs

The windows should be positioned to allow the occupants to move away from the building and not, for example, into a small enclosed courtyard beneath.

You may also need ground floor egress windows to serve ‘inner’ rooms. Inner rooms occur when you have to pass through another (access) room to reach the hall, stairway or external door. Therefore, a fire in the access room means escape is necessary through an egress window or an alternative door route.

Be wary of inadvertently creating inner rooms when extending or when creating open plan layouts on the ground floor by removing walls to hallways. This could mean having to replace windows, but it is usually possible to change standard scissor hinges for egress hinges on existing windows that do not open wide enough.

The notable exceptions are kitchens, utility rooms, bathrooms and dressing rooms which as inner rooms do not require egress windows.

Fire Safety in Three or Four-Storey Homes

For homes of three or more storeys where floors occur 4.5m or more above the outside ground level, egress windows are not an option for fire safety.

In new build three or four storey homes (with a top floor which does not 7.5m above ground level), a protected stairway must be created that is continuous to an external door at ground level. The stairway enclosure throughout should be constructed to be fire resistant for at least 30 minutes, with FD20-rated fire doors (which are resistant for at least 20 minutes) to all habitable rooms along it. Self-closers on these fire doors are no longer a requirement.

Homes with top floors above 7.5m require a second escape staircase or some added protection to compensate, such as a sprinkler system.

Do I Need a Sprinkler System?

In Wales, fitting sprinkler systems to new homes became mandatory in 2016.

In England, regulations make no requirements to use sprinklers. However, they are sometimes accepted as an alternative method of compliance by building inspectors where it is difficult to provide adequate means of escape — for example, when compensating for open plan ground floor layouts.

Preventing the Spread of Fire to or from Neighbouring Homes

Another area that can cause problems when it comes to fire safety is using combustible materials, such as plastic or timber cladding, close to a boundary, even when it is covering masonry walls. In addition to cladding, if the walls themselves consist of non-fire-resistant elements (such as windows) they must be at least 6m from the boundary to avoid size restrictions.

However, this is not to say that some combustible materials can’t be used closer to boundaries. For most homes, up to 24m length and no more than three-storeys high, the Building Regs’ provide a simple diagram which aids in this situation (below).

A certain area of non-fire-resistant construction (e.g. windows) can be introduced, depending on the proximity of the building from the boundary — these are known as unprotected areas (UPA).

Walls that are up to 1m from a boundary are restricted to 1m2 of UPA. This extrapolates out with greater distance from the boundary to over 6m, at which point there is no limit to the allowable UPA.

Where the site boundary is a road, river, railway line or canal — the centre line can be taken of that feature as the relevant notional boundary.

Preventing the Spread of Fire Internally

For all structural elements, such as floors, walls and beams, fire resistance of at least 30 minutes is required. This is usually achieved by using fire-rated plasterboard and plaster finishes at least 12.5mm thick, or two layers of standard plasterboard at least 9.5mm thick and a plaster set finish.

If you prefer to expose steel beams rather than clad them, intumescent paints are available. Usually they comprise a two-layer system with an intumescent first coat and a flame spread resistant top coat.

For the internal wall and ceilings finishes, materials need to be Class 1-rated to prevent fire spread. Thus, finishes such as plywood or interior timber cladding will need to be protected. Paint-on coatings are available that will protect timber to Class 1.

Small rooms of up to 4m2 floor area and domestic garages up to 40m2 can be lined with Class 3 (D-s3 d2) materials.

Again, in England, installing sprinklers throughout the home will allow you to halve the distance to the boundary (or double the UPA), so long as you are over 1m to the boundary.

Creating Access for Fire Engines

When a fire occurs and the alarm is raised, we expect the fire service to respond and arrive quickly. The emergency services need three main conditions to be satisfied to successfully deal with a fire in a house:

  • Fire engines must be able to get close to the building
  • Firefighters and their equipment must be able to reach the fire’s location in the building
  • An adequate supply of water, maintained at sufficient pressure, must be available to fight the fire.
  • As houses are usually classed as small buildings (that is, up to 2,000m2 floor area with a top storey less than 11m high), only access to within 45m of every point of the building, or to 15% of its perimeter, is needed.

A wide range of fire engines are in use throughout the UK. They vary in height, length and weight and, as such, require varying degrees of access. To ensure that these requirements are met, building control bodies and local fire safety authorities should be consulted early on when designing a new home to check that there are no restrictions to access.

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References: Homebuilding & Renovating