Unit System 67 Houses: A Comprehensive Guide for Home Buyers and Investors

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Understanding the Unit System 67 House

The Unit System 67 house, a product of the post-war housing boom, represents a unique chapter in the history of British architecture. Developed by Unit Construction Co. Ltd, these homes were built between 1967 and 1971, with approximately 700 units constructed. Known by various names such as Cawl, Unit, Unit Construction, and Unit System, these properties are predominantly found in suburban areas across the UK. As an expert surveyor, I will guide you through the intricacies of these homes, from their construction to potential hazards, ensuring you are well-informed before making a purchase.

Historical Context and Manufacturing

The Unit System 67 houses emerged during a period when the UK faced a significant housing shortage. The government encouraged the development of system-built homes to quickly address the demand. Unit Construction Co. Ltd, a prominent player in this movement, designed these homes to be cost-effective and efficient to build. The design was primarily aimed at providing affordable housing solutions for the growing population.

Design and Construction Characteristics

Unit System 67 houses are typically two-storey semi-detached or terraced homes. They feature a medium pitch gable roof covered with concrete tiles, which is a distinctive characteristic. The front and rear external walls are constructed using a combination of materials, including horizontal timber boarding, asbestos cement, profiled aluminium sheets, rendered panels, or tile hanging. The gable wall is consistently made of brick, providing structural stability.

The construction of these homes follows a platform frame method. Storey-height timber frame panels are sheathed externally with plywood, overlaid with a breather membrane. The front and rear walls are directly clad with render on expanded metal mesh up to the first-floor level, with horizontal timber boarding above. The gable wall is separately clad with brick and lined with foil-backed plasterboard. The separating wall consists of a timber frame cavity lined with plasterboard, with mineral fibre insulation between the frame studs.

Potential Hazards and Risks

When considering a Unit System 67 house, it is crucial to be aware of potential hazards and risks. One of the primary concerns is the presence of asbestos cement in some of the external cladding materials. Asbestos, when disturbed, can pose serious health risks. It is essential to have a professional survey conducted to assess the presence and condition of asbestos materials.

Another risk associated with these homes is the potential for timber decay. The timber frame construction, if not properly maintained, can be susceptible to rot and insect infestation. Regular inspections and maintenance are necessary to ensure the longevity of the structure.

Defective Premises Act Considerations

The Unit System 67 houses are not classified as defective under the Defective Premises Act. However, it is important to note that the Act primarily addresses issues related to the construction and design of new buildings. While these homes may not fall under the Act’s purview, it is still advisable to conduct thorough inspections to identify any potential defects or maintenance issues.

Inspection Tips for Unit System 67 Houses

When inspecting a Unit System 67 house, there are several key areas to focus on:

  1. Roof and Gable Walls: Check for any signs of damage or wear on the concrete tiles and brickwork. Look for any missing or cracked tiles and inspect the condition of the mortar joints.

  2. External Cladding: Examine the condition of the horizontal timber boarding, asbestos cement, or aluminium sheets. Look for any signs of rot, warping, or damage. If asbestos is present, ensure it is in good condition and not disturbed.

  3. Timber Frame: Inspect the timber frame for any signs of decay or insect infestation. Pay particular attention to areas where the frame meets the ground or is exposed to moisture.

  4. Insulation and Plasterboard: Check the condition of the mineral fibre insulation and plasterboard lining. Look for any signs of moisture damage or mould growth.

  5. Substructure and Footings: Examine the concrete strip footings and under-building for any signs of cracking or movement. Ensure the damp-proof course (DPC) is intact and functioning properly.

Typical Construction Details

Understanding the typical construction details of Unit System 67 houses can help you identify potential issues and make informed decisions:

  • Substructure: These homes are built on concrete strip footings with a concrete under-building. The damp-proof course (DPC) is a critical component to prevent moisture ingress.

  • External Walls: The platform frame construction features storey-height timber frame panels sheathed with plywood and overlaid with a breather membrane. The front and rear walls are clad with render on expanded metal mesh and horizontal timber boarding.

  • Gable Wall: The gable wall is separately clad with brick and lined with foil-backed plasterboard, providing additional insulation and stability.

  • Separating Wall: The timber frame cavity separating wall is lined with plasterboard and filled with mineral fibre insulation.

  • Partitions: Internal partitions are constructed using timber studs lined with plasterboard.

  • Floors: The ground floor is typically concrete, while the first floor consists of plywood on timber joists.

  • Ceilings: Ceilings are lined with plasterboard, with foil-backed plasterboard used in the roof space.

  • Roof: The roof is constructed using timber trusses, bituminous felt, and concrete tiles.

Common Defects in Unit System 67 Houses

While Unit System 67 houses offer a unique architectural style, they are not without their potential defects. Being aware of these common issues can help you address them proactively:

  1. Asbestos Concerns: As mentioned earlier, the presence of asbestos cement in some cladding materials is a significant concern. It is crucial to have a professional asbestos survey conducted to assess the condition and safety of these materials.

  2. Timber Decay: The timber frame construction can be susceptible to decay if not properly maintained. Regular inspections and maintenance are essential to prevent rot and insect infestation.

  3. Moisture Ingress: The effectiveness of the damp-proof course (DPC) is vital in preventing moisture ingress. Check for any signs of dampness or water damage, particularly in the substructure and footings.

  4. Insulation and Plasterboard Issues: Inspect the condition of the mineral fibre insulation and plasterboard lining. Look for any signs of moisture damage, mould growth, or deterioration.

  5. Roof and Gable Wall Damage: Regularly inspect the roof and gable walls for any signs of damage or wear. Address any missing or cracked tiles and ensure the mortar joints are in good condition.

Variants and Modifications

Over the years, some Unit System 67 houses may have undergone modifications or variations. It is important to be aware of these potential changes when considering a purchase:

  • Pier and Beam Footings: Some homes may feature pier and beam footings instead of the standard concrete strip footings. This variation can affect the stability and maintenance requirements of the property.

  • Alternative Cladding Materials: In some cases, the front and rear external walls may be directly clad with asbestos cement or profiled aluminium sheets. Alternatively, they may be separately clad with tile hanging on timber battens.

  • First Floor Construction: While the typical first floor consists of plywood on timber joists, some homes may have chipboard flooring instead. This variation can impact the durability and maintenance of the flooring.

Conclusion

The Unit System 67 house is a distinctive and historically significant property type in the UK. Understanding its construction, potential hazards, and common defects is crucial for home buyers and investors. By conducting thorough inspections and addressing any issues proactively, you can ensure the longevity and safety of your investment.

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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