Historical Context and Manufacturing Background

The Tenaplas house, a unique and rare property type, was manufactured by Tenaplas Ltd in collaboration with Edron Trust. These properties were designed and constructed in the 1940s, a period marked by significant innovation in the construction industry. Only two of these houses were ever built, making them an intriguing subject for property enthusiasts and investors alike.

Tenaplas Ltd, the manufacturer, was known for its pioneering efforts in system-built properties. The company aimed to address the housing shortage post-World War II by developing innovative construction techniques. The Tenaplas house stands as a testament to their ingenuity and forward-thinking approach.

Typical Characteristics of the Tenaplas House

Design and Structure

The Tenaplas house is a two-storey semi-detached property with a medium pitch hipped roof covered in clay tiles. The external walls are rendered with roughcast, giving the house a distinctive appearance. The design reflects the architectural trends of the 1940s, combining functionality with aesthetic appeal.

Construction Details

Substructure

The substructure of the Tenaplas house consists of concrete underbuilding and a concrete slab. A damp-proof course (DPC) is also included to prevent moisture from rising through the structure.

External Walls

The external walls are constructed using 3′ x 1′ 6″ x 8″ hollow woodwool slabs, reinforced with a 6″ reinforced concrete (RC) sill course poured over rag bolts cast into the concrete substructure. The walls also feature 8″ x 8″ RC corner columns reinforced with 1/2″ bars, and 6″ x 4″ concrete posts at window jambs and door posts. Additionally, the walls include an 8″ x 6″ RC string course at the first-floor level and a 6″ x 6″ RC string course at the eaves level. Galvanised wire wall ties and steel flats provide additional structural support.

Separating Wall

The separating wall between the semi-detached units is constructed using concrete posts and hollow woodwool slabs, ensuring both structural integrity and sound insulation.

Partitions

Internal partitions are made of 4″ clinker aggregate concrete blocks with 2″ woodwool slabs extending to the first-floor level. This combination provides both strength and thermal insulation.

Ground Floor

The ground floor comprises 9″ x 3″ urea-resin bonded blocks laid on a bitumen damp-proof membrane (DPM) on concrete. This construction method ensures a stable and moisture-resistant ground floor.

First Floor

The first floor features timber boarding on timber joists, providing a sturdy and flexible flooring solution.

Roof

The roof structure includes timber rafters and purlins, covered with clay tiles. This traditional roofing method offers durability and weather resistance.

Variants

Some variants of the Tenaplas house feature external wall render reinforced with wire mesh, providing additional strength and durability.

Typical Hazards and Risks

Structural Integrity

One of the primary concerns with the Tenaplas house is the potential for structural degradation over time. The use of reinforced concrete and woodwool slabs, while innovative, can be susceptible to issues such as corrosion of steel reinforcements and degradation of concrete.

Moisture Ingress

Despite the inclusion of a damp-proof course, moisture ingress can still be a concern, particularly if the DPC has deteriorated over time. This can lead to issues such as rising damp and mould growth, which can affect both the structural integrity and the indoor air quality of the property.

Thermal Insulation

The construction materials used in the Tenaplas house, such as woodwool slabs and clinker aggregate concrete blocks, provide some level of thermal insulation. However, these materials may not meet modern insulation standards, potentially leading to higher energy costs and reduced thermal comfort.

Asbestos

Given the era in which the Tenaplas house was constructed, there is a possibility that asbestos-containing materials were used. Asbestos was commonly used in building materials during the 1940s for its fire-resistant properties. However, it poses significant health risks if disturbed.

Defective Premises Act Considerations

The Tenaplas house is not explicitly classed as defective under the Defective Premises Act. However, given its age and the potential for structural and material degradation, it is essential to conduct a thorough inspection to identify any defects that could pose a risk to occupants.

Inspection and Assessment Guide

External Inspection

Roof

Inspect the clay tiles for any signs of damage or displacement. Check the timber rafters and purlins for signs of rot or insect infestation. Ensure that the roof structure is sound and free from leaks.

Walls

Examine the rendered external walls for cracks, bulges, or signs of moisture ingress. Pay particular attention to the reinforced concrete elements, checking for signs of corrosion or spalling.

Windows and Doors

Check the condition of window jambs and door posts, ensuring that the concrete posts are free from cracks and that the woodwool slabs are intact. Look for signs of moisture ingress around window and door openings.

Internal Inspection

Ground Floor

Inspect the ground floor for signs of moisture ingress or rising damp. Check the condition of the urea-resin bonded blocks and the bitumen DPM. Look for any signs of structural movement or settlement.

First Floor

Examine the timber boarding and joists for signs of rot, insect infestation, or structural weakness. Ensure that the floor is level and free from excessive deflection.

Partitions

Check the condition of internal partitions, looking for cracks, bulges, or signs of moisture ingress. Ensure that the clinker aggregate concrete blocks and woodwool slabs are in good condition.

Structural Elements

Reinforced Concrete

Inspect all reinforced concrete elements, including the sill course, corner columns, string courses, and posts. Look for signs of corrosion, spalling, or cracking. Use a cover meter to assess the depth of concrete cover over the steel reinforcements.

Woodwool Slabs

Examine the woodwool slabs for signs of degradation, moisture ingress, or insect infestation. Ensure that the slabs are securely fixed and free from significant damage.

Moisture and Insulation

Damp-Proof Course

Check the condition of the damp-proof course, ensuring that it is intact and effective. Look for signs of rising damp or moisture ingress at the base of walls.

Insulation

Assess the thermal insulation properties of the building materials. Consider upgrading insulation to meet modern standards if necessary.

Asbestos

Given the potential presence of asbestos-containing materials, it is essential to conduct an asbestos survey. Identify any asbestos materials and assess their condition. If asbestos is found, follow appropriate procedures for its safe removal or encapsulation.

Typical Defects and Maintenance

Common Defects

Corrosion of Steel Reinforcements

One of the most common defects in the Tenaplas house is the corrosion of steel reinforcements within the concrete elements. This can lead to spalling, cracking, and a reduction in structural integrity. Regular inspections and maintenance are essential to address this issue.

Moisture Ingress

Moisture ingress can occur due to a deteriorated damp-proof course, damaged render, or poor detailing around windows and doors. This can lead to rising damp, mould growth, and degradation of building materials. Addressing moisture ingress promptly is crucial to prevent further damage.

Thermal Insulation

The original construction materials may not provide adequate thermal insulation by modern standards. Upgrading insulation in walls, floors, and roofs can improve energy efficiency and thermal comfort.

Asbestos

If asbestos-containing materials are present, they pose a significant health risk if disturbed. It is essential to manage asbestos safely, either by encapsulation or removal by a licensed contractor.

Maintenance Tips

Regular Inspections

Conduct regular inspections of the property, focusing on key structural elements such as reinforced concrete, woodwool slabs, and timber components. Identify and address any signs of degradation or damage promptly.

Moisture Management

Ensure that the damp-proof course is intact and effective. Address any signs of moisture ingress, such as rising damp or leaks, promptly. Consider installing additional moisture barriers if necessary.

Insulation Upgrades

Upgrade thermal insulation in walls, floors, and roofs to meet modern standards. This can improve energy efficiency, reduce heating costs, and enhance thermal comfort.

Asbestos Management

If asbestos-containing materials are present, manage them safely by encapsulation or removal by a licensed contractor. Follow all relevant regulations and guidelines to ensure the safety of occupants.

Conclusion

The Tenaplas house, with its unique construction and historical significance, offers both opportunities and challenges for home buyers and investors. Understanding the typical characteristics, potential hazards, and maintenance requirements of this property type is essential for making informed decisions.

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.