The Permacrete House

The Permacrete house, also known as Cemacrete and Cemalite, represents a distinctive form of 1940s non-traditional housing developed in response to acute post-war demand. Manufactured by Cemacete Ltd and designed by H.E. Cavell, these properties were conceived as robust, cost-effective homes using reinforced concrete and pre-cast elements.

Although exact production numbers are unclear, Permacrete houses were predominantly constructed during the 1940s and are typically found in suburban locations where rapid housing delivery was required.

A typical Permacrete house showing rendered reinforced concrete walls, medium pitch hipped roof and first-floor string course detailing.

Permacrete houses are generally two-storey semi-detached dwellings constructed on concrete strip footings with reinforced concrete under-building and a concrete slab base incorporating a damp-proof course.

External walls are formed from 9-inch reinforced concrete incorporating 3-inch by 2-inch by 1-inch pre-cast slabs, 6.5-inch reinforced concrete infill and 1.5-inch pre-cast slabs. Mild steel ties and bars provide reinforcement. All elevations are rendered.

Separating walls between adjoining dwellings comprise 9.5-inch reinforced concrete with a similar pre-cast and infill arrangement, with 9-inch brickwork present within the roof space. Internal partitions are 6-inch reinforced concrete with pre-cast slabs and infill to first-floor level, and clinker concrete blockwork above.

Ground floors typically consist of tongue-and-groove timber blocks laid on sand/cement screed over a concrete base. First floors comprise timber boarding on timber battens cast within a 6-inch reinforced concrete slab with 1.5-inch pre-cast slab permanent shuttering.

Roofs are of timber rafter and purlin construction, generally finished with concrete tiles, although clay tiles are seen in some variants. The roof form is usually medium pitch and hipped.

The principal risk in Permacrete construction relates to the long-term durability of reinforced concrete. Corrosion of embedded steel reinforcement, often associated with carbonation or chloride ingress, can result in cracking and spalling of the concrete and localised structural weakness.

Moisture ingress is also a recurring issue where damp-proof courses have deteriorated or external render has failed. Persistent dampness can affect internal finishes and create conditions conducive to mould growth.

Thermal performance is generally modest by modern standards due to the concrete construction and limited original insulation. Upgrading insulation levels can be technically achievable but may require careful detailing.

Where structural concerns are suspected, more detailed investigation such as concrete sampling or non-destructive testing may be appropriate.

Purchasers considering a Permacrete house should understand the implications of reinforced concrete construction and the potential for age-related deterioration of embedded steel.

• Commission a detailed building survey with specific reference to reinforced concrete condition
• Review any previous structural repairs or concrete treatment works
• Assess the current condition of render, roof coverings and damp-proof detailing

Condition and maintenance history are central to assessing suitability.

As a non-traditional reinforced concrete system, lender acceptance can vary depending on condition and classification. Properties exhibiting significant concrete deterioration or unresolved damp issues may present additional scrutiny.

Clear professional reporting and evidence of appropriate remedial works are often influential in supporting lending and future resale.

A building survey provides an informed assessment of the visible condition and construction of a Permacrete house. Inspections are non-intrusive and limited to areas that are accessible at the time of inspection.

• Identify visible cracking and spalling to reinforced concrete walls and associated render
• Assess signs of dampness, moisture ingress, and condensation risk
• Comment on roof coverings, drainage details, and external envelope condition
• Review the general condition of accessible floors, ceilings, and structural elements
• Highlight defects that may require repair, monitoring, or further investigation

However, there are limitations to what a survey can determine without intrusive investigation.

• Confirm the condition of concealed steel reinforcement within reinforced concrete
• Assess hidden structural elements behind finishes or linings
• Determine the full extent of carbonation or chloride contamination within concrete
• Inspect areas that are inaccessible or covered at the time of inspection

Where higher-risk indicators are identified, further specialist or intrusive investigation may be recommended.

For a thorough building survey in Greater London, an instant quotation can be obtained through the online survey calculator.