Cantilever balcony are usually unsupported and extend outwards, so the problem with Cantilever balconies are

☛ Excess deflection or bounce

☛ Weakness of the deck structure

☛ Rot and water damage to the interior of the house

☛ Unevenness inside the house

☛ Can’t use the balcony for gardening or other purposes as it is not designed to lift excess amount of weight