Loft Conversion Roof Structure

Changing the roof structure for a loft conversion.

Loft conversion roof structure.

Altering the roof structure floor joists most roofs are constructed with internal support struts in the loft propping up the rafters and purlins horizontal roof beams in traditional cut and pitched roofs and making up the web of braces in modern trussed rafter roofs. This type of loft conversion involves one or both slopes of the roof being replaced with a new structure with very steep sloping sides almost as steep as the walls. However the average dormer loft conversion with a double bedroom and en suite costs about 35 000 45 000. This design is used where the original roof had little or no headroom and creates sufficient volume for an additional storey.

Most loft conversions employ at least one pair of steel beams to support the new floor structure and the roof slopes at purlin level and sometimes also at ridge level e g. In the roof space as the name suggests the ridge board is the length of timber which runs horizontally along the apex of the roof. An almost flat roof is placed over the top. Internal roof elements to consider during loft conversions consist of a number of sub structures such as ridge boards rafters purlins joists wall plates and steel beams.

This option is the most expensive as it requires the complex removal and rebuild of the existing roof. This could be a hip to gable loft conversion or a mansard conversion for example.