PART A: Structure

(2004 Edition, incorporating 2004, 2010 and 2013 Amendments)

The building shall be constructed so that the combined dead, imposed and wind loads are sustained and transmitted by it to the ground.

PART B: Fire Safety Volume 1 Dwellings

(2019 Edition, incorporating 2020 amendments & 2022 Amendments)

Requirement B1 – Means of Escape

Where a flat roof forms a means of escape it should comply with the following:

• It should be part of the same building from which the escape is being made

• The route across the roof should lead to a storey exit or external escape route

• The part of the roof forming the escape route and any opening within 3m of the escape route, should be of fire resisting construction (minimum REI 30).

A flat roof intended to form part of an escape route should be provided with guarding in accordance with Approved Document K.

Requirement B2 Internal Fire Spread (Linings)

To inhibit the spread of fire within the building the internal linings shall adequately resist the spread of flame over their surfaces and if ignited, have either a rate of heat release or rate of fire growth which is reasonable in the circumstances. (Internal linens applies to any partition, wall, ceiling or other internal structure).

Wall and ceiling linings should meet the classifications in Table 4.1 of Approved Document Part B Volume 1.

For rooflight requirements refer to Approved Document Part B Volume 1.

Requirement B3 Internal Fire Spread (Structure)

The building shall be designed and constructed so that , in the event of fire its stability will be maintained for a reasonable period.

Where reasonably necessary to inhibit the spread of fire within the building, measures shall be taken, to an extent appropriate to the size and intended use of the building, comprising either or both of the following:

• Subdivision of the building with fire-resisting construction

• Installation of suitable automatic fire suppression systems

The building shall be designed and constructed so that the unseen spread of fire and smoke within concealed spaces in its structure and fabric is inhibited.

Cavities

To reduce the potential for fire spread cavity barriers must be provided to divide cavities and to close the edges of cavities.

Cavity barriers should be provided:

• at the edges of cavities, around openings such as windows, doors etc,

• at the junction between external cavity wall and every compartment floor and wall

• at the junction between an internal cavity wall and every compartment floor, compartment wall or other wall or door assembly forming a fire resisting barrier

Refer to the regulations for full requirements.

Requirement B4

External Fire Spread

The roof of the building shall adequately resist the spread of fire over the roof and from one building to another, having regard to the use and position of the building.

Resisting fire spread over roof coverings The risk of a fire spreading from the building to a building beyond the boundary should be limited.

Refer to Approved Document Part B, Volume 1, Section B4 for limitations on roof coverings in relation to boundaries. Table 12.1, 12.2, 12.3.

The above notes do not contain guidance for flats, for full requirements refer to the regulations.

PART C: Site Preparation and Resistance to Contaminants and Moisture

(2004 Edition, incorporating 2004, 2010 and 2013 Amendments)

Resistance to moisture

The roof of the building shall adequately protect the building and people who use the building from harmful effects caused by; precipitation including wind driven spray, interstitial and surface condensation.

Resistance to moisture from the outside Any roof will meet the requirement if; it is jointless or has sealed joints and is impervious to moisture or, it has overlapping dry joints, is impervious or weather resisting and is backed by a material which will direct precipitation with enters the roof towards the outer face.

Resistance to damage from interstitial condensation

A roof will meet the requirement if it is designed and constructed in accordance with Clause 8.4 of BS5250:2002 and BS EN ISO 13788:2002.

To avoid excessive moisture transfer to roof voids gaps and penetrations for pipes and electrical wiring should be filled and sealed (especially in areas of high humidity such as kitchens and bathrooms). An effective draught seal should be provided to loft hatches to reduce inflow of warm air and moisture.

PART F: Ventilation

(2021 Edition)

There shall be adequate means of ventilation provided for people in the building.

PART H: Drainage and Waste Disposal

(2015 Edition)

Rainwater drainage

Adequate provision shall be made for rainwater to be carried from the roof of the building.

The flow into a gutter depends on the area of surface being drained and whether the surface is flat or pitched.  Refer to Approved Document Part H for calculation tables of drained areas and gutter/ outlet sizes.

Refer to Approved Document Part H Diagram 1 for rainfall intensities for design of gutter and rainfall pipes.

Gutters should be laid with any fall towards the nearest outlet. Gutters should also be laid so that any overflow in excess of the design capacity, caused by conditions such as above normal rainfall, will be discharged clear of the building, reducing the risk of overspilling of rainwater into the building or structural overload.

Rainwater pipes should discharge into a drain or gully, but may discharge to another gutter or another surface if it is drained.

PART K: Protection from falling, collision and impact

(2013 Edition)

K2 Protection from falling Pedestrian guarding should be provided to any roof that people have access to.

PART L: Conservation of fuel and power, Volume 1: Dwellings

(2021 Edition)

Reasonable provision shall be made for the conservation of fuel and power in buildings by:

• limiting heat gains and losses through thermal elements and other parts of the building fabric,

• from pipes, ducts and vessels used for space heating, space cooling and hot water services.

New roofs must achieve a U-value of 0.11W/m2K

Upgrading existing roofs must achieve a U-value of 0.15 W/m2K

(Refer to Approved Document Part L for full requirements for new elements in existing dwellings, extensions, renovating elements in existing dwellings and necessary U-values.)

Insulation

Insulation should be installed tight to the structure, without air gaps, and should extend to the wall insulation. For roofs insulated at ceiling level, the long term protection of the insulation layer should be considered: boarded areas should be provided above the insulation to give access for maintenance.

Thermal Bridging

Continue insulation across the wall-to-eaves and wall-to-gable junctions. Wall insulation should be installed to the top of the wall plate, in some cases this may be above the cavity closure or barrier. Roofs insulated at ceiling level; loft insulation at the eaves should extend beyond the wall insulation without any reduction in thickness due to the pitch of the roof. At gables and party walls, insulation should extend to the wall; if the space between the wall and joist is less than 100mm, perimeter insulation may be required.

Part 0: Overheating

(2021 edition)

Reasonable provision must be made to:

• limit unwanted solar gains in summer;

• provide an adequate means to remove heat from the indoor environment.