Lacedelli was born in Cortina d'Ampezzo. His climbing career began as a young teenager when he followed a mountain guide up a local summit. He soon came under the tutelage of Luigi 'Bibi' Ghedina, one of the best Dolomite rock climbers of the age. In 1946 he was accepted into the prestigious "Cortina Squirrels" club. Lacedelli was known for fast ascents of difficult routes, including: the "Constantini-Apollonio South Face Direct" (500 m V+ A2) on the Pilastro di Rozes (repeat with Ghedina); the first ascent of the "Southwest Face" of Cima Scotoni (Fanis Group) with Guido Lorenzi; first one-day ascent of the "Solda Route" on the SW Face of the Marmolada di Penia (with Lorenzi); and the fourth ascent of the "Gabriel-Livanos Diedre" on the Cima su Alto with Beniamino Franceschi.