Overview
The Grid House, also known as RM housing, is a system-built form of residential construction developed during the mid-20th century. Designed and manufactured by Morrison and Partners, these properties were constructed in 1966, with approximately 160 units built across various locations in the UK.
Typical characteristics & construction
Grid Houses are typically arranged as detached, semi-detached, or terraced two-storey dwellings. The structural frame comprises steel hollow box stanchions with rolled steel channel beams supporting floors and the roof.
External walls are formed using storey-height timber frame infill panels. These are clad externally with materials that can include tile or slate hanging, horizontal timber boarding, coloured asbestos cement sheets, aluminium or plastic sheets, or concrete panels.
Internally, partitions and linings are generally formed using honeycomb plasterboard. Insulation is provided by mineral wool placed between timber frame studs, which falls below modern thermal performance expectations.
| Element | Typical construction | Inspection focus |
|---|---|---|
| Substructure | Concrete pads with perimeter-thickened slab | Movement, cracking, stability |
| Structural frame | Steel stanchions and rolled steel channel beams | Corrosion, movement, connections |
| External walls | Timber infill panels with varied cladding | Decay, moisture ingress, asbestos presence |
| Floors | Concrete ground floor, chipboard on timber joists above | Deflection, dampness, wear |
| Roof | Timber joists with plywood and plastic sheet covering | Water ingress, deterioration, drainage |
Potential hazards & inspection priorities
The most significant risks associated with Grid Houses relate to moisture ingress affecting timber infill panels and the condition of flat roof coverings. Prolonged damp exposure can lead to timber decay and loss of structural performance.
Coloured asbestos cement sheets were commonly used as external cladding. While generally stable if undisturbed, their presence requires careful management and professional assessment before any alteration or repair work.
Insulation levels are modest by current standards, and condensation risk can be elevated if ventilation and heating have not been appropriately upgraded.
Is this house right for you?
A Grid House may be suitable for purchasers who understand non-traditional construction and are prepared to assess condition rather than age alone.
- Commission a full building survey
- Review past maintenance and repair records
- Be prepared for ongoing management of moisture and materials
Mortgage & resale considerations
Lending decisions for system-built properties are influenced by construction type, condition, and the clarity of professional reporting. Acceptance criteria can vary between lenders and may change over time.
Clear survey findings, documented maintenance, and the absence of unresolved defects are commonly influential factors.
What a survey can — and cannot — tell you
A building survey provides an informed assessment of the visible condition and construction of a Grid House. Inspections are non-intrusive and limited to areas that are accessible at the time of inspection.
- Identify visible defects to cladding, timber infill panels, and roof coverings
- Assess signs of dampness, moisture ingress, and condensation risk
- Comment on flat roof condition, drainage details, and external envelope performance
- 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 connections or timber elements
- Assess hidden structural components behind linings or finishes
- Determine the full extent of timber decay within enclosed panels
- 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.
