The flat seam method of roofing as illustrated on this page is most commonly used on roofs with a slight pitch. However, the flat seam method is also used for covering towers or domes. The seams may be sealed except where the pitch is less than 3 in./ft in which case they must be soldered.

Roofs of slight pitch should be divided by expan sion battens into sections not exceeding 30 ft square.

Before the roof is installed, the wood deck should be thoroughly dry, smooth, and covered with building paper. Roofing using flat seams should have continuous (solid) sheathing for metal sup port.

The roof is covered by pans made from sheets 20 x 28in. For soldered joints these pans may be pre-tinned 11/2 in. back from all edges on both sides of the sheet.

Pans are formed by notching and folding the sheets as shown in Detail 1. The pans are held in place by cleating as shown. After pans are in place, all seams are malleted and soldered or sealed.

In Detail 2 a trapezoid shaped batten is covered with metal formed and installed as illustrated. Batten covering is cleated to deck on 2 ft centers. Pans are locked and soldered or sealed to batten covering.

Copper (minimum 16 oz), terne (minimum 0.15 in. 40 lb coating) or .015 dead soft stainless steel is recommended for flat seam roofs.

Detail 3 shows the junction of a roof and parapet wall. Metal base flashing is cleated to deck on 2 ft centers and extended up wall 8 in. Pans are locked and soldered to base flashing. Metal counter flashing covers 4 in. of the base flashing. Detail 4 illustrates the installation of flashing at edge of the roof. Flashing is formed as shown and attached to the face by a continuous cleat nailed on 1 ft centers and is cleated to the roof deck. Pans are locked and soldered or sealed to the flashing.