Historical Context and Origins

The Mac-Girling house, a notable example of system-built properties, emerged in the 1940s as a response to the urgent need for housing in post-war Britain. Designed by J E M MacGregor and manufactured by Girlings Ferro-Concrete Co. Ltd, these houses were part of a broader movement to provide quick, affordable, and durable homes for the burgeoning population. The Mac-Girling house is a two-storey semi-detached property, characterized by its medium pitch hipped roof covered with concrete tiles and external walls made of vertically fluted reconstituted stone-faced hollow precast (PC) blocks.

Manufacturers and Designers

Girlings Ferro-Concrete Co. Ltd

Girlings Ferro-Concrete Co. Ltd was a prominent manufacturer in the mid-20th century, specializing in the production of precast concrete components. Their expertise in ferro-concrete technology allowed them to produce durable and cost-effective housing solutions, which were in high demand during the post-war reconstruction period.

J E M MacGregor

J E M MacGregor, the designer of the Mac-Girling house, was an innovative architect who embraced the use of precast concrete in residential construction. His designs focused on creating functional and aesthetically pleasing homes that could be rapidly constructed to meet the housing needs of the time.

Typical Characteristics of the Mac-Girling House

External Features

• Roof: The Mac-Girling house features a medium pitch hipped roof covered with concrete tiles. This design not only provides a distinctive aesthetic but also ensures durability and weather resistance.
• Walls: The external walls are constructed from vertically fluted reconstituted stone-faced hollow PC blocks. This unique design element adds to the visual appeal of the property while providing structural integrity.
• Canopy: An inverted scallop shell concrete canopy over the front door is a distinctive feature of the Mac-Girling house, adding a touch of elegance to the entrance.

Internal Features

• Ground Floor: The ground floor is typically made of concrete, providing a solid and durable base for the property.
• First Floor: The first floor consists of timber boarding on timber joists, offering a balance of strength and flexibility.
• Partitions: Loadbearing walls are constructed from PC blocks, while non-loadbearing walls are made from lightweight PC blocks, ensuring both stability and ease of construction.

Typical Hazards and Risks

Structural Concerns

One of the primary concerns with Mac-Girling houses is the potential for structural issues related to the use of precast concrete. Over time, the concrete can deteriorate, leading to problems such as cracking, spalling, and corrosion of the steel reinforcement within the concrete.

Moisture Ingress

Due to the nature of the construction materials, Mac-Girling houses can be susceptible to moisture ingress. This can lead to issues such as dampness, mould growth, and deterioration of the internal finishes.

Thermal Performance

The thermal performance of Mac-Girling houses may not meet modern standards, leading to higher energy consumption and reduced comfort levels for occupants. Upgrading the insulation and improving the thermal efficiency of the property can be a significant consideration for potential buyers.

Defective Premises Act and Mac-Girling Houses

The Mac-Girling house is classified as defective under the Defective Premises Act. This classification means that the property may have inherent defects that could affect its structural integrity and safety. It is essential for potential buyers to be aware of this classification and to undertake a thorough inspection and assessment of the property before making a purchase.

Inspection and Assessment Guide for Surveyors

Reinforced Concrete Durability

When inspecting a Mac-Girling house, surveyors should pay close attention to the durability of the reinforced concrete components. Guidance on this can be found in the following resources:

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

Substructure

• Footings: Inspect the concrete strip footings for signs of cracking, settlement, or other structural issues.
• DPC: Ensure that the damp-proof course (DPC) is intact and functioning correctly to prevent moisture ingress.

External Walls

• PC Cavity Blocks: Check the condition of the 4′ x 2′ x 11″ PC cavity blocks, paying particular attention to the vertically fluted external leaf and the plain-faced inner leaf of cellular concrete.
• RC Columns: Inspect the 6″ x 3″ reinforced concrete (RC) columns cast within the cavity for signs of corrosion or deterioration.
• Lintels and Jambs: Examine the fluted PC lintels over openings and the PC window jambs and sills for any signs of structural issues.

Separating and Partition Walls

• Separating Wall: Inspect the 4″ lightweight cellular concrete block cavity wall for any signs of movement or cracking.
• Partitions: Check the loadbearing and non-loadbearing walls for structural integrity and any signs of damage.

Floors

• Ground Floor: Inspect the concrete ground floor for any signs of cracking, settlement, or moisture ingress.
• First Floor: Check the timber boarding and joists for signs of rot, insect infestation, or structural weakness.

Roof

• Timber Joists and Purlins: Inspect the timber joists and purlins for signs of rot, insect infestation, or structural issues.
• Concrete Tiles: Check the condition of the concrete tiles for any signs of damage or weathering.

Typical Defects Common in Mac-Girling Houses

Concrete Deterioration

Over time, the precast concrete components of Mac-Girling houses can deteriorate, leading to issues such as cracking, spalling, and corrosion of the steel reinforcement. Regular maintenance and timely repairs are essential to address these issues and ensure the structural integrity of the property.

Moisture-Related Issues

Due to the nature of the construction materials, Mac-Girling houses can be prone to moisture ingress, leading to dampness, mould growth, and deterioration of internal finishes. Ensuring that the DPC is intact and functioning correctly, as well as addressing any issues with the external walls, can help mitigate these problems.

Thermal Efficiency

The thermal performance of Mac-Girling houses may not meet modern standards, leading to higher energy consumption and reduced comfort levels for occupants. Upgrading the insulation and improving the thermal efficiency of the property can be a significant consideration for potential buyers.

Construction Details

Substructure

The substructure of Mac-Girling houses consists of concrete strip footings and two courses of plain-faced PC blocks. A damp-proof course (DPC) is installed to prevent moisture ingress.

External Walls

The external walls are constructed from 4′ x 2′ x 11″ PC cavity blocks, with a vertically fluted external leaf of reconstituted stone and a plain-faced inner leaf of cellular concrete. Reinforced concrete (RC) columns are cast within the cavity formed by the profiled ends of the cavity blocks and connected to PC eaves units with an RC core forming a continuous tie. Fluted PC corner blocks and fluted PRC lintels over openings are also characteristic features.

Separating Wall

The separating wall is constructed from 4″ lightweight cellular concrete block cavity wall bonded to the external wall by steel cramps.

Partitions

Loadbearing walls are constructed from PC blocks, while non-loadbearing walls are made from lightweight PC blocks.

Floors

The ground floor is made of concrete, while the first floor consists of timber boarding on timber joists.

Roof

The roof is constructed from timber joists and purlins, covered with concrete tiles. In some variants, the first floor may consist of 6″ deep hollow rectangular PRC beams, and the roof may be constructed from steel trusses.

Variants

There are some variants of the Mac-Girling house, including:

• First Floor: In some cases, the first floor may consist of 6″ deep hollow rectangular PRC beams.
• Roof: Some variants may feature a roof constructed from steel trusses instead of timber joists and purlins.

Conclusion

The Mac-Girling house, with its distinctive design and construction, represents an important chapter in the history of British housing. While these properties offer unique architectural features and historical significance, potential buyers must be aware of the typical hazards and risks associated with this type of construction. Thorough inspection and assessment, guided by expert knowledge and resources, are essential to ensure the safety and longevity 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.

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