An architectural addition is an extension or alteration to an existing building. The crossword solutions for the term 'architectural addition' are ANNEX (5 letters), ELL (3 letters), Doric (5 letters), Ionic (5 letters), and OGEE (4 letters). An ANNEX is a separate building that is connected to the main building, while an ELL is an extension of the main building. Doric and Ionic are two of the five classical orders of architecture, which are styles of building design. Lastly, an OGEE is an S-shaped curve used in architecture and furniture design.