![]() With one side of the roof ready, Ben cuts a couple of gage blocks so they can stringline the roof framing to remove any last humps. ![]() They begin with a ledger strip installed perpendicular to the rafters so they can butt rafter tails to establish a straight fascia. These ripped-down 2x4s are screwed into the i-joists. This roof ventilation scheme is called a Sarked Roof. ![]() Because the existing deck is sealed, this roof assembly needs to be able to dry upward if it gets moist or wet. Above the i-joists, Ben and Ryan install a smart vapor membrane, which allows drying and prevents bulk water intrusion.Ī ventilation space is created above this membrane with various furring strips in a cross hatched pattern to allow continuous airflow under a top layer of roof decking and a metal roof. This over roof adds an extra 16 inches for cellulose insulation. The valley line is snapped on the decking strip and rafter locations marked along the line. This can be done with a stringline and a tape measure, a framing square, or math.Įven still, Sometimes rafters need to be trimmed to fit. They they put it on the line and nail it. It makes carrying lumber a lot easier. To look at the valley flashing, we are going to follow along with Ryan Olivieri-the Carpenter of the Year-and Ben Bogie his biggest fan. ![]() Instead, the compound bevel at the bottom of the jack rafters are reversed, to flush into the existing roof. This means laying down a strip of roof decking before framing is complete.Īnother benefit of framing on top of an existing roof deck is that you can walk on decking between the rafters. When I arrived, much of the roof had been framed, but I was able to climb up for a little valley framing.īecause the framing is overlaid, there is no valley rafter. Framing a roof with I-joists over the existing roof makes a ton of room for insulation and offers a short lesson in vapor movement through assembliesĪ little while ago, we looked at a deep energy retrofit striving for Passive House certification by thickening the walls with I-joists, screwed to the outside.Ī new roof was framed on top of the existing roof deck, which was air sealed with high performance tape. ![]()
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