Section 2A: Basic requirements for stability

2A1This section must be used in conjunction with sections 2B and 2C and its principles relate to all forms of low-rise residential buildings. 2A2Adequate provision shall be made to ensure that the building is stable under the likely imposed and wind loading conditions. This will commonly necessitate meeting the following requirements:

  • aThat the overall size and proportioning of the building are limited in accordance with the specific guidance for each form of construction.
  • bThat a suitable layout of walls (both internal and external) forming a robust 3 dimensional box structure in plan is constructed with restriction on the maximum size of cells measured in accordance with the specific guidance for each form of construction.
  • cThat the internal and external walls are adequately connected either by masonry bonding or by using mechanical connections.
  • dThat the intermediate floors and roof are of such construction and interconnection with the walls that they provide local support to the walls and also act as horizontal diaphragms capable of transferring the wind forces to buttressing elements of the building.
  Notes:A traditional cut timber roof (i.e. using rafters, purlins and ceiling joists) generally has sufficient built in resistance to instability and wind forces (e.g. from hipped ends, tiling battens, rigid sarking or the like). However, the need for diagonal rafter bracing equivalent to that recommended in BS EN 1995-1-1:2004 with its UK National Annex and additional guidance given in BSI Published Document PD 6693-1:2012 and BS 8103-3:2009 for trussed rafter roofs should be considered, especially for single-hipped and non-hipped roofs of greater than 40° pitch to detached houses.

  1. Section 2A Basic Requirements for Stability

    Section 2A Basic Requirements for Stability

    2A1. This section must be used in conjunction with sections 2B and 2C and its principles relate to all forms of low-rise residential buildings. 2A2. Adequate provision shall be made to ensure that the building is stable under the likely imposed and wind loading conditions. This will commonly necessitate meeting the following requirements:

    • a. That the overall size and proportioning of the building are limited in accordance with the specific guidance for each form of construction.
    • b. That a suitable layout of walls (both internal and external) forming a robust 3 dimensional box structure in plan is constructed with restriction on the maximum size of cells measured in accordance with the specific guidance for each form of construction.
    • c. That the internal and external walls are adequately connected either by masonry bonding or by using mechanical connections.
    • d. That the intermediate floors and roof are of such construction and interconnection with the walls that they provide local support to the walls and also act as horizontal diaphragms capable of transferring the wind forces to buttressing elements of the building.
    Notes:A traditional cut timber roof (i.e. using rafters, purlins and ceiling joists) generally has sufficient built in resistance to instability and wind forces (e.g. from hipped ends, tiling battens, rigid sarking or the like). However, the need for diagonal rafter bracing equivalent to that recommended in BS EN 1995-1-1:2004 with its UK National Annex and additional guidance given in BSI Published Document PD 6693-1:2012 and BS 8103-3:2009 for trussed rafter roofs should be considered, especially for single-hipped and non-hipped roofs of greater than 40° pitch to detached houses.

    • 1 Size and proportion of residential buildings of not more than three storeys Diagram 1 Size and proportion of residential buildings of not more than three storeys
    • 2 Size and proportion of non-residential buildings and annexes Diagram 2 Size and proportion of non-residential buildings and annexes
    • 3 Determination of wall thickness Diagram 3 Determination of wall thickness
    • 4 Parapet walls - height Diagram 4 Parapet walls - height
    • 5 Maximum floor area enclosed by structural walls Diagram 5 Maximum floor area enclosed by structural walls
    • 6 Fig 1-2 - Map showing wind speeds in m per s for maximum height of buildings Diagram 6 Fig 1-2 - Map showing wind speeds in m per s for maximum height of buildings
    • 6 Fig 3 - Map showing wind speeds in m per s for maximum height of buildings Diagram 6 Fig 3 - Map showing wind speeds in m per s for maximum height of buildings
    • 7 Max height of buildings Diagram 7 Max height of buildings
    • 8 Measuring storey and wall heights Diagram 8 Measuring storey and wall heights
    • 9 Declared compressive strenght of masonry units Diagram 9 Declared compressive strength of masonry units
    • 10 Maximum span of floors Diagram 10 Maximum span of floors
    • 11 Differences in ground levels Diagram 11 Differences in ground levels
    • 12 Openings in a buttressing wall Diagram 12 Openings in a buttressing wall
    • 13 Buttressing Diagram 13 Buttressing
    • 14 Sizes of openings and recesses Diagram 14 Sizes of openings and recesses
    • 15 Lateral support by floors Diagram 15 Lateral support by floors
    • 16 Lateral support at roof level Diagram 16 Lateral support at roof level
    • 17 Size and location of openings Diagram 17 Size and location of openings
    • 18 Wall thinckness Diagram 18 Wall thinckness
    • 19 Lateral restraint at roof level Diagram 19 Lateral restraint at roof level
    • 20 Proportions for masonty chimneys Diagram 20 Proportions for masonry chimneys
    • 21 Elevation of stepped foundation Diagram 21 Elevation of stepped foundation
    • 22 Piers and chimneys Diagram 22 Piers and chimneys
    • 23 Foundation dimensions Diagram 23 Foundation dimensions
    • 24 Area at risk of collapse in the event of an accident Diagram 24 Area at risk of collapse in the event of an accident
    • Table 1 Areas at risk from house longhorn beetle Table 1 Areas at risk from house longhorn beetle
    • Table 2 Wall types considered in this section Table 2 Wall types considered in this section
    • Table 3 Minimum thickness of certain external walls, compartment Table 3 Minimum thickness of certain external walls, compartment
    • Table 4 Imposed loads Table 4 Imposed loads
    • Table 5 Cavity wall ties Table 5 Cavity wall ties
    • Table 6 Declared compressive strength of masonry units complying with BS EN 771-1 TO -5 [N PER nn SQ] Table 6 Declared compressive strength of masonry units complying with BS EN 771-1 TO -5 (N/mm SQ)
    • Table 7 Normalised compressive strength of masonry units of clay and calcium silicate blocks complying with BS EN 771-1 and 2 [Nn/mm SQ] Table 7 Normalised compressive strength of masonry units of clay and calcium silicate blocks complying with BS EN 771-1 and 2 (N/mm SQ)
    • Table 8 Value of Factor X - see Dia 14 Table 8 Value of Factor 'X' (see Dia 14)
    • Table 9 Lateral support for walls Table 9 Lateral support for walls
    • Table 10 Minimum width of strip footings Table 10 Minimum width of strip footings
    • Table 11 Building consequence Table 11 Building consequence