Underlayment is installed beneath the outer roofing material (shingles or metal panels) and directly on top of the roof deck. Its primary purpose is to provide an extra layer of protection against water infiltration and to enhance the overall weather resistance of the roof.

Underlayment Calculators

• Underlayment for a Gable Roof: Estimates the cost of underlayment to cover a basic gable roof based on the area of a roof computed from the dimensions (length, span, pitch and overhang) and the unit price underlayment material. 
• Underlayment for a Hip Roof: Computes the surface area of a hip roof based on the dimensions and uses the surface area to compute the cost of underlayment based on the unit price (price per square feet) of underlayment material.
• Underlayment for a Gambrel Roof:  Computes the total surface area of a gambrel roof for underlayment based on the dimensions below and the estimated cost based on the area and unit price of underlayment material.
• Underlayment for a Shed Roof: Computes the surface area of a shed roof and the cost estimate for underlayment based on the roof dimensions and a unit price of underlayment.
• Pyramid Roof Underlayment: Computes the surface area of a pyramid hip roof based on the dimensions, and uses the surface area to compute the cost of underlayment based on the unit price (price per square feet) of underlayment material.
• Underlayment of Dormers: This computes the amount of underlayment needed for one or more dormers and estimates the cost of underlayment materials.