|Carpentry for Vocational Schools - A Teachers Handbook|
The length of timber laid across the bearers are called joists. Joists should not be packed under to bring them to a level surface, but if a small amount of packing is needed on individual joists, this may be done with hardboard or plywood .
Floor joists are spaced between 500 mm and 700 mm (centre to centre) apart. If there is a wall erected on a joist, you have to double the joist and space it 25 mm apart for outside walls. For inside walls you have to space them 50 mm apart.
The fixing of the floor joists is a most important operation. The top surface of the joists serve as a base for the walls, as well as for the flooring, so the aim is to finish with a surface which is absolutely flat and level.
Make sure that the top edge is perfectly straight and that the joists are at the right angle to the bearers. When nailing each joist, look along it and take out any side bend.
a) Joining Joists:
- Generally joists are joint together with a butt joint.
- Sometimes a splayed joint is used to join joists together.