Use class (wood protection)

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Use class is a term from wood protection .

Depending on the installation situation, built-in wood is exposed to different degrees to attack by wood-destroying fungi and / or insects . The usage classes represent a classification with the help of which the type and scope of any chemical wood protection measures that may be necessary can be assessed. In Germany, DIN 68800 Part 1 is decisive for this. (With the new edition of DIN 68800 in 2011/2012, the "usage class" replaced the previously used term " hazard class ".)

Before using chemical wood protection measures , it must be checked to what extent adequate protection of the wood can also be achieved through preventive structural measures (according to Part 2 of the above-mentioned DIN), because wood is most effectively protected through construction measures by keeping it dry at all times (max . Humidity up to 70% / max. Wood moisture up to 20%). The following overview shows the conditions under which chemical wood protection must be used:

Use classes

Use class Stress  required wood protection Test rating alternatively wood of the durability class
 0 Wood built inside, always dry. Approach by wood-damaging insects is not possible or the cross-section of the wood can be controlled (visible from at least three sides). No chemical wood protection required  -  -
 1 Wood built inside, always dry. Approach by wood-damaging insects is possible. Preventive against insects  Iv 3   ( sapwood content ≤10%)
 2 Wood that is neither in contact with the ground nor directly exposed to weathering or leaching. Temporary moistening is possible. Preventive against insects and fungi  Iv, P 3   ( sapwood content ≤5%),
including heartwood from Douglas fir , larch and pine
 3.1 Wood not under the roof, but without constant contact with the ground or water. Accumulation of water in the wood - even spatially limited - is not to be expected. This means that the entire wooden structure can dry out quickly after it has been soaked through. Preventive against insects and fungi, wood preservatives protected against leaching (fixation)  Iv, P, W 2   ( sapwood content ≤5%),
including heartwood from Douglas fir and larch
 3.2 Wood not under the roof, but without constant contact with the ground or water. Accumulation of water in the wood - also spatially limited - is to be expected. Preventive against insects and fungi, wood preservatives protected against leaching (fixation)  Iv, P, W 2   ( sapwood content ≤5%)
 4th Wood in constant contact with the ground or exposed to constant strong moisture. Preventive against insects and fungi including rot, wood preservatives protected against leaching (fixation)  Iv, P, W, E 1   ( sapwood content ≤5%)

Iv = preventive action against insects
P = preventive action against fungi (protection against rot)
W = for wood that is exposed to direct weathering, but without constant contact with earth or water
E = for wood with constant contact with earth and / or water

  • Parts 2 and 3 of DIN 68800 have been introduced by the building authorities (Part 3 not in Baden-Württemberg) and are therefore binding for load-bearing and stiffening wooden components. Wood preservatives used on such components must have general building inspectorate approval .
  • Universal wood preservatives for all four hazard classes are no longer permitted. Depending on the type of hazard or infestation, it must be decided which agents are to be used.
  • The effectiveness combination must be recorded on all containers. (Check marks)

Chemical wood protection can generally be dispensed with if wood types are used that have the natural durability (resistance) specified in the last column of the table .

For the commercial use of chemical wood preservatives , a successfully passed examination is required, which is documented by the "certificate of competence in wood preservation in construction". This certificate of competence confirms the qualification required in DIN 68 800, Part 4 and states that the owner has the knowledge and skills according to the state of science and technology for the preparation, guidance, implementation and testing of non-hazardous and environmentally friendly wood protection measures to combat wood-destroying fungi and insects as well as other influences.

See also

Footnotes

  1. ↑ a b Dr. Constantin Sander: Building Inspectorate Approval , In: Kebony.com