The year 1842 in architecture involved some significant events.

• March 28 – The Teatr Skarbkowski in Lviv (Ukraine), designed by Jan Salzmann and Ludwig Pichl, opens.
• October 18 – The Walhalla memorial in Bavaria, designed by Leo von Klenze, is inaugurated.
• Treasury Building (Washington, D.C.), designed by Robert Mills, central and east wings completed,
• Construction of Berry Hill, near Halifax, Virginia starts.
• Iglesia de la Matriz, Valparaíso, Chile, completed.
• Kawaiahaʻo Church, Honolulu, Hawaii, designed by Rev. Hiram Bingham, completed.
• St Mary's Church, Wreay, Cumberland, England, designed by Sara Losh, consecrated.^[1]
• Ak Mosque, Tashkent, Uzbekistan, completed.
• Circular church of the Holy Sepulchre, Cambridge, England, restored by Anthony Salvin.
• Cologne Cathedral construction work is recommenced after 400 years by the Central-Dombauverein zu Köln (Central Cathedral Building Society).

• Andrew Jackson Downing – Cottage Residences

• Grand Prix de Rome, architecture: Philippe-Auguste Titeux.

• June 12 – Harry Hems, English architectural and ecclesiastical sculptor (died 1916)
• September 17 – Basil Champneys, English architect (died 1935)
• December 12 – Alfred Parland, Russian architect (died 1919)
• December 15 – George Keller, American architect (died 1935)

• October 18 – John Harper, English architect (born 1809)