The Genesis of Dyke CCC Houses

The Dyke CCC house, a product of post-war Britain, stands as a testament to the ingenuity and resourcefulness of the era. Manufactured by Clothed Concrete Construction Ltd and designed by H.G. Dyke, these properties were constructed in the 1940s, with approximately 450 units built. These houses, also known as Clothed Concrete Construction or simply Dyke houses, were part of a broader effort to address the housing shortage following World War II.

Typical Locations and Identification Characteristics

Dyke CCC houses are predominantly found in suburban areas across the UK, particularly in regions that experienced significant bomb damage during the war. These properties are easily identifiable by their distinct architectural features:

• Structure: 2-storey semi-detached houses.
• Roof: Medium pitch hipped roof covered with tiles.
• External Walls: Storey height Precast Reinforced Concrete (PRC) panels.
• First Floor Panels: Generally finished in darker aggregate, oversailing the ground floor panels.

Construction Details

Substructure

The substructure of Dyke CCC houses consists of concrete strip footings with integral pad foundations and a brick underbuilding. A Damp Proof Course (DPC) is present, along with Precast Concrete (PC) plinth units.

Main Frame

The main frame is constructed using storey height L-section PC corner columns joined by connecting plates cast into the ground floor column and bolted to the upper column. Storey height PC columns are connected with bolted steel connection plates, and Rolled Steel Angle (RSA) is bolted to columns at the first floor and eaves level. PRC beams are used at the first floor and eaves level.

External Walls

The external walls feature 5″ x 3″ PRC posts and storey height textured finish tray-shaped PRC panels, stiffened by 3″ webs on the ground floor and exposed aggregate finish stiffened by 5″ webs on the first floor. These walls also include a cavity and PC panels.

Separating Wall

The separating wall consists of storey height PRC columns, 5″ PRC panels, a cavity, and plasterboard.

Partitions

Partitions are made of clinker PC blocks.

Ground Floor

The ground floor is constructed from concrete.

First Floor

The first floor features inverted T-shaped PRC secondary beams on RSA bolted to PRC beams, with a 1/4″ restraining bar.

Ceilings

Ceilings are lined with plasterboard.

Roof

The roof comprises inverted T-shaped PRC secondary beams on RSA bolted to PRC beams, timber rafters, and tiles.

Variants

Some Dyke CCC houses have external walls lined with plasterboard backed with ‘Corkcrete’ corkboard or expanded rubber and building paper, or with hollow clay block tiles. Partitions on the ground floor may be made of hollow blocks, while timber stud partitions filled with granulated cork and lined with plasterboard are used above.

Typical Hazards and Risks

Cracking and Spalling

One of the most common issues with Dyke CCC houses is the cracking and spalling of PRC external wall components. This can lead to significant structural concerns if not addressed promptly.

Cast-in Chlorides

While cast-in chlorides are not present in the panels, columns, and main beams, they are found in posts and secondary beams. This can lead to corrosion and further structural degradation.

Corrosion of RSA

The corrosion of RSA fixed to the foundation plinth is another prevalent issue. This can cause the outward displacement of the base of the ground floor wall, compromising the structural integrity of the property.

High Alumina Cement (HAC) Concrete

Some posts in Dyke CCC houses are made of HAC concrete, which is known for its susceptibility to chemical degradation over time.

Designated Defective

Dyke CCC houses are classified as defective under the Defective Premises Act. This designation is due to the inherent structural issues and the use of materials that are prone to degradation over time. As a result, these properties may require significant remedial work to ensure their safety and longevity.

Inspection Guide for Surveyors

When inspecting a Dyke CCC house, surveyors should pay close attention to the following areas:

External Walls

• Cracking and Spalling: Look for signs of cracking and spalling in the PRC panels.
• Corrosion: Check for corrosion in the RSA fixed to the foundation plinth.
• Displacement: Inspect for any outward displacement of the base of the ground floor wall.

Posts and Beams

• Chlorides: Test for the presence of cast-in chlorides in posts and secondary beams.
• HAC Concrete: Identify any posts made of HAC concrete and assess their condition.

Roof and Floors

• Structural Integrity: Examine the condition of the inverted T-shaped PRC secondary beams and RSA bolted to PRC beams.
• Water Damage: Check for any signs of water damage or leaks in the roof and floors.

Internal Partitions

• Material Condition: Assess the condition of clinker PC blocks and timber stud partitions filled with granulated cork.

Typical Defects

Cracking and Spalling

As mentioned earlier, cracking and spalling of PRC external wall components are common defects in Dyke CCC houses. This can lead to water ingress and further structural damage if not addressed.

Corrosion

Corrosion of RSA fixed to the foundation plinth is another typical defect. This can cause the outward displacement of the base of the ground floor wall, leading to potential structural failure.

Chloride Contamination

The presence of cast-in chlorides in posts and secondary beams can lead to corrosion and structural degradation over time.

HAC Concrete Degradation

Posts made of HAC concrete are prone to chemical degradation, which can compromise the structural integrity of the property.

Remedial Measures

External Wall Repairs

To address cracking and spalling, it is essential to repair or replace the affected PRC panels. This may involve the use of modern materials and techniques to ensure long-term durability.

Corrosion Treatment

Corrosion of RSA fixed to the foundation plinth can be treated by removing the corroded sections and replacing them with new, corrosion-resistant materials. Protective coatings can also be applied to prevent future corrosion.

Chloride Mitigation

To mitigate the effects of cast-in chlorides, it may be necessary to replace the affected posts and secondary beams with new, chloride-free materials.

HAC Concrete Replacement

Posts made of HAC concrete should be replaced with new, durable materials to prevent chemical degradation and ensure the structural integrity of the property.

Conclusion

Dyke CCC houses, with their unique construction and historical significance, present both opportunities and challenges for home buyers and investors. Understanding the typical characteristics, hazards, and defects associated with these properties is crucial for making informed decisions. By conducting thorough inspections and implementing appropriate remedial measures, it is possible to preserve the structural integrity and value of these homes.

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.

---