Liability for construction problems

Questioner

We have submitted an application for the construction of an extension (bedroom) on an existing utility room of the house. This was approved by the municipality and the extension was installed last Thursday. However, during installation, the window frames of the underlying utility room sagged; it now appears that there are wooden beams resting on the window frames, while it is apparently customary (according to the construction company, mandatory?) for there to be a steel construction, which would have prevented the subsidence. We didn't know that there were only wooden beams and neither did the construction company. It can now be repaired but this means more work and purchase of extra material to realize a steel construction. The construction company does not feel liable and wants to share the costs with us. We think that they should have checked the construction before starting construction and should not have simply assumed that there was a steel construction, even though this is common or mandatory in construction. Who should pay the costs? Or is sharing the costs really fair?

Lawyer

As far as possible, the contractor must examine the construction. This can be done via the original construction drawings, but also by looking at the parts of the construction that are visible. If the construction is not visible, then what is on the construction drawing is important. If it is no longer there, then it is important how old the house is. I share the opinion of the contractor that a concrete or steel construction is normally installed above window frames. If it is an older house (approximately older than 60 years), then it is known that a wooden construction was also used and the contractor should have investigated this.