Loft conversions are a very useful way of creating that extra space. The main structural issues are whether the existing roof is strong enough to support the additional weight of the new ceiling and insulation, and whether the existing ceiling is strong enough to be used as the new floor.

With a hipped roof, the rafters are often found to be adequate without strengthening, but the purlins seldom are. In fact in many cases the purlins are barely capable of supporting the existing roof! The existing ceiling joists invariably need strengthening because of the increase in the loading which is necessary for the room to be used as a habitable room.

Our structural calculations for a loft conversion includes checking the capacity of both the existing roof and the floor. Our structural design also includes preparing the calculations for any necessary strengthening work.

We need the following information to design this type of loft conversion:

a plan of the floor(s) below the level of the loft conversion showing the position of the loadbearing walls. The plan should be to scale or have dimensions marked on it

the approximate ridge height of the roof above ceiling joist level

the size, number and positions of the existing purlins

the size and spacing of the existing rafters

the type of roof covering (concrete or clay tiles, slate etc)

the approximate location of the building

Design information

All design work is carried out in accordance with BS5268 (The structural use of timber).

The calculations provided will be suitable for Building Regulation approval.