Vapor-barrier mil, roll coverage & overlap
Crawl-space liner comes in rolls that vary by mil thickness and coverage; you overlap seams by about 6–12 inches (~10%). These are labeled planning bands — check your product label. Compute rolls with the vapor-barrier calculator: rolls = ceil(area × (1 + overlap) ÷ roll coverage).
| Convention | Typical value | Notes |
|---|---|---|
| Roll coverage (typical) | ~200 sq ft/roll | Varies by mil & roll width |
| Overlap at seams | ~6–12 in (6–12%) | More on uneven ground |
| Common thickness | 6–20 mil | Thicker = more durable liner |
Labeled planning bands — check your product label. Rolls = ceil(area × (1 + overlap) ÷ roll coverage).