Can contractor be held liable for serious defects?

Questioner

Our apartment complex (12 apartments and 1 penthouse) was completed in 2003. The penthouse has been built on the roof. During its construction, a significant portion of the outer walls/base was made of sand-lime brick blocks with a layer of plaster on top. Moisture forms behind this layer of plaster, which over time causes cracks to form and ultimately the plasterwork to crumble - which was already "temporarily" repaired in 2011 under goodwill (as he himself says) by the contractor -. Now there is again a case of detachment that affects an essential part of the construction. As a director of the VvE, I have held the contractor liable for this on the grounds that it can be qualified as a “serious defect”, for which the contractor is still responsible for a period of twenty years after completion. In 2002 I signed a Purchase-Construction Agreement which included the conditions of a serious defect (which you are probably familiar with). In the meantime, I have oriented myself on this issue. It appears that outdoor applications of sand-lime brick are not recommended (including by a manufacturer/supplier). However, the contractor now states that: 1) built according to the specifications; 2) they do not regard this as a serious defect; 3) they followed this because it was a technical regulation and, in their opinion, was still common practice at that time; 4) have built on those insights and in good faith and that 5) The insights regarding the use of lime sand brick outdoors have changed over the years and are now discouraged. I understand that even if the specifications indicate building with sand-lime brick, the contractor remains responsible. In 2002, contrary to what the contractor claims, it was known that such walls are porous and attract moisture and are therefore not suitable for outdoor use. The construction company boasts years of experience on their site. Incidentally, the contractor has not proven unwilling. He is willing to carry out repairs, but for a considerable amount. Then the lime sand brick walls will be replaced by facade bricks. Apparently he himself feels that there is a construction error and he wants to cooperate What do you think: 1) Is the contractor still liable? 2) Is there a legal article in the Civil Code or other provision that substantiates this? I would like to hear your response today as I have a follow-up meeting with the contractor about this tomorrow.

Lawyer

What time frame should I link to the fact that a defect has been discovered again after repair? Have so many years passed in the meantime? Everything stands or falls with the limitation of legal actions and the strength of the evidence, you state something technical but you must ultimately prove it.