Overview of the SB2 House

The SB2 house, also known as the Sawston SB2 or Wales Sindall, is a distinctive type of system-built property that emerged in the mid-1960s. Designed by C. Davidson and manufactured by Sawston Concrete Products Ltd, these homes were constructed between 1965 and 1967. A total of 170 units were built, comprising both bungalows and two-storey terraced houses. This article delves into the various aspects of the SB2 house, from its construction characteristics to potential hazards and inspection tips, providing a thorough understanding for prospective buyers and investors.

Historical Context and Manufacturers

Period and Location

The SB2 houses were constructed during a period of rapid post-war development in the UK, specifically between 1965 and 1967. This era saw a significant demand for quick and cost-effective housing solutions, leading to the rise of system-built properties. The SB2 houses were primarily located in urban and suburban areas, catering to the growing need for affordable housing.

Designers and Manufacturers

The SB2 house was designed by C. Davidson, a notable figure in the field of system-built housing. The manufacturing was handled by Sawston Concrete Products Ltd, a company known for its expertise in producing pre-cast concrete components. The collaboration between Davidson and Sawston Concrete Products Ltd resulted in a unique housing solution that met the demands of the time.

Identification Characteristics

Structural Features

The SB2 houses are easily identifiable by their distinct structural features. They come in two main forms: bungalows and two-storey terraced houses. One of the most notable characteristics is the flat roof covered with asphalt, a common feature in many system-built homes of that era. The external walls are made of storey-height pre-cast (PC) panels, with sections of the front and rear walls featuring horizontal timber boarding. Some houses also have a single-storey entrance lobby on the front elevation, adding to their unique appearance.

Additional Features

Other identifying features include a timber fascia at the eaves and the use of cellular lightweight concrete reinforced over openings. These elements not only contribute to the aesthetic appeal of the SB2 houses but also play a crucial role in their structural integrity.

Construction Details

Substructure

The substructure of the SB2 house consists of concrete underbuilding and pre-cast ground beams. A damp-proof course (DPC) is also included to prevent moisture from rising through the structure, which is essential for maintaining the durability of the building.

External Walls

The external walls are constructed using storey-height, room-sized 8-inch foamed aggregate lightweight PC panels. These panels are bolted together and have grouted concrete joints, ensuring a robust and stable structure. The panels also feature cast-in insulation, providing thermal efficiency. Additionally, storey-height timber frame panels clad with horizontal timber boarding are used in some sections, adding to the overall aesthetic and functional design.

Separating and Partition Walls

The separating walls between units are made of 8-inch dense PC panels, providing sound insulation and structural stability. Loadbearing partitions within the units are also constructed using 8-inch foamed aggregate lightweight PC panels. Non-loadbearing partitions are made of prefinished laminated panels with butt joints, offering flexibility in interior design.

Floors

The ground floor of the SB2 house is made of concrete, providing a solid and durable base. The first floor consists of 8-inch dense concrete slabs, ensuring structural integrity and sound insulation between floors.

Roof

The roof of the SB2 house is a pre-cast slab covered with asphalt. This design choice was common in system-built homes of the era, offering a cost-effective and durable roofing solution.

Typical Hazards and Risks

Structural Issues

One of the primary concerns with SB2 houses is the potential for structural issues, particularly related to the pre-cast concrete components. Over time, these components can suffer from degradation due to factors such as carbonation and corrosion of the steel reinforcement. This can lead to cracks and other structural problems, which may require significant repairs.

Moisture Ingress

Another common issue with SB2 houses is moisture ingress, particularly in the flat roof and external walls. The asphalt covering on the roof can deteriorate over time, leading to leaks and water damage. Similarly, the joints between the pre-cast panels can become compromised, allowing moisture to penetrate the structure.

Insulation and Energy Efficiency

While the SB2 houses were designed with cast-in insulation, the level of thermal efficiency may not meet modern standards. This can result in higher energy costs for heating and cooling, as well as potential issues with condensation and mould growth.

Defective Premises Act

Classification

The SB2 house is not classified as defective under the Defective Premises Act. However, it is essential to be aware of the potential issues and risks associated with this type of property. Regular inspections and maintenance are crucial to ensure the long-term durability and safety of the building.

Inspection Tips for Surveyors

Structural Integrity

When inspecting an SB2 house, it is essential to assess the structural integrity of the pre-cast concrete components. Look for signs of cracking, spalling, and other forms of degradation. Pay particular attention to areas around openings, such as windows and doors, where the concrete may be more susceptible to damage.

Moisture and Dampness

Check for signs of moisture ingress and dampness, particularly in the roof and external walls. Look for water stains, mould growth, and other indicators of water damage. Use a moisture meter to assess the extent of any dampness issues.

Insulation and Energy Efficiency

Evaluate the level of insulation and energy efficiency in the property. Check for any gaps or deficiencies in the insulation, particularly in the external walls and roof. Consider recommending upgrades to improve thermal efficiency and reduce energy costs.

Roof Condition

Inspect the condition of the flat roof, paying particular attention to the asphalt covering. Look for signs of wear and tear, such as cracks, blisters, and areas of ponding water. Ensure that the roof drainage system is functioning correctly to prevent water accumulation.

External Walls and Joints

Examine the external walls and joints between the pre-cast panels. Look for signs of movement, cracking, and deterioration. Check the condition of the horizontal timber boarding and ensure that it is adequately maintained and protected from the elements.

Typical Defects in SB2 Houses

Concrete Degradation

One of the most common defects in SB2 houses is the degradation of the pre-cast concrete components. This can occur due to carbonation, which reduces the alkalinity of the concrete and allows the steel reinforcement to corrode. Over time, this can lead to cracking, spalling, and other structural issues.

Roof Leaks

The flat roof design of the SB2 house can be prone to leaks, particularly if the asphalt covering is not adequately maintained. Water ingress can lead to damage to the roof structure and internal finishes, as well as potential issues with dampness and mould growth.

Joint Deterioration

The joints between the pre-cast panels can deteriorate over time, allowing moisture to penetrate the structure. This can lead to issues with dampness, as well as potential structural problems if the joints become compromised.

Insulation Deficiencies

While the SB2 houses were designed with cast-in insulation, the level of thermal efficiency may not meet modern standards. This can result in higher energy costs and potential issues with condensation and mould growth.

Maintenance and Repair Recommendations

Regular Inspections

Regular inspections are crucial to identify and address any potential issues with the SB2 house. This includes checking the condition of the pre-cast concrete components, roof, external walls, and joints. Early detection of problems can help prevent more significant issues and costly repairs.

Roof Maintenance

Maintaining the flat roof is essential to prevent leaks and water damage. This includes regular inspections of the asphalt covering and roof drainage system. Any signs of wear and tear should be addressed promptly to prevent further deterioration.

Concrete Repairs

If any signs of concrete degradation are identified, it is essential to carry out repairs promptly. This may involve patching cracks, addressing spalling, and applying protective coatings to prevent further damage. In some cases, more extensive repairs may be required, such as replacing damaged sections of the pre-cast panels.

Insulation Upgrades

Upgrading the insulation in the SB2 house can help improve thermal efficiency and reduce energy costs. This may involve adding additional insulation to the external walls and roof, as well as addressing any gaps or deficiencies in the existing insulation.

Joint Sealing

Ensuring that the joints between the pre-cast panels are adequately sealed is crucial to prevent moisture ingress. This may involve applying new sealant or grout to the joints, as well as addressing any signs of movement or deterioration.

Conclusion

The SB2 house, with its unique design and construction, offers a fascinating glimpse into the post-war housing solutions of the 1960s. While these properties come with their own set of challenges and potential issues, they can also provide a cost-effective and practical housing solution for many buyers and investors. By understanding the typical characteristics, hazards, and maintenance requirements of the SB2 house, you can make informed decisions and ensure the long-term durability 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.

---