Introduction to Building Systems Ltd Houses

When it comes to purchasing a property in the UK, understanding the intricacies of different construction types is crucial. One such type that often piques the interest of home buyers and investors is the Building Systems Ltd house. These properties, constructed between 1964 and 1967, are a testament to the innovative building techniques of their time. In this article, we will delve into the history, characteristics, and potential risks associated with Building Systems Ltd houses, providing you with a thorough understanding to make an informed decision.

Historical Context and Manufacturers

Building Systems Ltd houses were manufactured during a period of rapid post-war reconstruction in the UK. The need for quick and efficient housing solutions led to the development of various system-built properties. Building Systems Ltd, with designers A Wilson and P H Johnson & Sons, played a significant role in this era. These houses, also known as British Ropes, BSL, or Doncaster houses, were primarily constructed between 1964 and 1967, with a total of 310 units built.

Identification Characteristics

Architectural Features

Building Systems Ltd houses are typically two-storey semi-detached or terraced houses. They are easily identifiable by their shallow pitch gable roofs, which are covered with either profiled asbestos cement sheets or profiled steel sheets. The external walls of these houses vary; some are entirely brick, while others feature a combination of brick and timber boarding. The front and rear walls often have timber boarding below the ground floor windows, and the first floor level and gable wall are clad with vertical timber boarding and tile hanging.

Structural Elements

One of the distinctive features of these houses is the exposed eaves height PRC (Precast Reinforced Concrete) columns at the corners and separating walls. These columns are paired with exposed PSRC (Pre-Stressed Reinforced Concrete) beams at the first-floor level, centrally located in the gable wall. Some houses also have a single-storey flat roof entrance with vertical timber boarding on the front elevation.

Construction Details

Substructure

The substructure of Building Systems Ltd houses consists of concrete pads below the columns, 9″ x 5″ PRC ground beams, and air vents. A Damp Proof Membrane (DPM) is also incorporated to prevent moisture ingress.

Frame

The frame of these houses includes eaves height PRC columns, typically 6″ x 6″ at the corners and 6″ x 5″ or 7″ x 4″ internally. Steel plates are fixed to each column base, and 8″ x 4″ PSRC beams are used at the first floor and eaves levels.

External Walls

The external walls are constructed with storey-height timber frame panels. These panels are clad with vertical timber boarding up to the first-floor level on the front and rear walls, and brick on the gable wall. Tile hanging on timber battens is used above the first-floor level, and the walls are lined with hardboard or chipboard. Insulation is placed between the frame studs to enhance thermal performance.

Separating Wall

The separating wall between properties consists of PRC columns and beams, with a honeycomb plasterboard cavity wall separated from the columns by an asbestos felt barrier.

Partitions

Internal partitions are made of honeycomb hardboard or plasterboard, providing a lightweight yet sturdy structure.

Floors

The ground floor is constructed with chipboard on timber joists, while the first floor also uses chipboard on timber joists. This construction method ensures a solid and stable flooring system.

Ceilings

Ceilings in these houses are typically made of plasterboard or chipboard, providing a smooth and even finish.

Roof

The roof structure includes a plywood lattice ridge beam, galvanised sheet steel roof components with integral gutters, fascia, and soffit units. The roof covering is made of asbestos cement sheets, which were commonly used during the construction period.

Typical Hazards and Risks

Asbestos

One of the primary concerns with Building Systems Ltd houses is the presence of asbestos, particularly in the roof sheets and possibly in other areas such as the separating wall barrier. Asbestos poses significant health risks if disturbed, so it is crucial to have a professional asbestos survey conducted before any renovation or demolition work.

Concrete Durability

The PRC columns and beams used in these houses can be susceptible to corrosion, especially if the concrete has not been adequately maintained. Corrosion of the steel reinforcement within the concrete can lead to structural weaknesses. Guidance on inspecting and assessing the durability of reinforced concrete can be found in BRE Digest 444 (Parts 1-3) and BR 254.

Thermal Insulation

While the original construction included insulation between the frame studs, it may not meet current standards for thermal performance. Upgrading the insulation can improve energy efficiency and reduce heating costs.

Damp and Moisture Ingress

The presence of a Damp Proof Membrane (DPM) is essential to prevent moisture ingress. However, over time, the effectiveness of the DPM can diminish, leading to potential damp issues. Regular inspections and maintenance are necessary to ensure the property remains dry and free from damp-related problems.

Defective Premises Act

Building Systems Ltd houses are not specifically listed as defective under the Defective Premises Act. However, given their age and the potential issues with asbestos and concrete durability, it is advisable to conduct thorough inspections and assessments to ensure the property meets current safety and structural standards.

Inspection Guide for Surveyors

External Inspection

1. Roof: Check for any signs of damage or deterioration in the asbestos cement or steel sheets. Look for any missing or broken tiles and inspect the gutters and fascia for blockages or damage.
2. Walls: Examine the brickwork and timber boarding for any signs of decay, cracks, or movement. Pay particular attention to the areas around windows and doors.
3. Columns and Beams: Inspect the exposed PRC columns and PSRC beams for any signs of corrosion or spalling. Use a cover meter to check the depth of concrete cover over the reinforcement.
4. Damp Proof Membrane: Look for any signs of rising damp or moisture ingress at the base of the walls. Check the air vents for blockages.

Internal Inspection

1. Partitions: Check the condition of the honeycomb hardboard or plasterboard partitions. Look for any signs of damage, damp, or mould.
2. Floors: Inspect the chipboard flooring for any signs of movement, warping, or damage. Pay attention to any areas that feel soft or spongy underfoot.
3. Ceilings: Examine the plasterboard or chipboard ceilings for any cracks, sagging, or water stains.
4. Insulation: Check the insulation between the frame studs. If possible, use a thermal imaging camera to identify any areas of heat loss or inadequate insulation.

Structural Assessment

1. Concrete Durability: Use a carbonation depth test to assess the condition of the concrete. This test will help determine the extent of carbonation and the potential risk of reinforcement corrosion.
2. Asbestos Survey: Conduct a thorough asbestos survey to identify any asbestos-containing materials. Ensure that any asbestos is managed or removed by a licensed professional.

Typical Defects in Building Systems Ltd Houses

Roof Defects

• Asbestos Cement Sheets: Over time, asbestos cement sheets can become brittle and prone to cracking. This can lead to water ingress and potential health risks if the asbestos fibres are disturbed.
• Steel Sheets: Steel sheets can suffer from corrosion, especially in areas with high humidity or salt exposure. Regular maintenance and protective coatings can help mitigate this risk.

Wall Defects

• Timber Boarding: Timber boarding can be susceptible to rot and decay, particularly if it has not been adequately treated or maintained. Look for signs of woodworm, fungal decay, and moisture damage.
• Brickwork: Brickwork can suffer from cracking, spalling, and movement. Pay attention to any areas where the mortar has deteriorated or where there are signs of structural movement.

Concrete Defects

• PRC Columns and Beams: The primary concern with PRC columns and beams is the potential for reinforcement corrosion. Look for signs of spalling, cracking, and rust staining on the concrete surface.
• Ground Beams: Ground beams can be susceptible to settlement and movement, particularly if the soil conditions are poor. Look for any signs of cracking or movement in the ground beams.

Internal Defects

• Partitions: Honeycomb hardboard or plasterboard partitions can suffer from damage, particularly if they have been exposed to moisture. Look for signs of damp, mould, and structural damage.
• Floors: Chipboard flooring can become damaged over time, particularly if it has been exposed to moisture. Look for signs of warping, movement, and damage to the timber joists.

Variants and Modifications

Over the years, some Building Systems Ltd houses may have undergone modifications or upgrades. These can include:

• Foundations: Some houses may have foundations at the base of the columns located in pockets cast in the foundation slab.
• External Walls: Variants may include external walls of brick panels instead of timber boarding.
• Separating Wall: Some houses may have a glass fibre curtain in the cavity of the separating wall.
• Roof: Variants may include roofs with timber rafters and purlins or profiled steel sheets instead of asbestos cement sheets.

Conclusion

Building Systems Ltd houses are a unique and historically significant type of property in the UK. While they offer a glimpse into the innovative construction techniques of the 1960s, they also come with potential risks and challenges. Understanding the typical characteristics, hazards, and defects associated with these houses is crucial for home buyers and investors. By conducting thorough inspections and assessments, you can ensure that your investment is safe and sound.

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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