Historical Context and Background

The Webb House, a notable example of post-war British architecture, was designed by H.F. Webb and manufactured by Permanent Pre-cast Constructions Ltd. These properties were constructed in 1947, a period marked by a significant housing shortage in the UK. The government sought rapid and cost-effective solutions to address the housing crisis, leading to the development of various system-built properties, including the Webb House.

These homes were primarily built in suburban areas, providing affordable housing for the growing population. The Webb House is a two-storey semi-detached property, characterized by its flat roof covered with bituminous felt and rendered external walls. The design includes shallow protruding string courses at the first-floor level and at ground and first-floor window sill and head levels. Exposed cantilevered beams, known as modillions, are visible on the soffit of the roof overhang, adding a distinctive architectural feature.

Manufacturers and Designers

The Webb House was a collaborative effort between Permanent Pre-cast Constructions Ltd and designer H.F. Webb. Permanent Pre-cast Constructions Ltd was a prominent manufacturer during the post-war era, specializing in pre-cast concrete components. Their expertise in this field allowed for the rapid construction of durable and cost-effective homes.

H.F. Webb, the designer, played a crucial role in the architectural and structural design of these properties. Webb’s innovative approach to using pre-cast concrete elements ensured that the homes were not only quick to build but also met the necessary standards for durability and safety.

Typical Characteristics and Hazards

Structural Features

The Webb House is easily identifiable by its unique architectural features. These include:

• Flat Roof: Covered with bituminous felt, providing a waterproof barrier.
• Rendered External Walls: The walls are rendered throughout, giving the house a uniform appearance.
• String Courses: Shallow protruding string courses at various levels add to the aesthetic appeal.
• Modillions: Exposed cantilevered beams on the soffit of the roof overhang.
• PC Window Sills: Pre-cast concrete window sills.
• Flat PC Canopy: A flat pre-cast concrete canopy over the front door.
• Monopitch Roof Extension: Some houses feature a two-storey monopitch roof extension to the flank wall.

Construction Details

The construction of the Webb House involves several key components:

• Substructure: Concrete strip footings, concrete under-building, concrete slab, and damp-proof course (DPC).
• Frame: A 9″ x 9″ pre-cast reinforced concrete (PRC) column in the centre of the house.
• External Walls: Rendered storey-height PRC panels with dense aggregate concrete outer leaf and clinker aggregate no-fines concrete inner leaf.
• Separating Wall: Storey-height no-fines clinker aggregate PRC panel cavity wall.
• Partitions: Rendered no-fines clinker aggregate PC blocks and dense aggregate concrete panels.
• Ground Floor: Fibreboard on concrete.
• First Floor: Fibreboard on dense aggregate PRC panels cramped together over the spine wall capping beam.
• Ceilings: Two-coat lime plaster applied directly to concrete components.
• Roof: Dense aggregate PRC panels with cast-in gutters, insulation board, and bituminous felt.

Typical Hazards and Risks

While the Webb House was designed to be durable and cost-effective, there are several hazards and risks associated with this property type:

• Corrosion of Steel Reinforcement: The steel reinforcement within the concrete can corrode over time, leading to structural weaknesses.
• Carbonation: The concrete can undergo carbonation, reducing its alkalinity and increasing the risk of steel reinforcement corrosion.
• Water Ingress: The flat roof design, while practical, can be prone to water ingress if not properly maintained.
• Thermal Insulation: The original design may not meet modern thermal insulation standards, leading to higher energy costs.
• Asbestos: Some properties may contain asbestos in the construction materials, posing a health risk if disturbed.

Defective Premises Act and Classification

The Defective Premises Act 1972 imposes a duty on builders, developers, and landlords to ensure that properties are constructed and maintained to a reasonable standard. The Webb House, like many post-war system-built properties, has been scrutinized under this Act.

While the Webb House is not universally classified as defective, certain issues such as corrosion of steel reinforcement and carbonation of concrete can lead to structural defects. It is essential for potential buyers and investors to conduct thorough inspections and assessments to identify any potential issues.

Inspection and Assessment Guide

Pre-Inspection Preparation

Before conducting an inspection of a Webb House, it is crucial to gather relevant information and tools. This includes:

• Historical Data: Obtain any available historical data on the property, including previous inspection reports and maintenance records.
• Inspection Tools: Ensure you have the necessary tools, such as a moisture meter, concrete cover meter, and endoscope.
• Safety Gear: Wear appropriate safety gear, including gloves, safety glasses, and a hard hat.

External Inspection

1. Roof: Inspect the flat roof for signs of water ingress, damage to the bituminous felt, and any visible cracks or deterioration in the concrete panels.
2. Walls: Examine the rendered external walls for cracks, spalling, and signs of corrosion in the steel reinforcement. Pay particular attention to the string courses and modillions.
3. Windows and Doors: Check the condition of the PC window sills and the flat PC canopy over the front door. Look for any signs of movement or deterioration.
4. Extensions: If the property has a two-storey monopitch roof extension, inspect it for structural integrity and any signs of water ingress.

Internal Inspection

1. Ground Floor: Inspect the fibreboard on concrete for any signs of dampness or damage. Check for any unevenness or movement in the floor.
2. First Floor: Examine the fibreboard on dense aggregate PRC panels for signs of wear and tear. Ensure the panels are securely cramped together over the spine wall capping beam.
3. Ceilings: Check the two-coat lime plaster for any cracks or signs of water damage. Look for any areas where the plaster may be detaching from the concrete components.
4. Partitions: Inspect the rendered no-fines clinker aggregate PC blocks and dense aggregate concrete panels for any signs of cracking or movement.

Structural Assessment

1. Steel Reinforcement: Use a concrete cover meter to assess the depth of the steel reinforcement within the concrete. Check for any signs of corrosion or deterioration.
2. Carbonation: Conduct a carbonation test to determine the depth of carbonation in the concrete. This will help assess the risk of steel reinforcement corrosion.
3. Water Ingress: Use a moisture meter to check for any signs of water ingress in the roof, walls, and floors. Pay particular attention to areas around windows and doors.
4. Thermal Insulation: Assess the thermal insulation of the property. Consider upgrading the insulation to meet modern standards if necessary.

Typical Defects and Maintenance

Common Defects

1. Corrosion of Steel Reinforcement: This is a common issue in Webb Houses due to the carbonation of concrete. Regular inspections and maintenance are essential to prevent structural weaknesses.
2. Water Ingress: The flat roof design can be prone to water ingress if not properly maintained. Regular inspections and repairs to the bituminous felt are necessary to prevent leaks.
3. Cracking and Spalling: Cracks in the rendered external walls and spalling of concrete can occur due to thermal movement and corrosion of steel reinforcement. These issues should be addressed promptly to prevent further damage.
4. Thermal Insulation: The original design may not meet modern thermal insulation standards, leading to higher energy costs. Upgrading the insulation can improve energy efficiency and reduce costs.

Maintenance Tips

1. Regular Inspections: Conduct regular inspections of the roof, walls, windows, and doors to identify any potential issues early.
2. Roof Maintenance: Ensure the bituminous felt on the flat roof is in good condition and repair any damage promptly to prevent water ingress.
3. Wall Repairs: Address any cracks or spalling in the rendered external walls promptly to prevent further damage.
4. Steel Reinforcement: Monitor the condition of the steel reinforcement within the concrete and address any signs of corrosion promptly.
5. Thermal Insulation: Consider upgrading the thermal insulation to meet modern standards and improve energy efficiency.

Conclusion

The Webb House, a product of post-war innovation and necessity, remains a significant part of the UK’s architectural heritage. While these properties were designed to be durable and cost-effective, they do come with certain risks and maintenance requirements. Potential buyers and investors should conduct thorough inspections and assessments to identify any potential issues and ensure the property meets modern standards.

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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