Overview
The MeTraCon house is a system-built house combining precast concrete and timber frame panels, designed and manufactured by Selleck, Nicholls & Williams Ltd over a fifteen-year period from 1964 to 1979. The firm aimed to provide affordable, quickly built housing at a time of significant demand, using prefabricated components to speed up construction.
Only 40 MeTraCon houses were built, which makes them rare. They include bungalows and two- and three-storey houses, and they are typically found in suburban areas, often on estates developed during the 1960s and 1970s. There are no known variants, although the system was also used for flats.
Typical characteristics & construction
The substructure of the MeTraCon house is not well documented. The front and rear walls are storey-height exposed aggregate precast concrete panels infilled with storey-height timber frame panels up to first floor level, with timber frame panels clad in horizontal timber boarding above. The gable walls follow the same pattern: exposed aggregate panels to first floor level and horizontal timber boarding above.
The separating wall is a timber frame cavity wall backed with insulation and lined with plasterboard, giving some thermal and acoustic separation. Internal partitions are Paramount partitions, and the spine wall through the centre of the house is timber studs lined with plasterboard. The ground floor is concrete and the upper floors are timber. Ceilings are plasterboard, and the roof is timber trusses covered with concrete tiles.
| Element | Typical construction | Inspection focus |
|---|---|---|
| Substructure | Not well documented | Signs of movement in the floors and walls above |
| Front, rear and gable walls | Storey-height exposed aggregate PC panels to first floor, timber frame infill panels, horizontal timber boarding above | Cracks, spalling, signs of corrosion; rot, warping or insect damage to boarding |
| Separating wall | Timber frame cavity wall, insulation, plasterboard lining | Dampness or mould, sound transmission |
| Partitions and spine wall | Paramount partitions; timber stud spine wall lined with plasterboard | Damage, wear, plasterboard secure and sound |
| Floors | Concrete ground floor; timber upper floors | Movement, sagging, damage |
| Ceilings | Plasterboard | Cracks, stains, water damage |
| Roof | Timber trusses, concrete tiles | Missing or cracked tiles, wear, truss condition |
Potential hazards & inspection priorities
Primary concern: the precast concrete panels
The steel reinforcement within the concrete panels corrodes, especially where the concrete has been exposed to moisture, and this compromises the structural integrity of the panels. Carbonation adds to the risk: carbon dioxide from the air penetrates the concrete and reacts with calcium hydroxide to form calcium carbonate, reducing the alkalinity of the concrete and allowing the reinforcement to corrode. The exposed aggregate panels should be checked for cracks, spalling and signs of corrosion, and cracks and spalling repaired promptly. Carbonation depth and reinforcement condition are assessed by specialist testing such as core sampling and chemical analysis, with guidance in BRE Digest 444 and BR 19.
Primary concern: the timber frame
The timber frame is susceptible to rot and insect infestation, particularly where it has been exposed to damp. The timber boarding should be checked for rot, warping and insect damage, and the separating walls for dampness or mould, which can point to problems with the insulation or frame. Rot or insect damage needs treating and repairing to maintain structural integrity. Moisture meters and borescopes are used to look for rot or infestation within the frame.
Long-term consideration: thermal and acoustic performance
The timber frame cavity walls give some insulation, but they do not meet modern standards for thermal and acoustic performance. The result is higher energy bills and less effective soundproofing between rooms and between neighbouring houses. Maintenance and repair in general is more challenging because of the unusual construction methods and materials.
Is this house right for you?
The MeTraCon house has a distinctive style and historical significance, and it brings its own risks and challenges. Before inspection, it pays to gather as much information as possible, including previous surveys and maintenance records, so that known issues are followed up.
- Commission a full building survey
- Establish the condition of the precast concrete panels and any signs of reinforcement corrosion
- Check the timber frame and boarding for rot and insect damage
- Obtain previous surveys and maintenance records
- Allow for improvements to thermal and acoustic insulation
Understanding the construction methods, typical defects and maintenance requirements is what allows a buyer to make an informed decision.
Mortgage & resale considerations
The MeTraCon house is not designated defective under the Housing Defects Act 1984, but its construction methods and materials present challenges in meeting modern standards.
Where a MeTraCon house is found to have significant defects affecting habitability or safety, buyers should take professional advice where necessary. Thorough inspection, prompt attention to defects and appropriate maintenance are what keep the property in condition.
What a survey can — and cannot — tell you
A building survey provides an informed assessment of the visible condition and construction of a MeTraCon house. Inspections are non-intrusive and limited to areas that are accessible at the time of inspection.
- Identify visible cracks, spalling and signs of corrosion in the exposed aggregate panels
- Identify visible rot, warping or insect damage in the timber boarding
- Assess signs of dampness and mould, including at the separating walls
- Comment on the roof, floors, ceilings and partitions
- 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 reinforcement concealed within the precast panels
- Measure carbonation depth without core sampling and testing
- Assess the timber frame concealed behind boarding and linings
- 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.
