What is the 25% rule in roofing?

The 25% rule is a roofing guideline stating that if more than 25% of a roof's surface is damaged or deteriorated, the entire roof should be replaced rather than repaired. Many local building codes also use this threshold to determine whether a permit is required for a full replacement. For example, if a 2,000 sq ft roof has 500+ sq ft of compromised shingles, replacement is typically the recommended course of action.

Late winter and early spring — typically January through March — tend to offer the lowest prices for roof replacement. Demand for roofing contractors drops significantly during colder months, which can lead to lower labor costs and faster scheduling. Some contractors offer off-season discounts to keep crews working. However, extreme cold can affect material installation, so it's worth confirming that conditions meet manufacturer requirements before scheduling work.

Labor is the most expensive part of replacing a roof, typically accounting for 40–60% of the total project cost. Roofing work is physically demanding, requires skilled trades knowledge, and involves significant liability, which drives up labor rates. Material costs — particularly for premium shingles, underlayment, and decking — are the second largest expense and can significantly raise the total depending on the product tier selected.

Estimating roof replacement cost involves several straightforward steps. 1. Measure your home's footprint in square feet. 2. Add 10–15% for roof pitch and waste factor. 3. Divide the total by 100 to get the number of roofing squares. 4. Multiply roofing squares by the material cost per square (typically $150–$500+). 5. Add estimated labor costs, which often equal or exceed material costs. 6. Include additional costs for underlayment, flashing, and permit fees.

Most 2,000 square-foot homes can be reroofed in one to two days under normal conditions. The timeline depends on roof pitch, number of layers being removed, complexity of the design, and crew size. Steeper or more intricate roofs may require an additional day. Weather delays, decking repairs, and material availability can also extend the project. Trill Roofing and other local contractors in the Godfrey, IL area typically complete standard jobs within this window. Learn more about selecting a qualified roofing contractor.

Calculating roof replacement cost requires a few key measurements and estimates. 1. Determine your roof's total square footage by measuring the home's footprint. 2. Adjust for roof pitch by multiplying by a slope factor (1.0–1.5x). 3. Convert to roofing squares by dividing by 100. 4. Multiply squares by the chosen material's cost per square. 5. Add labor costs, typically equal to or greater than material costs. 6. Factor in disposal fees, permits, and any decking repairs needed.

The cheapest time of year for a new roof is late winter, roughly January through early March. Demand for roofing services is at its lowest during this period, giving homeowners more negotiating leverage and access to contractor availability. Some roofing companies offer discounted rates to maintain workflow during slow seasons. The trade-off is that cold temperatures may require specific installation precautions, particularly for asphalt shingles that need proper sealing.

It depends. on the roofing material, installation quality, and current condition. Standard 3-tab asphalt shingles are rated for 20–25 years, so a 20-year-old roof of that type is likely nearing the end of its useful life. Architectural shingles may have 10+ years remaining. Signs like granule loss, curling shingles, frequent leaks, or sagging decking indicate replacement is needed regardless of age. A professional inspection provides the most accurate assessment.

Labor is the most expensive part of a new roof, commonly representing 40–60% of the total installation cost. Skilled roofing work demands physical expertise, safety equipment, and liability coverage, all of which contribute to higher labor rates. Among materials, the roofing shingles or primary surface covering represent the next largest cost, with premium options like metal, slate, or architectural shingles significantly increasing the overall project budget.