BISON PRECAST STAIRS SPECIFICATION D

1 1 BISON PRECAST STAIR SPECIFICATION SCOPE OF THE SPECIFICATION Relates to: This SPECIFICATION covers the design, manufacture and associated site work of the following types of STAIRS :- Prestressed STAIRS Reinforced Concrete STAIRS Description of STAIRS The PRECAST STAIRS are designed and manufactured as prestressed PRECAST STAIRS or as reinforced PRECAST STAIRS . MATERIALS Standards: All materials are to be in accordance with the appropriate British Standard and this SPECIFICATION . Concrete: The design strengths of concrete used in the design and manufacture of BISON units is as follows:- Prestressed Design Ultimate Concrete Strength is to be a minimum of 55 Concrete Strength at transfer is to be 30 Reinforced Design Ultimate Concrete Strength is a minimum of 45 Admixture: Concrete used is of a self compacting nature, and therefore does contain some additives.

2 This additive is to provide adequate suspension in our mix to achieve the self leveling nature of the concrete. Reinforcement: Reinforcement for prestressed PRECAST STAIRS is generally 5mm diameter high tensile wire complying with the requirements of BS 5896:1980. Reinforcement for reinforced PRECAST STAIRS is generally high yield, high bond bars complying with the requirements of BS 4449:2005 and BS 4483:2005, and is detailed in accordance with BS 4466 unless specified. DESIGN Code: The design of BISON units is in accordance with the requirements and recommendations of BS 8110:1997 The Structural Use of Concrete . Service Class: The design of BISON Prestressed stair units is to Serviceability classification, Class 3 with a limiting crack width of , and RC stair units to crack width.

3 Durability: The standard BISON stair is designed to comply with the durability requirements of BS8500:2006. Fire: Fire resistance is based upon the tabulated data contained within BS 8110 : Part 2 Section 4. Sections are available for fire periods of 1 hour or 2 hours without the addition of further finishes. These period of fire resistance may be further enhanced by the application of appropriate finishes. Horizontal and Vertical Ties: Ties necessary to satisfy the requirements for accidental damage should be specified by the Engineer with the responsibility for the design of the overall structure in accordance with the relevant Codes of Practice. To accommodate tie details, a C40 structural topping may be required in lieu of screed zones.

4 To comply with class 2B structures and greater, generally STAIRS are tied at bearing ends as per BISON standard details. MANUFACTURE Method of Manufacture: BISON standard PRECAST STAIRS are manufactured in precision engineered steel moulds United Kingdom patent numbers 2193922 and 2217359. Other STAIRS to suit specialist requirements may be made using ramp moulds with timber stringers and risers. Mould: The design of the mould is such that any riser height within the range of 150mm to 210mm is available. Alternative tread dimensions of 250mm, 275mm and 305mm are available. These are fixed dimensions, as is the angle of the receding riser (all BISON standard moulds have a nominal 25mm recede). Thus the going varies very slightly with the riser dimension as shown in the table below.

5 To achieve the economic benefits in offering BISON standard PRECAST staircases, it is assumed that minor modifications can be made to the stairwell dimensions to accommodate the standard units. RISER 152 156 160 164 168 172 176 180 Recede Tread 250 Going 275 305 Dimensions: BISON Standard staircases may be manufactured up to wide. Special widths may be provided using ramp moulds which are of timber manufacture.

6 The maximum length of the BISON standard staircase is However the length of the stair may be restricted due to the weight considerations during manufacture and this is set at maximum of 10 tonnes. Permitted Deviations: Cross-sectional tolerances are within the limits set out in clause of BS 8110:1997. Erection tolerances are as per BS5606. Balustrade Fixings: It is recommended that these are drilled on site by others to suit individual requirements. A minimum dimension of 50mm, 75mm preferred, should be allowed between the edge of a pocket of fixing and the edge of the concrete and to a maximum depth of 100mm Lifting points: These will be provided in the factory as proprietary inserts to be made good on site by others.

7 Finishes: The BISON Standard staircase is cast on its side, all surfaces with the exception of one string are from an engineered steel mould face giving excellent quality. Concrete surface finish to soffit, treads, riser and one string is to a Type A finish (minimum) as described in clause of BS8110:1997. The treads and risers are suitable for the direct application of carpet or tiles or for a screed finish applied with a suitable bonding agent. Landings: BISON can supply flights with attached landings and these must have a minimum of 50mm sand/cement screed added so as to allow for manufacturing tolerances. Due to this requirement, the top step contains a recess thus creating a screed stop see BISON general arrangement drawings.

8 3 Separate reinforced landings are also available. These also are to be used in conjunction with a screed again to allow for manufacturing tolerances and to cover up the support angle cast in to the BISON flights. Angles: Purpose made angles may be provided at the end of flights or STAIRS to bear onto other concrete members such as landings or beams. The design of these is subject to strict limits and may require that additional support is provided. SITE WORK Standard: All site work is to be undertaken in accordance with the best current practice and Health & Safety legislation. For further advice reference should be made to the "Code of Practice for the Safe Erection of PRECAST Concrete Flooring". Bearings: Level and structurally adequate bearings for BISON PRECAST units are to be provided by others.

9 These should generally be 100mm for concrete and masonry and a minimum of 75mm for steelwork, but subject to the requirements of clause of BS 8110:1997. Temporary Bearings/Propping: Unless the design specifically allows for units to seat onto temporary bearings ( head trees and bearers, etc.) this practice shall be avoided wherever possible. In cases where such measures are unavoidable, fixing must not progress until permission has been obtained from a competent technical authority within the BISON organisation. We shall specify on our working drawings details and duration of any temporary propping that may be required. Holes and Cutouts: Small holes up to 60mm diameter may be drilled on site. Larger holes may be cut subject to the design capacity of the staircase.

10 Lifting sockets: All sockets formed for lifting purposes are to be filled and made good by others, when erection is complete. Soffit fixings: Several fast and cost effective proprietary systems are available for direct fixing to concrete and we shall be pleased to offer recommendations on request. QUALITY MANAGEMENT SYSTEM QMS Reference: BISON are members of the BSI Registered Firm Scheme for Quality Management Systems to BS EN ISO 9001:2000 for the design, manufacture and installation of PRECAST products. Scope: Membership of the scheme ensures that all processes relevant to the design, manufacture and installation of PRECAST products, are subject to independent review and approval by the British Standards Institution.