Strips of landscape fabric are laid side by side, and where two meet they overlap. That shared strip of fabric covers ground twice, so the more overlap, the less each extra strip adds.
n strips cover n × roll width − (n − 1) × overlap
Strips = round up ((bed width − overlap) ÷ (roll width − overlap))
Overlap must be less than the roll width
One bed, five overlaps
A 30 × 10 ft bed with strips running across the 30 ft side, so each strip is 10 ft long, and a 3 ft × 50 ft roll, which gives five strips per roll. Only the overlap changes. The overlaps are examples chosen to show the effect:
| Overlap | Strips | Fabric length | Rolls to buy |
|---|---|---|---|
| None | 10 | 100 ft | 2 rolls |
| 3 in | 11 | 110 ft | 3 rolls |
| 6 in | 12 | 120 ft | 3 rolls |
| 8 in | 13 | 130 ft | 3 rolls |
| 12 in | 15 | 150 ft | 3 rolls |
The strip count rises with every step. The rolls change less often, because a roll supplies five strips here, so the order moves only when the strips pass a multiple of five.
Why it is not just area
Without overlap each strip adds the full roll width, so the strips needed are the bed width divided by the roll width, rounded up. Each overlap reduces that gain: with an overlap of 6 in, a strip adds only 2.5 ft of new ground, not 3 ft, so more strips are needed to reach the same width. The planner rejects an overlap equal to or larger than the roll width, which would add no new ground at all.
Which overlap to use
The one in your fabric’s instructions, for your application. As one example, DeWitt’s installation guide calls for an overlap of at least 6 to 8 inches in its under-pathways steps. That is one manufacturer’s instruction for one setting, not a rule for all landscape fabric, and another product or use can differ. This page does not recommend an overlap, and the planner leaves the field blank so the figure comes from the product.
This example assumes
- 3 ft × 50 ft rolls and a 30 × 10 ft bed are example values
- Overlaps of none, 3, 6, 8 and 12 in are examples
- Strips run across the 30 ft side as single 10 ft pieces
What changes the estimate?
- The overlap your fabric’s instructions give
- The roll width, which sets how much new ground each strip adds
- The strip length and roll length, which set strips per roll
- Which way the strips run
For the whole method, including how the two layouts compare, see how much landscape fabric you need.