Roof Rafter Bridging

Most codes allow foil faced foam to be left exposed.

Roof rafter bridging.

Structures such as sheds or barns can be frames with rafters every 24 again make sure to consult local codes. The uninsulated roof framed with wood r value around 1 1 per inch means rafter lines covered with snow. Steel framing typically reduces the in cavity r value by as much as 50 while wood framing reduces in cavity r value by a bit less than 10. The weight of the piano is centered over a single joist but the bridging transfers some of the weight to the adjacent joists.

It can consist of lateral members spanning in between trusses t or i bracing on individual members sheathing or metal strapping. Brush up on thermal bridging 101 here. Plus you get the highest r value per inch for any type of insulation. The main purpose for this type of bracing is to reduce the bucking length of the individual truss members and to assist in erection spacing of the trusses.

In either case seal the foam edges well to the rafters with spray foam. It is always better to have a large rafter rather than be concerned with a sagging roof. Thermal bridging is the movement of heat through a material that s more conductive than the air around it. If your project had a rafter length of 8 or less a safe and strong method is to use 2x8 framed 16 on center.

Failure to mitigate can account for overall heat loss of up to 30 so it s not a thermodynamics lesson to be taken lightly. Place a short piece of framing lumber against the rafter above it so that the two boards form a continuous line. With steel framing at about r 04 per inch it s thermal bridging on a whole different scale. The blocking or bridging between joists or rafters also contributes to this phenomenon.

Drive a nail into either end to hold the board in place.