Historical Context and Manufacturers

The Unit No-Fines house, a distinctive type of system-built property, emerged in the UK between 1927 and the 1950s. This period saw a significant demand for affordable and quickly constructed housing, driven by the need to rebuild after World War I and later, World War II. The Unit No-Fines house was a response to this demand, offering a practical solution to the housing crisis of the time.

The primary manufacturers of these houses were Unit Construction Co. Ltd and Wilson Lovatt and Sons Ltd. These companies were pioneers in the field of system-built properties, leveraging innovative construction techniques to produce homes rapidly and efficiently. The design and construction of these houses were spearheaded by Unit Construction Co. Ltd, which played a crucial role in shaping the architectural landscape of post-war Britain.

Identification Characteristics

Unit No-Fines houses are easily identifiable by several key characteristics. Typically, these properties are two-storey semi-detached or terraced houses. They feature a medium pitch hipped or gable roof, usually covered with clay or concrete tiles. The external walls are rendered throughout, giving the houses a uniform and somewhat austere appearance.

These houses are also known by several alternative names, including Lovatt, No-Fines, UCO, Unit, Wilson Lovatt, and Wilson Lovatt 83. Despite the different names, the core design and construction principles remain consistent across these variants.

Construction Details

Substructure

The substructure of Unit No-Fines houses typically consists of concrete strip footings and dense concrete underbuilding. A concrete slab forms the base, with a damp-proof course (DPC) integrated to prevent moisture ingress.

External Walls

The external walls are a defining feature of these houses. They are rendered and constructed from 8-inch clinker no-fines reinforced concrete (RC). This type of concrete is characterized by the absence of fine aggregates, which gives it a distinctive texture and appearance. Reinforcement is provided by 1/2-inch bars at the ground floor window head and below openings, extending up to 18 inches beyond the reveals.

Separating Walls and Partitions

Separating walls are made from 8-inch foamed slag concrete, a material known for its lightweight and insulating properties. Internal partitions are constructed from clinker concrete blocks, which are tied to the external and separating walls using iron hoops grouted into cored recesses. Below the DPC level, dense concrete blocks are used to ensure structural stability.

Floors

The ground floor is typically a concrete slab, providing a solid and durable base. The first floor consists of timber boarding laid on timber joists, offering a balance of strength and flexibility.

Roof

The roof structure comprises timber trusses, which support the weight of the concrete or clay tiles. This combination of materials ensures a robust and weather-resistant roof.

Chimney Breast

The chimney breast is constructed from foamed slag concrete, a material that offers good thermal insulation and fire resistance.

Variants

Pre-War Houses

Pre-war Unit No-Fines houses exhibit some variations in construction. The first floor may feature lightweight steel joists, and the roof may be supported by lightweight steel trusses. These modifications were likely introduced to reduce construction costs and time.

Post-War Houses

Post-war variants of these houses typically have external walls made from foamed slag concrete. The separating wall is also constructed from foamed slag no-fines concrete, while internal partitions are made from clinker blocks. The roof is usually covered with clay tiles, and the chimney breast is constructed from brick.

Typical Hazards and Risks

Cracking

One of the most common issues with Unit No-Fines houses is cracking. In pre-war houses, cracking is often observed in the clinker concrete above communal walkways and around door and window openings. In post-war houses, horizontal cracking is frequently seen in the foamed slag concrete external walls, coinciding with the reinforcement. This type of concrete is friable and weak, but generally sufficient for use in two-storey houses.

Unstable Aggregates

Another potential hazard is the presence of unstable fractions of unburnt coal in the aggregate. This can lead to long-term structural issues, as the unburnt coal can degrade over time, compromising the integrity of the concrete.

Moisture Ingress

Despite the presence of a damp-proof course, moisture ingress can still be a problem, particularly if the DPC has been damaged or compromised. This can lead to damp and mould issues, which can be detrimental to both the structure and the health of the occupants.

Defective Premises Act

Unit No-Fines houses are not generally classified as defective under the Defective Premises Act. However, the specific condition of each property can vary significantly, and it is essential to conduct a thorough survey to identify any potential issues. The presence of cracking, unstable aggregates, and moisture ingress can all impact the overall condition and safety of the property.

Inspection Guide for Surveyors

When inspecting a Unit No-Fines house, surveyors should pay close attention to several key areas:

External Walls

Check for signs of cracking, particularly around door and window openings. Horizontal cracking in post-war houses can indicate issues with the reinforcement in the foamed slag concrete. Also, look for signs of moisture ingress, such as damp patches or mould growth.

Roof

Inspect the roof for any signs of damage or wear. Check the condition of the tiles and the timber trusses. Look for any signs of water ingress, which can indicate issues with the roof covering or the flashing.

Floors

Examine the ground floor for any signs of cracking or movement. Check the condition of the timber joists and boarding on the first floor. Look for any signs of damp or rot, which can indicate issues with the DPC or moisture ingress.

Chimney Breast

Inspect the chimney breast for any signs of cracking or movement. Check the condition of the foamed slag concrete or brickwork. Look for any signs of water ingress, which can indicate issues with the flashing or the chimney cap.

Internal Partitions

Check the condition of the internal partitions, particularly around the iron hoops and cored recesses. Look for any signs of cracking or movement, which can indicate issues with the clinker concrete blocks.

Typical Defects

Cracking

As mentioned earlier, cracking is a common issue with Unit No-Fines houses. This can be caused by a variety of factors, including movement in the foundations, thermal expansion and contraction, and issues with the reinforcement in the concrete.

Moisture Ingress

Moisture ingress is another common defect, particularly if the DPC has been damaged or compromised. This can lead to damp and mould issues, which can be detrimental to both the structure and the health of the occupants.

Unstable Aggregates

The presence of unstable fractions of unburnt coal in the aggregate can lead to long-term structural issues. This can cause the concrete to degrade over time, compromising the integrity of the structure.

Friable Concrete

The foamed slag concrete used in post-war houses is friable and weak, which can lead to issues with the structural integrity of the external walls. This can be exacerbated by the presence of horizontal cracking, which can indicate issues with the reinforcement.

Conclusion

The Unit No-Fines house is a distinctive and historically significant type of system-built property. While these houses offer a practical and affordable housing solution, they are not without their issues. Cracking, moisture ingress, and unstable aggregates are all common defects that can impact the overall condition and safety of the property.

When considering the purchase of a Unit No-Fines house, it is essential to conduct a thorough survey to identify any potential issues. By understanding the typical characteristics and common defects of these houses, buyers and investors can make informed decisions and ensure the long-term safety and stability of their 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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