Historical Context and Background
The Malthouse house, a distinctive property type, was manufactured by W Malthouse Ltd and designed by the Sheffield City Architect. These properties were constructed during the 1940s and 1950s, a period marked by post-war reconstruction efforts in the UK. With only 50 units built, these houses are relatively rare, making them a unique find for home buyers and investors.
These properties are typically found in urban areas where rapid housing solutions were needed to accommodate the growing population. The Malthouse house is also known by alternative names, but its unique construction and design features make it easily identifiable.
Identification Characteristics
Exterior Features
Malthouse houses are 2-storey semi-detached homes with a medium pitch hipped roof covered with asbestos cement tiles or a flat roof covered with bituminous felt. The external walls are constructed of brick or dense Precast Reinforced Concrete (PRC) panels, with visible junctions between adjacent panels. The door and window frames are surrounded by PRC, and there is a PRC canopy over the front door. For hipped roof houses, the eaves height features a rectangular flat-roofed bay containing the front door.
Interior Features
Internally, these houses have a variety of construction elements that are characteristic of the period. The ground and first floors are made of Reinforced Concrete (RC) topped hollow clay blocks and RC beams. The ceilings are rendered with foamed slag, and the staircase is constructed from PRC units with cork treads and oak nosings.
Construction Details
Substructure
The substructure of Malthouse houses consists of concrete strip footings with a 2-course blue brick Damp Proof Course (DPC). This foundation type was common in the mid-20th century and provides a stable base for the structure.
External Walls
The external walls are lightly reinforced brick cavity walls lined with 2 inches of rendered foamed slag concrete or 1/2 inch cork grooved and keyed to the concrete. The PRC surrounds to door and window frames, along with wall ties, are notable features. In some variants, the external walls and separating walls are made entirely of dense PRC panels.
Separating Wall
The separating wall between semi-detached units is a brick cavity wall, providing both structural support and sound insulation.
Partitions
Internal partitions are made of hollow clay blocks, which were a common material choice for their lightweight and insulating properties. In some variants, partitions are constructed from woodwool slabs or 3-inch foamed slag concrete panels.
Floors
Both the ground and first floors are constructed using RC topped hollow clay blocks and RC beams, with the ends toothed to fit recesses formed in the external walls. This method provides a robust and durable flooring system.
Ceilings
Ceilings are rendered with 3/4 inch foamed slag, a material known for its insulating properties and ease of application.
Roof
The roof construction varies between RC slabs covered with bituminous felt and RSA trusses with asbestos cement tiles. The choice of roofing material impacts the maintenance and longevity of the roof.
Typical Hazards and Risks
Movement at Junctions Between PRC Panels
One of the common issues with Malthouse houses is movement at the junctions between PRC panels. This movement can lead to cracks and gaps, which may compromise the structural integrity and thermal efficiency of the property.
Corrosion of Light Reinforcement in PRC Panels
The light reinforcement within the PRC panels is susceptible to corrosion, especially in areas exposed to moisture. This corrosion can weaken the panels and lead to structural issues over time.
High Rates of Carbonation in Dense PRC Panels
Dense PRC panels in Malthouse houses are prone to high rates of carbonation, a process where carbon dioxide from the air reacts with the calcium hydroxide in the concrete to form calcium carbonate. This reaction reduces the alkalinity of the concrete, making the reinforcement more susceptible to corrosion.
Defective Premises Act Considerations
Malthouse houses are not typically classified as defective under the Defective Premises Act. However, the specific issues related to PRC panels, such as movement at junctions and corrosion of reinforcement, should be carefully assessed during a survey. These issues can impact the safety and habitability of the property, and addressing them may require significant repairs.
Inspection Guide for Surveyors
When inspecting a Malthouse house, surveyors should pay close attention to the following areas:
External Walls
- Check for Movement at Junctions: Look for signs of movement at the junctions between PRC panels, such as cracks or gaps.
- Inspect for Corrosion: Examine the PRC panels for signs of corrosion, particularly in areas exposed to moisture.
- Assess Carbonation Levels: Use a carbonation test to determine the extent of carbonation in the dense PRC panels.
Roof
- Inspect Roofing Material: Check the condition of the asbestos cement tiles or bituminous felt. Look for signs of wear, damage, or leaks.
- Examine Roof Structure: Assess the condition of the RC slabs or RSA trusses. Look for signs of structural issues or deterioration.
Floors
- Check for Structural Integrity: Inspect the RC topped hollow clay blocks and RC beams for signs of damage or wear.
- Assess Floor Levels: Ensure that the floors are level and free from significant movement or settlement.
Ceilings
- Inspect for Cracks or Damage: Look for signs of cracks or damage in the foamed slag render.
- Check for Moisture Issues: Assess the ceilings for signs of moisture ingress or damage.
Staircase
- Examine PRC Units: Check the condition of the PRC units, cork treads, and oak nosings. Look for signs of wear or damage.
- Assess Structural Integrity: Ensure that the staircase is structurally sound and free from significant movement or settlement.
Typical Defects Common in Malthouse Houses
Movement at Junctions Between PRC Panels
As mentioned earlier, movement at the junctions between PRC panels is a common issue. This movement can lead to cracks and gaps, which may compromise the structural integrity and thermal efficiency of the property.
Corrosion of Light Reinforcement in PRC Panels
The light reinforcement within the PRC panels is susceptible to corrosion, especially in areas exposed to moisture. This corrosion can weaken the panels and lead to structural issues over time.
High Rates of Carbonation in Dense PRC Panels
Dense PRC panels in Malthouse houses are prone to high rates of carbonation, a process where carbon dioxide from the air reacts with the calcium hydroxide in the concrete to form calcium carbonate. This reaction reduces the alkalinity of the concrete, making the reinforcement more susceptible to corrosion.
Roofing Issues
The roofing materials used in Malthouse houses, such as asbestos cement tiles and bituminous felt, are prone to wear and damage over time. Asbestos cement tiles can become brittle and crack, while bituminous felt can deteriorate and develop leaks.
Moisture Ingress
Moisture ingress is a common issue in Malthouse houses, particularly in areas where the PRC panels have been compromised. This can lead to dampness, mould growth, and further structural issues.
Thermal Efficiency
The construction materials used in Malthouse houses, such as PRC panels and foamed slag render, may not provide the best thermal efficiency. This can result in higher energy bills and a less comfortable living environment.
Maintenance and Repair Considerations
Addressing Movement at Junctions
To address movement at the junctions between PRC panels, it may be necessary to install additional reinforcement or apply a flexible sealant to the joints. This can help to prevent further movement and improve the structural integrity of the property.
Corrosion Protection
To protect the light reinforcement within the PRC panels from corrosion, it may be necessary to apply a protective coating or replace the affected panels. This can help to extend the lifespan of the panels and prevent further structural issues.
Carbonation Mitigation
To mitigate the effects of carbonation in dense PRC panels, it may be necessary to apply a carbonation-resistant coating or replace the affected panels. This can help to protect the reinforcement and improve the durability of the panels.
Roof Repairs
To address roofing issues, it may be necessary to replace damaged asbestos cement tiles or bituminous felt. This can help to prevent leaks and improve the overall condition of the roof.
Moisture Management
To manage moisture ingress, it may be necessary to repair or replace compromised PRC panels, install additional damp proofing measures, and improve ventilation. This can help to prevent dampness and mould growth, and protect the structural integrity of the property.
Improving Thermal Efficiency
To improve the thermal efficiency of a Malthouse house, it may be necessary to install additional insulation, upgrade windows and doors, and improve the overall airtightness of the property. This can help to reduce energy bills and create a more comfortable living environment.
Conclusion
The Malthouse house is a unique and distinctive property type with a rich history and characteristic features. While these houses offer a range of benefits, they also come with specific challenges and risks that must be carefully considered by home buyers and investors.
By understanding the typical construction details, common defects, and maintenance considerations, you can make an informed decision when purchasing a Malthouse house. Whether you are a first-time home buyer or an experienced investor, it is essential to conduct a thorough survey and address any issues promptly to ensure the safety and longevity of your investment.
At Flettons, we’re committed to safeguarding your investment. When considering a property purchase, trust our seasoned expertise to uncover any hidden risks. For a thorough building survey, get your instant quote through our online calculator or call us directly on 0330 043 4650. Your home’s safety is our top priority. Disclaimer: This article is provided for general educational purposes only and is based on industry research, professional knowledge, and experience. It does not relate to any specific property and should not be relied upon when making a purchasing decision. Prospective purchasers should always commission an independent RICS-qualified surveyor to conduct a full inspection and provide a report on the actual condition of any property of interest.
