Adding ceiling joists requires safety precautions in several areas: 1) Workers should wear safety harnesses and nets should be installed to prevent falls from heights or slippery conditions. High visibility markings should also be used at roof edges. 2) Noise from power tools could exceed limits, so hearing protection for workers and noise control is needed. 3) Adequate ventilation is required when sawing to prevent dust inhalation if the roof is enclosed. 4) Proper communication and safety equipment like gloves and helmets are needed when cranes carry heavy timber overhead. Manual handling of timber also requires training and multiple workers.