To provide a joint material maintaining sealing performance at a joint even with a slight change of joint width owing to high sealing performance of a hollow part in which the whole curved part is elastically deformable in the joint material having the hollow part of semi-cylindrical outline cross section made of resin or rubber and formed of a flat part and the curved part, and a thermally expansive refractory material 14 thermally expanded in case of a fire to close the joint and to shut out flames and heat.

This joint material 10 has a recessed groove 12 in the outer surface of the flat part 11a of the hollow part 11, and the thermally expansive refractory material 14 is fitted into the recessed groove 12 and bonded to the bottom of the recessed groove by a pressure sensitive adhesive double coated tape 13. A pressure sensitive adhesive double coated tape 15 is provided for bonding the joint material 10 to the end face of an external facing material 1a.