Where you re adding a large dormer.
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.
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.
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.
An almost flat roof is placed over the top.
Changing the roof structure for a loft conversion.
However the average dormer loft conversion with a double bedroom and en suite costs about 35 000 45 000.
This option is the most expensive as it requires the complex removal and rebuild of the existing roof.
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.
The most common style of structural loft conversion these are an extension to the existing roof building out sections with vertical walls from the roof to add floor space and room for windows.