NTR wood protection classes in relation to EN 351-1 and EN 335

Penetration class according to EN 351-1

Use classes UC1-UC5 according to EN 335 and their relation to the wood protection classes NTR M, NTR A, NTR A pole, NTR AB, NTR B, NTR GRAN and NTR GW

Relation between Wood protection class according to NWPC and Use class according to EN 335-1

Penetration class according to EN 351-1Penetration requirementUse Class 1Use Class 2Use Class 3Use Class 4Use Class 5
NP1NoneNTR GRAN** NTR GW**
NP 2Min 3 mm lateral into sapwood
NP 3Min 6 mm lateral into sapwoodNTR B
NP 4*Min 25 mm
NP 5Full sapwoodNTR ABNTR A NTR A poleNTR M
NP 6Full sapwood + 6 mm into heartwood