Timber and concrete upper floors

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6.4.3Upper floor design

Upper floors shall support and transmit loads safely to the supporting structure without undue deflection. Issues to be taken into account include:

  1. loads and support to partitions
  2. steelwork.

Loads and support to partitions

Structural design of timber and concrete upper floors should be in accordance with BS EN 1991-1-1.

The design of upper floors should account for dead loads, including:

  • floor structure, decking and finishes
  • ceilings and applied finishes
  • walls and partitions supported by the floor
  • permanent fixtures such as boilers, water tanks etc.

Imposed loads should be calculated in accordance with the relevant British Standards, including BS EN 1991-1-1 which recommends:

  • 1.5kN/m2 for self-contained homes
  • values for communal areas serving flats or maisonettes.

Bearers or additional joists should be used to support heavy loads.

Joists built into separating walls may provide lateral support, and should be detailed to ensure that sound insulation and fire resistance requirements are met.

Masonry partitions

Where first floor masonry partitions cannot be built directly in line with ground floor masonry walls, steel or reinforced concrete support should be specified. Masonry should not be supported on joists.

Lightweight partitions

Where multiple solid timber joists support lightweight non load-bearing partitions which are parallel to the joists, they should be suitably fixed together. Where I-joists and metal web joists are used, they should:

  • be positioned centrally below a non load-bearing partition and, where necessary, additional joists should be doubled or tripled in accordance with the manufacturer’s recommendations
  • support the weight of the non load-bearing partition by noggings or bearers fixed to the joists on either side. Unless designed otherwise, noggings should be a minimum 38mm x 90mm minimum at 600mm centres and fixed with metal clips. The sole plate of the non load-bearing partition should be fixed to the noggings, or
  • be in accordance with the manufacturer’s recommendations.


Steelwork should be:

  • designed by an engineer in accordance with Technical Requirement R5 and comply with Chapter 6.5 ‘Steelwork’
  • sized to allow an adequate joist bearing.

Structural continuity of the floor should be provided by the use of continuous decking fixed to joists on both sides of a transverse steel joist.

Steel beams should be protected by a suitably durable paint coating as detailed in Chapter 6.5 ‘Steelwork’.