Understanding the Calverley Type I House

The Calverley Type I house, also known as the Calverley Modular or CM, is a distinctive property type that emerged during the late 1960s and early 1970s. Designed by J L Heap and manufactured by Calverley Ltd, these homes were part of a broader movement towards system-built properties in the UK. With approximately 300 units constructed between 1966 and 1972, these houses are primarily found in urban and suburban areas, offering a unique architectural style that reflects the era’s innovative building techniques.

Historical Context and Manufacturing Details

The Calverley Type I house was developed during a period when the UK faced a significant housing shortage. The government and private developers sought efficient and cost-effective solutions to meet the growing demand for homes. System-built properties, like the Calverley Type I, were designed to be quickly assembled using prefabricated components, reducing construction time and costs.

Calverley Ltd, the manufacturer, was at the forefront of this movement, producing homes that were both modern and functional. The design by J L Heap incorporated modular elements, allowing for flexibility in layout and construction. These homes were marketed under various names, including Calverley Modular, CM Yuill, and CMX, reflecting their adaptability and appeal to different markets.

Architectural Characteristics and Design Features

The Calverley Type I house is a two-storey terraced property, characterized by its flat roof covered with bituminous felt. The front and rear external walls feature a combination of vertical timber boarding and asbestos cement tiles, creating a distinctive façade. The ground floor is clad with vertical timber boarding up to the window head level, while the first floor is adorned with asbestos cement tiles up to the eaves level between windows. Horizontal timber boarding is used above the windows, adding to the property’s unique aesthetic.

The flank wall is constructed entirely of brick, providing structural stability and a contrasting visual element. Inside, the homes are designed with a platform frame construction, utilizing storey-height timber frame panels sheathed externally with plywood. This method of construction was innovative for its time, offering both durability and ease of assembly.

Potential Hazards and Risks

While the Calverley Type I house offers many appealing features, potential buyers and investors should be aware of certain hazards and risks associated with this property type. One of the primary concerns is the use of asbestos cement tiles, which can pose health risks if disturbed. Asbestos was commonly used in construction during the mid-20th century due to its fire-resistant properties, but it has since been identified as a hazardous material.

Additionally, the construction methods used in these homes can lead to issues such as interstitial condensation, which occurs when moisture becomes trapped within the walls. This can result in dampness, mould growth, and structural damage if not properly addressed. The narrow cavities between the brickwork and timber frame panels, along with inadequate fixings, can also contribute to these problems.

Defective Premises Act and Legal Considerations

The Calverley Type I house is not classified as defective under the Defective Premises Act. However, potential buyers should still conduct thorough inspections to identify any issues that may require attention. Engaging a qualified surveyor is essential to ensure that the property meets current safety and building standards.

Inspection Tips for Calverley Type I Houses

When inspecting a Calverley Type I house, there are several key areas to focus on to ensure the property’s condition and safety:

1. Roof and Ceiling: Check the flat roof for signs of wear or damage to the bituminous felt. Inspect the ceilings for any signs of water ingress or staining, which could indicate roof leaks.

2. External Walls: Examine the vertical timber boarding and asbestos cement tiles for any signs of deterioration or damage. Pay particular attention to the fixings and joints, as these can be prone to failure.

3. Brickwork and Foundations: Inspect the brick flank wall for any signs of cracking or movement. Check for overhanging brickwork on the foundations, which can indicate structural issues.

4. Internal Walls and Partitions: Look for signs of dampness or mould on the plasterboard linings, particularly in areas with foil-backing. Check the timber frame panels for any signs of rot or decay.

5. Floors and Joists: Inspect the concrete ground floor and chipboard first floor for any signs of movement or damage. Ensure that the timber joists are securely fixed and free from rot.

6. Insulation and Ventilation: Check the insulation between the frame studs for any signs of moisture or damage. Ensure that the property has adequate ventilation to prevent condensation and dampness.

Construction Details and Variants

The Calverley Type I house features a concrete slab foundation with a damp-proof course (DPC) to prevent moisture ingress. The external walls are constructed using a platform frame method, with timber frame panels sheathed in plywood. The front and rear walls are clad with vertical timber boarding and asbestos cement tiles, while the flank wall is clad with brick.

The separating wall between properties is a timber frame cavity backed with plywood and lined with plasterboard, with a 4 1/2″ block core in the cavity. Internal partitions are constructed using timber studs lined with plasterboard.

The ground floor is made of concrete, while the first floor consists of chipboard on timber joists. Ceilings are lined with foil-backed plasterboard, with additional plasterboard in the roof space. The roof is constructed using timber rafters, chipboard decking, fibreboard, and bituminous roofing felt.

Some variants of the Calverley Type I house include concrete edge beams around the perimeter of the foundations, providing additional structural support.

Common Defects and Maintenance Considerations

Owners of Calverley Type I houses should be aware of common defects that may arise over time. These include:

• Corrosion of Foil-Backing: The foil-backing on plasterboard linings can corrode over time, leading to reduced effectiveness and potential moisture ingress.

• Interstitial Condensation: As mentioned earlier, interstitial condensation can occur within the walls, leading to dampness and mould growth. Ensuring proper ventilation and addressing any moisture ingress is crucial.

• Timber Joist Fixings: The fixings between timber joists and metal joist hangers can become inadequate over time, leading to structural issues. Regular inspections and maintenance are essential to ensure stability.

• Asbestos Management: Given the presence of asbestos cement tiles, it is important to manage and monitor these materials to prevent health risks. Professional removal or encapsulation may be necessary if the tiles are damaged or deteriorating.

Conclusion

The Calverley Type I house represents a unique chapter in the history of UK housing, offering a blend of modern design and innovative construction techniques. While these homes have their challenges, they also provide an opportunity for buyers and investors to own a piece of architectural history. By understanding the potential risks and conducting thorough inspections, you can ensure that your investment in a Calverley Type I house is both safe and rewarding.

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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