Historical Context and Manufacturing Details

The Corolite house, a notable example of early 20th-century system-built properties, was manufactured by Corolite Construction Co. Ltd. These homes were designed and constructed between 1923 and 1927, a period marked by a significant housing shortage in the UK. The Corolite house, also known as the “No-Fines” house, was part of an innovative approach to quickly and efficiently provide housing. Approximately 700 of these properties were built, primarily as two-storey terraced houses.

Design and Construction Characteristics

External Features

Corolite houses are easily identifiable by their medium pitch hipped roofs, which are typically covered with concrete tiles or slates. Some variants feature flat roofs covered with bitumen. The external walls of these homes are rendered throughout, giving them a distinctive appearance. The use of clinker aggregate no-fines concrete in the construction of these walls is a hallmark of the Corolite design.

Internal Structure

The internal structure of Corolite houses is equally distinctive. The substructure consists of clinker aggregate concrete strip footings and pads. The external walls are made of 8-inch clinker aggregate no-fines concrete, reinforced over windows and door openings. The separating walls between properties are also constructed from 8-inch clinker aggregate no-fines concrete.

Floors and Ceilings

The ground floor typically features timber boarding on timber joists, supported by timber bearers on clinker aggregate concrete pads. The first floor is constructed with timber boarding on timber battens, laid over a 6.5-inch clinker aggregate reinforced concrete slab. Some variants of the Corolite house have a first floor made of 3-inch clinker aggregate reinforced concrete slabs. Unfortunately, detailed information about the ceilings is not well-documented.

Roof Structure

The roof structure of Corolite houses consists of timber rafters covered with concrete tiles. In some variants, the roof is covered with slates or features a flat roof made of clinker aggregate reinforced concrete slab and bitumen.

Typical Hazards and Risks

Unstable Aggregate

One of the primary concerns with Corolite houses is the potential presence of unstable fractions of unburnt coal in the aggregate. This can lead to various structural issues over time, including cracking and shrinkage of the clinker aggregate no-fines reinforced concrete (RC) external walls.

Corrosion and Deflection

Corrosion of reinforcement in the clinker aggregate no-fines RC external walls and first floor slabs is another significant risk. This can lead to gross deflection of the first floor slabs, compromising the structural integrity of the property.

Defective Premises Act

Corolite houses are not specifically classed as defective under the Defective Premises Act. However, the aforementioned risks and hazards can lead to significant structural issues that may require extensive repairs. It is crucial for potential buyers and investors to be aware of these risks and to conduct thorough inspections before purchasing a Corolite house.

Inspection Guide for Surveyors

Identifying Characteristics

When inspecting a Corolite house, surveyors should look for the following identifying characteristics:
– Two-storey terraced house design
– Medium pitch hipped roof covered with concrete tiles or slates, or flat roof covered with bitumen
– Rendered external walls

Key Areas to Inspect

External Walls

Inspect the external walls for signs of cracking and shrinkage. Pay particular attention to areas around windows and door openings, where reinforcement may have corroded. Look for any signs of deflection or movement in the walls, which could indicate structural issues.

Floors

Examine the ground floor for signs of instability or movement. Check the timber boarding and joists for any signs of rot or damage. On the first floor, look for signs of deflection in the clinker aggregate reinforced concrete slab. Any noticeable sagging or movement could indicate significant structural issues.

Roof

Inspect the roof structure for signs of damage or wear. Check the condition of the timber rafters and the concrete tiles or slates. If the property has a flat roof, examine the bitumen covering for any signs of deterioration or leaks.

Internal Walls and Partitions

Check the internal walls and partitions for signs of cracking or movement. Pay particular attention to the separating walls between properties, as any issues here could affect multiple homes.

Typical Defects in Corolite Houses

Cracking and Shrinkage

Cracking and shrinkage of the clinker aggregate no-fines RC external walls are common defects in Corolite houses. These issues can be exacerbated by the presence of unstable fractions of unburnt coal in the aggregate.

Corrosion of Reinforcement

Corrosion of the reinforcement in the clinker aggregate no-fines RC external walls and first floor slabs is another typical defect. This can lead to significant structural issues, including gross deflection of the first floor slabs.

Deflection of First Floor Slabs

Gross deflection of the clinker aggregate RC first floor slabs is a common issue in Corolite houses. This can compromise the structural integrity of the property and may require extensive repairs.

Maintenance and Repair Considerations

Addressing Cracking and Shrinkage

To address cracking and shrinkage in the external walls, it is essential to identify and remove any unstable fractions of unburnt coal in the aggregate. This may involve extensive repairs to the affected areas, including the replacement of damaged sections of the walls.

Preventing Corrosion

Preventing corrosion of the reinforcement in the external walls and first floor slabs is crucial for maintaining the structural integrity of a Corolite house. This may involve applying protective coatings to the reinforcement and ensuring that the concrete is adequately sealed to prevent moisture ingress.

Repairing Deflected Slabs

Repairing deflected first floor slabs may require the installation of additional support structures or the replacement of the affected slabs. This can be a complex and costly process, so it is essential to thoroughly inspect the property before purchasing to identify any potential issues.

Conclusion

The Corolite house represents an important chapter in the history of UK housing. While these properties offer unique architectural features and historical significance, they also come with a range of potential risks and hazards. By understanding the typical characteristics, defects, and maintenance considerations associated with Corolite houses, home buyers and investors can make informed decisions and ensure the long-term stability and safety of their investment.

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.