Overview
The Woolaway house is a post-war precast reinforced concrete house built by W Woolaway & Sons Ltd from 1946 until the mid-1950s, mainly as two-storey semi-detached and terraced houses, with some maisonettes. About 5,500 Woolaway houses had been built in England and Wales by 1956. It is also known as the Western Woolaway.
It is a different system from the Woolaways Bungalow, a later single-storey design, and the two should not be confused when identifying a property.
Typical characteristics & construction
From the street, Woolaway houses are usually two-storey semi-detached or terraced houses with a medium pitch gable roof in tiles and walls rendered all over, often with a roughcast finish. A metal cowl to the chimney is a typical feature. Because the render hides the structure, identification usually rests on the overall form and, where visible, the pattern of cracking in the render described below.
The walls are built from storey-height precast columns, 6 inches square, set at 2 foot 6 inch centres. Half-storey-height panels, about 4 feet high and 2 feet wide, are bolted to the columns on both faces to form a cavity wall, with six bolts to each panel passing through steel ferrules cast into the concrete. Precast ring beam units sit on the tops of the columns and panels at first floor and roof level, located by a continuous tongue but with no mechanical connection or continuity steel. The columns, panels and ring beams are all made of aerated concrete reinforced with high-tensile twisted steel.
The first floor sits in mild steel joist hangers fixed to the first floor ring beam, so it gives the external walls little lateral restraint at that level. The roof is fixed to a wall plate on the eaves ring beam and ties the front and rear walls together, and the gables in the roof space are infilled with blockwork. The structure is often described as two open-ended concrete boxes, one on top of the other. Internal partitions are lightweight timber-framed plasterboard panels, the party wall is built like the external walls, the ground floor is suspended timber on precast plinth and sill courses over a concrete site slab, and the roof is conventional timber framing covered with tiles on felt.
Variations include maisonettes, whose internal construction may differ, houses where a column is interrupted by a wide ground floor window and replaced by a tubular steel column or lintel, and differences in porches and door positions.
| Element | Typical construction | Inspection focus |
|---|---|---|
| Substructure | Concrete site slab thickened under the walls, precast plinth and sill courses, bitumen felt damp-proof course | Settlement, cracking, ventilation of the suspended floor |
| External walls | Storey-height precast aerated concrete columns at 2 ft 6 in centres, with half-storey-height panels bolted to both faces to form a cavity; rendered externally | Vertical cracking at column and panel joints, bulging or spalled render over bolt heads |
| Ring beams | Precast aerated concrete units at first floor and roof level, located by a tongue with no mechanical connection | Horizontal cracking or spalling of the render at first floor and eaves level |
| Floors | Suspended timber ground floor; timber first floor in steel joist hangers on the ring beam | Deflection, dampness, timber condition |
| Roof | Timber framed, tiles on felt, blockwork gable infill | Covering condition, water ingress, roof structure |
Potential hazards & inspection priorities
The published investigation of Woolaway houses found that the aerated concrete is porous and had carbonated to the depth of the reinforcement at most of the places sampled, and that the steel was corroding wherever the concrete around it had carbonated. Corrosion had cracked some columns and panels, and the heads of the panel fixing bolts had corroded at one site, making the render bulge and spall over them. Chloride levels were low throughout. No cracking of the ring beams was found, although one appeared to have been repaired, and no panel was found with its reinforcement corroded right through.
Because the concrete is porous, it can hold a good deal of rust before it cracks, so substantial corrosion was found in some columns that showed no cracking at all; an absence of cracks is not proof that the steel is sound. The investigation also found, however, that visible signs of deterioration had appeared before any significant weakening of the components or their fixings, and that the bolts are substantial enough that considerable corrosion would be needed to weaken them.
No unsafe conditions were found, the investigation concluded that it was unlikely that any Woolaway house was unsafe because of the deterioration of its concrete, and there was no general need for urgent action; early remedial action was advised once cracking of the structural components is seen. Those findings describe the houses examined for the investigation published in 1983, a small sample of the 5,500 built, and not the present condition of any house today.
The stability of the house depends on the external walls, their fixings and the first floor ring beam staying intact, since the partitions are lightweight and the first floor is not fixed to the walls. Severe disruption of the first floor ring beam is the most serious possibility, as the walls could then move outwards at that level, which is why the ring beam needs to be kept in good condition.
The signs to look for in the render are vertical cracks, which can mark the column and panel joints and may be an early sign of corrosion; cracking, bulging or spalling over bolt heads; and horizontal cracking or spalling at first floor and eaves level or over lintels, which can reflect cracking in the ring beams or lintels behind.
Local repair of render over corroded bolt heads is cheap but the cracking is likely to come back, and corroded bolts can be replaced with sleeved stainless steel bolts. Local concrete repairs are practicable, but cracking may recur if corrosion continues, and replacing more than a few columns, panels or ring beams is likely to be uneconomic because of the temporary support needed. Keeping the render and coatings in good condition may slow corrosion.
Is this house right for you?
A Woolaway house may suit purchasers who understand non-traditional construction and its designation, and who are prepared to assess the property on its own condition and repair history.
- Commission a detailed building survey
- Establish early whether the house has been repaired or reinstated, and how
- Consider the implications of the designation for mortgage and resale
Mortgage & resale considerations
Mortgage availability and resale prospects for Woolaway houses are influenced by lender policies, overall condition, and the quality of professional reporting. The Woolaway house is designated defective under the Housing Defects Act 1984, whose provisions for England and Wales are now in Part XVI of the Housing Act 1985, and some lenders may apply restrictions because of that designation.
Clear survey findings and evidence of appropriate repairs can be influential when addressing lender and purchaser concerns.
What a survey can — and cannot — tell you
A building survey provides an informed assessment of the visible condition and construction of a Woolaway house. Inspections are non-intrusive and limited to areas that are accessible at the time of inspection.
- Identify vertical cracking in the render at column and panel joints
- Identify bulging or spalled render over the panel fixing bolts
- Identify horizontal cracking or spalling at first floor and eaves level and over openings
- Comment on roof coverings, drainage details, and external envelope condition
- 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 the columns, which are hidden within the wall behind the render
- Confirm the condition of the reinforcement, which can corrode substantially before the concrete cracks
- Confirm the condition of the ring beams and fixing bolts behind the render
- Inspect areas that are inaccessible or covered at the time of inspection
Where cracking or bulging render suggests corrosion, further specialist investigation may be needed. That can include looking at the columns in the cavity with an optical probe, or breaking through the edge of a panel at a joint to examine the column and its reinforcement, and taking samples of the concrete from the panels and columns, inside and out, to test for carbonation and chloride. This is separate from the survey itself: a survey is non-invasive, and any opening up, sampling or testing is a specialist investigation arranged afterwards, with the owner's permission.
