Low-slope copper roofs must be fully soldered, with pans sized no larger than 18 by 24 inches. Movement joints (seen to the rear of the carpenter) are necessary on larger roofs.
A worker presses a pre-shaped corner piece into place at an inside corner joint in a TPO roof. In his right hand is the heat-welding gun, used to melt both pieces in the joint before pressing them together to form a durable seal.
The roofer presses down on the TPO seam with a roller to achieve a good bond for a durable, watertight seal.
TPO makes a neat, attractive roof that clients often prefer to EPDM. In the roof edge shown here, the TPO has been turned down over the face of the trim about 2 inches, then the metal drip edge has been applied over the membrane. Finally, a strip of TPO has been welded on top to cover the metal. This prevents leaks at the joints in the metal.