Size Of Floor Joists In Loft Conversion

Surveyors and structural engineers use data from tables below to help calculate the size of timbers necessary to give adequate support to timber floors.

Size of floor joists in loft conversion.

Common sense tells you that large floor joists can carry more load and spacing joists closer together also increases the load bearing capacity of a floor. New floor joists are measured and trimmed to size then dropped into the joist hangers and secured in position. There are many ways of altering roof structures for loft conversions but they all have one common element the ceiling joists will almost certainly be inadequate as floor joists. The extra two inches of vertical distance when a floor is framed with 2 x 10 joists rather than 2 x 12s can be quite important for example.

It is unlikely that the existing ceiling joists will be adequate to support the weight loads that arise from the construction contents and use of a typical habitable room developed in a loft. This means that new floor joists are fitted alongside them slightly raised above the ceiling plasterboard to avoid contact with it. But larger is not always better when builders are constructing a home or adding a room addition. The new floor joists of your loft conversion will need to offer at least 30 minutes worth of fire protection which could mean replastering the ceilings in those first floor rooms below.

Floor joists and joist replacement in loft conversions attic dormer and roof conversion extensions. These tables can help calculate whether floor joists are strong enough to support themselves and the load they carry without the help of any walls underneath.