Historical Context and Background

The Forrester-Marsh house, also known as Edward’s Construction, is a unique property type that emerged in the 1920s. Designed and manufactured by Edwards Construction Co. Ltd, these houses were part of a broader movement to address the housing shortage in the UK during the post-World War I era. With only 50 units built, these properties are relatively rare, making them a point of interest for both home buyers and property investors.

Identification Characteristics

Forrester-Marsh houses are easily identifiable by their distinct architectural features. These are two-storey terraced houses with a medium pitch hipped roof covered with tiles. The external walls are rendered, either with pebbledash or a smooth finish. One of the most notable features is the re-entrant front door porch, which adds a unique aesthetic to the property.

Typical Locations

These houses are predominantly found in suburban areas, particularly in regions that experienced rapid urban expansion during the 1920s. They are often located in well-established neighbourhoods, offering a blend of historical charm and modern amenities.

Construction Details

Understanding the construction details of Forrester-Marsh houses is crucial for anyone considering purchasing or investing in one. These properties were built using a combination of reinforced concrete (RC) and clinker aggregate concrete, which was a common practice at the time.

Substructure

The substructure consists of an RC slab that is deepened below load-bearing walls to form downstand beams. A damp-proof course (DPC) is also included to prevent moisture ingress.

External Walls

The external walls are a key feature of Forrester-Marsh houses. They are rendered and consist of a 2 1/2″ dense aggregate RC outer leaf, a 2 1/2″ ventilated cavity, and a 3″ clinker aggregate RC inner leaf. Wall ties are used to connect the two leaves, and the internal corners of the inner leaf are rounded. A brick header course is present at eaves level, and a timber wall plate is used to support the roof structure.

Separating Walls and Partitions

The separating walls between terraced units are made of concrete, providing good sound insulation. Internal partitions are constructed using a combination of clinker and dense aggregate concrete.

Floors

The ground floor is an RC slab, while the first floor consists of timber boarding on timber joists. This combination provides a sturdy and durable flooring system.

Roof

The roof structure is made of timber rafters and purlins, covered with tiles. This traditional roofing method offers good durability and weather resistance.

Typical Hazards and Risks

While Forrester-Marsh houses have stood the test of time, they are not without their hazards and risks. Understanding these issues is essential for potential buyers and investors.

Carbonation of Dense Aggregate RC External Walls

One of the primary concerns is the carbonation of the dense aggregate RC external walls. Over time, the concrete can become fully carbonated, leading to minor corrosion of the reinforcement. This can compromise the structural integrity of the walls if not addressed promptly.

Unsound Clinker Aggregate Concrete

The inner leaf of the external walls and internal partitions are made of clinker aggregate concrete, which can be unsound. This material is prone to degradation, leading to potential structural issues.

Cracking

Horizontal and vertical cracking of the dense aggregate RC external walls is another common issue. These cracks can allow moisture ingress, leading to further deterioration of the concrete and reinforcement.

Defective Premises Act

Forrester-Marsh houses are not classed as defective under the Defective Premises Act. However, the issues mentioned above can still pose significant risks if not properly managed. It is essential to conduct a thorough survey to identify and address any potential problems.

Inspection Guide for Surveyors

When inspecting a Forrester-Marsh house, surveyors should pay close attention to several key areas. This guide provides a step-by-step approach to ensure a comprehensive assessment.

External Walls

Inspect the external walls for signs of carbonation and corrosion. Look for any horizontal or vertical cracks, and assess their severity. Use a carbonation depth indicator to determine the extent of carbonation in the concrete.

Internal Partitions

Check the internal partitions for signs of degradation in the clinker aggregate concrete. Look for any cracks or areas of weakness that could indicate structural issues.

Roof Structure

Examine the roof structure for any signs of damage or deterioration. Check the condition of the timber rafters and purlins, and ensure that the tiles are intact and securely fastened.

Floors

Inspect the ground and first floors for any signs of damage or wear. Check the condition of the timber joists and boarding on the first floor, and ensure that the RC slab on the ground floor is free from cracks or other issues.

Damp-Proof Course

Ensure that the damp-proof course is intact and functioning correctly. Look for any signs of moisture ingress, such as damp patches or mould growth, which could indicate a failure of the DPC.

Typical Defects and How to Address Them

Understanding the typical defects associated with Forrester-Marsh houses is crucial for maintaining their structural integrity and value. Here are some common issues and how to address them.

Carbonation and Corrosion

To address carbonation and corrosion, it is essential to remove the affected concrete and replace it with new, non-carbonated material. This process may involve removing and replacing sections of the external walls, as well as treating the reinforcement to prevent further corrosion.

Cracking

Cracks in the external walls should be repaired promptly to prevent moisture ingress and further deterioration. This may involve filling the cracks with a suitable repair mortar and applying a protective coating to the surface of the walls.

Degradation of Clinker Aggregate Concrete

If the clinker aggregate concrete in the internal partitions is found to be unsound, it may be necessary to replace the affected sections with new, more durable material. This can help to ensure the structural integrity of the partitions and prevent further issues.

Roof Repairs

Regular maintenance of the roof structure is essential to prevent damage and ensure its longevity. This may involve replacing damaged or missing tiles, repairing or replacing timber rafters and purlins, and ensuring that the roof is properly ventilated to prevent moisture buildup.

Conclusion

The Forrester-Marsh house, with its unique architectural features and historical significance, offers a fascinating opportunity for home buyers and investors. However, understanding the construction details, typical hazards, and potential defects is crucial for making an informed decision. By conducting a thorough survey and addressing any issues promptly, you can ensure the longevity and value of these remarkable properties.

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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