Trusteel MKII Steel Framed House

Trusteel MKII Steel Framed House 1
  • Name: Trusteel Mk II
  • AKA: Also known as: Minox or Trusteel.
  • Manufacturer: Trusteel Corporation (Universal) Ltd.
  • Period Built: 1946–66.
  • Number Built: 20 000. Designer: C.R.Stapleford.
Trusteel MKII house Belfast

Trusteel Identification Characteristics

  • Bungalows, chalet bungalows and 2-storey detached, semi-detached and terraced houses.
  • Medium pitch hipped or gable roof covered with plain or interlocking concrete tiles.
  • External walls of brick, plain or harled (pebbledash) render, tile hanging or shiplap boarding throughout or in combination.
  • Steelwork visible in roof space.
Trusteel MKII Steel Framed House 2
  • Notes for Surveyors:
  • Severe corrosion of steel lattice stanchions, particularly at bases.
  • Severe corrosion of steel lintels and sill supports.
  • DPC’s near or below ground level.
  • Debris and mortar droppings in cavity bottom.
  • Sulfate attack to concrete ground floor slab.
  • Corrosion of galvanised windows.
  • Due to the construction detailing, there is a risk of cold bridging through the steel frame and condensation forming behind the brickwork, placing the steel frame at an increased risk of corrosion.
  • Party walls consist of two leaves of lightweight concrete block separated by a cavity.
  • The internal partitions are usually built of the same.
  • The ground floor is typically of solid in-situ construction whilst the first floor is built off steel joists which span between the stanchions located in the front and rear external walls.
  • The pitched roof construction comprises steel lattice roof trusses, sarking felt, battens and concrete tiles.
Trusteel MKII Steel Framed House 4

The typical house structure is based around a framework of steel sections made of thin gauge steel strip lattice components to form columns, floor beams and roof trusses.
The properties are all clad in conventional brickwork and give the appearance of traditionally constructed houses of the post-war period. There are no distinctive external features that can be used to identify them as clearly containing a steel frame.
However, the cavity of the wall is 150mm wide to accommodate the columns and this increased overall wall thickness can offer an indication of the construction.
The internal leaf of the wall is generally made from wood-wool slabs. The steel frame was commonly protected from contact with the brickwork by using a layer of bituminous tape along the outer face of the stanchions.

Trusteel MKII Steel Framed House 6

History of Trusteel Corporation Ltd

The Trusteel Corporation (Universal) Ltd was first registered in 1945. It was not initially set up as a building company.
The company used to supply steel frames alongside comprehensive design and technical services for customers and clients.

Trusteel provided all drawings necessary for obtaining planning consent and building regulations approval, drawings for site use such as steelwork erection drawings and joinery details. The company also provided site supervisors to oversee the assembly of the steel framing in relation to the first few houses that were constructed.

Trusteel MKII Steel Framed House 8

The designation MkI or MkII as applied to the lattice frame system has not been seen on any Trusteel literature or drawings. However, many articles describing the system use these terms and the designation has become common usage. MkI may refer only to the prototype design and MkII to later modified frames. For the purpose of this report, MkII is used as a generic term to denote the lattice frame system as distinct from the latter ‘3M’ steel frame which was introduced in 1966.

The Trusteel Corporation are understood to have supplied over 20,000 MkII type properties between 1946 and the mid 1960s to both the public and private sectors.

Image Gallery

Further Reading

Trusteel News Article PDF

Trusteel houses Bletchley during World War Two 1945 – 1947 PDF

Trusteel News Article PDF

Trusteel News Article PDF

M Dyson – Summary of Trusteels report 2011BFINAL PDF

PIA technithermTrusteel PDF


  1. great to see some info on the trusteel mk2 houses. i own from what I’ve been able to gather this type of build but still have some questions about its construction, mainly around the window areas. are the windows tied into the frame? are they able to be taken out easily and replaced with upvc windows??? many thanks in advance phill.

  2. Hi Phil, Welcome to the site and thank you for your comments.


    The window frames of the Trusteel house aren’t normally tied to the frame.

    There is a lower inner windowsill that sits on top of the horizontal steel just below the sill. the window frame is anchored into the brickwork or the timber vertical sidestrips, which is very similar to fitting windows into a traditional house,

    I’ve attached an image below and although the windows have been removed in this photograph, I have indicated where the original casement frame once sat as if you look carefully, you can see the line of silicone sealant that once sealed the frame in place. 

    I hope this helps and please let me know how you get on.

    trusteel house window opening


    1. hi mark, thanks for this info, i don’t have a clue how my windows are designed as they don’t actually look like the setup in the picture above. they seem to be more of a solid full window system, its hard to describe i will try get round to posting a picture and see if you can decipher anything from it if that is ok? please see attached pictures of what u mean.

      20171121 224413
      20171121 224403
      20171121 224218
      20171121 224209