1.01 - As with the wall finishes, the prime requirement of the floor playing surface, is that it should be uniformly hard, smooth and level to the required falls. The achievement of these requirements will be dependent on the materials which are used and the workmanship employed.
1.02 - Old Eton Fives courts often had floors of York stone which created difficulties (wear causing dishing in well-used areas, joints giving untrue bounce etc). Others used stone for nosings with screed infill behind. This approach certainiy has its attractions, overcoming problems in forming a round edge along the two steps but still leaving a potential for uneven bounce at the junction between stone and screed.
1.03 - Consideration has been given to the use of a proprietry steel or aluminium nosing embedded in the finish along the step edges but this has been discounted on the grounds that a different material will again increase the likelihood of uneven bounce. A carefully executed construction by either of the methods described below should produce a satisfactory result.
1.04 - After carefully considering the various options and having taken advice from the Building Research Establishment, it is suggested that specifiers select either a cement and sand topping laid under strictly controlled conditions described below (see 2.00 - 5.00) or, alternatively a specification using products by Ardex UK Ltd (see 6.00 below).
1.05 - The Ardex method will be more expensive but will produce a crisp and hard wearing edge to steps and the material is fast-drying. Any technical enquiries about Ardex products should be addressed to the manufacturer. At the time of writing the Chief Chemist at Ardex is Mr C Potter and their technical representative Mr J Oliver, Ardex UK Ltd., Homefield Road, Haverhill, Suffolk, CB9 8QP, Tel: 01440 714939.
1.06 - Traditionally, screeds were laid wet and received a good deal of trowelling. This brings laitence to the surface and produces a smooth wearing surface which is very hard but likely to craze. Modern screed laying uses the mix "semi-dry". This tends to limit workability, producing a coarser texture with more even distribution of the constituent parts.
1.07 - A balance has to be achieved and whilst over-trowelling should be avoided, more work will be required than for a normal screed which is to receive a covering. It is essential that the method of mixing, laying and the drying period and conditions are carefully controlled. The aim is to have the materials thoroughly mixed and to have sufficient water to allow the mix to be workable, but without bringing large quantities of water to the surface when trowelling.
1.08 - Screed also has a tendency to 'dust' initially. Whilst achieving the correct balance between workability and dryness will limit this effect, some dusting must be expected during early use.
1.09 - Specifiers of conventional toppings should consider the merits of using ready-mixed material. Provided access is available for delivery, mixing proportions are strictly controlled and skilled screeders are ready to receive and place the material as soon as it arrives, a ready-mix supply will reduce risks associated with batching and inconsistent mixing.
1.10 - It should be noted that where the word 'screed' is used, reference is being made to an in situ concrete wearing surface. Conventional cement and sand screeds are designed to receive applied surface finishes and are covered by BS 8204: Part 1: 1987. This standard is unlikely to produce a satisfactory finish and will be liable to unacceptable 'dusting'. The appropriate design standard which should be observed is BS 8204: Part 2: 1987, in situ floorings, Code of Practice for concrete wearing surfaces. Workmanship is also covered in BS 8000: Part 9: 1989. Workmanship on Building Sites, Code of Practice for cement/sand floor screeds and concrete floor toppings. Specifiers and contractors should make themselves familiar with these documents. The folowing notes are extracted from those documents but do not remove the obligation to comply in full with their contents. Reference should also be made to BCA Guide: Floor Levelling Screeds by Ralph G Chaplin published by the British Cement Association.
The cement used should be ordinary Portland cement complying with the requirements of BS 12:1989. The supplier of OPC should be registered as being of Assessed Capability under the British Standards Institution Registered Firms scheme with assessment against the appropriate part of BS 5750: Quality Systems.
2.02 - All cement should be stored off the ground, stacked clear of walls, away from all damp surfaces and undercover. Stacking should be arranged so that bags can be taken out for use in the same order in which they were delivered.
2.03 - Coarse aggregates for high strength concrete toppings shoud comply with BS 882.
2.04 - Fine aggregates should be natural sand complying with grading limit M of tabe 5 of BS 882: 1983.
2.05 - Aggregates should not contain any deleterious material.
2.06 - Admixtures should only be present if they comply with the appropriate part of BS 5075, for the purposes of air entraining water reducing, superplasticising, accelerating, waterproofing or retarding and then only in strict compliance with the standard.
3.01 - It is not within the scope of these notes to cover sub-base or concrete slab design except as they affect the finish. Designers will need to ensure that base and sub-base design is appropriate for the particular conditions. Wherever possible though, it is preferable to ensure that any damp-proof membrane is incorporated below the base rather than between the base and the topping.
3.02 - The choice of method of topping will be between the following options:
a) direct finished structural slab to provide the wearing surface.
b) topping laid monolithically with the base.
c) topping bonded to a set and hardened concrete base.
d) unbonded construction which should be made thick enough to provide sufficient rigidity and reduce the
likelihood of curling.
It is recommended that wherever possible option (d) is avoided. Option (a) will probably not be available in most cases. These notes therefore cover options (b) and (c). Specialist advice should be sought for options (a) and (d).
3.03 - Factors influencing cracking and curling of slabs and toppings.
a) Water content: increasing the water content of a mix will increase drying shrinkage, increasing the
risk of cracking. The quantity of water used should be kept to the minimum necessary to ensure thorough compaction.
b) Curling: shrinkage occurs as concrete dries. Slabs and toppings should therefore be kept continuously
moist for at least 7 days starting immediately after laying to enable them to develop sufficient strength to resist
the stresses due to further shrinkage which may continue for several months.
c) Drying: slabs and toppings should be allowed to dry out as slowly as practicable after ensuring to
reduce the risk of curling.
Designers should call for Class SR1 from the clarifioation of surface regularity for wearing surfaces (maximum permissable departure from a 3m straightedge laid in contact with floor of 3mm).
Surface hardeners or sealers should not normally be required.
Class AR2 from the Classification of abrasion resistance should be achieved. The following factors will influence
the standard:
a) Concrete quality. The mix should be designed to be cohesive and to limit the amount of free water which
may bleed to the surface.
b) Surface finishing. It is essential to ensure good compaction at the surface by trowelling twice followed
by curing.
c) Curing. Proper curing immediately after laying, is essential.
d) Choice of coarse aggregate. Normal good quality concrete aggregates will be satisfactory.
The width of the court falls within the maximum recommended bay width of 4.5m. The upper and lower court areas should be laid as separate bays.
Concrete grade C50 should be used. The maximum size of coarse aggregate should be 1Omm single size in accordance with BS 882:1983. Minimum cement content should be 400 Kg/m3.
Thickness will depend on the age and condition of the base and the position of the damp-proof membrane. For the 4 methods of topping listed in 3.02 above, the relevant thickness should be as follows.
3.02 (a) and (b) monolithic construction : 15 +/- 5mm at any point.
3.02 (c) separate bonded construction: minimum thickness 20mm with a design thickness to take account of any unevenness in the base, of a maximum of 40mm.
3.02 (d) separate unbonded construction: 100mm.
3.10 - Falls: Where possible if it preferable for the court falls to be formed in the base concrete so that the topping or overslab is of uniform thickness. When working from a level base the topping will have to be increased above 40mm. This can increase the risk of loss of adhesion with the base due to differential shrinkage stresses and in these cases, specialist advice should be sought.
The following clauses 4.0l - 4.09 apply to all the methods of topping listed in 3.02 (a) - (d).
Good workmanship and efficient supervision are essential. The works should be carried out by trained operatives.
The wearing surface should be protected against damage during any subsequent operations.
Cold weather work should be in accordance with BS 8110: Part 1. Aggregates and cement should be maintained at above freezing point. The surface of the laid concrete should be kept above 5 degrees Centigrade during construction and for 4-5 days after laying. Cover exposed concrete with tarpaulins or sheeting carefully lapped and supported clear of the surface on a framework, in a manner which will prevent the wind from blowing underneath.
Concreting in hot or drying weather should be in accordance with BS 8110: Part 1. Care should be taken to avoid rapid stiffening preventing full compaction. Drying should not be permitted to be too quick. To avoid this and to provide protection from direct sunlight and wind covering as in 4.03 above should be provided.
Rain should not be allowed to fall on the finished surface.
Use a mechanical compacting beam or other surface method whilst avoiding excess laitance being brought to the surface.
After the concrete has been fully compacted and has stiffened sufficiently and any bleed water has evaporated (normally 1-6 hours) it should be levelled and floated smooth by hand or machine. During the next 3-6 hours the surface should be trowelled twice to produce a uniform and hard surface. Operations should be timed to prevent excess laitance. The final trowelling should be made when considerable pressure is required to make any impression on the surface but avoiding excessive trowelling producing a polished or slippery finish.
Do not sprinkle neat cement to absorb bleed water.
Do not add water between trowelling operations.
4.08 - Alternatively the surface can be ground after compaction and levelling and after initial floating. Grinding the surface should be carried out in accordance with BS 8204: Part 2: 1987: 7.7(b).
As soon as the surface has hardened sufficiently to prevent damage, the concrete should be cured continuously for at least 7 days using waterproof sheeting kept in close contact with the surface for the full curing period. Sheeting should overlap at the sides and ends and laps at joints should be at least 150mm.
4.10 - The following clauses should be adhered to in addition to 4.01-4.09, for toppinq methods 3.02 (b) and (c).
4.11 - Monolithic toppings (3.02 (b)). No special preparation of the surface of the base concrete is required.
Separate bonded toppings (3.02 (c)).
4.12 - Laitance on the in situ concrete base should be removed by shot-blasting or scrabbling to expose the coarse aggregate. Remove all loose material with vacuum equipment. For several hours before the topping is to be laid, the base concrete should be kept wet, any excess water being brushed off before grouting. The aim is to achieve as nearly as practicable a saturated, but surface dry condition in the base.
4.13 - Within 30 minutes of laying the topping, a thin layer of neat cement grout of creamy consistency should be brushed into the surface of the base. It is essential that the compaction of the topping takes place whilst the grout is still wet. Proprietary bonding agents should only be used strictly in accordance with manufacturer instructions.
4.14 - Unbonded construction (3.02 (d)) either on a new or an old base.
The base should be clean and sufficiently smooth to receive any separating material.
Materials should be batched by mass or if impracticable, by equivalent volume. Cement should be batched in whole bags.
Use a forced action mechanical mixer. The amount of water should be the minimum necessary to give sufficient workability and to ensure full compaction.
The topping to the risers of the steps should be applied by separate bonded construction. Preparation should be as 4.l2-4.13. Formwork should then be set to the finished profile and the topping mix should be well tamped into the cavity between the riser board and the face of the base. On removal of the formwork any small cavities or pinholes in the topping surface should be filled with cement mortar (note: this applies to the riser face only) using a fine aggregate with a wood float. Rub the surface with a stone to remove laitance.
5.01 - Inspect the works during progress and on completion.
5.02 - Test on completion for levels and surface regularity against the standard set in 3.04 above.
5.03 - Test on completion for adhesion of bonded toppings to base, by tapping with a rod or hammer. A hollow sound will indicate lack of adhesion. Loss of adhesion will not necessarily mean that the topping is unsatisfactory but if it is accompanied by visible or mearurable lifting at edges, it should be considered unsatisfactory. Any such arears will need to be isolated by sawing, cutting out and relaying taking care to minimise the effect of the remedial work on the adhesion of adjacent parts.
The following specification should only be used where the damp proof membrane is positioned below the base. Subject to confirming that the base is satisfactory, it may be used on existing surfaces but note that the maximum thickness which can be laid in a single operation is 50mm i.e. less than the fall on each of the playing areas. It should not be used if the open end of the court results in regular exposure to rain.
6.01 - Product data sheets for the materials referred to are available from Ardex UK Ltd. It is essential that specifiers and contractors observe the manufacturers instructions. If in doubt, seek advice from the technical department at Ardex UK Ltd.
6.02 - New ground bearing concrete bases should be prepared as described in part B Option One above. Falls should be set and formed, where possible in the base, to ensure that the proprietary topping is of consistent thickness.
6.03 - Having prepared the base and having allowed for curing and ensured the absence of laitance the surface should be prepared as described in the data sheet and primed with Ardion 51.
6.04 - The primed surface should then be coated with Ardit SD-T as descibed. A minimum thickness of 6mm is required. Allowance should be made for the maximum thickness to accommodate any unevenness in the surface of the base.
6.05 - The faces of the two steps should be formed using Ardurapid 45 mortar in aocordance with the data sheet and instruction leaflet no.6. provided by Ardex UK Ltd.
6.06 - Tolerances should be as set out in part B Option One and must be checked for compliance during installation and on completion.
Court Finishes - John Pattle (1992)
Prepared 6th February 2002
efa@etonfives.co.uk