Overview of the Arcal House

The Arcal house, a notable example of system-built properties in the UK, was manufactured between 1964 and 1970. These homes were primarily constructed by Gee Walker & Slater Ltd, with designs by G80 Developments Ltd. Approximately 700 units were built during this period, making them a significant part of the mid-20th-century housing landscape. These properties are commonly found in various regions across the UK, often in suburban areas.

Identifying Characteristics

Arcal houses come in several configurations, including two-storey detached, semi-detached, and terraced houses. They feature a medium pitch gable roof covered with interlocking concrete tiles. The front and rear external walls are rendered up to the first-floor level, with glazed asbestos cement sheets above. Gable walls are rendered throughout, and the houses often include a recessed porch.

Detached houses are typically oriented with the gable in the front elevation and are rendered and spar dashed throughout. They also feature a central front door. Terraced houses, on the other hand, are rendered and spar dashed throughout and often include a single-storey porch extension.

Construction Details

Substructure

The substructure of Arcal houses consists of a concrete slab over an existing concrete foundation, incorporating a damp-proof membrane (DPM).

Frame

The main frame includes:
– 3 RSJ stanchions
– 4 RS hollow box single-storey stanchions
– 2 RSJ floor support beams
– 4 RSC floor ties
– 2 steel rod ties
– 1 RSA roof truss in two sections

The protective coating for these elements typically involves red oxide paint and black bituminous paint.

External Walls

The external walls are constructed from storey-height timber frame panels sheathed externally with plywood and rendered on the gable wall and up to the first-floor level on the front and rear walls. Above this, glazed asbestos cement sheets are used. The walls are lined with foil-backed plasterboard.

Separating Wall

The separating wall is a block cavity wall, with 9″ blocks laid flat in the roof space.

Partitions

Internal partitions are made from timber studs lined with plasterboard.

Floors

The ground floor is concrete, while the first floor consists of tongue-and-groove boarding on timber joists.

Ceilings

Ceilings are constructed from plasterboard.

Roof

The roof structure includes:
– 4 Z-section PS purlins
– Timber rafters
– Bituminous felt
– Interlocking concrete tiles

Typical Variants

Detached Houses

Detached Arcal houses feature a repeat of the gable steel framework.

Terraced Houses

Terraced houses have a simplified steel framework.

Common Defects and Hazards

Corrosion

One of the most significant issues with early detached and semi-detached Arcal houses is severe corrosion of the RSJ stanchion bases. In terraced houses, this corrosion is usually superficial.

Rain Penetration

Rain penetration at the panel-window joint is a common problem, leading to potential water damage inside the property.

Rot and Disintegration

Rot in plywood sheathing and timber studs, as well as the disintegration of plasterboard lining, are frequent issues. These problems can compromise the structural integrity of the house.

Poorly Constructed Separating Walls

Separating walls in the roof space are often poorly constructed, which can lead to issues with sound insulation and structural stability.

Roof Issues

Rain penetration of the roof at chimney gutter flashings is a common defect. Additionally, missing or poorly fixed asbestos cement sheet claddings can pose a significant hazard.

Fire Protection

Fire protection is often missing in the first floor and eaves void, which can be a serious safety concern.

Render Issues

Fine cracks and spalling of render are typical defects, along with minor corrosion of galvanised trimming beads.

Asbestos

Asbestos cement sheet claddings and fire protective casings are common in Arcal houses. Asbestos poses a significant health risk if disturbed, so it is crucial to handle it with care.

Defective Premises Act

Arcal houses are not classed as defective under the Defective Premises Act. However, the various issues and defects mentioned above can still pose significant challenges for homeowners and investors.

Inspection Tips for Surveyors

When inspecting an Arcal house, surveyors should pay close attention to the following areas:

RSJ Stanchion Bases

Check for severe corrosion in detached and semi-detached houses and superficial corrosion in terraced houses.

Panel-Window Joints

Inspect for signs of rain penetration and water damage.

Plywood Sheathing and Timber Studs

Look for rot and disintegration, which can compromise the structural integrity of the house.

Separating Walls

Examine the construction quality of separating walls in the roof space.

Roof

Check for rain penetration at chimney gutter flashings and ensure that asbestos cement sheet claddings are properly fixed.

Fire Protection

Ensure that fire protection is present in the first floor and eaves void.

Render

Look for fine cracks and spalling of render, as well as minor corrosion of galvanised trimming beads.

Asbestos

Identify any asbestos cement sheet claddings and fire protective casings, and ensure they are handled with care.

Conclusion

Arcal houses, with their unique construction and design, offer a fascinating glimpse into mid-20th-century housing in the UK. While they are not classed as defective under the Defective Premises Act, they do present several challenges and potential hazards that homeowners and investors should be aware of. By understanding the typical characteristics, construction details, and common defects of Arcal houses, you can make informed decisions when buying or investing in these properties.

At Flettons, we’re committed to safeguarding your investment. When considering a property purchase, trust our seasoned expertise to reveal any hidden threats. For a thorough building survey, get your instant quote through our quote calculator or reach out directly at 0203 691 0451. Your home’s safety is our top priority.

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