Understanding the HSSB House

The High-Speed System Building (HSSB) house, also known as the Lindsay Parkinson house, is a unique type of property that emerged in the UK during the mid-1960s. Manufactured by SLP Industrialised Building and designed by Lindsay Parkinson, these properties were constructed between 1964 and the late 1960s. With a total of 660 units built, the HSSB house is a notable example of system-built properties that aimed to address the housing shortage of the time.

Typical Locations and Characteristics

HSSB houses are predominantly found in urban and suburban areas across the UK. They come in various forms, including bungalows and two- and three-storey terraced houses. The design of these properties is characterized by a medium pitch roof covered with concrete tiles or a flat roof covered with asphalt. The external walls are constructed using brick panels, horizontal or vertical timber boarding, or infilled with timber frame panels. Some dwellings also feature exposed Precast Reinforced Concrete (PRC) ring beams at the first floor and eaves level.

Construction Details

Substructure

The substructure of HSSB houses typically includes concrete strip footings, a concrete ground beam, and a concrete slab with a Damp Proof Course (DPC). This robust foundation ensures the stability and durability of the property.

External Walls

The external walls are constructed using 4 1/2″ brick panels, cavity walls, and approximately 5′ x 12′ x 4 1/2″ no-fines Precast Concrete (PC) panels. The brick panels are bonded with cement mortar grout, and galvanised Mild Steel (MS) wall ties are used for added strength. Aluminium cavity flashing and 4″ x 6″ PRC corner posts are also integral components of the external walls. The PRC ring beam, measuring 10″ x 18″, is located at the first floor and eaves level, providing additional structural support. Expanded polystyrene insulation is used to enhance thermal efficiency.

Separating Walls and Partitions

Separating walls in HSSB houses are constructed using 8″ half-storey height PC panels. Partitions are made from half-storey height PC panels lined with plasterboard, ensuring sound insulation and privacy between rooms.

Floors

The ground floor is typically made of concrete, while the upper floors consist of asphalt on screeded hollow core PRC floor panels. This construction method provides a solid and durable flooring system.

Roof

The roof of HSSB houses is constructed using PRC hollow-cored roof slabs, lightweight sand/cement screed, and asphalt. Some variants feature roofs made of timber trusses and concrete tiles.

Typical Defects and Hazards

Misplaced or Missing Vertical Lacing and Loop Reinforcement

One common issue with HSSB houses is the misplaced or missing vertical lacing and loop reinforcement between panels. This can compromise the structural integrity of the property and may require remedial work to ensure safety.

Missing or Incorrectly Placed Steel Ties

Another common defect is the missing or incorrectly placed steel ties between the floor slab and PRC ring beam. This can lead to structural weaknesses and may necessitate repairs to maintain the stability of the property.

Varying Levels of Compaction

The varying levels of compaction of in-situ and precast concrete can result in uneven settling and potential structural issues. It is essential to inspect the property for signs of uneven settling and address any issues promptly.

Spalling of Concrete

Spalling of concrete in PRC ring beams, PRC corner posts, and external staircase areas is a common problem in HSSB houses. This occurs when the concrete surface flakes or peels away, exposing the underlying reinforcement and potentially leading to further deterioration.

High Rates of Carbonation and Chloride Levels

HSSB houses are also prone to high rates of carbonation and significant levels of chloride in PRC ring beams and corner posts. Carbonation can reduce the alkalinity of the concrete, leading to corrosion of the reinforcement. High chloride levels can accelerate this process, further compromising the structural integrity of the property.

Classification Under the Defective Premises Act

HSSB houses are not typically classified as defective under the Defective Premises Act. However, due to the potential structural issues and common defects associated with these properties, it is crucial to conduct a thorough survey before purchasing. Identifying and addressing any defects early on can prevent costly repairs and ensure the safety and longevity of the property.

Inspection Guide for Surveyors

When inspecting an HSSB house, surveyors should pay close attention to the following areas:

Vertical Lacing and Loop Reinforcement

Check for the presence and correct placement of vertical lacing and loop reinforcement between panels. Any missing or misplaced reinforcement should be noted and addressed.

Steel Ties

Inspect the steel ties between the floor slab and PRC ring beam. Ensure they are correctly placed and in good condition. Missing or incorrectly placed ties should be rectified to maintain structural stability.

Concrete Compaction

Examine the levels of compaction of in-situ and precast concrete. Look for signs of uneven settling or structural weaknesses that may require remedial work.

Concrete Spalling

Check for spalling of concrete in PRC ring beams, PRC corner posts, and external staircase areas. Any spalling should be repaired to prevent further deterioration and potential safety hazards.

Carbonation and Chloride Levels

Assess the levels of carbonation and chloride in PRC ring beams and corner posts. High levels of carbonation and chloride can lead to corrosion of the reinforcement and should be addressed promptly.

Variants and Their Characteristics

HSSB houses come in several variants, each with its unique characteristics:

Timber Trusses and Concrete Tiles

Some HSSB houses feature roofs made of timber trusses and concrete tiles. This variant provides a more traditional appearance and may offer better thermal insulation compared to the standard PRC hollow-cored roof slabs.

T&G Boarding on Timber Joists

Another variant includes the first floor constructed using Tongue and Groove (T&G) boarding on timber joists. This construction method provides a solid and durable flooring system with a more traditional feel.

Lightweight PC Panels with Timber Cladding

Some HSSB houses have external walls made of lightweight PC panels clad with building paper, timber battens, and vertical or horizontal timber boarding. This variant offers a more aesthetically pleasing appearance and may provide better thermal insulation.

PRC Panel Cavity External Walls

Another variant features PRC panel cavity external walls with a brushed aggregate finish. This construction method provides a unique appearance and may offer better thermal and sound insulation.

Storey Height Timber Frame Panels

Some HSSB houses are constructed using storey height timber frame panels with various claddings. This variant offers a more modern appearance and may provide better thermal and sound insulation.

Brick-Faced PRC Ring Beams

Another variant includes brick-faced PRC ring beams, providing a more traditional appearance and potentially better thermal insulation.

Conclusion

The HSSB house, with its unique construction and design, offers a fascinating glimpse into the history of system-built properties in the UK. While these properties are not typically classified as defective under the Defective Premises Act, they do come with their own set of potential defects and hazards. Conducting a thorough survey and addressing any issues promptly can ensure the safety and longevity of the property.

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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