Historical Context and Manufacturing

The Wessex house, a notable example of system-built properties, emerged during the post-war period in the UK. These properties were primarily constructed between the 1940s and 1960s, a time when there was a significant demand for rapid housing solutions due to the destruction caused by World War II and the subsequent baby boom. The Wessex house was manufactured by Orlit Ltd, a company renowned for its expertise in prefabricated reinforced concrete (PRC) construction.

Orlit Ltd, along with other manufacturers, played a crucial role in addressing the housing crisis of the time. The Wessex house, also known as Concrete Construction (Wales) or simply Orlit, was designed to be a cost-effective and quick-to-assemble housing solution. These properties were predominantly built in suburban areas and new towns across the UK, providing affordable housing to thousands of families.

Design and Characteristics

Architectural Features

The Wessex house is typically found in two main configurations: bungalows and two-storey houses. These properties are easily identifiable by their medium pitch hipped or gable roofs, which are usually covered with concrete tiles. The external walls are constructed using storey-height PRC panels, a hallmark of Orlit’s design. These panels are connected by bent steel rods inserted through holes cast in the panel flanges, ensuring structural integrity.

One of the distinctive features of the Wessex house is the PRC ring beam at the first-floor level, which provides additional support and stability. The window surrounds and ground floor sill units are also made of PRC, contributing to the uniform appearance of the property. The gable apex is often adorned with tile hanging, adding a touch of aesthetic appeal to the otherwise utilitarian design.

Construction Details

Substructure

The substructure of the Wessex house consists of concrete strip footings and a concrete slab. This foundation provides a stable base for the PRC panels and other structural elements.

External Walls

The external walls are made of storey-height PRC panels, which are typically 1′ to 2′ in width. These panels are lined with plasterboard on timber battens fixed to timber noggins in the panel joints. The panels are connected by bent steel rods inserted through holes cast in the panel flanges and located on dowels cast into the first-floor ring beam.

Separating Walls and Partitions

The details of the separating walls and partitions in Wessex houses are not well-documented. However, it is known that the PRC panels and ring beams provide the primary structural support.

Floors

The ground floor is constructed of concrete, providing a durable and stable surface. The first floor features inverted T-section PRC primary beams on the ground floor PRC panels, with I-section PRC secondary beams providing additional support. The concrete cover to the continuity bar ensures the structural integrity of the floor system.

Ceilings and Roof

The ceilings are typically made of plasterboard, providing a smooth and finished appearance. The roof structure consists of timber rafters and purlins, covered with concrete tiles. The gable apex is often finished with tile hanging on timber battens, adding a decorative element to the property.

Common Defects and Hazards

Carbonation of PRC Panels and Beams

One of the most significant issues with Wessex houses is the carbonation of PRC panels and first-floor beams. Carbonation is a chemical reaction that occurs when carbon dioxide from the air penetrates the concrete, reducing its alkalinity and leading to the corrosion of the embedded steel reinforcement. This can compromise the structural integrity of the property and lead to serious safety concerns.

Low Cover to Continuity Steel

Another common defect is the low cover to continuity steel in the first-floor PRC ring beams. The concrete cover is essential for protecting the steel reinforcement from corrosion. When the cover is insufficient, the steel is more susceptible to environmental factors, leading to deterioration and potential structural failure.

Negative Bearing of PRC Spine Beam

The negative bearing of the PRC spine beam on the separating wall is another critical issue. This design flaw means that the spine beam relies on the projecting steel cast into the ring beam for support. Over time, this can lead to the deterioration of the PRC corner panels and compromise the overall stability of the property.

Deterioration of PRC Corner Panels

The PRC corner panels are particularly vulnerable to deterioration due to their exposure to environmental factors and the stresses placed on them by the structural design. This can lead to cracking, spalling, and other forms of damage that can affect the safety and longevity of the property.

Defective Premises Act and Wessex Houses

The Wessex house is classified as defective under the Defective Premises Act. This legislation was introduced to address the issues associated with certain types of system-built properties, including those constructed using PRC panels. The Act provides a framework for identifying and addressing defects in these properties, ensuring that they meet modern safety and performance standards.

Inspection Guide for Surveyors

Identifying Characteristics

When inspecting a Wessex house, surveyors should look for the following identifying characteristics:

• Bungalows or two-storey houses
• Medium pitch hipped or gable roof covered with concrete tiles
• External walls made of storey-height PRC panels
• PRC ring beam at the first-floor level
• PRC window surrounds and ground floor sill units
• Tile hanging to the gable apex

Inspection Checklist

Substructure

• Check for signs of settlement or movement in the concrete strip footings and slab.
• Look for cracks or other damage in the foundation that could indicate structural issues.

External Walls

• Inspect the PRC panels for signs of carbonation, such as cracking, spalling, or rust stains.
• Check the connections between panels for signs of deterioration or movement.
• Look for any damage to the plasterboard lining and timber battens.

Separating Walls and Partitions

• Although details are not well-documented, check for any signs of movement or cracking in the separating walls and partitions.

Floors

• Inspect the ground floor for signs of cracking or movement.
• Check the first-floor PRC beams for signs of carbonation and corrosion.
• Look for any damage to the concrete cover and continuity bar.

Ceilings and Roof

• Inspect the plasterboard ceilings for signs of sagging, cracking, or water damage.
• Check the timber rafters and purlins for signs of rot, insect infestation, or other damage.
• Look for any missing or damaged concrete tiles on the roof.

Common Defects

• Carbonation of PRC panels and first-floor beams
• Low cover to continuity steel in first-floor PRC ring beams
• Negative bearing of PRC spine beam on separating wall
• Deterioration of PRC corner panels

Maintenance and Repair Considerations

Addressing Carbonation

To address carbonation in PRC panels and beams, it is essential to remove the affected concrete and replace it with new, high-quality concrete. This process may also involve applying a protective coating to the steel reinforcement to prevent further corrosion.

Improving Concrete Cover

If the concrete cover to the continuity steel is insufficient, it may be necessary to add additional concrete or apply a protective coating to the steel. This can help to prevent corrosion and extend the lifespan of the property.

Reinforcing PRC Spine Beams

To address the negative bearing of the PRC spine beam, it may be necessary to add additional support, such as steel brackets or additional concrete. This can help to distribute the load more evenly and prevent further deterioration of the PRC corner panels.

Repairing PRC Corner Panels

Deteriorated PRC corner panels should be repaired or replaced as needed. This may involve removing the damaged concrete and replacing it with new concrete, as well as applying a protective coating to the steel reinforcement.

Conclusion

The Wessex house, a product of post-war innovation and necessity, remains a significant part of the UK’s housing landscape. While these properties provided much-needed housing solutions in their time, they come with a unique set of challenges and considerations for modern home buyers and investors. Understanding the historical context, design characteristics, common defects, and maintenance requirements of Wessex houses is essential for making informed decisions and ensuring the safety and longevity of these properties.

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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