Historical Context and Origins

The Edinburgh Foamed Slag house, a unique and rare property type, was constructed during a period of significant innovation in the UK housing sector. Built in 1944, these houses were a product of the post-war era, a time when the demand for affordable and quickly constructed homes was at an all-time high. Only two of these houses were ever built, making them a rare find in today’s property market.

The construction of these houses was undertaken by Holland and Hannen and Cubitts, a well-known construction firm of the time. The design was the brainchild of S Bunton, who aimed to create a durable and cost-effective housing solution using innovative materials and construction techniques. The use of foamed slag aggregate concrete was a notable feature, setting these houses apart from other post-war constructions.

Typical Characteristics and Identification

External Features

Edinburgh Foamed Slag houses are typically two-storey, semi-detached properties. They feature a medium pitch gable roof covered with tiles, which is a common characteristic of houses from this era. The external walls are rendered throughout, providing a uniform and somewhat modern appearance. A flat canopy over the front door is another distinctive feature, adding to the aesthetic appeal of these homes.

Internal Features

Internally, these houses were designed with practicality in mind. The ground floor consists of timber boarding on a foamed slag aggregate concrete base, while the first floor features timber boarding on timber joists. Ceilings are typically plasterboard, providing a smooth and clean finish. Loadbearing partitions are made of 7″ foamed slag aggregate concrete, ensuring structural integrity, while non-loadbearing partitions are constructed from 4″ foamed slag aggregate PC blocks.

Construction Details

Substructure

The substructure of Edinburgh Foamed Slag houses includes a concrete underbuilding and a concrete slab. A damp-proof course (DPC) is also present, which is essential for preventing moisture ingress from the ground.

External Walls

The external walls are rendered and constructed from 7″ foamed slag aggregate concrete. This material was chosen for its lightweight and insulating properties. Precast reinforced concrete (PRC) lintels and trims around windows are also used, adding to the structural robustness of the building.

Separating Walls

Separating walls between the semi-detached units are made from 4″ foamed slag aggregate concrete cavity walls with a 2″ cavity. This design helps in sound insulation and provides additional thermal efficiency.

Partitions

Loadbearing partitions are constructed from 7″ foamed slag aggregate concrete, while non-loadbearing partitions are made from 4″ foamed slag aggregate PC blocks. In some variants, non-loadbearing partitions are made from 2″ gypsum plaster planks.

Floors

The ground floor consists of timber boarding on a 2″ foamed slag aggregate concrete base, which sits on a 4″ concrete layer. This is further supported by a 1/2″ cold asphalt damp-proof membrane (DPM) on 3″ ashes on a 6″ concrete slab. The first floor features timber boarding on timber joists, providing a sturdy and reliable structure.

Roof

The roof is constructed using timber rafters and timber sarking, covered with bituminous felt and tiles. This combination ensures durability and weather resistance, essential for the UK’s variable climate.

Typical Hazards and Risks

Structural Integrity

One of the primary concerns with Edinburgh Foamed Slag houses is the potential for structural issues. The use of foamed slag aggregate concrete, while innovative, can lead to problems over time. The material is prone to carbonation, which can reduce the alkalinity of the concrete and lead to corrosion of the embedded steel reinforcement. This can compromise the structural integrity of the building.

Moisture Ingress

Despite the presence of a damp-proof course, moisture ingress can still be a concern, particularly if the DPC has deteriorated over time. This can lead to damp issues within the property, which can cause further structural damage and create an unhealthy living environment.

Thermal Efficiency

While the foamed slag aggregate concrete provides some level of insulation, these houses may not meet modern thermal efficiency standards. This can result in higher energy bills and a less comfortable living environment, particularly during the colder months.

Asbestos

As with many properties built during this period, there is a potential risk of asbestos being present in the construction materials. Asbestos was commonly used for its fire-resistant properties, but it poses significant health risks if disturbed.

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 Edinburgh Foamed Slag houses were innovative for their time, they may not meet modern building standards. If significant defects are found, these properties could be considered defective under the Act.

Inspection and Assessment Guide

Preliminary Inspection

When inspecting an Edinburgh Foamed Slag house, start with a thorough external examination. Look for signs of cracking or deterioration in the render, as this can indicate underlying issues with the foamed slag aggregate concrete. Pay particular attention to the areas around windows and doors, where PRC lintels and trims are used.

Internal Inspection

Inside the property, check for signs of damp or moisture ingress, particularly on the ground floor. Inspect the condition of the timber boarding and look for any signs of rot or decay. Examine the loadbearing and non-loadbearing partitions for any cracks or structural issues.

Roof Inspection

Inspect the roof from both the inside and outside. Check the condition of the tiles and the bituminous felt. Inside the loft space, look for any signs of water ingress or damage to the timber rafters and sarking.

Specialist Testing

Given the potential for carbonation and corrosion of the steel reinforcement, it may be necessary to carry out specialist testing. This can include measuring the carbonation depth and assessing the condition of the steel reinforcement. Guidance on these tests can be found in BRE Digest 444 and BR 254.

Typical Defects and Maintenance

Cracking and Spalling

Cracking and spalling of the foamed slag aggregate concrete are common defects in these properties. This can be caused by carbonation and subsequent corrosion of the steel reinforcement. Regular inspections and maintenance are essential to address these issues promptly.

Damp and Moisture Ingress

Damp and moisture ingress can lead to significant problems if not addressed. Ensure that the DPC is intact and consider installing additional damp-proofing measures if necessary. Regularly check for signs of damp and take action to address any issues promptly.

Roof Maintenance

The roof is a critical component of the property and requires regular maintenance. Ensure that the tiles and bituminous felt are in good condition and replace any damaged or missing tiles promptly. Regularly inspect the loft space for signs of water ingress and address any issues immediately.

Asbestos Management

If asbestos is present in the property, it is essential to manage it safely. Do not disturb any materials that may contain asbestos and seek professional advice if you need to carry out any work that could disturb these materials.

Conclusion

The Edinburgh Foamed Slag house is a unique and rare property type with a fascinating history. While these houses were innovative for their time, they come with specific challenges and risks that potential buyers and investors need to be aware of. By understanding the typical characteristics, construction details, and potential hazards, you can make an informed decision when considering the purchase of one of these properties.

Regular inspections and maintenance are essential to ensure the longevity and safety of these homes. If you are considering buying an Edinburgh Foamed Slag house, it is highly recommended to seek the expertise of a professional surveyor who can provide a thorough assessment and guide you through the process.

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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