It's a moderate sized tree reaching about 25ft in the open and somewhat taller if surrounded by other trees. If you have clay soil, I wouldn't plant it any closer than 25ft from the property just to be safe. Lighter sandy soils perhaps a little closer 15-20ft. If you keep it pruned, it could be closer still.

Hornbeam is quite often grown in place of beech for hedging, which could go fairly close to buildings. But if you want to grow it as a tree then Fractal's advice is correct.