Oxford Method Research Programme

The following detailed specification gives clear instructions as to the procedure of the work.

SPECIFICATION FOR OXFORD METHOD - FLOOR SYSTEMS FINISHES

1. GENERAL
2. DAMP PROOF MEMBRANCE
3. SCREED MATERIALS
4. BATCHING
5. MIXING
6. LAYING
7. CURING
8. LEVEL TOLERANCES
9. REINFORCEMENT
10. APPLIED FINISHES
11. SPECIAL ATTENDANCE

1. GENERAL

The Oxford Method flooring system caters for two basic conditions:

Ground floor slab condition

• 50mm zone comprosing:
• 3mm floor finish
• 44mm K-screed
• 3mm Ventrot damp proof membrane

Suspended floor slab condition

• 33mm zone comprising:
• 3mm floor finish
• 30mm chemically bonded K-screed mesh reinforced over long span floor units.

2. DAMP PROOF MEMBRANE

• Preparation
  The floor must be swept clean and all debris, plaster, mortar droppings etc. fully
  cleaned off.
• Application
  The damp-proof membrane shall be Ventrot which should be applied in accordance with the instructions of Shell Composites Ltd. by licencees of Isocrete Group Sales Ltd. The top surface should be lightly sanded. K-screed slurry grouting is necessary before laying the screed. (see 6. 1)

3. MATERIALS

• General
  K-screeds to be supplied and laid by licensees of Isocrete Group Sales Ltd.
• Cement
  The cement shall be Portland Ordinary Cement (B.S. 12) and shall be stored dry under cover.
• The sand used shall be clean washed concreting sand with a sieve grading in zone 2 (B.S. 882). Stock piles shall be suitably placed and protected to avoid contamination from other materials and/or the ground.
• K-Additive
  K-Additive supplied by Isocrete Group Sales Ltd in 50kg drums shall be well stirred and diluted one part additive to three parts water before use.
• Bonding Additive
  The propriety bonder to be used to bond the 30mm K-screed shall be diluted and used in accordance with the instruction of Isocrete Group Sales Limited.
• Water
  Only clean water from a mains supply shall be used.

4. BATCHING

• Cement
  The cement shall be batched by using a three gallon bucket or similar graduated or measured container.
• Sand
  The sand shall be batched by volume to a specified level in the cylindrical pan of the mixer.
• K-Additive
  The K-Additive shall be kept stirred to prevent the settlement of solid matter. The quantity used per mix shall be measured in a container marked with the required level of the liquid.
• Water
  Additional water shall be added to each batch to give correct workability, the amount varying according to the dampness of the sand. Correct water content can be checked by squeezing a handful of the mix. It should ball together but it should not be possible to squeeze water out of it.

5. MIXING

• Mixing method
  The materials shall be mixed in a pan mixer of the type approved by lsocrete Group Sales Limited, for a sufficient time to ensure a homogenous mix. This time is normally one to two minutes. The material should then be laid within twenty minutes of being mixed.

6. LAYING

• Grouting for screeds 44mm thickness on damp proof membrane.
  The sanded damp proof membrane shall be grouted with K-screed slurry, well distributed with a stiff broom. The recommended slurry mix is one bucket of cement to one bucket of sand plus adequate diluted Additive, to give a flowing consistency.
• Grouting for screeds 30mm thick on precast concrete floor units.
  The floor must be swept clean and all plaster, mortar droppings etc. fully cleaned off. A preliminary wetting of the concrete floor units is recommended the evening before laying commences in order to control excessive suction. The floor should then be primed with a solution of one part Isocrete polymer to five parts water applied with a watering can and then well brushed into the surface. Surplus primer is brushed away and the surface allowed to dry. A special bonding slurry is then applied comprising equal parts of cement and sand mixed into a slurry with Isocrete polymer diluted 1 part polymer to 3 parts water. The slurry is well brushed into the surface with a stiff broom providing a layer approximately 1-2 mm thick.
• Bond
  If carried out correctly, the grouting will produce a good bond, but if some hollowness does occur without measurable lifting, it should not be detrimental. Referring to Building Research Station Digest no. 104 (April 1969) page 7 on Hollowness, which reads:
  "If the adhesion of a screed to its base is examined by tapping the surface with a rod or hammer, a hollow sound indicating poor adhesion might be detected in some areas, most commonly at the edges and corners of bays. Only if the hollow areas have actually lifted by a visible or measurable extent, so that there is a risk of fracture under superimposed loads, should the screed be considered unsatisfactory on this account."
• Compacting and Trowelling
  While the slurry is still wet, the mixed K-screed should be distributed, thoroughly compacted and ruled off. The surface is then closed with a wooden float and steel trowelled. Alternatively, the screed may be left for a short period, the duration of which will depend upon the ambient conditions, and then finished with a power float. The aim is to produce a compact material with a matt surface closed but not over trowelled.
  The screed should not be laid in bays but, as far as possible, in a continuous area in order to avoid edge curling or uneveness at the junction of bays. Any random cracks which do develop should be easily repaired. (This procedure is in accordance with the recommendations of Building Research Station Digest no. 104). When finishing off any area at daywork joints, etc., the joints must be cut off clean and any surplus material removed.

7. CURING

• Screeds are to be cured using polythene sheets. The sheets are to be placed on the damp screed immediately it is hard enough to receive them without damage. The protection should be lift on for a minimum of three days, longer periods being desirable if the construction programme permits. All foot traffic must be kept off the screeds for 36 hours and construction traffic should be forbidden for the first 4 days. Protection by the main contractor is advisable in heavily trafficked areas.

8. LEVEL TOLERANCES

• The surface shall be laid to an accuracy of + or - 6mm from datums given, local accuracy being + or - 3mm under a 3,000 mm straight edge (the ends of the straight edge should have small feet at either end which are placed on the floor so that variations can be measured from the underside of the straight edge to the floor surface). (See British Standard Code of Practice C.P.204, Clause 120 Tolerances on level).

9. REINFORCEMENT

• Where screed is layed on suspended floors consisting of long-span floor units, i.e. those floor units 300mm wide and 1800mm and above in length, the screed is to be reinforced with one layer of wire mesh ref. D31, B.S.4483 1969.
• The mesh shall be supplied in 4.8 x 2.4 metre sizes and securely supported in position above the structural floor surface by means of 10mm diameter steel rods wired to the mesh, 1 no. 150 mm rod being used to every square metre of floor. The mesh shall be laid with 200mm laps. Mesh at laps is to be wired together as 1 metre intervals.

10. APPLIED FINISHES

• General
  Flooring finishes to be supplied and fixed by Variety Floors Ltd., 263 Cowley Road, Oxford.
• Floor finishes are required in sheet or tiled form to provide when laid, a continuous smooth surface on a flat plane.
  Like components fabricated from like materials must be indistinguishable one from another in colour and texture on all visible surfaces in each complete range of surface finishes offered.
• Adhesion
  The types of adhesives used between the wearing surface of floor finishes and the Kscreed are to be suitable and adequate for their purpose.
• Liability to develop and shed Electrostatic charges.
  Anti-static flooring systems must comply with the requirements and recommendations of Hospital Technical Memorandum no. 2 "Anti-static precautions - Flooring in Anaesthetising Areas". No part of any component used in the flooring system shall develop and shed electrostatic charges.
• Maintenance
  Variety Floors Ltd will recommend the maintenance and cleaning procedure (method and frequency) for the visible face of the flooring finish, for each flooring material used.
• General Installation
  Sheet vinyl floor finishes shall be seam welded.
  100mm high 'set in' type PVC skirting shall be used in conjunction with sheet vinyls and welded to floor finish.
  100mm high 'sit on'type PVC skirting shall be used in conjunction with tiled floors.
  When cork tiles are specified these shall be finished with no less than 3 coats of Ronseal hardglaze.

11.1 SPECIAL ATTENDANCE BY MAIN CONTRACTOR

• Special attendance - screed and finish sub-contractors.
• Hard road access to take a loaded 10 ton lorry to within 3.0 m of hoist.
• Unloading materials
• Adequate hoisting facilities (minimum load 762kg) and operator to be supplied to within 45 m of internal working area.
• Either hoisting mixer to required level (subject to Structural Engineers approval) or adequate batching area at base of hoist to requirements of subcontractor.
• Lockage, dry and frost free store within 30.0 m of hoist.
• Electricity supply (240 volts 30 amps or 110 volts 80 amps single phase) for mixer during laying of screed or welding guns and other floor layers tools.
• Setting out levels for screeding by suitable "dots" located on a 3.0m square grid.
• Heating to keep temperature of working areas above freezing point during laying and curing of screeds (minimum of 4 days).
• Heating to keep temperature of working areas at not less than 18deg c for 2 days prior to and during laying of floor finishes. (in cases where underfloor heating is employed, the heating must be on for 7 days prior to the laying of floor finishes) screed surface temperature must never exceed 29deg c. Provision of conditions of temperature and humidity in accordance with BSCP 203:1969 where applicable.
• A continuous supply of main water to be provided at location of mixer.
• Adequate protection of floor finishes after completion of sub-contractor's work.

11.2 Special Attendance - Screed only sub-contractors.

• Hard road access to take a loaded 10 ton lorry to within 3.0m of hoist.
• Unloading materials.
• Adequate hoisting facilities (minimum load 762kg) and operator to be supplied to within 45m of internal working area.
• Either hoisting mixer to required level (subject to Structural Engineers approval) to adequate batching area at base of hoist to requirements of subcontractor.
• Lockable, dry and frost free store within 30.0m of hoist.
• Electricity supply (240 volts 30 amps or 110 volts 80 amps single phase) for mixer during laying of screed.
• Setting out levels for screeding by suitable "dots" located on a 3.0m square grid.
• Heating to keep temperature of working areas above freezing point during laying and curing of screeds (minimum of 4 days).
• At the first practical opportunity after completion of each screeded area the surface of the screed is to be inspected by representatives of the floor finish layer and the main contractor, together with the Clerk of Works to confirm that the screed has been finished to a standard suitable for receiving the floor finish. Thereafter the screed is to be maintained in a cleanly swept condition and adequately protected.
• A continuous supply of clean mains water to be provided at location of mixer.

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