The British Iron & Steel Federation (BISF) Type A1 house is a significant part of the UK’s architectural history, particularly in the post-World War II era. These homes were designed to address the urgent housing shortage and were constructed using innovative methods and materials. As an expert surveyor, I will delve into the intricate details of BISF Type A1 houses, covering their history, construction, typical characteristics, and common defects. This guide aims to provide home buyers, investors, and fellow surveyors with a thorough understanding of these unique properties.

Historical Context and Manufacturers

Origins and Purpose

The BISF Type A1 house emerged in the aftermath of World War II, a period marked by a severe housing crisis in the UK. The government sought quick and efficient solutions to rehouse the population, leading to the development of system-built properties. The BISF Type A1 house was one such solution, designed to be rapidly constructed using prefabricated components.

Key Players

The British Iron & Steel Federation (BISF) spearheaded the initiative, collaborating with British Steel Homes Ltd. Renowned architects Frederick Gibberd and Donovan Lee were instrumental in the design process. Their expertise ensured that the houses were not only functional but also aesthetically pleasing.

Construction Period and Numbers

The construction of BISF Type A1 houses took place between 1944 and 1950. During this period, approximately 35,000 units were built across the UK. These homes were primarily located in urban and suburban areas, where the demand for housing was most acute.

Identification Characteristics

Structural Features

BISF Type A1 houses are typically two-storey semi-detached or terraced properties. One of the most distinctive features is the shallow pitch gable roof, which is covered with profiled asbestos cement sheets. The external walls are rendered up to the first-floor level, with vertically profiled steel sheets above. Large ground floor windows and PS trims to windows and doors are also characteristic features.

Variants

Some BISF Type A1 houses include a single-storey lean-to structure at the gable wall. This variant was designed to provide additional living space and is a common modification seen in these properties.

Construction Details

Substructure

The substructure of BISF Type A1 houses consists of concrete strip footings and brick under-building. The concrete slab is thickened around the perimeter, and a damp-proof course (DPC) is included to prevent moisture ingress.

Main Frame

The main frame is constructed using 17 rolled steel channel (RSC) stanchions and three double rolled steel angle (RSA) single-storey stanchions, each forming a hollow box. The frame also includes one rolled steel joist (RSJ) floor support beam, two RSA floor joist supports, seven RSJ floor joists, and seven RSJ ceiling joists. RSA cladding rails, bracings, two tubular steel roof trusses, one mock truss, and RSA purlins complete the frame layout.

Protective Coating

To protect the steel components from corrosion, they were coated with red lead paint and black bituminous paint. The steel sheets were galvanised and also coated with red lead paint for added protection.

External Walls

The external walls feature rendered expanded metal lathing up to the first-floor level, with vertically profiled steel sheets above. The cavity is filled with a glass fibre insulation blanket, and the timber framing is lined with plasterboard.

Internal Walls and Partitions

The separating wall is constructed using breeze concrete block cavity wall faced with timber framing lined with plasterboard. In the roof space, a single leaf block is used. Internal partitions are made of timber stud lined with plasterboard.

Floors and Ceilings

The ground floor is a concrete slab, while the first floor consists of tongue and groove (T&G) boarding on timber joists. Ceilings are lined with plasterboard.

Roof

The roof is covered with profiled asbestos cement sheets, a common material used during the period of construction.

Typical Hazards and Risks

Corrosion

One of the most significant risks associated with BISF Type A1 houses is corrosion. The rolled steel channel (RSC) and rolled steel angle (RSA) stanchions are particularly susceptible, especially at the bases and corners. Corrosion of sheeting rails, metal lathing, and steel flashings is also common.

Asbestos

The use of asbestos cement sheets for the roof poses a health risk. Asbestos fibres can become airborne if the sheets are damaged or deteriorate over time, leading to potential respiratory issues.

Structural Cracking

Cracking of the ground floor slabs, particularly at the corners, is another common issue. This can be caused by settlement or movement in the substructure.

Render and Cladding Deterioration

The render on the external walls can fail due to corrosion of the metal lathing. Similarly, the vertically profiled steel sheets and steel flashings can corrode, leading to deterioration of the cladding.

Flue Pipes and Cowling

Corrosion of cast-iron flue pipes and metal cowling is also a typical defect. This can affect the functionality of the heating system and pose safety risks.

Defective Premises Act

BISF Type A1 houses are not classed as defective under the Defective Premises Act. However, the presence of common defects and hazards means that thorough inspections and maintenance are essential to ensure the safety and longevity of these properties.

Inspection Guide for Surveyors

Preliminary Checks

Before conducting a detailed inspection, gather as much information as possible about the property. This includes historical records, previous surveys, and any known issues. Familiarise yourself with the typical characteristics and common defects of BISF Type A1 houses.

External Inspection

Roof

Inspect the roof for signs of deterioration or damage to the asbestos cement sheets. Look for any areas where the sheets may be cracked or broken, as this can release asbestos fibres.

Walls

Examine the external walls for signs of corrosion in the metal lathing and steel sheets. Check for any cracks in the render, particularly at the corners and around windows and doors.

Windows and Doors

Inspect the PS trims around windows and doors for signs of wear or damage. Ensure that the windows and doors are functioning correctly and that there are no gaps or leaks.

Internal Inspection

Ground Floor

Check the ground floor slab for any signs of cracking, particularly at the corners. Look for any signs of settlement or movement in the substructure.

First Floor

Inspect the first floor for any signs of movement or deflection in the timber joists. Check the T&G boarding for any signs of wear or damage.

Walls and Partitions

Examine the internal walls and partitions for any signs of cracking or movement. Check the plasterboard linings for any signs of damage or deterioration.

Ceilings

Inspect the ceilings for any signs of sagging or damage. Check the plasterboard linings for any signs of wear or deterioration.

Services

Heating System

Inspect the heating system, including the cast-iron flue pipes and metal cowling, for any signs of corrosion or damage. Ensure that the system is functioning correctly and safely.

Electrical System

Check the electrical system for any signs of wear or damage. Ensure that the wiring and fittings are up to current standards and that there are no safety hazards.

Final Checks

After completing the inspection, compile a detailed report outlining any defects or issues found. Provide recommendations for repairs or maintenance to address these issues and ensure the safety and longevity of the property.

Maintenance and Repair Recommendations

Corrosion Treatment

To address corrosion in the steel components, consider applying a protective coating such as red lead paint or black bituminous paint. This can help to prevent further corrosion and extend the lifespan of the components.

Asbestos Management

If asbestos cement sheets are present in the roof, it is essential to manage them safely. Avoid disturbing the sheets and consider encapsulating them to prevent the release of asbestos fibres. If removal is necessary, ensure that it is carried out by a licensed asbestos removal contractor.

Structural Repairs

Address any cracking in the ground floor slab or external walls promptly. This may involve underpinning or other structural repairs to stabilise the substructure and prevent further movement.

Render and Cladding Repairs

Repair any damaged or deteriorated render and cladding to prevent water ingress and further deterioration. This may involve replacing corroded metal lathing and steel sheets and applying a new render coat.

Heating System Maintenance

Regularly inspect and maintain the heating system, including the cast-iron flue pipes and metal cowling. Replace any corroded or damaged components to ensure the system functions safely and efficiently.

Electrical System Upgrades

Ensure that the electrical system is up to current standards and that any outdated or damaged wiring and fittings are replaced. This can help to prevent electrical hazards and ensure the safety of the property.

Conclusion

BISF Type A1 houses are a unique and significant part of the UK’s architectural heritage. While they were designed to address the urgent housing needs of the post-World War II era, they come with their own set of challenges and risks. Understanding the typical characteristics, common defects, and maintenance requirements of these properties is essential for home buyers, investors, and surveyors.

By conducting thorough inspections and addressing any issues promptly, it is possible to ensure the safety and longevity of BISF Type A1 houses. 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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