Overview
Dorlonco houses are an early form of system-built housing developed during the inter-war period. They were manufactured by Dorman Long & Co. Ltd and constructed between the early 1920s and 1928 as part of a response to the post-First World War housing shortage.
Approximately 10,000 Dorlonco houses were built, mainly in urban and suburban areas across the UK, reflecting both industrial capacity and contemporary housing policy.
Dorlonco houses were produced by Dorman Long & Co. Ltd, a major British steel manufacturer. Their construction reflects early use of steel framing in domestic housing.
Typical characteristics & construction
Dorlonco houses are generally two-storey semi-detached or terraced properties. Roofs are medium pitch hipped or gabled and finished with concrete tiles, slates, or pantiles.
External walls are either fully rendered or a combination of brickwork and render. Front and rear elevations commonly have brickwork up to first-floor level with render above, while gable walls are often entirely brick.
Internally, floors are of concrete construction. The ground floor is a solid concrete slab, with the first floor formed using concrete on expanded metal lathing. Ceilings are finished in sand and cement, with clinker concrete used to upper floors.
| Element | Typical construction | Inspection focus |
|---|---|---|
| Substructure | Concrete ground beam and slab with DPC | Cracking, movement, damp penetration |
| Frame | Steel RSA stanchions with RSC spine beam | Corrosion, particularly at stanchion bases |
| External walls | Rendered expanded metal lathing with clinker block cavity | Cracking, carbonation, moisture ingress |
| Roof | Timber rafters and purlins with tile covering | Tile condition, felt integrity, leaks |
Potential hazards & inspection priorities
The most significant issue affecting Dorlonco houses is corrosion of the steel frame. RSA stanchions, particularly at their bases, are susceptible to deterioration where moisture is present.
Carbonation of render and vertical cracking to brickwork and render at stanchion locations are common. These defects can allow water ingress and accelerate corrosion if not addressed.
Wall tie corrosion is also a known concern and can compromise cavity wall stability if left unmanaged.
Is this house right for you?
Dorlonco houses require purchasers to understand non-traditional construction and the maintenance demands associated with steel-framed systems.
- Condition of the steel frame is critical
- Ongoing maintenance of render and coatings is essential
- Past repairs and alterations should be carefully reviewed
Mortgage & resale considerations
Dorlonco houses are not designated as defective under the Defective Premises Act. However, lender acceptance is often influenced by condition, corrosion management, and the clarity of professional reporting.
Evidence of effective maintenance and a clear survey assessment are important factors for both lending and resale.
What a survey can — and cannot — tell you
A building survey provides an informed assessment of the visible condition and construction of a Dorlonco house. Inspections are non-intrusive and limited to areas that are accessible at the time of inspection.
- Identify visible corrosion to steel stanchions and metal lathing
- Assess cracking, carbonation, and moisture-related defects
- Comment on roof coverings, drainage, and external envelope condition
- Review the condition of accessible floors, ceilings, and structural elements
- Highlight defects requiring repair or further investigation
However, there are limitations to what a survey can determine without intrusive investigation.
- Confirm the concealed condition of steel within walls or floors
- Assess hidden wall ties or embedded metal components
- Determine the full extent of corrosion behind finishes
- Inspect inaccessible or covered areas
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.
Considering a Dorlonco house?
A detailed building survey can help clarify construction-specific risks before committing to a purchase.
Get your instant survey quoteDisclaimer: 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.
