Understanding the Calder House

The Calder House, a distinctive type of system-built property, holds a unique place in the UK’s architectural history. Constructed between 1964 and 1967, these homes were the brainchild of Calders Ltd, with designs crafted by the Harding and Horsman Architects Design Group. With only 600 units built, Calder Homes are a rare find, often located in suburban areas across the UK. Known for their innovative design and construction techniques, these properties offer both opportunities and challenges for potential buyers and investors.

Historical Context and Manufacturing Details

Calders Ltd, a prominent name in the construction industry during the mid-20th century, spearheaded the development of Calder Homes. The period of 1964 to 1967 was marked by a housing boom in the UK, driven by the need for affordable and quickly constructed homes. The Calder House emerged as a solution, utilizing system-built techniques that allowed for rapid assembly and cost-effective production.

The design of these homes was a collaborative effort with the Harding and Horsman Architects Design Group, who were known for their innovative approach to residential architecture. The result was a series of bungalows and two-storey semi-detached and terraced houses, each with a unique aesthetic and functional design.

Key Characteristics of Calder Homes

Calder Homes are easily identifiable by their architectural features. They typically feature shallow pitch gable, monopitch, or flat roofs covered with bituminous felt. The external walls are constructed from storey-height asbestos cement sheets, with inset painted asbestos cement boards below the windows. Horizontal bands of timber boarding are present at various levels, adding to the distinctive look of these homes.

The front doors are often flanked by horizontal timber boarding, and a valley gutter is a common feature between dwellings. These design elements not only contribute to the visual appeal of Calder Homes but also play a role in their structural integrity.

Potential Hazards and Risks

While Calder Homes offer unique architectural features, they also come with certain risks and hazards that potential buyers should be aware of. One of the primary concerns is the use of asbestos cement in the construction of external walls and boards. Asbestos, a material commonly used in the mid-20th century, is now known for its health risks, particularly when disturbed or damaged.

Additionally, the bituminous felt used in roofing can be prone to splitting, leading to potential water ingress and damage. Leaking valley gutters are another common issue, which can result in water damage to the structure if not addressed promptly.

Defective Premises Act Considerations

When considering the purchase of a Calder House, it’s important to understand its classification under the Defective Premises Act. This legislation, enacted to protect homeowners from substandard construction, may apply to Calder Homes due to their use of asbestos and other materials now considered hazardous.

While not all Calder Homes are automatically classified as defective, it’s crucial for buyers to conduct thorough inspections and assessments to determine the condition of the property. Engaging a professional surveyor with experience in system-built homes can provide valuable insights and help identify any potential issues.

Inspection Tips for Calder Homes

Inspecting a Calder House requires a keen eye and attention to detail. Here are some key areas to focus on during an inspection:

1. Roofing: Check for signs of splitting in the bituminous felt roof cover. Look for any evidence of water ingress or damage, particularly around the valley gutters.

2. External Walls: Examine the asbestos cement sheets for any signs of damage or deterioration. Pay close attention to the boards below windows, as these are often more susceptible to wear.

3. Internal Linings: Inspect the plasterboard linings for any signs of corrosion in the foil-backing. This can indicate moisture issues within the property.

4. Structural Integrity: Assess the overall structural integrity of the timber frame units. Look for any signs of movement or instability, particularly in the separating and partition walls.

5. Insulation: Check the condition of the polystyrene insulation between frame studs and joists. Ensure it is intact and providing adequate thermal performance.

Construction Details of Calder Homes

Understanding the construction details of Calder Homes can provide valuable insights into their strengths and potential weaknesses. Here’s a breakdown of the typical construction elements:

• Substructure: Calder Homes are built on concrete strip footings with vented masonry underbuilding. A damp-proof course (DPC) is included to prevent moisture ingress.

• External Walls: The volumetric box construction features storey-height timber frame units sheathed externally with asbestos cement sheets. These are directly clad with additional asbestos cement sheets, providing a robust yet lightweight structure.

• Separating Walls: Timber frame cavity walls are lined with three layers of plasterboard, with mineral fibre insulation in the cavity. This construction provides sound insulation and fire resistance.

• Partition Walls: Timber stud construction is used for partition walls, lined with plasterboard throughout. This allows for flexibility in interior layout and design.

• Floors: The ground floor consists of plywood on timber joists, with polystyrene insulation between joists. The first floor features plywood on double timber joists, providing strength and stability.

• Ceilings: Plasterboard ceilings are used throughout, with foil-backed plasterboard conforming to the pitch in roof spaces.

• Roof: Timber rafters support a plywood decking, covered with bituminous felt. This construction provides a lightweight yet durable roofing solution.

Common Defects in Calder Homes

Despite their innovative design, Calder Homes are not without their defects. Here are some common issues to be aware of:

• Roofing Issues: As mentioned earlier, splitting of the bituminous felt roof cover is a common problem. Regular maintenance and timely repairs can help mitigate this issue.

• Gutter Leaks: Leaking valley gutters can lead to water damage if not addressed promptly. Regular inspections and cleaning can help prevent blockages and leaks.

• Corrosion: The foil-backing on plasterboard linings can corrode over time, particularly in areas with high moisture levels. This can compromise the integrity of the internal linings and should be addressed promptly.

• Asbestos Concerns: The use of asbestos cement in construction poses health risks if disturbed. It’s important to engage professionals for any repairs or renovations involving asbestos materials.

Variants of Calder Homes

While the standard Calder House design is well-documented, there are variants that potential buyers should be aware of. Some Calder Homes feature flat roofs instead of the more common shallow pitch gable or monopitch designs. These variants may have different maintenance requirements and potential issues, so it’s important to conduct thorough inspections and assessments.

Final Thoughts

Calder Homes represent a unique chapter in the UK’s architectural history. Their innovative design and construction techniques offer both opportunities and challenges for home buyers and investors. By understanding the key characteristics, potential hazards, and common defects of Calder Homes, you can make informed decisions and ensure a successful property purchase.

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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