Introduction to the Modus House

The Modus house, a distinctive type of system-built property, emerged during the mid-20th century as a solution to the UK’s post-war housing shortage. Manufactured by The Amey Chivers Housing Co. Ltd and designed by Alex Robertson, Peter Francis and Partners, and R H Sims, these homes were constructed between 1966 and 1970. With a total of 280 units built, the Modus house is a notable example of the era’s innovative construction techniques. This article delves into the various aspects of the Modus house, from its construction characteristics to potential hazards and inspection tips, providing a thorough understanding for home buyers and investors.

Historical Context and Manufacturers

The Modus house was developed during a period when the UK faced a significant housing crisis. The need for rapid and cost-effective housing solutions led to the rise of system-built properties. The Amey Chivers Housing Co. Ltd, a prominent manufacturer of the time, took on the challenge of producing these homes. The design team, comprising Alex Robertson, Peter Francis and Partners, and R H Sims, aimed to create a versatile and durable housing solution that could be quickly assembled on-site.

Typical Characteristics of the Modus House

Design and Structure

The Modus house comes in various forms, including bungalows and two-storey semi-detached and terraced houses. One of the defining features of these homes is their roof design. They typically have a shallow or medium pitch gable roof covered with concrete tiles. Some houses also feature a shallow pitch roof with a gable to the front elevation.

External Walls

The external walls of Modus houses are either rendered or made of textured storey-height precast concrete (PC) panels. In some cases, the front and rear walls are constructed with timber boarding up to the first-floor level, combined with PC spandrel panels and additional PC panels above. The gable apex is often made of PC panels or tile hanging.

Construction Details

Substructure

• Foundations: Concrete pad foundations.
• Ground Beams: Precast concrete (PC) ground beams.
• Damp Proof Course (DPC): Incorporated to prevent moisture ingress.

External Walls

• Composition: Storey-height double skin large PC panels with a 2 1/2″ outer leaf, 1″ insulation, and 3 1/2″ inner leaf.
• Junctions: Lead flashing at cruciform junctions, preformed rubber bitumen sealant, and flat mild steel (MS) plates bolted across vertical junctions.

Separating Walls

• Construction: Storey-height PC panels fixed to external walls with 5″ x 5″ rolled steel angles (RSAs), loop reinforcement, and vertical site bars.

Partitions

• Materials: Storey-height PC panels and compressed strawboard panels.

Floors

• Ground Floor: Concrete.
• First Floor: Timber boarding on timber joists.

Ceilings

• Material: Plasterboard.

Roof

• Structure: Timber trusses with MS wind braces attached to wall panels by RSAs.
• Covering: Concrete tiles.

Variants

Some Modus houses feature rendered external wall panels, while others have front and rear walls made of timber frame panels clad with timber boarding up to the first-floor level, combined with double leaf PC spandrel panels and double leaf PC panels above. The roof in these variants is constructed with timber purlins and rafters.

Potential Hazards and Risks

Structural Concerns

One of the primary concerns with Modus houses is the durability of the reinforced concrete used in their construction. Over time, concrete can suffer from various issues, including carbonation, which reduces the pH of the concrete and leads to the corrosion of embedded steel reinforcement. This can compromise the structural integrity of the building.

Water Ingress

The design of Modus houses includes several junctions and seals that can be prone to water ingress if not properly maintained. Lead flashing, rubber bitumen sealants, and other components must be regularly inspected and maintained to prevent moisture from penetrating the structure.

Thermal Insulation

While the Modus house design includes insulation within the external walls, the level of thermal performance may not meet modern standards. Upgrading the insulation can improve energy efficiency and reduce heating costs.

Asbestos

Given the period during which Modus houses were constructed, there is a possibility that asbestos-containing materials were used in some components, such as insulation or ceiling tiles. Asbestos poses significant health risks if disturbed, so it is crucial to have a professional survey conducted to identify and safely manage any asbestos present.

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 the Modus house was not specifically investigated by the Building Research Establishment (BRE), general guidance on the inspection and assessment of reinforced concrete durability is available. It is essential for buyers and investors to be aware of potential defects and ensure that any necessary repairs or maintenance are carried out to comply with the Act.

Inspection Tips for Modus Houses

External Inspection

• Roof: Check for any signs of damage or wear to the concrete tiles and timber trusses. Look for any evidence of water ingress or leaks.
• Walls: Inspect the external walls for cracks, spalling, or other signs of deterioration. Pay particular attention to the junctions and seals, ensuring they are intact and functioning correctly.
• Foundations: Examine the concrete pad foundations for any signs of movement or cracking.

Internal Inspection

• Floors: Check the condition of the concrete ground floor and timber first floor. Look for any signs of sagging, warping, or damage.
• Walls: Inspect the internal walls for cracks, dampness, or other issues. Ensure that the separating walls and partitions are secure and free from defects.
• Ceilings: Examine the plasterboard ceilings for any signs of water damage, cracks, or other issues.

Special Considerations

• Reinforced Concrete: Given the potential for corrosion of steel reinforcement, it is advisable to have a professional survey conducted to assess the condition of the concrete and identify any necessary repairs.
• Asbestos: If there is any suspicion of asbestos-containing materials, a professional asbestos survey should be carried out to identify and manage any risks.

Typical Defects in Modus Houses

Concrete Deterioration

As mentioned earlier, the reinforced concrete used in Modus houses can suffer from carbonation and other forms of deterioration. This can lead to cracking, spalling, and ultimately, structural issues if not addressed promptly.

Water Ingress and Dampness

The various junctions and seals in Modus houses can be prone to water ingress if not properly maintained. This can lead to dampness, mould growth, and other related issues. Regular inspection and maintenance of these components are essential to prevent water-related problems.

Thermal Performance

The insulation within the external walls of Modus houses may not meet modern standards, leading to higher heating costs and reduced energy efficiency. Upgrading the insulation can improve the thermal performance of the property.

Asbestos

Asbestos-containing materials may be present in some Modus houses, posing significant health risks if disturbed. It is crucial to have a professional survey conducted to identify and safely manage any asbestos present.

Conclusion

The Modus house represents a unique and innovative approach to post-war housing in the UK. While these homes offer several advantages, including rapid construction and distinctive design, they also come with potential hazards and risks that buyers and investors must be aware of. By understanding the typical characteristics, construction details, and common defects of Modus houses, you can make informed decisions and ensure that any necessary repairs or maintenance are carried out to maintain the property’s value and safety.

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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