Understanding the NCB House

The National Coal Board (NCB) house is a unique and intriguing property type that emerged in the late 1960s and continued into the 1970s. These homes were part of a broader initiative to address the housing shortage in the UK during that period. Designed by T P Bennett & Son, only ten of these properties were built, making them a rare find in today’s property market. This article aims to provide a detailed overview of NCB houses, including their construction, typical characteristics, potential hazards, and what to look for when inspecting these properties.

Historical Context and Manufacturing

Period Built and Typical Locations

NCB houses were constructed between 1968 and the 1970s. These properties are typically found in areas that were heavily influenced by the coal industry, given their association with the National Coal Board. While they are not widespread, their unique construction and design make them a point of interest for property enthusiasts and investors alike.

Manufacturers and Designers

The National Coal Board was responsible for the construction of these houses, with the design work carried out by T P Bennett & Son. The collaboration aimed to create functional and durable homes that could be quickly assembled to meet the urgent housing needs of the time.

Typical Characteristics of NCB Houses

External Features

NCB houses are generally two-storey terraced homes with a medium pitch gable roof covered with concrete tiles. Some variations include shallow pitch roofs with gables on the front elevation. The external walls are a mix of brick slips or storey-height precast (PC) panels, often infilled with eaves-height shiplap timber boarding. The gable apex is also typically clad in shiplap timber boarding. Some houses feature aluminium windows, adding to their distinctive appearance.

Internal Features

Internally, NCB houses have a straightforward yet functional layout. The ground floor is usually a concrete slab, while the first floor consists of plywood on timber joists. Partitions are made of timber stud lined with plasterboard, and the ceilings are also plasterboard. The separating walls between properties are storey-height PC panels with cast-in pockets to accommodate the first-floor joists.

Construction Details

Substructure

The substructure of NCB houses includes concrete strip footings, brick under-building, and a concrete slab with a damp-proof course (DPC). This foundation provides a stable base for the rest of the structure.

External Walls

The external walls are a key feature of NCB houses. They are typically brick-faced storey-height lightweight PC panels, with panel widths in multiples of 12 inches. These panels are joined by conventional open drain jointing or with mild steel (MS) ties and dry-pack. The brick joints are pointed with mortar or mastic. Eaves-height timber frame panels are clad with shiplap timber boarding and lined with plasterboard, with insulation between the frame studs.

Roof

The roof structure consists of timber trusses covered with concrete tiles. This design provides both durability and a traditional aesthetic.

Typical Hazards and Risks

Structural Concerns

One of the primary concerns with NCB houses is the potential for structural issues, particularly related to the reinforced concrete elements. Over time, concrete can suffer from carbonation, leading to the corrosion of embedded steel reinforcement. This can compromise the structural integrity of the property.

Timber Decay

The use of timber in the external cladding and internal partitions means that NCB houses are susceptible to timber decay, particularly if the timber has been exposed to moisture. This can lead to rot and structural weakening.

Insulation and Energy Efficiency

While the original design included insulation between the frame studs, the standards of the 1960s and 1970s are not up to modern energy efficiency requirements. As a result, these homes may require additional insulation to meet current standards and improve energy efficiency.

Defective Premises Act Considerations

Under the Defective Premises Act, properties must be fit for habitation and free from significant defects. While NCB houses were not specifically investigated by the Building Research Establishment (BRE), general guidance on the inspection and assessment of reinforced concrete durability can be found in BRE Digest 444 (Parts 1-3), BR 254, and BR 19. These documents provide valuable information on the corrosion of steel in concrete, repair and maintenance of reinforced concrete, and carbonation depths in structural-quality concrete.

Inspection Guide for NCB Houses

External Inspection

1. Roof: Check the condition of the concrete tiles and timber trusses. Look for signs of wear, damage, or leaks.
2. Walls: Inspect the brick slips and PC panels for cracks, movement, or signs of deterioration. Pay particular attention to the joints and any evidence of corrosion in the reinforcement.
3. Timber Cladding: Examine the shiplap timber boarding for signs of rot, decay, or insect infestation. Ensure that the timber is adequately protected from moisture.
4. Windows and Doors: Check the condition of any aluminium windows and doors. Look for signs of corrosion, damage, or poor sealing.

Internal Inspection

1. Floors: Inspect the concrete ground floor and plywood first floor for signs of movement, cracking, or dampness.
2. Partitions: Check the timber stud partitions for signs of damage, rot, or structural weakness.
3. Ceilings: Examine the plasterboard ceilings for cracks, sagging, or water damage.
4. Insulation: Assess the insulation between the frame studs. Consider upgrading to modern standards if necessary.

Structural Elements

1. Reinforced Concrete: Use non-destructive testing methods to assess the condition of the reinforced concrete elements. Look for signs of carbonation and corrosion.
2. Timber Frame: Inspect the timber frame for signs of decay, particularly in areas exposed to moisture.

Typical Defects in NCB Houses

Concrete Deterioration

Over time, the reinforced concrete elements in NCB houses can suffer from carbonation, leading to the corrosion of embedded steel reinforcement. This can result in cracking, spalling, and a loss of structural integrity.

Timber Decay

The timber elements in NCB houses, particularly the shiplap timber boarding and internal partitions, are susceptible to decay if exposed to moisture. This can lead to rot, structural weakening, and potential insect infestation.

Insulation Issues

The original insulation in NCB houses may not meet modern standards, leading to poor energy efficiency and higher heating costs. Upgrading the insulation can improve comfort and reduce energy bills.

Window and Door Failures

Aluminium windows and doors, while durable, can suffer from corrosion and poor sealing over time. This can lead to drafts, water ingress, and reduced energy efficiency.

Variants of NCB Houses

While the basic design of NCB houses is consistent, there are some variations in the construction of the external walls. These include:

1. Reinforced and Tied External Walls: Some NCB houses feature external walls with additional reinforcement and ties for added stability.
2. Single Leaf PC Panels: In some cases, the external walls are constructed from 4 1/2-inch single leaf PC panels, with or without returns.
3. Cavity Walls: Some NCB houses have external cavity walls made of brick and lightweight concrete, with polystyrene insulation in the cavity.
4. Brick-Faced PC Panels: Another variation includes external walls made of PC panels faced with brick slips.

Conclusion

NCB houses are a unique and rare property type with a distinct construction and design. While they offer a fascinating glimpse into the housing solutions of the late 1960s and 1970s, they also come with specific challenges and potential hazards. Understanding the typical characteristics, construction details, and common defects of NCB houses is crucial for anyone considering purchasing or investing in one of these properties.

When inspecting an NCB house, it is essential to pay close attention to the condition of the reinforced concrete elements, timber components, and insulation. Addressing any issues promptly can help maintain the structural integrity and energy efficiency of the property.

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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