Vapor Barrier & Moisture Retarder Calculator – Wanjaaro Material & Cost Calculator
Calculate poly film rolls (6, 10, 15, 20 mil), overlap square footage, seam tape rolls, termination bars, and fasteners. Free, instant deterministic calculations with waste margin, material takeoffs, and contractor cost breakdown.
Category: Concrete & Masonry
Last Modified: 2026-10-18
Available Building Material Calculators
- Concrete Slab & Footing Calculator – Calculate volume in cubic yards, pre-mixed bags (40, 60, 80 lb), and rebar grid requirements.
- Brick & Mortar Calculator – Calculate total modular, king, or queen bricks, mortar bags (Type N/S), and tons of sand.
- Concrete Block (CMU) Calculator – Estimate standard CMU blocks, core-fill grout volume, mortar bags, and vertical rebar.
- Vapor Barrier & Moisture Retarder Calculator – Calculate poly film rolls (6, 10, 15, 20 mil), overlap square footage, seam tape rolls, termination bars, and fasteners.
- Wall Framing & Stud Calculator – Calculate common studs, double top plates, bottom sill, headers, corners, and board feet.
- Door Frame Material & Rough Opening Calculator – Calculate rough opening dimensions, king and jack studs, structural header, jamb boards, casing trim, hinges, and fasteners.
- Garage Door Size & Framing Opening Calculator – Calculate finished and rough opening dimensions, goalpost jambs, LVL header sizing, headroom clearance, and track specs.
- Stair & Handrail Calculator – Calculate stair risers, tread run, stringer boards, handrail length, baluster spacing, and ADA/IRC code compliance.
- Plywood & OSB Sheathing Calculator – Determine 4x8 / 4x10 sheets for walls, subfloors, and roof decks plus framing nail counts.
- Drywall & Sheetrock Calculator – Calculate 4x8, 4x10, 4x12 drywall sheets, joint compound buckets, screws, and tape rolls.
- Paint & Primer Coverage Calculator – Estimate gallons of wall/ceiling paint and primer with window and door deduction.
- Roofing Shingle & Pitch Calculator – Calculate roofing squares, architectural bundles, pitch multipliers, felt, and ridge caps.
- Siding Material & House Wrap Calculator – Calculate siding squares (vinyl, fiber cement, cedar, board & batten), starter strips, J-channels, corner posts, and housewrap.
- Tile, Grout & Flooring Calculator – Calculate square footage, tile boxes with waste, grout weight (lbs), and thin-set bags.
- Construction Cost & Budget Estimator – Estimate total project budget with material subtotal, labor rates, GC markup, and contingency.
Frequently Asked Questions
What mil thickness vapor barrier is required for crawl spaces and concrete slabs?
IRC Section R408.3 mandates a minimum 6 mil (0.006 inch) polyethylene vapor retarder for unvented crawl spaces with sealed seams. For heavy-duty crawl space encapsulation and under concrete slabs, building science and ASTM E1745 recommend 10 mil, 15 mil (Stego-grade), or 20 mil reinforced puncture-resistant poly.
How much should vapor barrier seams overlap?
Code requires a minimum 6-inch overlap between adjacent sheets, but contractors and building scientists recommend a 12-inch overlap. All seams must be taped continuously with specialized acrylic or butyl seam tape (minimum 3.75 to 4 inches wide).
How is a crawl space vapor barrier fastened to foundation walls?
The poly film should run up foundation perimeter walls and support piers at least 6 inches above outside ground grade (or up to within 2 inches of the sill plate), secured using rigid termination bars and masonry drive pins spaced 12 to 18 inches apart, and sealed behind with polyurethane or acoustic mastic sealant.
What is a perm rating in vapor retarder classification?
Permeance measures water vapor transmission. Class I vapor retarders have a perm rating of 0.1 perms or less (completely impermeable, like 10+ mil poly). Class II retarders measure between 0.1 and 1.0 perms (kraft paper facing). Class III retarders measure 1.0 to 10 perms (latex paint).