Oxford Method Research Programme

6M Internal Works

 

Sequence of Work 

• Compartment walls were in 150 mm lightweight concrete block dry-lined both sides. 100 mm blockwork was used in wet locations.
• All other partitions, which were either 100 mm or 200 mm wide overall, consisted of two layers of 12 mm plasterboard either side of steel studs spanning between channels at floor and ceiling.
• Half hour and non-rated partitions may have included glazed openings.

Suspended Ceilings 

• The ceilings consist of 600 x 600 prefinished metal tiles supported in spring 'T's in turn supported by channels on hangars from the underside of the profiled metal deck or from the grid of support angles below the tied portal roof. The ceiling provides one hour fire protection to the structure.
• By the addition of an extra layer above the grid of primary channels, the ceiling acted as a half-hour separating membrane.
• Set out between external and compartment walls and movement joints from a central point so as to minimise creep.
• The ceiling was installed complete before the removal of temporary access tiles required for the completion of the services installations.
• The removal and replacement of the tiles was carried out by the specialist fixer.

Fire Barriers 

• One hour compartment walls are continuous up to the underside of the roof covering.
• Sub-compartment and all other half-hour rated partitions had a fire barrier in the ceiling void in line with and fixed to the head of the partition and the structural soffit above.
• Below an open pitched roof void (no plantroom) the fire barrier over a half-hour membrane ceiling was used. Roof and service voids were then further sub-divided so that the barriers were no more than 20m apart.

Services 

• Foul drainage was generally in uPVC (Glass for waste including solvents, spun iron for high temperature wastes). All drainage, and M & E services were planned and co-ordinated with structural elements so as to minimise the risk of clashes.
• Most vertical services are concealed within partitions, which demands a very high standard of accuracy in setting out drainage terminations at ground and upper floor levels and in plumbing and electrical first fix.

Ground Floor 

• Weak mix laid on ground stripped of topsoil and filled as necessary. If the weak mix was laid before erection of the steel frame, pockets were left for column bases. Excavation for services and placing of weak mix base layer were delayed until after upper floors had been concreted. In this case temporary expanding forms could be used to support the metal deck and leave the ground floor area clear for working.
• It was recommended that the external wall was brought up to 150 mm below finished ground floor level and the weak mix laid up to this.
• The weak mix fixed the buckets protecting incoming services and drains permanently in place.
• The finish of the weak mix was sufficiently smooth to receive the liquid d.p.m.
• The bituminous damp-proof membrane was applied to the surface of the weak mix and over the perimeter blockwork.
• 150mm slab laid by continuous strip method between steel edge forms and powerfloated as described in the specification. A high level of supervision was necessary to achieve the required finish and test areas were completed and approved prior to the remainder.
• In poor weather conditions, it was well worth temporary protection of the newly laid concrete in addition to the normal curing membrane.
• A poor or damaged surface finish was very difficult to rectify later.

Upper Floors 

• The profiled metal deck was both tension reinforcement and permanent formwork. Composite action was achieved through deck welded shear studs.
• Concreting of upper floors preceded the ground floor when adequate access could be maintained.
• The concrete was laid in strips parallel to the deck span with softwood framing or framed plastic plugs to form openings and with a galvanised edge pressing trimming stairwells and at the external wall.
• The powerfloated finish required careful supervision. Formers were removed and the metal deck cut away after the concrete had cured.

Roof 

• Completion of the roof preceeded the construction of ground and upper floors, but the finish had to be kept back from block junctions. If the roof was completed before the construction of external walls, gutters had to be installed and provision made for the temporary disposal of rainwater. The soffit was fixed after construction of the external walls.

Internal Sub-division 

• Concrete over buckets broken out and drainage and other services extended to finished floor level, and d.p.m. and floor made good. Drainage was tested and temporarily sealed off. The final location of services that were to coincide with hollow partitions had to be set out accurately.
• Floor and ceiling channels were set out from the ceiling grid. To facilitate movement in fire the head channel was in 1.8 m lengths, fixed to not more than three tiles. The floor channel stops either side of drainage. The channels had to be drilled for minor services.
• Column casings were installed as partitioning proceeded. If casings were fixed before partitioning, they had to be carefully set out to be flush with the partitions to which they were fixed.
• Casings were bonded to columns. The glue could be omitted if the casing was adequately braced by incoming partitions.
• Studs, window and door linings were then installed.
• Openings for sanitary assemblies were marked out.
• Two layers of board were fixed to one face only of the partition, chosen to facilitate services first fix.
• At junctions with the external wall, the last stud was fixed through the drylining to a metal firring channel.
• Drylining of external wall could proceed in conjunction with partitioning. If drylining was delayed, so was the fixing of the last stud of incoming partitions.
• All first fix services were then completed and tested.
• Complete second side of partitions after installing provision for heavy fixings (eg grab rails) and terminate services as detailed could then be done.

Finishes and Fittings 

• Light fittings, ventilation grilles, radiator brackets fixed. If radiators required painting they could be temporarily installed to facilitate completion of supply pipework, and then disconnected for decoration.
• Wall and floor finishes (other than carpet) then preceded the fixing of sanitary equipment and storage fittings. For walls to be painted, the top coat was left until later.
• Electrical equipment, wall-plates, sanitary equipment, toprail and fixed storage was then installed.
• Final paint coat to walls.
• Carpets laid.

Commissioning 

• Any further disruption to the suspended ceiling was to be minimised. Tiles removed temporarily were to be kept clean and stored carefully prior to replacemen