Size Of Floor Joists In Loft Conversion

How to insulate between new floor joists in a loft conversion using 100 mm rockwool fibre insulation and chicken wire.

Size of floor joists in loft conversion.

New floor joists are measured and trimmed to size then dropped into the joist hangers and secured in position. This means that new floor joists are fitted alongside them slightly raised above the ceiling plasterboard to avoid contact with it. Surveyors and structural engineers use data from tables below to help calculate the size of timbers necessary to give adequate support to timber floors. But larger is not always better when builders are constructing a home or adding a room addition.

Floor joists and joist replacement in loft conversions attic dormer and roof conversion extensions. 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. 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. 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.

To overcome this problem new floor joists would need to be installed to take these new loads. 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.