Historical Context and Manufacturing

The Wimpey No-Fines house, a hallmark of post-war British architecture, emerged as a solution to the housing crisis following World War II. Manufactured by George Wimpey & Co. Ltd, these homes were constructed between the 1940s and the 1970s. Over this period, approximately 300,000 units were built, making them a significant part of the UK’s housing stock. These properties are also known by various names, including Butterfly, Butterfly No-Fines, Formwall, Gateshead Butterfly, Gateshead No-Fines, Wimpey, and Wimpey W6M.

Typical Locations

Wimpey No-Fines houses are predominantly found in suburban areas across the UK. They were built in large numbers in cities and towns where the demand for affordable housing was high. Areas such as Gateshead, Birmingham, and parts of London have a notable concentration of these properties.

Manufacturers and Designers

George Wimpey & Co. Ltd, a prominent construction company, was the primary manufacturer of these homes. The design was innovative for its time, focusing on rapid construction and cost-effectiveness. The use of “no-fines” concrete, which lacks fine aggregates like sand, was a key feature that set these homes apart from traditional brick-and-mortar constructions.

Characteristics and Construction Details

Identification Characteristics

Wimpey No-Fines houses come in various forms, including bungalows, two-storey semi-detached, and terraced houses. They typically feature a medium pitch hipped or gable roof covered with tiles, or a flat or shallow valley roof covered with bituminous felt or asphalt. The external walls are usually rendered throughout, or rendered on the front and rear walls with brick on the flank wall. Some dwellings also have front bay windows, adding to their distinctive appearance.

Substructure

The substructure of Wimpey No-Fines houses consists of concrete strip footings, brick under-building, a concrete slab, and a damp-proof course (DPC). This robust foundation was designed to provide stability and durability.

External Walls

The external walls are a defining feature of these homes. They are constructed from 10-inch no-fines reinforced concrete (RC) with horizontal tie reinforcement. Dense RC eaves beams and precast concrete (PRC) lintels with projecting reinforcement above openings are also common. Timber wall plates are used to support the roof structure.

Separating Walls and Partitions

Separating walls are made from 10-inch no-fines RC with tie reinforcement, ensuring structural integrity. Internal partitions are typically timber stud walls lined with plasterboard, providing a lightweight and flexible solution for interior layouts.

Floors

The ground floor is usually a concrete slab, while the first floor consists of timber boarding on timber joists supported by metal corbels. This combination of materials offers a balance of strength and flexibility.

Ceilings and Roof

Ceilings are generally made from plasterboard, while the roof structure comprises timber rafters, purlins, and tiles. Variants of the roof design include flat or bowstring roofs covered with bituminous felt or asphalt.

Variants and Evolution

1945–1952

During this period, external walls were constructed from 12-inch no-fines concrete. RC eaves beams and PRC lintels above openings were standard, with lintels being 2 inches deep at the external face and 3 inches deep at the internal face.

1957 Onward

From 1957, gable or flank external walls featured two 5/8-inch reinforcing bars or a 16-inch band of mesh reinforcement at ground floor level. This enhancement improved the structural stability of the homes.

1964 Onward

In 1964, the design evolved to include external walls of 8-inch no-fines concrete with a 21-inch band of mesh reinforcement at the first-floor level. PRC rectangular or boot lintels above openings and a bituminous damp-proof membrane (DPM) above lintels were also introduced. The separating wall was made from 9-inch no-fines concrete, possibly rendered. Ground floors were either suspended concrete or timber boarding on timber joists, while first floors featured timber joists in pockets cast into external walls.

Typical Defects and Hazards

Vertical and Horizontal Cracking

One of the most common issues with Wimpey No-Fines houses is vertical cracking of the no-fines concrete external walls. Horizontal cracking of render above window drips is also frequently observed. These cracks can compromise the structural integrity and aesthetic appeal of the property.

Corrosion and Carbonation

Scarcity and corrosion of wall ties to brick cladding are significant concerns. Additionally, dense aggregate concrete ring beams can exhibit low to high rates of carbonation, which can weaken the concrete over time.

Damp and Moisture Issues

Due to the nature of no-fines concrete, these homes can be prone to damp and moisture ingress. The absence of fine aggregates creates larger voids within the concrete, which can allow water to penetrate more easily.

Roof and Ceiling Problems

Flat or shallow valley roofs covered with bituminous felt or asphalt can suffer from water pooling and leaks. Over time, the roofing material can deteriorate, leading to potential water damage to the interior of the home.

Defective Premises Act Considerations

Wimpey No-Fines houses are not generally classified as defective under the Defective Premises Act. However, due to the age and construction methods used, they may require more frequent maintenance and repairs compared to modern homes. It is essential for potential buyers to be aware of these considerations and to conduct thorough inspections before purchasing.

Inspection Tips for Surveyors

External Walls

When inspecting Wimpey No-Fines houses, surveyors should pay close attention to the external walls. Look for signs of vertical and horizontal cracking, as well as any evidence of corrosion in wall ties. Check for areas where the render may be deteriorating or separating from the underlying concrete.

Roof and Ceilings

Inspect the roof for signs of wear and tear, particularly if it is a flat or shallow valley roof. Look for pooling water, damaged bituminous felt or asphalt, and any signs of leaks. Inside the home, check the ceilings for water stains or sagging, which could indicate roof problems.

Damp and Moisture

Use a moisture meter to check for dampness in the walls and floors. Pay special attention to areas around windows and doors, as these are common entry points for moisture. Look for any signs of mould or mildew, which can indicate ongoing damp issues.

Structural Integrity

Examine the overall structural integrity of the home. Check for any signs of movement or settlement, particularly around the foundation and load-bearing walls. Ensure that the timber elements, such as joists and rafters, are in good condition and free from rot or insect damage.

Conclusion

Wimpey No-Fines houses represent a significant chapter in the UK’s post-war housing history. While they offer unique architectural features and historical value, potential buyers and investors must be aware of the typical defects and maintenance requirements associated with these properties. Conducting a thorough inspection and understanding the construction details can help ensure a sound investment.

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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