STOCK FIT

Vapor barrier — roll width scenarios.

How does changing roll width affect vapor barrier when the other inputs stay fixed?

What this decision changes

Full required pieces must fit usable stock. Aggregate area or length alone cannot prove a feasible cut or roll allocation. Method basis: Rolls are estimated from strip length with allowance. Edge upturns and penetrations are not included; add them to your supplied dimensions.

The focus is roll width. All other shared inputs remain fixed for each evaluated range.

Strips = ceil((width − overlap) ÷ (roll width − overlap))Vapor Barrier Calculator

Evaluate your supplied alternatives

Start with your measured plan and selected product data. The initial values and range are illustrative. Each scenario changes only roll width; the other entered values stay fixed.

Display units

Measured plan and product inputs

Length

Where to get this value

Measure this dimension in your plan or on site and use the displayed unit. For irregular shapes, divide the geometry into the supported sections.

Width

Where to get this value

Measure this dimension in your plan or on site and use the displayed unit. For irregular shapes, divide the geometry into the supported sections.

Roll width

Where to get this value

Use the actual usable quantity or dimensions of the product you intend to buy. Check the label and the unit shown here.

Roll length

Where to get this value

Use the actual usable quantity or dimensions of the product you intend to buy. Check the label and the unit shown here.

Specified strip overlap

Waste allowance

Shortcuts only; choose your own allowance above.

Where to get this value

Enter your own allowance. Presets are input shortcuts, not a construction recommendation.

Supplied comparison range for roll width

Lower supplied comparison value

Where to get this value

Use the actual usable quantity or dimensions of the product you intend to buy. Check the label and the unit shown here.

Upper supplied comparison value

Where to get this value

Use the actual usable quantity or dimensions of the product you intend to buy. Check the label and the unit shown here.

Nine evenly spaced values are evaluated. Whole counts are rounded to distinct integer scenarios. Values between the listed samples are not calculated.

9 evaluated scenarios

Baseline: Rolls to purchase — 2 rolls. Rejected combinations remain visible below.

Quantity to plot

Each bar is one actual calculated rolls to purchase. Horizontal values: roll width in m.

Roll width	Rolls to purchase	Change from baseline	Use this scenario
1.2 m	3 rolls	1 roll	Open in calculator Exact quantity breakdown Sheeting strips 5 Total roll length 22 m Slab area 20 m²
1.45 m	2 rolls	0 rolls	Open in calculator Exact quantity breakdown Sheeting strips 4 Total roll length 17.6 m Slab area 20 m²
1.7 m	2 rolls	0 rolls	Open in calculator Exact quantity breakdown Sheeting strips 4 Total roll length 17.6 m Slab area 20 m²
1.95 m	2 rolls	0 rolls	Open in calculator Exact quantity breakdown Sheeting strips 3 Total roll length 13.2 m Slab area 20 m²
2.2 m	2 rolls	0 rolls	Open in calculator Exact quantity breakdown Sheeting strips 3 Total roll length 13.2 m Slab area 20 m²
2.45 m	2 rolls	0 rolls	Open in calculator Exact quantity breakdown Sheeting strips 3 Total roll length 13.2 m Slab area 20 m²
2.7 m	1 roll	-1 roll	Open in calculator Exact quantity breakdown Sheeting strips 2 Total roll length 8.8 m Slab area 20 m²
2.95 m	1 roll	-1 roll	Open in calculator Exact quantity breakdown Sheeting strips 2 Total roll length 8.8 m Slab area 20 m²
3.2 m	1 roll	-1 roll	Open in calculator Exact quantity breakdown Sheeting strips 2 Total roll length 8.8 m Slab area 20 m²

Read the evaluated results

Look for jumps in purchased stock and rejected fits. The rows show actual evaluated allocations, not an assumption that every intermediate size will behave identically.

Replace every illustrative baseline measurement and selected product value with the inputs for your actual task.
Enter a comparison range on the focused input's stated unit and quantity basis.
Review rejected combinations and use the exact detail lines to distinguish measured demand from whole purchases.
Open an evaluated scenario in the full calculator to save its original inputs and quantity breakdown to a browser material project.

Keep the comparison within scope

Permitted orientation, complete-run requirements and reserved cut losses remain supplied inputs; sampled layouts do not promise a globally optimal cut plan.

Only quantities from supplied dimensions and specifications are calculated.

No material-property reference values are bundled; obtain product values from the selected supplier's data sheet.

Only the listed samples are evaluated. Intermediate values, alternate constraints and global cutting optimality are not inferred from the graph.

Continue with this quantity method

Vapor Barrier Calculator

Other independent input decisions

Prepare the actual material data

Read the measurement and purchase guides

Account for both side and end laps in roof rolls

Quantity method and illustrative scenarios checked 6 October 2026. Methods and scope.