Overview of Orlit Type II Houses

The Orlit Type II house is a notable example of post-war British architecture, specifically designed to address the housing shortage in the 1940s and 1950s. These properties were part of a broader initiative to provide affordable and quickly constructed homes for the burgeoning population. Manufactured by Orlit Ltd, these houses are a significant part of the UK’s architectural history, with approximately 17,000 units built, including both Type I and Type II variants.

Historical Context and Manufacturers

The Orlit Type II house emerged in the aftermath of World War II, a period marked by a desperate need for rapid housing solutions. The government and private sector collaborated to develop system-built properties that could be constructed swiftly and economically. Orlit Ltd, the manufacturer behind these homes, played a crucial role in this housing revolution. The design and construction methods employed were innovative for their time, focusing on pre-cast reinforced concrete (PRC) components to expedite the building process.

Typical Locations

Orlit Type II houses are predominantly found in suburban areas across the UK. These properties were often built in clusters, forming entire neighbourhoods of similar architectural style. Common locations include parts of Scotland, the Midlands, and various regions in England where post-war housing demand was particularly high.

Characteristics of Orlit Type II Houses

Architectural Features

Orlit Type II houses are easily identifiable by their distinct architectural features. They typically come in two forms: bungalows and two-storey semi-detached or terraced houses. The roofs are either medium-pitched gable roofs covered with tiles or flat roofs covered with asphalt or bituminous felt. The external walls are constructed from PRC slabs, with gable apexes often featuring tile hanging.

Construction Details

Substructure

The substructure of Orlit Type II houses consists of pad foundations with pre-cast (PC) stub columns cast into these foundations. This method provided a stable base for the rest of the structure.

Frame

The main frame is composed of 5 1/2″ x 5 1/2″ PRC columns with integral beam stubs and bolted steel flange connectors. The primary and secondary beams are 7 1/2″ PRC units with concrete cover, ensuring structural integrity.

External Walls

The external walls are a composite of various materials, including 2″ PC base bonding units, 2″ PC slabs, a cavity, and 2 1/2″ lightweight PC slabs. These walls are supported by timber framing lined with plasterboard and galvanised mild steel (MS) ties.

Separating Walls and Partitions

Separating walls feature a PRC frame infilled with foamed slag aggregate concrete blocks, while internal partitions are made from lightweight concrete slabs.

Floors

The ground floor is typically concrete, providing a solid and durable base. The first floor consists of timber boarding on timber beams, supported by PRC secondary beams.

Ceilings and Roof

Ceilings are generally plasterboard, while the roof structure includes PRC beams spanning between internal columns, inverted PRC trough-shaped units with concrete fill, timber wall plates, timber trusses, and purlins. The roofing material varies between tiles for pitched roofs and asphalt or bituminous felt for flat roofs.

Typical Hazards and Risks

Structural Issues

One of the primary concerns with Orlit Type II houses is the deterioration of PRC components. The main PRC columns and beams often have only up to 30 mm of concrete cover, making them susceptible to carbonation and chloride ingress. Carbonation depths can reach up to 20 mm, and significant chloride content has been found in some beams, leading to corrosion of the steel reinforcement.

Cracking and Concrete Quality

Cracking is a common issue, particularly in the ordinary Portland cement (OPC) and high alumina cement (HAC) stitches. The quality of HAC concrete in these stitches is often low, contributing to further structural weaknesses. Secondary beams are also prone to cracking, exacerbating the overall structural integrity concerns.

Designation as Defective

Under the Defective Premises Act, Orlit Type II houses are designated as defective. This classification stems from the inherent structural issues associated with PRC construction, particularly the susceptibility to carbonation and chloride-induced corrosion. As a result, these properties may require significant remedial work to ensure safety and longevity.

Inspection Guide for Orlit Type II Houses

Preliminary Assessment

When inspecting an Orlit Type II house, start with a thorough visual assessment of the exterior and interior. Look for signs of cracking, particularly around the PRC columns and beams. Pay close attention to any areas where the concrete cover appears thin or damaged.

Structural Integrity

Assess the structural integrity of the main frame, including the PRC columns and beams. Use a cover meter to measure the depth of concrete cover and identify areas with potential carbonation or chloride ingress. If significant deterioration is detected, further investigation by a structural engineer may be necessary.

Roof and Walls

Inspect the roof for signs of wear and tear, particularly if it is a flat roof covered with asphalt or bituminous felt. Check for any leaks or water damage that could indicate underlying issues. Examine the external walls for cracks or other signs of deterioration, especially around the gable apexes and tile hanging areas.

Internal Components

Inside the house, inspect the separating walls and partitions for any signs of cracking or movement. Check the condition of the ground and first floors, looking for any unevenness or damage. Ensure that the ceilings are intact and free from water damage or other issues.

Remedial Work

If significant defects are identified, consider the scope of remedial work required. This may include repairing or replacing damaged PRC components, addressing carbonation and chloride ingress, and reinforcing the overall structure. Consult with a structural engineer to develop a comprehensive repair plan.

Common Defects in Orlit Type II Houses

Carbonation and Chloride Ingress

As previously mentioned, carbonation and chloride ingress are significant concerns for Orlit Type II houses. These issues can lead to the corrosion of steel reinforcement, compromising the structural integrity of the property.

Cracking

Cracking is a prevalent issue, particularly in the OPC and HAC stitches. This can be exacerbated by the low quality of HAC concrete used in some areas. Cracks can also appear in secondary beams and other PRC components, further weakening the structure.

Deterioration of PRC Components

Over time, PRC components can deteriorate due to environmental exposure and the inherent weaknesses in the construction materials. This can lead to a range of issues, from minor cosmetic damage to significant structural concerns.

Roof and Wall Issues

Flat roofs covered with asphalt or bituminous felt are prone to leaks and water damage, which can lead to further structural issues if not addressed promptly. External walls may also show signs of wear and tear, particularly around the gable apexes and tile hanging areas.

Practical Tips for Home Buyers and Investors

Due Diligence

When considering the purchase of an Orlit Type II house, due diligence is crucial. Obtain a comprehensive building survey from a qualified surveyor to identify any potential issues. This will provide a clear understanding of the property’s condition and any remedial work required.

Budget for Repairs

Given the potential for significant structural issues, it’s essential to budget for repairs and maintenance. Factor in the cost of addressing carbonation, chloride ingress, and other common defects when evaluating the property’s overall value.

Consult with Experts

Engage with structural engineers and other experts to assess the condition of the property and develop a plan for any necessary repairs. Their expertise will be invaluable in ensuring the safety and longevity of the house.

Consider Long-Term Viability

Evaluate the long-term viability of the property, particularly if significant remedial work is required. Consider whether the investment is worthwhile given the potential costs and the property’s future value.

Conclusion

Orlit Type II houses are a significant part of the UK’s post-war architectural heritage, offering unique insights into the housing solutions of the 1940s and 1950s. While these properties come with inherent risks and potential structural issues, they can also present valuable investment opportunities for informed buyers. By conducting thorough inspections, budgeting for repairs, and consulting with experts, home buyers and investors can make well-informed decisions and safeguard their investments.

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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