This is jointed to the metal sheets, the length of which gives the correct joint spacing as mentioned above. The metal sides of the T-Pren should overlap the metal sheets by a minimum of 25mm and the joint should be made at least 75mm from the neoprene, or 100mm for aluminium and copper due to their better conductivity.

The jointing process depends on the metal. TIG welding is best for aluminium and stainless steel, but low currents must be used on these light gauge metals. Copper joints can be soldered but brazing will make a stronger joint. Terne coated stainless and zinc are best soldered, and where additional strength is required the overlap can be rivetted before soldering. For lead, the traditional lead sheet welding technique for a flat lapped seam is used. A single loading should be sufficient for Code 5 lead, but where the T-Pren joint is on top of a lead sheet of Code 6 or higher, two loadings may be beneficial.

Jointing is easiest on flat sheets but in certain situations the metal sheets and T-Pren joints have to be pre-formed to shape before jointing. The jointing will then require extra care, particularly on the vertical sides. 

The gutter lining with the T-Pren expansion joints is then formed to take up the shape of the gutter, placed into position, and cover flashings formed over the sides.

The normal health and safety procedures for welding, brazing, soldering and working with lead should be carried out. The correct protective clothing should be worn, ventilation provided for indoor work, and hands should be washed before eating or smoking.