Planning a roof replacement starts with more than counting shingles. A complete materials list includes underlayment, flashing, starter strips, ridge caps, fasteners, and ventilation components, with quantities based on roof area, slope, layout, and local code. This guide explains what is typically needed to shingle an asphalt roof, how to estimate amounts, and which details should be confirmed before purchasing.
Start With the Roof Measurements
Roofing materials are usually estimated in squares. One roofing square covers 100 square feet of roof surface. The roof’s surface area—not the home’s floor area—is the starting point for estimating shingles and many accessories.
For a simple roof, measure each sloped plane’s length from eave to ridge and its width along the eave, then multiply length by width. Add the areas of all planes. More complex roofs may have hips, valleys, dormers, or intersecting sections that require separate measurements. A professional measurement or scaled roof plan can reduce ordering errors.
A roof’s pitch changes its surface area. If only the home’s horizontal footprint is known, a pitch factor can provide a rough estimate: multiply the footprint area by the factor for the roof’s slope. For example, a 6:12 roof has a factor of about 1.12. This shortcut is less reliable for roofs with many projections or irregular shapes.
After calculating surface area, add a waste allowance for cutting, starter and ridge details, and damaged pieces. A straightforward gable roof may need roughly 10% extra; complicated roofs, steep slopes, or patterns with significant cutting may need more. The roofing contractor or shingle manufacturer can help refine the allowance. Do not treat the allowance as a substitute for a measured takeoff.
Core Materials Needed to Shingle a Roof
Asphalt shingles
Architectural and three-tab asphalt shingles are common in the United States. Packages are sold by coverage, and the number of bundles per square varies by product. Read the package label and installation instructions rather than assuming every bundle covers the same area. Some premium or specialty products require more bundles per square.
Choose shingles that meet the project’s performance, appearance, and warranty requirements. Check the required roof slope, exposure limits, wind-resistance conditions, and approved installation method. A manufacturer’s warranty may depend on using specified accessories or following particular installation details.
Starter strips
Starter strips are installed along eaves and, where required, rakes. They help seal the first shingle course against wind uplift and provide a properly positioned adhesive edge. Some shingles have a manufacturer-approved starter product; others allow shingles to be cut into starter pieces according to the installation instructions. Estimate the needed length by measuring the eaves and applicable rakes, then check the product’s coverage per bundle.
Underlayment
Underlayment is installed over the roof deck beneath the shingles. Common choices include asphalt-saturated felt and synthetic underlayment. Product selection depends on the roofing system, slope, local code, and manufacturer requirements. Underlayment is generally sold in rolls; use the roll’s stated coverage and account for required overlaps, which reduce the usable area.
Underlayment is not a substitute for correctly installed flashing or water protection at vulnerable edges and penetrations. Follow the shingle and underlayment instructions for fastening, overlap, and exposure limits, especially when the roof may be exposed to weather before shingles are installed.
Ice-and-water protection
Self-adhering ice-barrier membrane is used in locations where required by code or specified by the roof design. It is commonly installed at eaves and may also be needed in valleys, around penetrations, or at other vulnerable areas. Local requirements vary, including how far protection must extend beyond the exterior wall. Measure these areas separately and confirm the required membrane width and placement with the local building department or a qualified roofer.
Roofing nails and fasteners
Use corrosion-resistant roofing nails of the type, length, and gauge specified for the shingles and roof assembly. Nail length must be sufficient to penetrate the roof deck as required by the applicable instructions and code; longer nails may be needed when shingles are installed over existing layers or thicker decking. Short staples or general-purpose construction nails are not interchangeable with approved roofing fasteners.
Fastener count depends on the shingle, wind exposure, and installation requirements. Many shingles call for four nails per shingle, while higher-wind installations or specific products may require six or another pattern. The exact number, placement, and nail-line location must come from the product instructions. A roofing nailer can speed installation, but incorrect pressure or nail placement can reduce holding performance.
Flashing and drip edge
Flashing directs water away from joints and roof openings. Typical materials include step flashing along sidewalls, apron or headwall flashing, valley flashing where the design calls for it, and flashing or boots for plumbing vents. Chimneys and skylights may need specialized flashing systems. Existing flashing should be inspected carefully; reusing damaged, corroded, or poorly integrated flashing can undermine a new roof.
Drip edge is metal flashing installed at roof edges to guide water into the gutter or away from the roof deck. It is commonly required by code, but installation details can differ at eaves and rakes. Measure edge lengths and account for overlaps and cuts when calculating how many pieces are needed. Follow local code and the roofing system’s instructions for the sequence of drip edge, underlayment, and ice barrier.
Ridge caps and hip shingles
Ridge and hip areas need compatible cap shingles, which may be supplied as a dedicated product or made from approved field shingles. Estimate the total ridge and hip length, then divide by the product’s stated coverage per bundle. Include overlaps and follow the specified exposure. Standard field shingles should not be assumed suitable for caps unless the manufacturer permits that use.
Roofing cement and sealant
Roofing cement or an approved sealant may be needed for limited details, such as certain flashing transitions or hand-sealing where the instructions require it. It is not a general replacement for mechanical fastening or correctly designed flashing. Use only products compatible with the roofing materials and apply them only where specified; excessive or misplaced sealant can interfere with drainage.
Ventilation and Roof-Deck Components
Roof ventilation may include ridge vents, intake vents at soffits or eaves, and compatible baffles that preserve airflow through attic insulation. Replacing shingles can reveal blocked vents, damaged vent housings, or inadequate intake. Ventilation requirements depend on the attic design, climate, insulation, and local code. A roofer should assess the system as a whole rather than adding exhaust vents without ensuring adequate intake.
Roofing work may also uncover deteriorated sheathing, fascia, or eave boards. These are not automatically included in a shingle order, so the estimate should explain how replacement will be handled and priced. The deck should be sound and suitable for fastening. Any repair should use materials and thicknesses appropriate to the existing structure and local requirements.
Estimating Materials: A Practical Checklist
Use measured roof planes and product packaging to create a takeoff. The table below describes common estimating methods; actual package coverage, overlaps, and installation rules vary by product.
| Material | How to Estimate | Important Check |
|---|---|---|
| Field shingles | Roof surface area ÷ 100 = squares; multiply by the stated bundles per square, then add a waste allowance. | Confirm product coverage and the roof’s layout. |
| Underlayment | Measure roof area and divide by usable roll coverage after overlaps. | Follow required laps and slope limits. |
| Ice barrier | Measure eaves, valleys, and other areas requiring membrane; calculate coverage using roll width and length. | Check local code and project specifications. |
| Starter strips | Measure eaves and any rakes where starter is required; divide by package coverage. | Use the approved starter and specified placement. |
| Ridge and hip caps | Measure combined ridge and hip length; divide by stated bundle coverage. | Use compatible caps and specified exposure. |
| Drip edge | Measure eaves and rakes; allow for overlap and cutting. | Verify edge details and local requirements. |
| Flashing | Count and measure valleys, walls, chimneys, skylights, and pipe penetrations. | Choose details suited to each junction. |
| Nails | Estimate from shingle quantity and required fasteners per shingle, with a practical allowance. | Confirm nail length, corrosion resistance, and placement. |
A worked example can help illustrate the process. If measured roof planes total 2,000 square feet, the roof has 20 squares before waste. With a 10% allowance, the order would cover about 22 squares. If a particular shingle covers three bundles per square, the estimate would be 66 bundles. That calculation is only an example; the actual bundle count must follow the selected product’s label.
Other Supplies and Job-Site Needs
Material planning should include more than the visible roof covering. Depending on the roof and work scope, the project may need replacement vent boots, flashing, ridge-vent components, sheathing panels, fascia repairs, and gutter protection. A contractor may also use tarps, temporary weather protection, and debris containers. These items should be listed separately from the shingle quantity so repair costs are clear.
Removal and disposal are also part of a roof replacement. The number of existing roof layers, material type, and local disposal rules affect labor and dumpster needs. Older homes can present additional considerations, including deteriorated decking or materials that require specialized handling. If suspect material is found, work should pause until it is assessed appropriately.
Safety Materials and Weather Protection
Roofing is hazardous work. OSHA fall-protection rules apply to covered construction work, with requirements influenced by the task and site. Appropriate fall protection may include guardrails, safety nets, or personal fall-arrest systems, along with properly selected anchors and training. Ladders must be stable and used correctly. Homeowners should not attempt steep or high roof work without suitable training, equipment, and a safe plan.
Weather protection is essential because an exposed roof deck can be damaged by rain. Contractors often plan tear-off and installation around the forecast and keep tarps or other temporary protection available. Shingles should be stored and installed within the temperature and weather conditions set by the manufacturer. Cold conditions can affect adhesive sealing; excessive heat can make shingles more vulnerable to scuffing.
Code, Manufacturer Instructions, and Warranty
Building codes are adopted and enforced by state and local jurisdictions, so requirements are not identical across the United States. They may address underlayment, ice barriers, drip edge, ventilation, wind resistance, fastening, and the number of permitted roof layers. A permit may be required for a reroof, depending on the location and scope. The local building department is the best source for applicable rules.
Manufacturer instructions should be treated as part of the material plan. They specify compatible accessories, installation patterns, slope limits, and conditions for warranty coverage. A roofing system that uses mismatched components or incorrect fastening may perform poorly even if the shingles themselves are high quality. Keep product labels and installation documentation with project records.
How to Avoid Common Material-Planning Mistakes
- Ordering from the home’s square footage: Measure the actual roof planes and account for slope and projections.
- Ignoring product coverage: Bundle counts and roll coverage differ; use the label for the selected product.
- Forgetting accessories: Starter strips, ridge caps, flashing, drip edge, and ice barriers can be easy to omit.
- Reusing questionable flashing: Inspect junctions and penetrations before deciding what can remain.
- Buying mismatched components: Check compatibility and installation instructions across the roofing system.
- Skipping a waste allowance: Valleys, hips, dormers, and cuts increase material use.
- Overlooking code and permits: Verify local requirements before work begins.
- Underestimating repairs: Budget for possible deck or edge-board replacement discovered during tear-off.
Reliable Sources for Specifications
For project-specific details, consult the selected shingle manufacturer’s installation instructions and product data, the local building department, and a qualified roofing contractor. Useful safety guidance is available from the Occupational Safety and Health Administration’s construction fall-protection resources. The International Code Council publishes model codes adopted in many jurisdictions, but the locally adopted edition and amendments control. Manufacturer instructions and local officials should resolve questions about exact quantities, fastening patterns, and required roof components.