When considering a property purchase in the UK, understanding the intricacies of different property types is crucial. One such property type that often piques the interest of home buyers and investors is the Cranwell house. Built in the post-war era, these houses have unique characteristics and potential risks that need careful consideration. As an expert surveyor with extensive knowledge of system-built properties, I will provide a detailed overview of Cranwell houses, including their construction, typical defects, and inspection tips.

Historical Context and Manufacturers

Cranwell houses were constructed between 1945 and 1948, a period marked by a significant housing shortage in the UK. The need for rapid and cost-effective housing solutions led to the development of various system-built properties, including the Cranwell house. Approximately 600 Cranwell houses were built during this period, primarily in suburban areas.

The construction of Cranwell houses was undertaken by several manufacturers, including Cranwell Construction Co., Cranwell Syndicate Ltd, and Mid-Kent Builders Ltd. These companies were responsible for the design and assembly of these properties, which were intended to provide affordable and durable housing for the growing population.

Identification Characteristics

Cranwell houses are typically two-storey semi-detached or terraced houses. They can be identified by several distinctive features:

• Roof: Medium pitch hipped or gable roof covered with interlocking concrete tiles or profiled asbestos cement sheets.
• External Walls: Rendered throughout, with the gable apex clad with tile hanging or profiled asbestos cement sheets.
• Door and Window Surrounds: Made of Precast Reinforced Concrete (PRC).
• Terraced Houses: Often have a passageway (ginnel) providing access to the rear garden.

These characteristics make Cranwell houses relatively easy to identify, even for those with limited experience in property inspection.

Construction Details

Understanding the construction details of Cranwell houses is essential for identifying potential defects and assessing the overall condition of the property. The construction of Cranwell houses can be broken down into several key components:

Substructure

The substructure of Cranwell houses consists of concrete trench fill incorporating a ground floor slab. A Damp Proof Course (DPC) is also included to prevent moisture from rising through the structure.

Frame

The frame of Cranwell houses is a critical component, providing structural support and stability. It includes:

• Setting Out Jig: Positioned around the perimeter.
• Stanchions: Four double RSA corner stanchions, 28 RSJ intermediate stanchions, one single-storey RS stanchion, and one RS floor support beam.
• Perimeter Ties: Eight RSA perimeter ties.
• Roof Trusses: One RSA roof truss, two RSA mock roof trusses, six RSA purlins, and two RST ceiling supports.
• Separating Wall Frames: Connected across the cavity with steel straps.

The frame is typically coated with red oxide, red lead, or black bituminous paint for protection.

External Walls

The external walls of Cranwell houses are constructed using rendered hollow clay blocks, with a cavity and wood wool slabs for insulation. The gable apex is clad with tile hanging or profiled asbestos cement sheets.

Partitions

Internal partitions are made of block, providing robust separation between rooms.

Floors

• Ground Floor: Concrete.
• First Floor: Tongue and Groove (T&G) boarding on timber joists.

Ceilings

Ceilings are typically made of fibreboard, providing a lightweight and cost-effective solution.

Roof

The roof structure includes timber rafters, bituminous felt, and interlocking concrete tiles. Some variants may have profiled asbestos cement sheet roof cover and cladding to the gable apex.

Typical Defects and Hazards

While Cranwell houses were designed to be durable and cost-effective, they are not without their potential defects and hazards. Understanding these issues is crucial for anyone considering purchasing or investing in a Cranwell house.

Corrosion

• RSJ Stanchions: Minor corrosion, particularly at the bases, is common.
• Setting Out Jig: Moderate corrosion can occur over time.
• PRC Door and Window Surrounds: Carbonation can lead to corrosion of the reinforcement.

Cracking

• Render and Plaster Linings: Fine vertical cracks are often found at stanchion locations.
• Magnesite Floor Screed: Cracking and lifting can occur, leading to uneven floors.

Shrinking and Bulging

• First Floor Joists: Shrinking can cause bulging of the floor boarding over RSJ floor support beams.

Asbestos

• Roof and Cladding: Some Cranwell houses have profiled asbestos cement sheets, which pose a health risk if disturbed.

Carbonation

Carbonation of PRC door and window surrounds can lead to corrosion of the reinforcement, compromising the structural integrity of these elements.

Defective Premises Act

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. Cranwell houses, like many other system-built properties from the post-war era, may be classed as defective under this act if they exhibit significant structural issues or fail to meet modern safety standards.

Inspection Tips for Cranwell Houses

When inspecting a Cranwell house, it is essential to be thorough and methodical. Here are some key areas to focus on:

External Inspection

• Roof: Check for missing or damaged tiles, and inspect the condition of any asbestos cement sheets.
• Walls: Look for cracks in the render and signs of corrosion around PRC door and window surrounds.
• Gable Apex: Inspect the cladding for damage or deterioration.

Internal Inspection

• Floors: Check for signs of cracking or lifting in the magnesite floor screed, and look for bulging of the floor boarding over RSJ floor support beams.
• Walls and Ceilings: Look for fine vertical cracks in the plaster linings at stanchion locations.
• Joists: Inspect the first-floor joists for signs of shrinking or other damage.

Structural Elements

• Stanchions: Check for corrosion, particularly at the bases of RSJ stanchions.
• Setting Out Jig: Inspect for moderate corrosion.
• PRC Surrounds: Look for signs of carbonation and corrosion of the reinforcement.

Asbestos

If the property has asbestos cement sheets, it is crucial to have these inspected by a qualified professional. Asbestos poses a significant health risk if disturbed, so proper handling and removal are essential.

Maintenance and Repair Considerations

Maintaining and repairing Cranwell houses requires a good understanding of their unique construction and potential defects. Here are some key considerations:

Corrosion Treatment

• RSJ Stanchions and Setting Out Jig: Treat any corrosion with appropriate rust inhibitors and protective coatings.
• PRC Surrounds: Address carbonation and corrosion issues by repairing or replacing affected elements.

Crack Repair

• Render and Plaster Linings: Repair fine vertical cracks with suitable fillers and ensure that the underlying cause is addressed.
• Magnesite Floor Screed: Repair or replace damaged sections to ensure a level and stable floor.

Structural Reinforcement

• First Floor Joists: Reinforce or replace joists that have shrunk or become damaged.
• RSJ Floor Support Beams: Ensure that any bulging floor boarding is addressed by reinforcing the underlying support beams.

Asbestos Management

• Inspection and Removal: Have any asbestos cement sheets inspected by a qualified professional and removed if necessary.
• Safe Handling: Ensure that any asbestos removal is carried out safely and in accordance with regulations.

Conclusion

Cranwell houses, with their unique construction and post-war heritage, offer a fascinating glimpse into the history of UK housing. However, they also come with potential risks and defects that require careful consideration. By understanding the construction details, typical defects, and inspection tips outlined in this guide, home buyers and investors can make informed decisions when considering a Cranwell 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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