Floor constuction specifications

 Ground Floor :

Timber frame construction offers potential for saving on foundations, particularly with multi-storey developments where lightweight cladding  (e.g. render, tiles or weatherboarding) is used instead of brick. In most cases, however, the depth of foundations is governed by  local building regulations requirements in each area mainly to avoid the effect of ground settlement or heave, while minimum width of footings is determined by the width of cavity wall construction

The Diagram below describes the typical construction of the  Ground floor slab detail and the insulation elements.


                                Standard Foundation Plan                                                                      Foundation laying

This construction plan will achieve a coefficient U = 0,23 Wn2K is also necessary 5cm.   further polystyrene underneath the insulation to an extra 10cm this is  underneath the reinforced concrete slab.

Base Preparation:

Preparing the base (foundations and ground floor slab) The timber frame designer will define the requirements for the ground floor slab (or footings in the case of a suspended timber ground floor) in terms of size, layout and tolerances and will be able to provide the line and point loads required for foundation design. The base construction should be programmed to provide a suitably accurate and cured base for timber frame construction. Generally the timber frame contracts manager will check the slab accuracy one week before erection. It is important that the ground floor slab is constructed within the tolerances specified by the timber frame designer since the wall panels of the timber frame are placed on sole plates which rest on the ground floor slab. The sole plates act as a template for the building as a whole. Therefore, the accuracy of this template is critical. Packing underneath the sole plates is acceptable (up to a limit of 15 mm) to enable tolerances to be met and also to reduce settlement of the frame as construction proceeds. Sometimes multiple-ply sole plates provide formwork for the ground floor screed. 

Optional extra on Ground Floor is- under floor heating:

For on the slab cross section

  • 8 mm laminate or other similar covering
  • 20 mm cement screed
  • 40 mm polystyrene 25kg/m3
  • Bitumin membrane 0.5 mm
  • 400 mm Reinforced concrete slab
  • 100 mm polystyrene
  • 100 mm sand ( sharp) or hard core ( TBA)


For the 1st floor - floor/ceiling element cross section: ( includes full insulation for accoustic and thermal control)

Intermediate Floors
The intermediate floors are  mostly composed of 250 x50mm beams (with variable joists, depending on the structural calculation) with  a 22mm P5 wood particle board like an OSB and filled with 50mm – 250mm thick fibreglass insulation, a vapour barrier and a 22 x40mm wooden battens (electrical services void) and finished with either 1 or 2 x 12.5mm gypsum boards (supplied by EBS elk but to be fitted by contractor).

In some instance I-Joists can be used instead of solid timber beams to allow for M&E installations. However, this may increase the depth of these beams.

Floor panels (or cassettes) are often used to form intermediate floors ( off ground)and can consist of solid timber joists, ply web or metal web beams, or other types of beam. The cassettes can incorporate all of the floor elements such as double joists to support partition loads, trimmers, and trimming joists for stairwell openings, noggins and blocking. For stability and strength around the floor perimeter, a header joist connects parallel  floor panels or acts as a ring beam for the structure. Typical maximum clear floor spans are 4.8 m, with the overall length of the floor panel up to 9.6 m with a typical width of 3.2 m on average . The floor cassettes arrive on site with predetermined lifting points for ease of construction and fit.

In the case of non separating floors, the structural decking (usually Type P5 particleboard) can be prefixed in position. For compartment floors a sub-deck of plywood or OSB is provided which is overlaid with a floating  screed floor after completion of the roof. This sub-deck provides a safe working platform during construction and can include  a temporary covering for the stairwell. Perimeter support noggins and struts can either be prefixed or supplied loose. Since all of the joists are set at the same level and properly restrained, this helps to reduce problems in service such as misfitting in levels between different parts of the building.


  • Plaster board 12 mm
  • Plaster and paint (ceiling finish)
  • Ceiling /floor joist 250mm
  • OSB board 20 mm
  • Damp membrane 0.2mm
  • Rock wool insultaion 250 mm
  • Screed float 20 mm
  • Compact polystyrene menbrane 6 mm
  • Laminate or tile floor covering 8-12 mm;


Top floor - Ceiling /under roof.( has partial insulation for thermal control as the roof then is fully insulated when this option is used)

  • Plaster board 12mm
  • Plaster and paint ( ceiling finish only)
  • Timber ceiling joist 120 -250mm
  • Damp membrane 0.2 mm
  • rock wool insulation 120-250 mm
  • OSB board 9-22mm

Top floor ceiling /under roof package is designed and agreed with final plans as this has varying options:

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