Roofing, siding, and exterior

The building envelope is one system, not four separate projects

Roof, siding, gutters, and attic ventilation work together as a single weather-protection system. Replace the roof without upgrading ventilation and the new shingles bake from underneath, shortening their life by 5 to 10 years. Replace siding without fixing deteriorated gutters and water runs behind the new cladding, rotting the sheathing you just paid to protect. These calculators cover each component individually, but the best results come from addressing all of them during the same renovation when scaffolding and access are already in place.

Roofing: pitch changes everything

The single most important variable in roofing material estimation is roof pitch. A 6/12 pitch (the most common residential pitch) adds 12 percent more surface area than the house footprint. A steep 12/12 pitch adds 41 percent. That difference translates directly into shingles, underlayment, and labor hours. A homeowner who measures their house footprint at 2,000 square feet and orders 20 squares of shingles will be short by 2 to 8 squares depending on pitch. The roofing calculator applies the correct pitch multiplier automatically and adds a 10 percent waste factor for hips, valleys, and starter strips.

Shingles come in three quality tiers. 3-tab shingles cost less per square but last only 15 to 20 years. Architectural shingles cost 30 to 50 percent more and last 25 to 30 years. Over 30 years, one architectural roof costs less than two 3-tab roofs. The cost to replace a roof guide breaks this down with line-item pricing for shingles, underlayment, tear-off, and accessories.

Siding: squares again, measured differently

Siding uses the same "square" unit as roofing (1 square = 100 square feet), but the measurement is wall area, not roof area. The siding calculator starts with house perimeter times wall height, adds gable triangle areas, and subtracts doors and windows. For material selection, the vinyl vs fiber cement buying guide compares 30-year total cost of ownership including the repaint cycles that fiber cement and wood require. The cost to install siding guide covers installed pricing by material type.

Gutters and downspouts

The gutter calculator sizes linear footage and downspout count based on roof line length and local rainfall intensity. The general rule is one downspout per 30 to 40 linear feet of gutter. In high-rainfall regions (Pacific Northwest, Gulf Coast), tighter downspout spacing prevents overflow during heavy storms. Replacing gutters during a roof job saves the cost of a second mobilization, which typically runs $800 to $1,500 just for scaffolding setup.

Attic ventilation

The attic ventilation calculator sizes the required net free vent area per IRC R806.2. The code requires 1 square foot of venting per 150 square feet of attic floor area, split evenly between intake (soffit vents) and exhaust (ridge vent). Balanced ventilation keeps the attic temperature close to outside temperature year-round, preventing ice dams in winter and reducing cooling load in summer. A new roof is the cheapest time to add or upgrade ridge vent because the labor is already on the roof.

Snow load

The snow load calculator compares actual snow weight on your roof against its structural design capacity. Ground snow loads range from 10 pounds per square foot in the southern tier to 300+ in high mountain regions. Roof load is typically 70 percent of ground load for standard residential roofs. If your home was built before current snow load codes were adopted, the design capacity may be lower than what modern winters deliver. The calculator helps identify this gap before a heavy snow season.

Garage doors

The garage door calculator handles sizing (width, height, headroom clearance) and opener HP recommendations. Standard single doors are 8 or 9 feet wide; double doors are 16 feet. The measurement most people miss is headroom: the space between the top of the door opening and the ceiling, which must be at least 12 inches for standard track or 3.5 inches for low-headroom hardware.

Project planner

The roof replacement planner chains shingles, ventilation, and gutter calculations into a single material list from your house footprint and pitch. It includes tear-off cost estimation and a quote comparison tool.