Roof Felt Calculator — Calculate Roofing Felt Requirements & Cost

Roof Felt Calculator

Calculate how much roofing felt you need for your project. Estimate costs based on roof dimensions, felt type, and overlap requirements.

Step 1: Roof Dimensions

25%

Measuring Your Roof

For accurate calculations, measure the total length and width of your roof area. Include all sections that need covering. Complex roofs with many valleys, hips, or dormers will require more felt.

Step 2: Felt Details

100mm

About Roofing Felt

Roofing felt provides a secondary waterproof layer beneath your main roofing material. Standard felt offers basic protection, while breathable membranes improve ventilation and reduce condensation.

Roof Felt Requirements

Summary
Material Comparison
Cost Analysis

Total Material Cost

£285.60
Roof Area: 80 m²
Felt Rolls Needed
7 rolls
Total Coverage
105 m²
Cost per m²
£3.57
Waste Allowance
15%

Material Comparison

Felt Type Lifespan Cost per Roll Rolls Needed Total Cost

Cost Analysis

Calculation Formula

Rolls Needed = Roof Area ÷ (Effective Roll Coverage)

The number of rolls required is calculated by dividing your total roof area (including waste allowance) by the effective coverage of each roll, accounting for overlaps and trimming.

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