Historical Context and Background

The Costain house, a notable example of post-war British architecture, emerged in the 1950s as a response to the urgent need for housing. Manufactured by Costain Concrete Co. Ltd and designed by Richard Costain Ltd, these properties were part of a broader movement towards system-built homes. The post-war era saw a significant demand for rapid construction methods, and the Costain house was one of the solutions that met this need.

These properties, also known by alternative names such as Cavi Costain, Cavicrete, and Costain-Wilson, were primarily constructed as bungalows and two-storey terraced houses. They are easily identifiable by their medium pitch gable roofs covered with tiles and external walls made of stone-faced precast concrete (PC) blocks. The number of Costain houses built during this period is substantial, reflecting their popularity and the efficiency of their construction.

Manufacturers and Designers

The Costain house was a product of collaboration between Costain Concrete Co. Ltd and Richard Costain Ltd. Costain Concrete Co. Ltd was responsible for the manufacturing process, ensuring that the materials used were of high quality and suitable for the rapid construction methods required at the time. Richard Costain Ltd, on the other hand, provided the architectural design, focusing on creating functional and durable homes that could be built quickly and efficiently.

Typical Characteristics and Identification

Architectural Features

Costain houses are characterized by their medium pitch gable roofs, which are typically covered with tiles. The external walls are constructed from dense aggregate PC blocks, giving the houses a robust and solid appearance. These properties often feature a concrete block cavity underbuilding and a concrete slab foundation, providing a stable and durable base.

Structural Elements

• Substructure: The substructure of a Costain house includes a concrete block cavity underbuilding and a concrete slab foundation. A damp-proof course (DPC) is also incorporated to prevent moisture ingress.
• External Walls: The external walls are made from dense aggregate PC blocks, with a cavity and lined with Leca concrete. Reinforced wall ties and PC lintels are used to enhance structural integrity.
• Separating Wall: Dense aggregate PC blocks are used for separating walls, ensuring sound insulation and fire resistance.
• Partitions: The main partitions include a brick spine wall, with other partitions not specifically known.
• Ground Floor: The ground floor is typically constructed from concrete, providing a solid and durable surface.
• First Floor: The first floor features hollow terracotta block and beam construction, which is both lightweight and strong.
• Ceilings: Ceilings are usually plastered, offering a smooth and clean finish.
• Roof: The roof is constructed from timber trusses and covered with tiles, providing both strength and aesthetic appeal.

Typical Hazards and Risks

Structural Concerns

One of the primary concerns with Costain houses is the potential for structural issues, particularly related to the reinforced concrete elements. Over time, reinforced concrete can suffer from corrosion, especially if the steel reinforcement is exposed to moisture. This can lead to spalling, where the concrete surface breaks away, exposing the steel and further accelerating the corrosion process.

Damp and Moisture Ingress

Due to the age of these properties, damp and moisture ingress can be a common issue. The damp-proof course (DPC) may have deteriorated over time, allowing moisture to penetrate the walls and floors. This can lead to issues such as mould growth, wood rot, and damage to internal finishes.

Thermal Efficiency

Costain houses, like many properties from the 1950s, may not meet modern standards for thermal efficiency. The original construction materials and methods may not provide adequate insulation, leading to higher energy costs and a less comfortable living environment.

Defective Premises Act Considerations

The Defective Premises Act 1972 imposes a duty on builders, developers, and landlords to ensure that properties are constructed and maintained to a reasonable standard. While Costain houses were built to the standards of their time, they may not meet current building regulations and standards. It is essential for buyers and investors to be aware of this and to consider the potential costs of bringing the property up to modern standards.

Inspection and Assessment Guide

Pre-Inspection Preparation

Before conducting an inspection of a Costain house, it is essential to gather as much information as possible about the property. This includes reviewing any available documentation, such as previous survey reports, maintenance records, and building plans. Understanding the typical construction methods and materials used in Costain houses will also help in identifying potential issues.

External Inspection

• Roof: Inspect the roof for any signs of damage or wear, such as missing or broken tiles, sagging, or leaks. Check the condition of the timber trusses and ensure they are free from rot and insect infestation.
• Walls: Examine the external walls for signs of cracking, spalling, or other damage. Pay particular attention to the condition of the PC blocks and the mortar joints. Look for any signs of damp or moisture ingress, such as staining or efflorescence.
• Foundation: Check the condition of the concrete slab foundation and the concrete block cavity underbuilding. Look for any signs of movement or settlement, such as cracks or uneven surfaces.

Internal Inspection

• Walls and Partitions: Inspect the internal walls and partitions for signs of cracking, damp, or other damage. Check the condition of the brick spine wall and any other partitions.
• Floors: Examine the ground and first floors for signs of damage or wear. Check for any uneven surfaces, cracks, or signs of moisture ingress.
• Ceilings: Inspect the ceilings for any signs of cracking, staining, or other damage. Ensure that the plaster is in good condition and free from any signs of damp or mould.
• Windows and Doors: Check the condition of the windows and doors, including the frames and seals. Look for any signs of damage, wear, or moisture ingress.

Special Considerations

• Reinforced Concrete Durability: Given the potential for corrosion of the steel reinforcement in the concrete elements, it is essential to assess the durability of the reinforced concrete. Guidance on this can be found in documents such as “Corrosion of steel in concrete” (BRE Digest 444, Pts 1–3), “Repair and maintenance of reinforced concrete” (BR 254), and “Carbonation depths in structural-quality concrete” (BR 19).
• Thermal Efficiency: Assess the thermal efficiency of the property, including the insulation levels in the walls, floors, and roof. Consider the potential costs of upgrading the insulation to meet modern standards.
• Damp and Moisture Ingress: Pay particular attention to any signs of damp or moisture ingress, both internally and externally. Check the condition of the damp-proof course (DPC) and consider the potential costs of remedial work if necessary.

Typical Defects and Maintenance

Common Defects

• Concrete Spalling: As mentioned earlier, spalling of the concrete elements can be a common issue in Costain houses. This occurs when the steel reinforcement corrodes, causing the concrete to break away and expose the steel.
• Damp and Moisture Ingress: Due to the age of these properties, damp and moisture ingress can be a common issue. This can lead to problems such as mould growth, wood rot, and damage to internal finishes.
• Thermal Efficiency: Costain houses may not meet modern standards for thermal efficiency, leading to higher energy costs and a less comfortable living environment.
• Structural Movement: Over time, the foundations and walls of Costain houses may experience movement or settlement, leading to cracks and other structural issues.

Maintenance Tips

• Regular Inspections: Conduct regular inspections of the property to identify and address any issues early. This includes checking the condition of the roof, walls, floors, and foundations.
• Damp Proofing: Ensure that the damp-proof course (DPC) is in good condition and consider upgrading it if necessary. Address any signs of damp or moisture ingress promptly to prevent further damage.
• Concrete Repairs: If spalling or other damage to the concrete elements is identified, carry out repairs promptly to prevent further deterioration. This may involve removing the damaged concrete, treating the steel reinforcement, and applying a suitable repair mortar.
• Insulation Upgrades: Consider upgrading the insulation in the walls, floors, and roof to improve the thermal efficiency of the property. This can help to reduce energy costs and create a more comfortable living environment.

Conclusion

The Costain house represents a significant chapter in the history of British housing, reflecting the post-war need for rapid and efficient construction methods. While these properties have stood the test of time, they do come with their own set of challenges and considerations. Understanding the typical characteristics, potential hazards, and common defects of Costain houses is essential for any home buyer or investor.

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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