Vapor Barrier Calculator

Calculate vapor barrier sheeting needed for crawl spaces, under slabs, and on walls. Includes overlap and seam tape quantities.

🛡️ Vapor Barrier Calculator

Area Length (ft)

Area Width (ft)

Overlap (in)

Roll Width (ft)

Roll Length (ft)

Results

Floor Area300.00 sq ft

Strips Needed2 strips

Rolls Needed1 rolls

Seam Tape20.00 lin ft

💡 How to Calculate Vapor Barrier Material

Vapor barriers are polyethylene sheeting (typically 6–20 mil thick) installed to prevent moisture migration. For crawl spaces, cover the entire floor and run 6 inches up the walls. For under-slab applications, use 10-mil or thicker.

Seams must overlap 6–12 inches and be sealed with vapor barrier tape. Calculate strips by dividing the width of the area by the effective roll width (roll width minus overlap). Standard roll sizes: 10 ft, 12 ft, or 20 ft wide × 100 ft long.

A 20×15 ft crawl space with 10 ft rolls and 12-inch overlap: effective width = 9 ft. Strips needed: 2. Material = 40 lin ft. 1 roll (10×100 ft) is sufficient. Seam tape: 20 lin ft.