Concrete & Masonry
Convert a measured slab footprint into a transparent vapor-barrier roll plan. Enter the overlap required by the selected system and the actual roll dimensions; the calculator does not decide membrane type, thickness, seam treatment or whether a vapor retarder is required.
Change the defaults to match your project and the product you plan to buy.
Project result
Review slab area, effective roll width after entered overlap, layout length and whole-roll quantity.
At a glance
Planning estimate only. Verify product coverage, package size, supplier specifications and project requirements before purchasing.
Budget scenario
Use a current supplier subtotal or reuse a priced calculator result, then add optional delivery, tax and contingency. Home Measure Lab does not fetch or guess live prices.
Enter a current supplier subtotal or reuse a priced calculator result.
Budget values are local planning inputs, not live quotes. Verify tax treatment, delivery, labor and supplier pricing before purchasing.
Methodology
length × width
Uses the measured covered slab area.
roll width − entered seam overlap
Overlap is a project/system input.
covered width ÷ effective width, rounded up
Models parallel strips across the slab.
strip length target ÷ roll length, rounded up
Adds the entered cut/handling allowance before whole-roll rounding.
Measure the slab footprint that will actually receive membrane and choose a practical roll direction before entering dimensions. Long irregular jogs, isolated pads and penetrations can create extra seams, so separate them instead of hiding all complexity in a large waste percentage. Record the actual roll width and roll length from the product being considered, and use the seam overlap required by that membrane system rather than a generic default.
Roll labels describe nominal dimensions, but seam overlap reduces effective installed width. The calculator models that loss explicitly and then converts total strip length to whole rolls. It does not account for proprietary seam tape, boots, termination details or puncture repair materials. Verify membrane thickness, compatibility, seam treatment and placement requirements from the selected product and project before purchasing.
Reference
| Layer | Record | Keep external |
|---|---|---|
| Footprint | actual covered slab area | Whether membrane is required. |
| Overlap | selected system seam rule | Seam tape / sealing detail. |
| Roll size | actual product width × length | Product thickness and performance. |
| Layout reserve | cuts / handling allowance | Penetrations and special detailing. |
Questions
No. Membrane type and thickness are external product and project decisions.
Adjacent sheets share material at the seam, so the full nominal roll width is not new covered width after the first strip.
No. Tape, boots, repair patches and penetration details are separate system materials.
Planning guides
Concrete & Masonry
Plan parallel membrane strips from slab dimensions and the selected system overlap without treating nominal roll width as full installed coverage.
Read guide →Concrete & Masonry
Translate effective membrane coverage into whole rolls while keeping cuts, cross seams and special detailing visible as separate planning factors.
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Open calculator → Concrete & MasonryEstimate compacted aggregate base volume beneath a concrete slab, add an explicit placement allowance, and convert the target to bulk cubic yards or whole bags.
Open calculator → MeasurementCalculate rectangular square feet or square meters from length and width without adding room perimeter, wall height or material-package assumptions.
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