|Making of Floors - Course: Timberwork Techniques. Trainees' Handbook of Lessons|
The beam systems must be prepared in such way that their surface is plane and horizontal and completely levelled before the boards are laid.
If supporting laths are placed on solid floors, strips of bituminous felt are laid under the laths for protection against moisture.
The supporting laths, too, are laid horizontally. Here, adjustment is achieved by putting short pieces of planks, bituminous felt or other suitable material under them. These backings are closely spaced and across the supporting laths in order to avoid that the laths deflect. Before being laid the supporting laths must be impregnated with a timber preservative for protection against rot.
What has to be considered, if boarding shall be laid on an already existing old layer of beams?