Overview of the Cosmos House

The Cosmos house, a product of the 1970s, stands as a testament to the era’s innovative approach to system-built properties. Designed by C. Davidson and manufactured by a consortium of selected manufacturers under the Open Systems initiative, the Cosmos house was a popular choice for residential developments. With 160 units built, these properties are typically found in suburban areas across the UK, offering a mix of bungalows and 2- and 3-storey houses.

Identifying Characteristics

Architectural Features

Cosmos houses are easily identifiable by their medium pitch gable roofs or flat roofs covered with bituminous felt. The external walls are constructed from storey-height exposed aggregate Precast Reinforced Concrete (PRC) panels, giving them a distinctive appearance. Aluminium sliding windows with top-hung night lights are another hallmark of these properties.

Structural Components

The construction of Cosmos houses involves several key elements:
– Substructure: Concrete footings and Precast Concrete (PC) ground beams with Damp Proof Course (DPC).
– External Walls: Storey-height PRC panels, bolted together to form a cavity wall system.
– Internal Walls: Storey-height PRC panel cavity walls for separating walls, and hardboard-faced sandwich panels for partitions.
– Floors: Concrete ground floors and plywood first floors on timber joists.
– Ceilings: Plasterboard ceilings.
– Roof: Plywood on timber joists covered with bituminous felt.
– Services: Storey-height ‘cupboard’ sub-assemblies containing water and waste connections, typically three per dwelling.

Typical Characteristics and Hazards

Structural Integrity

One of the primary concerns with Cosmos houses is the structural integrity of the PRC wall panels. These panels often contain significant levels of chloride, leading to high rates of carbonation. This can compromise the structural adequacy of the ground floor front and rear PRC wall panels, which do not comply with current standards.

Fire Protection

Another critical issue is the insufficient fire protection in these properties. The materials used in the construction, particularly the PRC panels, do not provide adequate fire resistance, posing a significant risk to occupants.

Asbestos

Asbestos is commonly found in the separating walls of Cosmos houses. This hazardous material, if disturbed, can release fibres into the air, posing severe health risks. Proper asbestos management and removal are essential when dealing with these properties.

Corrosion and Spalling

The cast-in sockets in the wall panels are prone to corrosion, leading to spalling of the concrete ribs. This not only affects the aesthetic appeal of the property but also its structural stability.

Inadequate Fixings

The first floor and roof timber panels are often inadequately seated and fixed to the PRC ring beams. Additionally, the trimmer beam adjacent to the staircase is typically undersized and overstressed, further compromising the structural integrity.

Lateral Restraint

There is often inadequate lateral restraint to the front wall at the first-floor level adjacent to the staircase. This can lead to movement and potential structural failure over time.

Defective Premises Act

Cosmos houses are classified as defective under the Defective Premises Act. This classification means that these properties do not meet the required standards for safety and habitability. Buyers and investors should be aware of this designation and the potential implications for insurance, financing, and resale value.

Inspection Guide for Surveyors

When inspecting a Cosmos house, surveyors should pay close attention to the following areas:

PRC Wall Panels

• Chloride Levels: Test for significant levels of chloride in the PRC wall panels.
• Carbonation: Assess the rate of carbonation in the panels.
• Corrosion: Check for corrosion of cast-in sockets and spalling of concrete ribs.

Structural Fixings

• First Floor and Roof Panels: Ensure that the timber panels are adequately seated and fixed to the PRC ring beams.
• Trimmer Beam: Inspect the trimmer beam adjacent to the staircase for signs of stress and undersizing.
• Lateral Restraint: Verify the adequacy of lateral restraint to the front wall at the first-floor level.

Fire Protection

• Materials: Evaluate the fire resistance of the materials used in the construction.
• Compliance: Ensure that the property meets current fire safety standards.

Asbestos

• Presence: Identify the presence of asbestos in the separating walls.
• Management: Recommend proper asbestos management and removal procedures.

Typical Construction Details

Roof

The roof of a Cosmos house is typically constructed from plywood on timber joists, covered with bituminous felt. This design provides a lightweight and cost-effective roofing solution but may require regular maintenance to prevent leaks and water damage.

Walls

The external walls are made from storey-height PRC panels, bolted together to form a cavity wall system. These panels provide good thermal insulation but are prone to structural issues due to chloride contamination and carbonation.

Floors

The ground floor is usually concrete, providing a solid and durable base. The first floor is constructed from plywood on timber joists, which can be susceptible to movement and deflection if not properly supported.

Main Frame

The main frame of a Cosmos house consists of PRC ring beams at the ground floor window head and roof level. These beams provide structural support but may require reinforcement to meet current standards.

Typical Defects

Chloride Contamination

High levels of chloride in the PRC wall panels can lead to accelerated corrosion of the steel reinforcement, compromising the structural integrity of the property.

Carbonation

Carbonation of the PRC panels can reduce the alkalinity of the concrete, leading to corrosion of the steel reinforcement and spalling of the concrete surface.

Inadequate Fixings

The first floor and roof timber panels are often inadequately seated and fixed to the PRC ring beams, leading to movement and potential structural failure.

Undersized Trimmer Beam

The trimmer beam adjacent to the staircase is typically undersized and overstressed, posing a risk of structural failure.

Inadequate Lateral Restraint

There is often inadequate lateral restraint to the front wall at the first-floor level adjacent to the staircase, leading to potential movement and structural issues.

Corrosion and Spalling

Corrosion of the cast-in sockets in the wall panels can lead to spalling of the concrete ribs, affecting both the aesthetic appeal and structural stability of the property.

Insufficient Fire Protection

The materials used in the construction of Cosmos houses do not provide adequate fire resistance, posing a significant risk to occupants.

Asbestos

Asbestos is commonly found in the separating walls of Cosmos houses, posing severe health risks if disturbed.

Variants

Some variants of the Cosmos house feature lightweight cladding panels for the external walls and timber trusses for the roof. These variants may have different structural characteristics and potential defects compared to the standard design.

Conclusion

The Cosmos house, with its distinctive architectural features and innovative construction methods, represents a significant chapter in the history of system-built properties in the UK. However, these properties come with a range of potential hazards and defects that buyers and investors need to be aware of. From structural issues related to chloride contamination and carbonation to the presence of asbestos and inadequate fire protection, there are several critical factors to consider when purchasing a Cosmos house.

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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