The timber floor joists should be sized correctly depending on their span (length between supports) and are normally laid across the shortest span from wall to wall with a gap underneath.
Rhaid i ddistiau'r llawr pren fod o'r maint cywir, a fydd yn dibynnu ar eu hyd. Yna, byddant yn cael eu gosod ar draws y rhychwant byrraf o wal i wal gan adael bwlch danynt.