SMDStructural Floor and Roof Solutions

Best Practice Data Sheet DATA/23

Surface Finishes

1 of 2SMD.DAT.126.V1Concrete Department

Surface finish is defined in BS EN 13670 Execution of concrete. This standard is adopted by NSCS 4th edition for concrete construction. For unformed finishes it is important not to ‘over-specify’ the quality of finish, particularly where it is covered up by following work; but whatever finish is specified, the concrete must be fully compacted.

The previous terminology was U1, U2 and U3 which generally correlates to Basic, Ordinary and Plain respectively. The default unformed finish assumed for all work is Basic.

Basic (Skip/Easy Float)Applicable for areas to receive a levelling or wearing screed. A closed finish is produced by levelling and use of a skip/easy float or similar type equipment. Float marks, localised ridges, surface laitance and a mottled effect will be evident in the final finish. There is also a risk of reinforcement ripple.

A Basic finish may be suitable to most areas but allowance should be given by the Project Team for the appropriate surface preparation (for the removal of float marks, localised ridges, weak layer) and possible use of primer necessary to resin fix pedestals or pass ‘pull off’ tests usually requested by the contractor responsible for raised access flooring or roofing finishes. A levelling screed or smoothing underlayment, in addition to appropriate surface preparation (for the removal of float marks, localised ridges and weak layer) and possible use of a primer, may also be required prior to the installation of thin sheet floorings.

Skip/Easy Fig. 4 Skip/Easy Fig. 5 Skip/Easy Fig. 6

Skip/Easy Fig. 1 Skip/Easy Fig. 2 Skip/Easy Fig. 3

Skip/Easy Fig. 7 Skip/Easy Fig. 8 Skip/Easy Fig. 9

Ordinary (Powerfloating - Pan or Combi)Applicable for areas to receive flooring materials, types of false floor or other raised finish. It may not be suitable for thin vinyl flooring without grinding or an underlayment. This is a flat surface produced typically by power-floating but not by Basic (Skip/Easy Float) methods of surface finishing. A Pan finish will exhibit ridges (although not to the degree of Basic methods), provide a rough textured surface and will vary in consistency in its final appearance. A Combi finish will be free from ridges but float marks are to be expected.

These types of surface finishes may be acceptable for the application of finishes such as tiles or carpet. Surface preparation may be less extensive if an Ordinary finish is provided.

Plain (Powerfloating - Full Polish)Applicable for areas without any other finish other than paint or surface coatings, and provides a uniform dense smooth surface typically produced by power-trowelling. This may be suitable for directly trafficked surfaces.

Due to its dense nature, a Plain finish may need abrading (typically, shot blast) to create a key to facilitate the application of subsequent finishes.

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SMDStructural Floor and Roof Solutions

Concrete DepartmentSMD.DAT.126.V1

Combi Fig. 13 Combi Fig. 14 Combi Fig. 15

Pan Fig. 10 Pan Fig. 11 Pan Fig. 12

Polish Fig. 16 Polish Fig. 17 Polish Fig. 18

Polish Fig. 19 Polish Fig. 20 Polish Fig. 21