Cruden Rural Steel Framed House

Manufacturer: Cruden Homes Ltd
Type: Steel Frame
Period Built: 1947-1950
AKA: Cruden Rural
Number Built: 3,000

Cruden House background information.

In the post-war years a group of skilled contractors joined forces to form Cruden Houses Limited.
In 1946, the company submitted plans to build the steel framed Cruden Rural House to the Inter-departmental Committee on House Construction (the Burt Committee), in response to the Governments non-traditional house building programme
The newly formed company, Cruden Houses Limited was formed through the joint collaboration of the following contractors;

Cruden Limited, Musselburgh
A Hall and Son, Aberdeen
The Alliance Construction Company, Dundee
J Wright and Company, Edinburgh
J Laidlaw and Son, Glasgow

Cruden dwellings are of semi-detached or terraced construction, with pitched roofs but some flats were also constructed from this design. The houses incorporated a light-weight cold-rolled steel frame, clad externally in concrete blockwork with each blocks being 3ft 6in long by 9ft 7/8 inch high.
In general, the external concrete blockwork was given a protective coat of paint, but in Scotland, the properties were generally rendered to provide extra protection from the harsh elements.
Cement was scarce in the 1940’s post-war years which led certain local authorities to substitute 4 1/2 inch bricks for the concrete cladding. Although identical in every aspect to the Cruden Rural House, apart from the brick cladding, this adapted version became known as The Cruden Brick-Clad House.
Over 3,000 of these properties were constructed in Scotland between 1947 and 1950.
The very first prototype of the Cruden house was erected near Milton Road Edinburgh. At the time, the new Temporary Housing Programme was in full swing, plasterboard and asbestos cement roofing tiles were in short supply, as the majority of these materials had been swallowed up by the Government run programme, during its attempt to mass produce homes quickly and cheaply. Cruden were thus forced to use fibreboard instead of plasterboard for wall linings, and heavy concrete roof tiles in place of tiles made from asbestos cement.

The steel framed Cruden House, also commonly known as the Cruden Rural or Cruden Brick-Clad, were typically constructed as 2-storey semi-detached and terraced houses. These dwellings were typically built containing 4-apartments of two-storey semi-detached or terraced houses. It should be noted that minor variations in the layout, general construction and external profile of these homes do exist.

Shortages of certain materials would sometimes lead to the adoption of alternatives in order to achieve the desired outcome, but in all cases, the integrity of the structural framework remained unchanged. A number of flats were also built to this form.

Surveyors Notes: The following issues have been noted during investigation into a number of these properties. It should be noted that the presence of defects depends largely upon a wide range of internal and external factors, including but not limited to, sheltered or exposed location, general maintenance and upkeep, water ingress, build defects etc. The defects/issues listed below, tend to highlight the more serious issues found during surveys.

Severe corrosion of the cold RSC stanchions (Frame Legs), has been observed in some properties. The corrosion is generally found to be more severe at the base of affected stanchions.
Corrosion of beam and stanchion connections at first floor level.
Corrosion of horizontal sill members.
Bowing of the external concrete block walls has been noted.
Cracking to the exterior render and external walling.
Cracking and spalling of concrete blocks has been noted at and around the windows.

Base Structure
The foundation consists of concrete strip footings and a Precast Concrete underbuilding of 9-inch thick precast or cast in situ concrete walls and honeycomb sleeper walls, built from concrete blocks.
The solum (soil layer) is covered with 3-inch of ashes and finished with 2 layers of bitumen emulsion. A bituminous felt damp proof course was then placed on top of the foundation walls.

The frame consists of:

24 cold Rolled Steel Channel (RSC) stanchions (per single storey).
4 cold Rolled Steel Angle (RSA) lateral perimeter ties.
8 cold Rolled Steel Channel (RSC) floor support beams, cold Rolled Steel Angle (RSA) sills.
8 cold Rolled Steel Channel (RSC) trusses and cold Rolled Steel Angle purlins, see frame layout below.

The frame stanchions are located at 3ft 6in centres, situated within the external walls and rag-bolted to the foundation. They extend upward to the roof line of the building.

At first floor level, cold-rolled steel channel beams span between the front and rear elevation. They are connected by three bolts to steel plates welded to each stanchion. Some of the beams are propped mid-span by single-storey cold rolled steel, lipped channel stanchions.

At eaves level, the stanchions to the front and rear elevation are tied laterally by steel angles.
Steel roof trusses span between the front and rear elevation, and are bolted to the head of each stanchion. Each rafter member and ceiling joist consists of two steel angles.
At corners, the two adjoining stanchions are connected by angle cleats, welded to both stanchions. Diagonal bracing straps extend from the bottom of the corner stanchion to the first-floor level of the adjacent stanchion on each elevation.
Similar diagonal bracing extends from each of the stanchions at the separating wall, to the adjacent stanchion in the same dwelling, within each pair.

For a more in depth description including frame components sizes, readers are encouraged to purchase the following report from the BRE website.

Cruden Rural Steel Framed Houses – BRE Library

The steel frame was generally protected with a layer of Zinc-Chrome paint to reduce the risk of corrosion.

External walls: Constructed from harled Precast Reinforced Concrete blocks.
Harling (or roughcasting) was originally applied to rough stone walls to protect them from the weather (in Scotland). It consisted of lime mortar mixed with small stones or shells being hurled or cast against the wall and produced a rough textured finish. Lime wash would sometimes be applied every few years to help seal small cracks.
Between the block walls there is a cavity followed by timber framework which was backed with building paper, before being lined with fibreboard and plasterboard. A type of Glass-fibre insulation was inserted between the timber studs.

Separating wall: Having a PRC block cavity wall also lined with timber framing and backed with building paper, fibreboard and plasterboard. Glass-fibre insulation is inserted between frame studs.

Partitions: Are of timber stud lined with plasterboard.

Ground floor: PRC slabs on Precast Concrete block, dwarf walls.

First floor: Tongue & Groove boarding onto timber joists mounted across steel beams.

Ceilings: Fibreboard and plasterboard on timber framing.

Roof: Bituminous felt, timber battens and interlocking concrete tiles. PS eaves fascia, soffit and bargeboards.

Misc: A Flat or sloping canopy was often fitted over front door.

Variants of this build

A concrete underbuilding.
Harled brick used for external walls.
Painted concrete block used for external walls.
A suspended timber or concrete ground floor.
Black bituminous paint was sometimes used to provide a protective coating to the steel frame.

GENERAL COMMENT ON CONDITION
The Building Research Establishment examined a number of Cruden Rural houses in Scotland and found that some properties were in their original condition whilst others had suffered from corrosion ranging from mild to severe.

The extent of deterioration varied considerably from house-to-house and site-to-site. In most instances some deterioration of the frame was noted whilst in others severe corrosion was found. The BRE advises that the full scale of corrosion, if present, can only be determined undertaking a full structural survey. However, in general, when a sample group of adjacent or nearby houses is being investigated, this may give a general representation as to the likely overall condition it should be possible to determine the general overall condition of the selected group.
Fortunately, as with all steel-framed houses, any deterioration to the frame or stanchions can be cut away and replaced very effectively.

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Cruden House background information.

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