A tarp placed over a flat, leaking roof can protect the interior of your home from further water damage. However, installing a tarp is a dangerous job, even on a flat roof. If at all possible, this task should be left to a professional. If you need to place the tarp on the roof yourself, wait until the weather is calm and the roof is dry. A leaking roof can cause a fair amount of interior damage. But it is not worth risking your safety to prevent it.
Cut a section of tarp that is wide enough to comfortably cover the damage plus an additional four feet on each end and an additional foot on each side. The tarp will be rectangular in shape. For clarification purposes, we will call one of the sides with an extra four feet side A and the other side C. The shorter sides will be called sides B and D so that the sides read A, B, C, D when read clockwise.
Bring all of your tools up to the roof.
Center the tarp over the damaged area.
Wrap the end of side A over a 2-by-4 that is 2 feet wider than the distance between sides B and D. Wrap the tarp around the 2-by-4 at least twice. Wrap the tarp over the 2-by-4 (not under it) to prevent the collection of debris.
Nail the 2-by-4 to the tarp and to the roof. Hammer two evenly spaced nails through the 2-by-4.
Lay another 2-by-4, equal in length to the first, on top of the first 2-by-4. Nail the two 2-by-4s together with at least two evenly spaced nails that do not overlap the first.
Repeat steps 3 through 5 on the opposite end of the tarp.
Lay one long 2-by-4 (or smaller sections of 2-by-4 that are no more than 10 inches apart) on the edge of side B. Nail the 2-by-4 down using at least two nails per 2-by-4. Repeat for side D.
Never stand on a tarp. They are slippery even when dry. An emergency tarp will protect your roof for no more than 90 days.