High tensile steel is commonly applied in prefabricated building due to it’s high strength and light weight.
Based on engineering & architect requirement, the structure material can be either hot rolled steel or light gauge steel, or it can also be the combination of both.
Necessary coating or painting need to be applied to the material surface as per local code requirement, light gauge steel normally comes pre-coated, hot rolled steel might need be coated/painted afterwards.
Welding/screw/bolts/rivets can be used for the connection of structure members due to engineering requirement.
Welding & screw connection is commonly used for hot rolled steel & light gauge steel structure.
Dont forget the treatment of your connection area for anti-corrosion problem.