British Iron & Steel Federation BISF House

The British Iron & Steel Federation (B.I.S.F) Steel Framed House

Prior to the end of WWII, the British Iron & Steel Federation worked closely with Architect Frederick Gibberd & Engineer Donovan Lee, to develop several steel framed prototype houses & flats, which could be erected quickly and efficiently with limited use of skilled labour. These prototypes were duly named BISF which is an acronym of the originating sponsors, ‘The British Iron & Steel Federation’. However, it was in fact the newly formed company, British Steel Houses Ltd, that went on to develop and manufacturer the BISF houses we see today.

Prototypes

In 1944, the Interdepartmental Committee on Housing Construction (Burt Committee), selected the A & B prototype house designs for further development. This resulted in the erection of two  prototype demonstration units, at the Ministry of Works Housing Demonstration Site at Northolt, Middlesex. After much consideration and some adjustment to the initial design, the BISF type ‘A’ house was selected for production. As a result, over 34,000 three-bedroom semi-detached houses and 1048 Terraced Houses were erected across England, Scotland and Wales.

The frame of the prototype ‘A’ frame house, was manufactured from rolled steel sections, with roof trusses of rolled steel or tubular sections. The roof was clad with metal sheeting on fibreboard insulation sheets. The lower exterior walls were constructed in traditional block & brick masonry.

A lightly modified version of the prototype ‘A’ house was renamed the ‘A1’, prior to entering full scale production. 
The final production design incorporated rendered mesh ground floor walls and the now familiar, profiled steel sheeting panels affixed to the upper storey. The preferred roofing material was generally corrugated asbestos cement, or corrugated metal sheeting. 

The frame of the prototype ‘B’ house was of the same general design as the type ‘A’ frame, but fabricated from flat light steel sections.
The roof trusses were also of light steel sections, and the roof cladding was the same as that used in the type A house. 
Both prototypes had been designed to accept a variety of external wall materials, including traditional brick masonry, if desired.

Several different floor layouts  were also considered during the early developmental stage, which are shown below.

BISF House Production Models

What are the different types of BISF Houses?

A1 BISF House – England & Wales.
The B.I.S.F type A.1 house soon formed the mainstay of production within the UK. British Steel Homes Ltd documents the erection of 36,052 B.I.S.F. houses in England, Scotland & Wales excluding prototypes, but records suggest that no BISF houses were built in Northern Ireland.
A2 BISF House – Scotland.
Ministry of Health Scotland requested a few minor adjustments to their A1 allocation. To aid identification, Scotland’s units were duly named as A2 houses.
A3 BISF House – Mainly England
The terraced version of the B.I.S.F house, which was built mainly in England, also received minor alterations and subsequently labelled as the type A3.

Cladding & Roof Profile

The Vertically ribbed upper storey cladding panels and corrugated roofing sheets were a prominent & distinguishing feature of the BISF house.

Unfortunately, visually similar external cladding was also used in the construction of other postwar homes by a variety of manufacturers and also frequently used to clad, temporary prefabricated bungalows.

Mis-identification

The external steel cladding that was affixed to the upper storey of the original BISF house appears visually similar to the external cladding that was used during the production of the unrelated Hawksley BL8, temporary bungalow.

This visual similarity caused many people to wrongly assume that the BISF House was a semi-detached version of the temporary bungalow, despite the fact that the BISF House was built as a permanent dwelling.

Prefab or System Built?

There is much debate as to what separates a true 100% prefabricated house and a system built property.
Factory built, production line houses are generally considered to represent the true 100% prefabricated house.

Almost every component, from wall to roof pre-manufactured specifically for the build and fully assembled prior to dispatch on the back of large transporter vehicles.

Prefab Construction

Many prefabricated buildings were transported in two or three complete sections.
Once on site, they were simply craned into position and bolted together to form a complete and habitable temporary dwelling.

System Built

The steel frame of the house was transported across the country by rail and road in a loose kit form of individually numbered components.
On arrival at site, the frame was bolted together in much the same way modern commercial buildings are erected today. The correct terminology for this type of construction is System built housing.

Lifespan

The BISF HOUSE was designed & built as a permanent dwelling with a projected lifespan equal to that of a traditional brick-built dwelling. 
The BISF house utilised large quantities of pre-manufactured steel components, but in contrast to the majority of temporary prefabricated bungalows, the permanent BISF house did not arrive at site pre-assembled. 

Construction Overview

The vast majority of BISF houses were built as two-storey semi-detached pairs. A smaller number of terraced houses were also built by replicating the standard semi-detached frame. A number of variations relating to the layout and materials used in the construction of this house have been noted, but in all cases, the original construction, design & construction of the steel framework, remains largely as described.

A1 House
Substructure

A minimum nine-inch brick wall is built on top of concrete strip foundations. These are overlaid with 4 inch thick in-situ concrete, thickened to 9 inches where it is carried over the walls.

The main vertical support stanchions were bolted to the concrete foundation by a rag large bolt.
The cross section shown identifies the ground floor concrete plinth, low height masonry work and lower strip foundation.

The lower exterior wall is cement render on mesh.  

BISF House Strip Foundation
Nine-inch brick walls are built onto concrete strip foundations.

They are then overlaid with 4 inches of in-situ poured concrete, which is thickened up to 9 inches where it is carried over the  brick walls.

The image Below shows the foundation prior to the laying of the concrete plinth.

Foundation Pad

The steel frame of the house was transported across the country by rail and road in a loose kit form of individually numbered components.

On arrival at site, the frame was bolted together in much the same way modern commercial buildings are erected today. The correct terminology for this type of construction is System built housing.

BISF House Steel Frame

• At first-floor level in the eaves walls, the stanchions are tied by 4 x 3 inch RS angles which support the ends of the floor beams.
• At eaves level in these walls the stanchions are tied by the outer ceiling joists.
• At first-floor level in gable walls the stanchions are tied by the outer floor beam and at eaves level by the collar beam of the roof truss.
• The corner bays, at the junction of eaves and gable walls, have diagonal bracings of RS angle between stanchions.
• The 4 x 1¾ inch RS joist floor beams run at 3ft 6in centres between eaves walls. They are supported near mid-span by a 5 x 3½ inch RS joist spine beam.
• At gable walls the ends of the beam are carried on 4 x 3in RS angle trimmer beams spanning between adjacent stanchions.
• The spine beam is supported across the width of the house by posts at 3ft 6in centres. The posts are made of two 2 x 2in RS angles welded longitudinally to form box sections

Roof Section

• Roof trusses are constructed of RS angle or tubular sections and span the eaves walls.
• At gable walls the truss is integral with the gable frame. There is a truss each side of the separating wall. There may be a single or two intermediate trusses.
• Purlins are of RS angle. Ceiling joists of 3 x 1½ inch RS joists at 3ft 6in centres run at right-angles to the trusses.
• Sheeting rails of 2 x l ½ inch RS angle run horizontally on the walls to the first floor at eaves, window-sill and floor levels.

External walls

At first-floor level in the eaves walls, the stanchions are tied by 4 x 3 inch RS angles which support the ends of the floor beams.

At eaves level the stanchions are tied by the outer ceiling joists.

Wall Cavity

The cavity between the external cladding and internal lining of the external walls is 6 7/8in wide. Insulation is enclosed in a brown paper wrapping.

The edges of the insulation is affixed directly to the timber battens and studwork with purpose made fixings.

External Cladding

The cladding of the walls to the ground floor up to ground-floor window head, is of render on expanded metal mesh.

The mesh is tied to the steel stanchions. Above this level the structure is clad in steel sheet which has a vertical, ribbed profile and is fixed to sheeting rails.

Internal walls

The internal lining is of 3/8in plasterboard or hardboard fixed to 2 x 1in timber framing secured to the steel framework.

Some upper floor rooms may be lined with plasterboard or hardboard despite guidelines against using hardboard in upper rooms. 

A paper covered glass-fibre quilt approximately 1 inch thick is sandwiched between the steel framework and timber framing in external facing walls and sometimes omitted totally inside internal partitions.

Party Walls

The separating wall is of cavity construction, comprising two leaves of 3in breeze block separated by a 2¾ in cavity. The leaves are tied together with vertical-twist wall ties.
In the roof space only one leaf of the wall is continued above first-floor ceiling level and the cavity is closed with asbestos felt. Internally, the separating wall is sealed with a cement slurry.
The separating wall is lined on both sides with 3/8in plasterboard on timber framing.

Floors

The ground floor is usually of solid construction.

The upper floor is generally of 7/8in tongued-and-grooved boarding fixed to 5 x 1¼ inch timber joists at 1ft 6in centres, spanning between the steel floor beams.

Some buildings were constructed with a concrete floor at ground & first floor level.

Ceilings

The ground floor ceiling is generally of 3/8 inch plasterboard or fibreboard fixed to the underside of the timber joists of the first floor.

The first floor ceiling is of 3/8 inch plasterboard or fibreboard, fixed to 3 x 1/4″ timber joists at 1.ft 6.inch centres, spanning between the steel ceiling joists. In some instances the spacing of the joists differs.

Roof

The BISF roof is clad with asbestos cement profiled sheets carried on purlins supported by the roof trusses.

Alternative roof coverings include corrugated, profile metal sheeting and the more recent addition of lightweight roofing systems such as Metrotile or Decra Tile.

Corrosion protection

The structural steelwork is painted with two coats of red lead paint, to which a coat of bitumen is added on-site after erection.
The profiled steel sheet cladding is hot-dip galvanised, treated with a mordant and painted with red lead. The sheeting is finished with two coats of a proprietary stone/ masonry paint.