Historical Context and Origins

The Blackburn No-Fines house is a distinctive type of system-built property that emerged in the 1950s, a period marked by a significant housing shortage in the UK. The post-war era necessitated rapid construction methods to address the urgent need for affordable housing. Blackburn (Dumbarton) Ltd, in collaboration with the Scottish Special Housing Association (SSHA), designed and manufactured these homes. Approximately 60 of these properties were built, primarily in Scotland, although some examples can be found in other parts of the UK.

The term “No-Fines” refers to the type of concrete used in the construction of these houses. Unlike traditional concrete, which includes fine aggregates like sand, no-fines concrete is made using only coarse aggregates and cement. This unique composition results in a lighter, more porous material that offers several advantages, including better thermal insulation and reduced weight.

Identification Characteristics

Blackburn No-Fines houses are typically two-storey, semi-detached properties. They are easily identifiable by their medium pitch gable roofs covered with concrete tiles and their fully rendered external walls. Some variations include a flat roof canopy over the front door, adding a touch of architectural diversity.

Key Features:

• Roof: Medium pitch gable roof with concrete tiles.
• External Walls: Fully rendered.
• Front Door Canopy: Some houses feature a flat roof canopy.

Construction Details

Understanding the construction details of Blackburn No-Fines houses is crucial for both buyers and surveyors. These properties were built using a combination of no-fines concrete and timber frame panels, resulting in a unique structural composition.

Substructure

• Footings: Concrete strip footings.
• Under-building: Brick.
• Slab: Concrete slab with Damp Proof Course (DPC).

External Walls

• Material: Rendered 8″ no-fines concrete.
• Frame: Storey height timber frame panels lined with plasterboard over building paper.
• Reinforcement: Reinforced concrete (RC) ring beam at first floor and eaves level with two reinforcing bars at the base.

Separating Wall

• Material: 6″ no-fines concrete.
• Reinforcement: RC beam at eaves level.

Partitions

• Material: Timber stud lined with plasterboard.

Floors

• Ground Floor: Concrete.
• First Floor: RC slab on RC spine beam and timber frame panels.

Ceilings

• Material: Plasterboard.

Roof

• Structure: Timber trussed purlins, timber rafters, sarking, and concrete tiles.

Typical Hazards and Risks

While Blackburn No-Fines houses offer several benefits, they also come with specific hazards and risks that potential buyers and investors should be aware of.

Structural Integrity

The use of no-fines concrete, while advantageous in some respects, can pose challenges related to structural integrity. Over time, the porous nature of the material can lead to issues such as:

• Carbonation: The process by which carbon dioxide from the air penetrates the concrete, leading to a reduction in alkalinity and potential corrosion of the reinforcing steel.
• Corrosion of Steel: As the steel reinforcement corrodes, it can expand and cause cracking or spalling of the concrete.

Thermal Performance

While no-fines concrete offers better thermal insulation compared to traditional concrete, it may still fall short of modern insulation standards. This can result in higher energy costs for heating and cooling.

Moisture Penetration

The porous nature of no-fines concrete can also make these houses more susceptible to moisture penetration, leading to damp issues and potential mould growth.

Defective Premises Act

One of the critical considerations for potential buyers is whether Blackburn No-Fines houses are classified as defective under the Defective Premises Act. As of 2024, these properties are not universally classified as defective. However, their unique construction and potential for specific issues mean that a thorough survey is essential before purchase.

Inspection Guidelines for Surveyors

When inspecting a Blackburn No-Fines house, surveyors should pay close attention to several key areas to ensure a comprehensive assessment.

External Inspection

• Walls: Check for signs of cracking, spalling, or other damage to the rendered surface.
• Roof: Inspect the condition of the concrete tiles and the underlying timber structure.
• Canopy: If present, examine the flat roof canopy for signs of water ingress or structural issues.

Internal Inspection

• Walls: Look for signs of damp, mould, or other moisture-related issues.
• Floors: Check the condition of the concrete slab and the RC spine beam.
• Ceilings: Inspect the plasterboard for any signs of sagging or damage.

Structural Assessment

• Carbonation Depths: Measure the depth of carbonation in the no-fines concrete to assess the risk of steel corrosion.
• Reinforcement Condition: Examine the condition of the reinforcing steel, particularly in areas where cracking or spalling is evident.

Thermal Performance

• Insulation: Assess the thermal performance of the property and identify any areas where additional insulation may be required.

Typical Defects and Maintenance

Understanding the typical defects associated with Blackburn No-Fines houses can help buyers and investors make informed decisions and plan for necessary maintenance.

Common Defects

• Cracking and Spalling: As mentioned earlier, the porous nature of no-fines concrete can lead to cracking and spalling, particularly in areas exposed to moisture.
• Damp and Mould: Moisture penetration can result in damp issues and mould growth, particularly in poorly ventilated areas.
• Thermal Bridging: The unique construction of these houses can lead to thermal bridging, where heat is conducted through the structure, resulting in cold spots and potential condensation issues.

Maintenance Tips

• Regular Inspections: Conduct regular inspections to identify and address issues early.
• Moisture Control: Implement measures to control moisture, such as improving ventilation and addressing any sources of water ingress.
• Thermal Upgrades: Consider upgrading the insulation to improve thermal performance and reduce energy costs.

Conclusion

The Blackburn No-Fines house represents a unique chapter in the history of UK housing. While these properties offer several advantages, including rapid construction and better thermal insulation compared to traditional concrete, they also come with specific challenges. Understanding the construction details, typical hazards, and maintenance requirements is crucial for potential buyers and investors.

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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References

• BRE Digest 444, Parts 1–3: Corrosion of Steel in Concrete
• BR 254: Repair and Maintenance of Reinforced Concrete
• BR 19: Carbonation Depths in Structural-Quality Concrete