Introduction to the BDG House

The BDG house, also known as the BDG Wessex or simply Wessex, is a unique property type that emerged in the mid-1960s. Designed by the Research Architect of the Basingstoke Development Group, this property type is a testament to the innovative construction methods of its time. With only 20 units built in 1965, these houses are a rare find in the UK property market. This article aims to provide a detailed overview of the BDG house, covering its construction, typical characteristics, potential hazards, and inspection tips for prospective buyers and investors.

Historical Context and Manufacturer Background

The BDG house was manufactured by the Basingstoke Development Group, a company known for its pioneering efforts in system-built properties during the 1960s. The design was the brainchild of the Research Architect at BDG, who sought to create a cost-effective and efficient housing solution. The BDG house was part of a broader movement towards prefabricated and system-built homes, which aimed to address the post-war housing shortage in the UK.

Typical Characteristics of the BDG House

Architectural Features

BDG houses are typically two-storey semi-detached or terraced homes. They are easily identifiable by their shallow pitch gable roofs covered with concrete tiles. The front and rear external walls feature mathematical tiling up to the first-floor level, with tile hanging or horizontal timber boarding above. The gable walls are constructed from storey-height textured finish precast concrete (PC) panels, with an exposed PC panel pier at the separating wall.

Construction Details

Substructure

• PC Ground Beams: The substructure consists of precast concrete ground beams, providing a stable foundation for the house.
• Concrete Slab: The ground floor is a concrete slab, offering durability and resistance to moisture.

External Walls

• Timber Frame Panels: The front and rear walls are made of storey-height timber frame panels, overlaid with a breather membrane and clad with mathematical tiles up to the first-floor level.
• Tile Hanging and Timber Boarding: Above the first-floor level, the walls are clad with tile hanging on timber battens or horizontal timber boarding.
• Plasterboard Lining: The internal side of the walls is lined with plasterboard backed with a polyethylene vapour control layer.
• Insulation: Insulation is placed between the frame studs to enhance thermal efficiency.

Gable Walls

• Textured Finish PC Panels: The gable walls are constructed from 7-inch storey-height textured finish PC panels, providing structural integrity and aesthetic appeal.

Separating Walls

• PC Panels: The separating walls between houses are made of 7-inch storey-height PC panels, ensuring sound insulation and fire resistance.

Partitions

• Timber Studs: Internal partitions are constructed from timber studs lined with plasterboard.

Floors

• Ground Floor: The ground floor is a concrete slab, offering robustness and stability.
• First Floor: The first floor consists of tongue-and-groove (T&G) boarding on timber joists, providing a solid and level surface.

Ceilings

• Plasterboard: Ceilings are lined with plasterboard, offering a smooth finish and ease of maintenance.

Roof

• Timber Trussed Rafters: The roof structure is made of timber trussed rafters, supporting the concrete tiles.
• Concrete Tiles: The roof is covered with concrete tiles, providing durability and weather resistance.

Potential Hazards and Risks

Structural Issues

One of the primary concerns with BDG houses is the potential for structural issues, particularly related to the precast concrete elements. Over time, these components can suffer from degradation, leading to cracks and other structural problems. It is essential to inspect the condition of the PC panels and ground beams regularly.

Corrosion of Steel Reinforcement

The steel reinforcement within the concrete elements can corrode over time, especially if the concrete has been exposed to moisture. This can compromise the structural integrity of the house. Guidance on inspecting and assessing the durability of reinforced concrete can be found in the following resources:

• Corrosion of Steel in Concrete (BRE Digest 444, Parts 1–3)
• Repair and Maintenance of Reinforced Concrete (BR 254)
• Carbonation Depths in Structural-Quality Concrete (BR 19)

Thermal Efficiency

While the BDG house was designed with insulation between the frame studs, the overall thermal efficiency may not meet modern standards. Upgrading the insulation and installing energy-efficient windows and doors can help improve the property’s energy performance.

Moisture Ingress

The concrete slab and PC panels can be susceptible to moisture ingress, leading to dampness and mould growth. It is crucial to ensure that the property has adequate damp-proofing measures in place and to address any signs of moisture promptly.

Defective Premises Act Considerations

The BDG house is not classified as defective under the Defective Premises Act. However, given its age and construction method, it is essential to conduct thorough inspections to identify any potential issues that may require remedial work.

Inspection Tips for BDG Houses

External Inspection

• Roof: Check the condition of the concrete tiles and timber trussed rafters. Look for signs of wear, damage, or missing tiles.
• Walls: Inspect the mathematical tiling, tile hanging, and timber boarding for any signs of damage or deterioration. Pay particular attention to the PC panels for cracks or signs of corrosion.
• Gable Walls: Examine the textured finish PC panels for any structural issues or signs of weathering.

Internal Inspection

• Walls: Check the plasterboard lining for any signs of dampness, mould, or damage. Ensure that the insulation between the frame studs is intact and effective.
• Floors: Inspect the concrete slab and T&G boarding for any signs of wear, damage, or moisture ingress.
• Ceilings: Look for any cracks or signs of water damage in the plasterboard ceilings.
• Partitions: Ensure that the timber stud partitions are in good condition and free from damage.

Structural Elements

• PC Ground Beams: Check for any signs of cracking or movement in the ground beams.
• Steel Reinforcement: Look for signs of corrosion in the steel reinforcement within the concrete elements. This may require specialist equipment and expertise.

Typical Defects in BDG Houses

Concrete Degradation

Over time, the concrete elements of BDG houses can degrade, leading to cracks and structural issues. Regular inspections and maintenance are essential to address any signs of degradation promptly.

Corrosion of Steel Reinforcement

As mentioned earlier, the steel reinforcement within the concrete can corrode, compromising the structural integrity of the house. It is crucial to monitor the condition of the steel reinforcement and address any signs of corrosion.

Thermal Bridging

The design of BDG houses can lead to thermal bridging, where heat is lost through the building’s structure. Upgrading the insulation and addressing any gaps in the thermal envelope can help improve energy efficiency.

Moisture Ingress and Dampness

Moisture ingress can lead to dampness and mould growth, particularly in the concrete slab and PC panels. Ensuring adequate damp-proofing measures and addressing any signs of moisture promptly is essential.

Timber Decay

The timber elements of BDG houses, such as the trussed rafters and timber boarding, can be susceptible to decay if exposed to moisture. Regular inspections and maintenance are necessary to prevent timber decay and ensure the longevity of the property.

Conclusion

The BDG house is a unique and historically significant property type that offers both opportunities and challenges for home buyers and investors. Understanding the construction details, potential hazards, and typical defects associated with these houses is essential for making informed decisions. Regular inspections and maintenance are crucial to preserving the structural integrity and value of BDG houses.

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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