Roof tarp installation is an anchoring problem
A tarp is a sail. Wind moving over a roof plane generates lift, and an inadequately secured tarp will catch that lift, balloon, work its fasteners loose and come off — often taking a course of shingles with it. Getting the material over the hole is the easy part of roof tarp installation. Keeping it there through 40mph gusts is the actual job.
Three variables decide the method: what the roof is covered with, how long the tarp needs to last, and whether the decking underneath is sound enough to hold a fastener at all.
The three anchoring methods we use
- Board-wrapped (furring strip) anchoring. The tarp edge is rolled around a 1x3 or 2x4 batten and the assembly is screwed down through the roof. Rolling the edge spreads load across the whole batten instead of concentrating it at individual fastener holes, which is what stops the tarp tearing free at its grommets. This is the standard for anything expected to last more than a few days.
- Ballasted, no-penetration anchoring. Sandbags, water bladders or weighted battens hold the tarp without any fastener entering the roof. Essential on tile, slate and standing-seam metal, where a screw creates a new leak that outlives the tarp. Also the right call on low-slope commercial decks. Covered in detail in our guide to tarping a roof without nails.
- Mechanical fixing to sound structure. Where decking is compromised, fasteners are driven into rafters or into undamaged decking outside the failure zone rather than into the weakened area, which would simply pull through.
Running the tarp over the ridge
When damage sits near the top of a slope, the tarp must continue over the ridge and down the opposite side. A tarp that stops short at the ridge line gives wind a leading edge to get under, and gives water running down the far slope a direct path beneath it. Carrying it over and anchoring on the back side removes both problems at once.
Why edges matter more than the middle
Water finds edges. A tarp laid flat with loose edges will shed the rain that lands on it and then let a meaningful share of that water run underneath at the perimeter. Every edge has to either be sealed down or oriented so that water sheds away from it:
- The upslope edge is the critical one. It must be secured tight and, where possible, tucked under the course of shingles above so water runs over the tarp rather than behind it.
- Side edges are battened or weighted along their full length, not just at corners.
- The downslope edge runs past the eave so water discharges into the gutter or clear of the fascia.
- Overlaps, where more than one tarp is needed, are shingled — upper over lower — never butted.
Sizing: cover past the damage, not to it
A tarp sized to the hole is a tarp that fails. Coverage extends well beyond the breach on all sides so the anchor points sit on sound, intact roof covering rather than on the damaged margin. On a roof where wind has lifted shingles across a wide area, the tarp covers the lifted zone too — those shingles are no longer watertight even though they are technically still in place.
Roof coverings and what changes
- Asphalt shingle. The most forgiving. Battens can be fastened through, and holes are sealed at repair. Standard board-wrapped method applies.
- Clay and concrete tile. Brittle and walkable only along specific lines. Foot traffic breaks more tile than the storm did. Ballasted anchoring, walking boards, minimal crossings.
- Standing-seam and corrugated metal. Never penetrated for a temporary cover. Seam clamps and ballast do the work.
- Low-slope and flat commercial. Water does not shed by gravity alone, so the tarp is laid and ballasted to avoid ponding, with attention to drains and scuppers. See commercial roof tarping.
What a finished installation should look like
Taut, not drum-tight — some give absorbs wind loading without stressing the anchors. No flapping anywhere along the perimeter. No standing water pockets. Every edge either battened, weighted or tucked. Anchors on sound material. And a set of photographs showing all of it, for your records and your insurer's.