He is the founder and director of hg merz architekten museumsgestalter, an architecture office that specializes in museum and exhibition design and in refurbishing listed buildings.
From 1993 to 2007, HG Merz was professor for exhibition design at the department of Visual Communication at the University of Applied Sciences in Pforzheim.
From 2008 until 2014, he was professor for experimental design at the department of Architecture at Technische Universität Darmstadt.
In 2014, he was awarded an honorary doctorate from TU Darmstadt.
In May 2018, Merz was elected new member in the section architecture of Academy of Arts, Berlin.