Wood flooring knots
Wood Knots: class of appearance of oak flooring, quality measure
In classification of oak parquet , i parquet knots they are distinguished by class of appearance (square or circle).
The UNI EN 13489 standard specifies that the material used for the upper layer must be selected, young and healthy hardwood or coniferous wood without cavities, fungi, mold or insect damage. There may be variations from one list to another, but the general impression of the floor installed must show the homogeneous character of each classification. Given the inevitable differences in classification, the standard in question admits that 3% of the elements of a lot may be of other classes.
The following table shows classification examples for oak (Quercus spp. – oak parquet)
| Features | Circle class | Triangle class | Square class |
|---|---|---|---|
| Healthy sapwood | Not allowed | Allowed up to 50% of the front face, if deployed | |
| Nodes (a) sound and adherent | Allowed if: diameter< = 3 mm | Allowed if: diameter< = 8 mm | |
| Knots (a) rotten | Allowed if: diameter< = 1 mm if not grouped (b) | Allowed if: diameter< = 2 mm | |
| Cretti (bristles) | Not allowed | Up to 20mm length allowed per list | All features are allowed with no size or quantity limits if they don’t compromise the strength or wear resistance quality of wooden floors |
| Inclusions of bark |
Do not allow | Do not allow | |
| Lightning strike | Not allowed | Not allowed | |
| Deviation of the grain |
Allowed, no limits | Allowed, no limits | |
| Color variations | Slight variation allowed | Allowed | |
| Parenchymal rays (mirrors) | Allowed | Allowed | |
| Biological alteration | Not allowed | Not allowed | Not allowed, except for blueing and forineri from insects (mottling) |
| PARTS NOT VISIBLE |
|---|
| All characteristics are allowed without limits of size or quantity if they do not compromise the strength or quality of wear resistance of the parquet flooring |
| (a) Cracks in knots and holes caused by knots must be filled (b) Knots are considered to be grouped if the distance that separates them, measured from edge to edge, is not greater than 30 mm |