Truss Roofs and Lofts

Truss Roofs and Lofts

Velux Diagram of Trussed Roof

A truss roof design has W shaped wood trusses. Trusses tie both loft floor and roof.

Attic trusses occupy the central loft space and have to be replaced with steel beams during all trussed loft conversions.

Trussed Roof Conversion

If your trussed roof (W shaped wood rafters) is sufficiently high for conversion then the distance between loft roof and floor is a minimum of 2.1 metres in height.

If not, then you may need to consider raising your roof line. We are experienced truss attic and loft conversion specialists and have the skills and techniques required to plan and design a new loft from an existing trussed roof.

Truss Frame

Truss Rafters

Exactly how loft conversion companies perform a trussed conversion will depend on their level of experience, use of techniques and materials.

Modifying the trussed rafters themselves is not possible as trusses have structural integrity.

The exact design of the roof trusses may depend on the age of your house as shapes, designs and construction techniques have evolved over time.

However, UK houses generally have used prefabricated (prefab.) roof trusses which are identifiable by a W shape and nail plates.

Prefab Attic Trusses

The wood truss frame is replaced with steel beams to support the roof when the truss frames are removed.

Without the trusses the loft is free of obstructions and we create the roof living space.

More on Trussed Roofs

Trussed rafter roofs are generally built to conventional designs. 3-inch timbers are locked together into a strong, load baring truss frame. Rectangular metal plates (helping to identify the prefabricated trusses) secure the timbers.

Truss Frame

Many modern (Post 1965) trussed roof designs tend to have shallow pitched styles and do not have the height required for conversion - 1.8 m minimum at the edge of a stair with 1.9 m at the centre line if the ceiling is sloping.

See page 7 of Approved Document Part K. Low lofts can now be developed for habitable use, adding significantly to the use and value of your home.

Standard Roof Trusses

Truss Connector Plate

The picture shows the precision required in premanufactured roof trusses at Truss Form Ltd. (part of Alpine Automation (U.K) Ltd. - a Truss Design Software Company) Working from plans the timbers are positioned within electric vices which then lock timbers so that connector plates (Gang Nails) can be mechanically pressed.

Trussed rafters carry direct loads vertical through diagonal bracing and tie batons.

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