Framing a Cold Roof

Build A Lower Deck

• 1

  Cover the roof trusses with ½-inch plywood and nail them into place with 8d nails. Space the nails 6 inches apart along the edge of the roof and 12 inches apart in the interior. This is the lower deck of your cold roof.

• 2

  Cover the lower deck with #15 bitumen-saturated roofing underlayment with 6 inch vertical overlaps and 3 inch horizontal overlap. Install them with 4d nails. The underlayment on the lower deck is not intended to waterproof the roof. It prevents moisture from condensing between the two decks.

• 3

  Cut a 3-inch strip in the plywood at the eave overhangs to allow air to circulate between the roof decks. Cover this strip with screen to prevent bugs from entering and birds from nesting inside.

Add An Upper Deck

• 4

  Install 2-by-4 sleepers directly over the rafters under the lower deck to provide the 3 inches of space between roof decks. Lay two-by-fours on their ends, not their sides. Run the sleepers the length of the roof. It is easiest to build a cold roof that is gabled. If you have a hip cold roof, the sleepers will direct the flow of air to the ridges.

• 5

  Build a second roof deck on top of them when the sleepers are in place. Use 8d nails with the same spacing as you used on the lower deck.

• 6

  Cover the top deck with #30 bitumen-saturated roofing underlayment as you did with the lower deck. This underlayment waterproofs the top deck.

• 7

  Install ridge vents that have overhangs to prevent snow from clogging them. These are called Boston roof vents.

• 8

  Install concrete or ceramic tiles, shingles, shakes or other covering appropriate for roofs with a steep pitch.