Exterior calculator

Vapor barrier

Poly roll count from floor or crawl area and the net coverage of one roll after the labelled lap.

Reviewed formula · v1.0.0

Project inputs

Enter field measurements. Imperial lengths take feet and inches. Unit conversion happens before the reviewed formula is applied.

Area lengthft + inCrawl, slab or wall length being coveredftinArea widthft + inAverage widthftinRoll coverageft²Net coverage of one roll. A common 10×100 ft 6-mil roll is 1,000 ft²Lap / waste%Allowance for seams, piers and upturns. 10% is a common planning figure

All values can be refined when you edit the estimate. This tool does not replace field verification or local requirements.

Calculated result

2rolls

Rolls to order

FormulaEXT-VAP-001

area × (1 + waste) ÷ roll coverage

1200 ft²

Net area

1320 ft²

Area including laps

Transparent cost view

Planning rates only. Pick a currency — badges, inputs, and totals follow. Material is a rate. Labour is hours × a planning hourly rate. Equipment and delivery are this-job amounts.

Material ratePlanning · per calculated unit · USDEquipmentPlanning · this job · USDDeliveryPlanning · this job · USDLabour hoursPlanning · this jobLabour ratePlanning · per hour · USDOverhead %%Contingency %%Markup %%Tax %%

Planning defaults are office figures, not a bid. US ready-mix in 2026 often lands around $125–165 per cubic yard delivered; place-and-finish commonly $2–4 per square foot. Replace every rate with a supplier or crew quote before you send the letter.

Indicative FX as of Aug 2026. Planning conversion, not a live bank rate.

Material costUSD 170

Labour (8 h)USD 280

Direct costUSD 560

Overhead + contingencyUSD 56.00

Markup + taxUSD 73.92

Estimated project totalUSD 690

View estimate Quote / invoice Add another item

Embed this calculator

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Paste on a contractor site or blog. The iframe is a planning takeoff, not a bid.

How this calculator works

A transparent vapor barrier takeoff.

Area divided by net roll coverage after a visible lap allowance, rounded up to whole rolls.

Worked example. Example: a 40 × 30 ft crawl at 1,000 ft² per roll with 10% laps rounds to 2 rolls.

1. Measure the crawl or slab that will receive poly, including a little extra for upturns at the wall.
2. Enter the labelled coverage of the roll you will buy.
3. Tape, boots and mastic are separate lines.

Need the broader workflow? Read the exterior planning guide.

Questions

Questions about vapor barrier

Is this a class I vapor retarder design?

No. It is a roll count. Perm rating, location in the assembly and local code stay with the wall or floor spec.

Walls vs floors?

Same area math. Run the calculator once per plane so a wall takeoff does not hide in the floor rolls.

What is the formula ID?

This calculator publishes formula EXT-VAP-001, version 1.0.0. The ID stays on the result and on the estimate line.

Is this engineering advice?

No. Construclytic is a planning website, not a registered engineering or contracting firm. Field checks, codes and product data still sit with you.

Does Construclytic fetch live supplier prices?

No. Costs use the rate you enter. Construclytic does not fetch live supplier prices.