Understanding the Incast House

The Incast house, also known as the No-Fines house, is a unique property type that emerged in the 1940s. Manufactured by the Metropolitan Concrete Co. Ltd, these houses were designed to address the post-war housing shortage in the UK. With only five units built, these properties are rare and hold a special place in the history of British architecture.

Historical Context and Manufacturing Details

Period Built and Typical Locations

The Incast houses were constructed in the 1940s, a period marked by a significant demand for affordable and quickly built housing solutions. These properties are typically found in suburban areas, where there was ample space for new developments. The design and construction methods used for Incast houses were innovative for their time, focusing on speed and cost-efficiency.

Manufacturers and Designers

The Metropolitan Concrete Co. Ltd was the primary manufacturer of Incast houses. The company specialized in concrete construction, which was a popular choice for post-war housing due to its durability and cost-effectiveness. The design of these houses was a collaborative effort, incorporating input from various architects and engineers to create a functional and aesthetically pleasing home.

Characteristics of Incast Houses

Structural Features

Incast houses are typically two-storey detached or semi-detached properties. They feature a medium pitch hipped roof covered with interlocking concrete tiles, which provides excellent weather resistance. The external walls are rendered throughout, giving the houses a uniform and clean appearance. One of the distinctive features of these houses is the two-storey flat-roofed bay window on the front elevation, which adds to their unique charm.

Construction Details

Substructure

The substructure of Incast houses consists of concrete strip foundations and reinforced concrete (RC) under-building. A concrete slab forms the base, with a damp-proof course (DPC) to prevent moisture ingress.

External Walls

The external walls are constructed using 4′ I-section no-fines precast concrete (PC) columns, rendered for a smooth finish. The walls are 10″ thick no-fines RC, reduced to 4″ at the front elevation bay window. Two layers of 1/4″ bar reinforcement provide additional strength, and an L-shaped no-fines RC eaves beam supports the roof structure. A timber wall plate is used to secure the roof to the walls.

Separating Walls and Partitions

The separating walls between properties are 8″ thick no-fines RC, ensuring sound insulation and structural integrity. Internal partitions are made from PC blocks, providing a sturdy and durable division between rooms.

Floors

The ground floor is constructed from concrete, offering a solid and stable base. The first floor consists of timber boarding on timber joists, with a reinforced steel joist (RSJ) encased in concrete adjacent to the bay window for added support.

Roof

The roof structure comprises timber rafters and purlins, covered with interlocking concrete tiles. The flat roof over the first-floor bay window is also made from timber, providing a consistent aesthetic with the rest of the house.

Typical Hazards and Risks

Structural Concerns

One of the primary concerns with Incast houses is the potential for structural issues due to the age and construction methods used. The no-fines concrete can be prone to cracking and spalling, particularly if the reinforcement bars are exposed to moisture and begin to corrode. This can compromise the structural integrity of the property and may require significant repairs.

Moisture Ingress

The concrete slab and DPC are designed to prevent moisture ingress, but over time, these elements can deteriorate. If the DPC fails, moisture can penetrate the walls and floors, leading to damp and mould issues. This can affect the health of the occupants and may require remedial work to rectify.

Thermal Efficiency

Incast houses were built before modern insulation standards were introduced, so they may not be as thermally efficient as newer properties. This can result in higher heating costs and a less comfortable living environment. Retrofitting insulation can improve thermal performance but may be challenging due to the construction methods used.

Defective Premises Act Considerations

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. While Incast houses were innovative for their time, they may not meet modern building standards. If significant defects are found, the property could be classed as defective under the Act, potentially leading to legal and financial implications for the owner.

Inspection and Assessment Guide

Pre-Inspection Preparation

Before inspecting an Incast house, it is essential to gather as much information as possible about the property. This includes reviewing any available documentation, such as previous survey reports, maintenance records, and planning permissions. Understanding the construction methods and materials used will help identify potential issues during the inspection.

External Inspection

Roof

Inspect the roof for any signs of damage or wear, such as missing or broken tiles, sagging, or water ingress. Pay particular attention to the flat roof over the bay window, as this area is more susceptible to leaks.

Walls

Examine the external walls for cracks, spalling, or other signs of deterioration. Check the render for any areas of damage or discolouration, which could indicate underlying issues. Look for signs of moisture ingress, such as damp patches or mould growth.

Windows and Doors

Inspect the windows and doors for any signs of damage or wear. Check the seals and frames for gaps or deterioration, which could allow draughts and moisture to enter the property.

Internal Inspection

Floors

Check the condition of the ground and first floors for any signs of damage or wear. Look for cracks, uneven surfaces, or areas of dampness, which could indicate structural issues or moisture ingress.

Walls and Partitions

Examine the internal walls and partitions for cracks, damp patches, or other signs of deterioration. Pay particular attention to the separating walls, as any issues here could affect the structural integrity of the property.

Ceilings

Inspect the ceilings for any signs of damage or wear, such as cracks, sagging, or water stains. These could indicate issues with the roof or upper floors.

Services

Check the condition of the plumbing, electrical, and heating systems. Look for any signs of leaks, corrosion, or other issues that could affect the functionality and safety of the property.

Common Defects in Incast Houses

Concrete Deterioration

One of the most common defects in Incast houses is the deterioration of the no-fines concrete. This can manifest as cracking, spalling, or delamination, particularly if the reinforcement bars are exposed to moisture and begin to corrode. Regular maintenance and repairs are essential to address these issues and prevent further damage.

Moisture Ingress

As mentioned earlier, moisture ingress can be a significant issue in Incast houses. This can result from a failed DPC, damaged render, or issues with the roof. Addressing the source of the moisture and carrying out remedial work is essential to prevent further damage and maintain a healthy living environment.

Thermal Efficiency

Improving the thermal efficiency of an Incast house can be challenging due to the construction methods used. However, retrofitting insulation, upgrading windows and doors, and improving the heating system can help reduce energy costs and improve comfort.

Structural Issues

Structural issues can arise due to the age and construction methods used in Incast houses. Regular inspections and maintenance are essential to identify and address any potential problems before they become more serious.

Maintenance and Repair Tips

Regular Inspections

Regular inspections are essential to identify and address any potential issues before they become more serious. This includes checking the condition of the roof, walls, floors, and services, as well as looking for signs of moisture ingress or structural issues.

Addressing Moisture Ingress

If moisture ingress is identified, it is essential to address the source of the problem and carry out remedial work to prevent further damage. This may include repairing or replacing the DPC, fixing damaged render, or addressing issues with the roof.

Improving Thermal Efficiency

Improving the thermal efficiency of an Incast house can help reduce energy costs and improve comfort. This may include retrofitting insulation, upgrading windows and doors, and improving the heating system.

Structural Repairs

If structural issues are identified, it is essential to carry out repairs as soon as possible to prevent further damage. This may include repairing or replacing damaged concrete, addressing issues with the reinforcement bars, or carrying out other remedial work.

Conclusion

Incast houses, with their unique construction and historical significance, offer a fascinating glimpse into post-war British architecture. While they come with their own set of challenges, understanding their characteristics and potential issues can help home buyers and investors make informed decisions. Regular inspections, maintenance, and repairs are essential to ensure the longevity and safety 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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