The invention proposes a configuration applied to envelope for tire retreading in a cold retreading process. In the state of the art, envelopes consisting of two parts are known. However, the known methods of sealing among the pieces are not satisfactory either due to sealing problems, or by reducing the useful life of the envelope. In order to overcome these limitations, the invention proposes an envelope (20) comprising three parts (22, 24, 26), in which a flap (224) of the first part (22) presents a free end with a differentiated cross-section (224b), in which a flap (244) of the second part (24) has a free end with a differentiated cross-section (244b) and in which the third part (26) presents a shape of an elastic ring with enough width to cover the differentiated cross-section (224b) of the flap (224) of the first part (22) and the differentiated cross-section (244b) of the flap (244) of the second part (24).