The Museum of Liverpool has been awarded £1.2m in damages after a judge found AEW Architects & Designers liable for a series of design problems that beset the museum’s £72m construction. It was also awarded £1.24m relating to design faults in ceiling tiles.

The museum took a case to the high court in London, claiming £3.2m in damages for negligence over work that it said fell below expected professional standards.

AEW accepted that it had altered its building plans without properly informing or seeking permission from the museum, after contractors warned of geometric flaws in the original design .

In late 2009, the architects decided to install a plinth arrangement to rectify the flaws. The museum’s executive director, Sharon Granville, told the court of her shock on first seeing the plinth, calling it an “abomination”.

The structure was then removed at high cost. Parts of the terrace are still closed to the public, as the museum has been unable to afford the necessary remedial works.

In his summary of the case, the judge said: “It is simply extraordinary that competent architects could consider that it was acceptable to adopt the plinth solution in any event, given their client’s aspirations and wishes and, even worse, without seeking the informed approval of its client.”

The joint building contractors Galliford Try and Danish firm Pihl were found partially liable by the judge, and ordered to pay £205,000 of the total damages.

The judge also found in the museum’s favour over flaws in the construction of the suspended ceiling, which have caused additional problems.

Weeks before the museum opened in 2011, ceiling panels in the Creative City gallery fell, injuring a workman and damaging the exhibition. In other areas, panels were found to be in danger of collapse.

In January 2012, high winds dislodged ceiling tiles, with one hitting a visitor.