Arcal Steel Framed House
- Manufacturer: Gee Walker & Slater Ltd
- Alternative name: Gee Walker & Slater
- Designer: G80 Developments Ltd
- Period built: 1964–70
- Number built: 700
The Arcal steel framed house was originally developed by G80 Developments Ltd of Hemel Hempstead. They were intended to replace the ageing post-war temporary prefabricated bungalows that had been erected in South Wales. This design was intended to be placed directly onto the foundation pad of the demolished bungalow that it was to replace. Minor modification/ extension of the existing foundation pad was required to accommodate the increased size of the new buildings footprint.
A possible Link between G80 Developments Ltd and the house builder, Gee, Walker and Slater Ltd is uncertain, but the first houses were manufactured and supplied in 1964 from the Gee, Walker and Slater factory based in Bridgend, Glamorgan.
Later developments led to the production of dwellings for new housing estates, designed to meet the revised Parker Morris standards on housing & living space requirements. Eventually the Arcal steel frame was phased out altogether and although externally their outward appearance remained much the same, the Arcal house evolved into a timber-framed construction.
Over 1000 of these dwellings are thought to have been built between 1964 and the late 1970s, with most of the stock located in South Wales. Estimates suggest that some 700 of these constructions were indeed of steel frame construction, with the remaining 300 or so, timber framed.
Dwellings are flat and plain in appearance. A number of distinctive external features can aid with positive identification.
The two-storey houses are built as detached, semi-detached or terraced dwellings. The earlier detached dwellings have the gable elevation to the front with a central front door; the semi-detached dwellings are aligned in the more usual fashion and have deeply recessed porches. The later designs of terraced dwellings have the same general
appearance as the earlier designs, but single-storey porch and storage extensions may be added to the front elevation and blocks of dwellings may be stepped or staggered.
The external walls are usually pebble dashed with a fine spar finish, but flat glazed asbestos cement sheet claddings or tile hanging were used at first-floor level. The timber-framed wall units may be clad with any of the finishes that were popular during the period of construction. The pitched roofs are gable-ended and clad with interlocking tiles.
The most accurate way to identify the Arcal houses is through the inspection of the roof structure as this is where the
plywood sheathing to the gable-end and the steel gable-end truss, and possibly the Z- section steel purlins, will be apparent.
Arcal steel framed houses Houses : Were constructed as two storey detached, semi-detached and terraced houses.
Brief Construction Details – See more below
- The lower half ground floor elevation of the Front and rear external walls were finished with a coat of render.
- The upper elevation of the front and rear external walls was fitted with glazed asbestos cement sheets.
- Gable walls were covered entirely in a spar dashed render.
- Some buildings were constructed with a Recessed porch.
- Detached houses were constructed with a gable visible to the front elevation.
- Many buildings were also constructed with a Centrally located front door.
- Terraced houses Were rendered and spar dashed throughout and were constructed with a single storey porch extension
- Arcal Refurbishment Case Study Structherm
Possible Defects Include:
- Severe corrosion of RSJ stanchion bases of detached and semi-detached houses.
- Superficial corrosion of RSJ stanchion bases in terraced houses.
- Rain penetration at panel-window joint.
- Rot in plywood sheathing and timber studs.
- Rain penetration and rot in cladding panels
- Disintegration of plasterboard lining.
- Poorly constructed separating walls in roof space.
- Rain penetration of roof at chimney gutter flashings.
- Missing or poorly fixed asbestos cement sheet claddings.
- Fire protection missing in first floor and eaves void.
- Fine cracks and spalling of render.
- Moderate cracking and spalling render.
- Minor corrosion of galvanised trimming beads.
- Asbestos cement sheet claddings and fire protective casings.
- Deterioration of protective coatings.
- Missing or poorly fixed asbestos cement sheet cladding.
Foundations and substructure:
Modification of the existing (bungalow) was required. A slightly larger reinforced 6″ concrete slab was cast over the original concrete slab. The stanchions of the steel framework were located within the area of the original foundation slab. A bituminous damp-proof membrane was then laid over the original concrete slab prior to the casting of the new slab.
The frame members – stanchions, beams, channels and angles – are of standard hot-rolled steel (RS) sections, the purlins are of Z-section pressed steel.
The steel frame for a semi-detached dwelling comprises:
5″ x 3″ RSJ section ridge and eaves height
21/2″ x 21/2″ box section single storey
5″ x 3″ RSJ section
4″ x 2″ RSC section
1/2 dia tie rods
3″ x 3″ RSA section rafters and ceiling chords
l.5″x 1.5″ RSA section struts
8″ x 2.5″ Z-section purlins
Drawings indicate that the basic concept of a gable-shaped framework is common to all designs, but the first-floor support arrangement varies with the span required of the timber joists.
Detached house prefab replacement
The framework is similar to that of the semi-detached house but with a gable-shaped steel framework located in both the front and rear elevations. The sizes of the steel components are the same with the exception of the roof trusses which are of heavier section. The rafters and ceiling chords are of 4″ x 2.5″ RSA sections and the struts of 2″ x 2″ RSA sections.
Terraced house to Parker Morris standards
The framework is similar to the earlier semi-detached dwelling.
The sizes of the steel components are largely the same but the gable-shaped framework is simplified; thc central stanchion is a single-storey prop. The floor support beam arrangement is also simpler.
The roof truss is fabricated in one piece with rafters of 3 3/4″ x 2.5″ RS angles, ceiling chords of 2.5″ x 2″ RS angles and struts of 2in x 2in RS angles.
Glazed asbestos cement sheets used as external wall claddings at first-floor level.
The first floors of 3 1/4″ thick chipboard on 7.5″ x 2″ timber joists spaced at 16″ centres.
Timber purlins used in the roof construction.