Only wood species known to be suitable for the production of glued wooden window scantlings such as spruce, fir, pine, larch, Douglas fir and oak may be used. Other types of wood can be found in the "HO 06" leaflet "Types of wood for window construction", published by the "Verband Fenster und Fassade und Gütegemeinschaft Holzfenster und Haustüren e.V.", Frankfurt, in its current edition.
The wood used must meet the quality requirements of the technical guideline "Solid, finger-jointed and laminated profiles for wooden windows". As a general rule, sapwood is permitted, but not for larch and oak on the visible surfaces of the scantling.
With regard to wood quality, a written agreement can also be made between the manufacturer and the customer on deviations from the provisions, which must then be checked, approved and deposited by the inspection body. Such agreements must not contain any deviations which impair the gluing quality and the service life of the window scantlings.
In order to detect unavoidable sorting errors, these sorting regulations apply to 95 % of the lot, i.e. a maximum of 5 % may be of lower quality.