What Is a Roof Jack Used For?

Roof Jack

• Roof jacks are usually constructed from steel and can be purchased from home centers, lumber yards or hardware stores. Most roof jacks are adjustable to compensate for different roof pitches. If the jack does not have an adjustment that will make the walking surface level, tilt the jack inward instead of outward for safety.

Wood Planks

• A roof jack will not do you any good without planks of lumber to span them. Standard 2- by 10-inch lumber with fit into the channel on most roof jacks and should be available at any lumber yard. Avoid using short pieces, as the risk of a length of lumber tipping upward if you should happen to step onto the end of it is greatly increased. Eight-foot long pieces should suffice, since they are still long enough to be safe but not as heavy as longer lengths. Avoid using cracked or split boards.

Roof Slope

• Certain roof slopes are safe enough to walk on without using roof jacks. For a slope of 4/12 -- four inches of rise to 12 inches of horizontal run -- roof jacks are probably not needed. Walking on a roof with a pitch of 5/12 or 6/12 is possible, but it is still a good idea to place a row of roof jacks along the bottom edge of the roof. This way, if you do slip, you will be caught before falling off the edge of the roof. For roof pitches of 6/12 and higher, several rows of roof jacks will be needed along the length of the roof for maximum safely.

Installing Roof Jacks

• Roof jacks are nailed to the roof directly over rafters for strength. The jacks must be properly nailed or leaks in the roof could occur. Lift up the tab of a shingle where you wish to install the jack. Slide the upper tab on the jack under the shingle so that nail hole in the jack is barely covered. Lift up the tab and nail the jack into place. Place a piece of lumber across several jacks, and slide it back against the screw holes in the jacks. Screw the lumber into place using wood screws and a power drill. Do not space roof jacks more than 48 inches apart.