The Conslab House

The Conslab House is an extremely rare form of non-traditional housing developed during the 1950s as part of the post-war housing programme in the United Kingdom. Designed by P M Powell and Charles Woodwood and manufactured by Leslie’s Ltd, only two examples were constructed.

These properties are understood to have been built as two-storey semi-detached houses with medium-pitched hipped roofs finished in concrete tiles and external walls rendered with pebbledash.

A Conslab House showing its semi-detached form, hipped roof with concrete tiles and pebbledash rendered external walls typical of this rare PRC construction.

Conslab Houses are two-storey semi-detached dwellings constructed using pre-cast reinforced concrete slabs forming the principal structural elements.

Substructures comprise concrete strip footings with a concrete ground-bearing slab and an incorporated damp-proof course. External walls are formed from approximately 1½” pre-cast reinforced concrete slabs with splayed edges, reinforced over openings using dense aggregate concrete. Clinker aggregate PRC slabs were also utilised.

Separating walls between adjoining dwellings were formed as 8″ pre-cast slab cavity walls filled with dense concrete. Loadbearing internal partitions are 6″ PRC slab cavity walls with dense concrete infill, bonded to the external walls with cast-in hoop ties. Non-loadbearing partitions comprise 3″ Hitchins partitions.

Ground floors are concrete. First floors are typically timber boarding on timber joists supported by galvanised joist hangers, although variants include concrete slab first floors. Roofs are constructed using timber joists, rafters and purlins, finished externally with concrete tiles.

The principal risks associated with Conslab Houses relate to reinforced concrete durability. Corrosion of embedded steel reinforcement can lead to cracking and spalling, particularly where carbonation has reduced the protective alkalinity of the concrete. Relevant technical guidance includes BRE Digest 444 (Corrosion of Steel in Concrete), BR 254 (Repair and Maintenance of Reinforced Concrete) and BR 19 (Carbonation Depths in Structural-Quality Concrete).

Carbonation is a progressive process whereby carbon dioxide penetrates the concrete and reduces alkalinity, increasing the likelihood of reinforcement corrosion. Assessment of carbonation depth may require specialist investigation where deterioration is suspected.

Dampness and moisture ingress can arise despite the presence of a damp-proof course, particularly where render is cracked or external maintenance has been neglected. Structural movement, evidenced by cracking, uneven floors or distortion to openings, also warrants careful evaluation.

A Conslab House requires an informed understanding of PRC construction and the implications of reinforced concrete durability.

• Commission a full building survey focused on concrete condition
• Review evidence of previous repairs or specialist reports
• Be aware of the implications of rarity for maintenance and repair

Particular caution is appropriate where cracking, spalling or long-term moisture exposure is evident.

Lending decisions for PRC properties are influenced by construction type, condition and the clarity of professional reporting. Given the extremely limited number of Conslab Houses constructed, lender familiarity may be limited.

Comprehensive documentation of condition, evidence of appropriate repairs and clear professional assessment are commonly significant factors.

A building survey provides an informed assessment of the visible condition and construction of a Conslab 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 wall panels
• 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 reinforcement within concrete slabs
• Assess hidden structural elements behind finishes or linings
• Determine the full extent of carbonation or internal concrete deterioration
• 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.