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Reema Conclad PRC House - AKA Ribbed, Waffle or Coffered Panel System.
Manufacturer: Reema Construction Co. Ltd.
Milford Manor, Salisbury, Wiltshire.
The first prototype Reema Conclad house was built in 1964. General production commenced in 1969 to meet the demand for a building system that would combine the speed of erection with the standard and economies of industrialized buildings using tailored external finishings and flexibility in planning and design. Reema based the Conclad system on a metric 300 mm planning grid in line with British Standards' institution guidelines. The Conclad system offered improved insulation over the earlier Reema Hollow Panel system.
The Reema Conclad system used precast reinforced concrete corner units, L-shaped in plan, to form the inner leaf of low-rise crosswall houses. The external leaf of the gables is of brickwork while prefabricated timber panel units fill in the front and rear walls
The Reema Conclad technique of construction utilised standardised precast panels which was successfully applied to a range of low, medium and high-rise dwellings up to 26 storeys high, and the system was also used to build a limited number public buildings.
The Conclad system was a development of the already successful Hollow Panel system but with slightly improved thermal properties, and the two were used concurrently: Conclad for dwellings and Hollow Panel for public buildings.
Reema Conclad Foundations
In situ concrete foundation pads are cast, their size and depth depended upon the bearing strength of the soil. Normally five such pads were cast along the façade of a pair of semi-detached houses. Hardcore was spread and a 4in-thick flooring slab was cast upon a polythene damp-proof membrane, to constitute the ground floor. Concrete edge beams were cast in situ to connect with the flooring slab, or else were precast. The ground floor was finished by casting a screed upon the base slab and attaching thermoplastic tiles.
Walls and floors
The external walls are of 7 inch thick pre-cast concrete panels, comprising of a 2in external concrete skin with 5inch deep cavities and ribs. The panels are finished externally with a wide range of exposed aggregates, fair faced or textured concrete finishes.
The vertical joints between units comprise of a baffle strip, an air space, a draught seal, damp-proof membrane and an in situ concrete bond.
Horizontal joints at ground-floor and first-floor level were made by pointing internally with mortar after positioning the panels on bearing pads. The lip of the upper unit overlaps the groove in the head of the lower wall unit. In addition, there are small drain holes cast into the bottom of the units, to enable any humidity build up in the space between the concrete leaf and the internal lining to dissipate into the joint before flowing outside of the property.
The panels were made to storey height, and normally the frontage of a pair of semi-detached houses will consist of eight facade panels, or 16 façade panels in total.
Windows and door frames were cast in at the works and the panels were transported to site pre glazed.
Gable walls were made in a similar way to the façade panels and eight of these are required per pair of houses.
A variety of external finishes could be applied to the first floor including weatherboarding on felt and tile hanging on battens.
Party walls consist of 7inch thick solid concrete panels, which were decorated directly.
A pair of Reema Conclad semi-detached houses required four of these room sized panels.
The units were designed to have a fire resistance rating of 1 hr and a sound reduction properties of 49dB against normal sound ranges.
The density of the party wall was given given as 84.5 lb / sq ft.
In the roof space, concrete panels are of similar form to the lower external panels but with 3in concrete skins. The first floor consists of 1 inch nominal tongued and grooved boarding, attached to timber joists, hung into rust-proofed steel hangers. The latter were attached to the tops of the ground-floor concrete units. Plasterboard was attached to the underside of the joists and decorated with plastic paint.
The floor-to-floor height is 8ft 4in.
Internal walls are of two types;
1. Loadbearing partitions are 4in-thick solid concrete units, which were finished smoothly on both sides to enable direct decorating.
2. Non-loadbearing partitions are 2 1/4 inch thick Paramount partitioning. The joints were taped and filled, thus enabling direct decoration to be carried out.
The external walls were finished on the inside by nailing expanded polystyrene/ plasterboard laminated dry lining directly to battens which had been cast into the concrete units. This dry lining could also be decorated directly without further preparation.
In the case of the timber frame units a similar 1 inch thick polystyrene/ plasterboard laminate was fixed internally.
The U-value of the outside wall was equal to 0.23 B.Th.U/hr sq ft deg F but this could easily be further improved if required. The fire resistance for one or two-storey dwellings at the time of construction was stated as 1/2 hr.
Reema Conclad Roof
A trussed rafter roof was used with either a projecting or flush fascia. It was covered over with concrete interlocking tiles on battens and felt according to British Standard 747. The ceiling was plasterboard with a plastic paint finish.
The U-value of the ceiling, which was insulated with glass fibre, was stated to be 0.9.
Reema produced a further two types of external panel for use in the Conclad system.
The Reema Sandwich Panel (below) was used mainly on a limited number of buildings up to five storeys high where extra strength was needed, as it is more expensive than the Conclad cladding panels but with similar thermal insulation properties. It consists of two concrete leaves connected by a regular system of ties, the intervening space being filled with expanded polystyrene. Inner leaves of panels are of different thicknesses for loadbearing or non-loadbearing use.
The Reema Celcore Panel (below) is an insulated, factory-finished component. It is based upon a Conclad panel with ribs, the cavities between being filled with lightweight foamed concrete. The panel was finished internally with wood wool and then plastered.
IMPORTANT NOTE: The Reema Conclad and Reema Contrad are NOT designated as defective under Housing Defects Legislation (now Part XVI of the Housing Act 1985).
However, the Reema Hollow Panel house IS classified as defective. This can sometimes lead to confusion wherby surveyors and estate agents wrongly classify non-defective Conclad houses as defective.
The Reema Conclad system has concrete external panels, strengthened by ribs on the inner face. Steel reinforcement protrudes into the cast-in-situ concrete column; this is not present in the Hollow Panel system.
Reema marketed the Conclad system as a standard range of bungalows, two-storey houses, low-rise flats, maisonettes, and as multi-storey flats and maisonettes to Parker-Morris standards.
Post 1972 constructions required a 2.6 m floor-to-floor height.
Heating by gas warm air, solid fuel or underfloor electric were also offered as options. Contracts were undertaken for 20 units upwards. On larger contracts the clients' designs and requirements could be produced subject to specifications. Since the first Reema prototype was built in 1946 the company went on to complete over 30,000 homes across the country.