Trusteel 3M – Steel Framed House

Trusteel 3M - Steel Framed House 1
  • Name: Trusteel 3M Also known as: Trusteel
  • Manufacturer: Trusteel Corporation (Universal) Ltd.
  • Period Built: 1966 -76.
  • Number built: 17 000.
  • Designers: M R Park and C R Stapleford.

Identification Characteristics:

  • Bungalows, flats, 2-storey semi-detached and terraced houses.
  • Shallow pitch gable roof or monopitch covered with interlocking concrete tiles or slates or flat roof covered with asphalt.
  • External walls of brick, concrete panel, tile hanging or shiplap timber boarding throughout or in combination.
  • Internal inspection will reveal visible steelwork in roof space. Sometimes, these properties can be mistaken for Crosswall built properties due to brickwork of the gable end wall protruding past the frontage of the property combined with surface cladding to upper storey of vertical hung tiles, timber or cement render.

Notes for surveyors

  • Superficial corrosion of cold RSC stanchions, particularly at bases.
  • Superficial corrosion of steel lintels over doors and windows.
  • DPC near or below ground level.
  • Debris and mortar droppings in cavity bottom.
  • Condensation and mould growth in living areas and roof space.
  • Damaged, loose of missing roof tiles and flashings
  • Inadequate fire stopping of separate wall.
  • Flue pipes misaligned, poor support and missing sections.
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Trusteel 3M Frame Design

The frames are based on modular dimensions of 2’9″ and main components are standardised in size to 6″ x 2 3/8 – Floor beams 7″ x 2 3/8.
Consisting of a steel channel base plate which has projecting lugs to locate every stanchion in its correct position. This plate is solidly embedded into the site slab. The remaining members comprise of full length stanchions, stud-stanchions for trimmed window openings, first-floor beams, lintel-beams, cill struts, lateral and diagonal braces, roof rafters, collar ties and eaves ties.

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The Main components are of four cold-rolled angles forming the flanges with a lattice web that is hydraulically riveted together.

Jointing methods of main components

The first-floor beam to stanchion: Stanchion to rafter and collar to rafter—is made by a mild steel plate at the end of one member sliding entirely through between the flange angles of the other member into prepared connecting plates, and locking with an expanding tubular pin driven into position on site.

Fixing Method: The space between the angles made by the insertion of the lattice web creates a gap of predetermined dimension. This gap is a major feature of the system as it enables a self-tapping screw to be used for all fixings to be made to the steelwork flanges, no drilling of steel members being required on site.

Protection in Factory: Protection of the steel is carried out after degreasing and chemically cleaning by total immersion in a zinc-chromate red-oxide base paint to Formula CS.2251 prepared by the Chief Chemical Inspectorate of the Ministry of Supply and stoved in infrared ovens at a temperature of 350 —400′ F. before fabrication.
After the small parts have been fabricated into major components these are again dipped and stoved a second coat.

Protection on Site: On site. the bases of the stanchions are treated by the Contractor with a heavy bitumen coating before being concreting into place. All external flanges of the stanchions are covered with “Denso” damp-proof and Insulating membrane to prevent contact with the external cladding material.

Numbering: Every member is numbered and steel erection drawings showing the relationship of every member to the structure are provided.

Handling: The frame components are delivered on site as separate units, roof trusses are not made up as complete trusses, the rafters, collars, ties and bracing members are separate components enabling clean flat packs for transport, ease of stacking on site and ease of handling.

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Resource Files

PIA technithermTrusteel

Trusteel 3m estate agent sales brochure


  1. Hi recently purchased a Trusteel 3M Mk2 property and am looking to improve the insulation to help save on energy bills. Does anyone have experience with this? The inside walls appear to be made from straw blocks while the outside is brick. The steel frame itself is painted and looks to be in good condition. I realise that cavity wall insulation is a big no no, so what can I do?

    I cant see any outside vents on the house so am not entirely clear on how the property ventilates itself. I can however see the steel is exposed in the loft so this must be part of the solution.

    Would external cladding compromise the steel? Is internal insulation with modern material a better approach? Any tips, advice or articles on this would be greatly appreciated.

    David Abbott.