By: IK Ideals Contractor Team • Reviewed by: Licensed Roofing Foreman • Last updated: September 2025
Key takeaways
- Correct prep, flashing, and ventilation matter more than the brand of shingle or panel.
- Shingles are approachable for handy DIYers; metal-over-shingles is usually a pro job.
- Do not install over a spongy deck or active leaks; fix the substrate first.
- Follow the manufacturer’s instructions exactly to keep your warranty valid.
Before you start (safety, codes, prep)
Safety: Wear fall protection, non-slip footwear, gloves, and eye protection. Use roof jacks or a properly tied ladder. Avoid windy or wet days.
Codes & permits: Check local requirements for tear-offs, ice/water shield at eaves, and ventilation. NYC/borough rules can differ; verify before you buy materials.
Assess the deck: From the attic and the roof surface, look for rot, delamination, sagging, or dark moisture stains. Replace compromised sheathing.
Ventilation & insulation: Plan a balanced intake (soffit) and exhaust (ridge) path. Poor airflow shortens roof life.
Site setup: Protect landscaping with tarps, set a debris chute or bin, stage materials close to the work area, and brief helpers on hand signals and tool use.
Tools & materials you’ll need
For shingles
- Architectural/asphalt shingles, starter strip, ridge cap
- Ice & water shield, synthetic underlayment, drip edge
- Roofing nails (length per spec), hammer/coil nailer, chalk line
- Step/chimney flashing, pipe boots, high-quality sealant
- Hook blade knife, shears, magnetic sweeper
For metal-over-shingles
- High-temp underlayment or slip sheet, optional battens/purlins
- Panels (steel/aluminum), trim: eave/rake/drip/valley
- Closure strips (foam), butyl tape, panel clips (if concealed-fastener)
- Self-drilling screws with washers, metal snips, bending tools, and an impact driver
How to install roof shingles?
Step 1 — Tear-off, repairs, and deck prep
Remove old shingles and nails. Sweep the deck clean. Replace any rotten or soft sheathing. Check fascia edges for damage and confirm the eave is straight.
Step 2 — Moisture protection & edges
Lay ice & water shield along eaves (and valleys/chimney sides in cold or high-risk areas). Install synthetic underlayment up the slope with proper overlaps. Nail or cap-staple per spec. Set the drip edge at the eaves first, then along rakes.
Step 3 — Starter course & layout
Snap a horizontal chalk line above the eave. Install the starter strip with adhesive edge toward the eave to seal the first shingle course. Verify overhang (typically 1/4–3/8 inch at drip edge). Snap vertical reference lines every 6–10 feet to control tracking.
Step 4 — Shingle courses
Begin at the eave corner and stagger courses per the manufacturer’s pattern. Place nails in the nailing zone only; don’t over- or under-drive. Use the specified number of fasteners (often 4–6 per shingle; more in high-wind zones). Keep joints offset and cut shingles cleanly at hips/valleys.
Step 5 — Flashings and penetrations
Install step flashing alongside sidewalls with each course; counterflash with siding/metal as required. Use pre-formed pipe boots for vents, sealed tightly to the shingle surface. For chimneys, wrap with ice & water shield, add step flashing up the sides, and a cricket on the high side for wider stacks.
Step 6 — Ridge vent and caps
Cut ridge slot (if using ridge vent) to the manufacturer’s width, stopping before hips/ends as specified. Install the vent and then the ridge caps with correct exposure and fastener length. Seal exposed cut edges as required.
Step 7 — Final QA & cleanup
Walk the roof and check: nail placement, loose tabs, flashing laps, sealed fastener heads. Clear all debris and run a magnetic sweeper around the property.
How to install a metal roof over shingles (what to know)
This can work, but only when the existing roof is flat, dry, and structurally sound—and when your code and the panel manufacturer allow it.
Pre-check: structure, code, manufacturer approval
Confirm the deck is solid and shingles aren’t curled or spongy. Ensure additional weight is acceptable. Verify local code and your panel brand’s rules for overlays—some require a tear-off.
Underlayment and leveling
Lay a high-temp synthetic underlayment over shingles for slip and heat protection. In cases of uneven shingle surfaces, add battens/purlins to create a flat plane and ventilation channel (follow your panel system’s design).
Panel planning & fastening
Start square to the eave. Pre-plan panel layout so seams land cleanly at ridges/edges and accessories. For exposed-fastener systems, drive screws perpendicular with washers seated, not crushed. For concealed-fastener (standing seam), set clips per spacing chart and lock panels with the proper seamer.
Trim, closures, and flashings
Fit eave/rake/valley trims with correct overlaps. Use foam closures at eaves and ridges to block pests and wind-driven rain. Flash chimneys, skylights, and pipes with boots/flanges designed for metal panels and seal with butyl tape.
Ventilation & condensation control
Metal gets cold and can sweat. Ensure a continuous airflow path (soffit intake + ridge exhaust) and, where needed, add vapor control layers or vented battens.
Final checks
Verify panel alignment, straightness at eaves, uniform fastener rows, and sealed laps. Remove metal shavings to prevent rust spots.
Costs, timelines, and when to DIY vs when to hire
- Time: A 1,700–2,000 sq ft shingle reroof can take a skilled crew 1–2 days; DIYers often need a long weekend or two. Metal-over-shingles usually takes longer due to trim/flashings and precision cutting.
- Costs: Materials, access, pitch, story count, and repairs drive price. Shingles are typically the budget pick; metal costs more up front but lasts longer and may save on maintenance.
- DIY vs pro: Comfortable on ladders and reading manufacturer specs? Shingles may be within reach. Complex roofs, multiple penetrations, or metal systems are best left to pros.
Know more:
- Explore our roof installation service.
- Need a leak fixed first? Book roof repair services.
- When a tear-off is smarter, see roof replacement.
Common mistakes to avoid
- Nailing above/below the shingle nailing strip.
- Skipping ice & water shield at eaves/valleys.
- Improper valley metal or woven shingles where a closed-cut is required.
- No step flashing at sidewalls.
- Inadequate attic ventilation leading to heat/moisture damage.
- For metal: misaligned panels, crushed washers, and missing closures.
Frequently Asked Questions
How to install roof shingles?
Prep the deck, lay ice & water at eaves and valleys, add synthetic underlayment and drip edge, install starter strip, then run staggered shingle courses within the nailing zone. Flash penetrations and walls, install ridge vent and caps, and finish with a full QA.
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How to install metal roofing over shingles?
Only if the deck is sound and local code, plus the panel manufacturer allows it. Add high-temp underlayment (and battens if needed), plan panel layout, fasten per spec, use closures at eave/ridge, and flash all penetrations correctly.
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Can you install a metal roof over shingles?
Yes, in many cases—but not over curled, soft, or wet shingles, and not where code prohibits overlays. When in doubt, tear off to the deck, fix issues, and start clean for the best result.
Also searched as: can a metal roof be installed over shingles; can I install a metal roof over shingles; can I install a metal roof over shingles.
When to call a pro (and what to expect)
Call a professional if you see structural sag, widespread leaks, rotten sheathing, complex valleys, multiple chimneys or skylights, or if fall protection isn’t something you can manage confidently. A good contractor will inspect, document with photos, explain options, provide a clear scope and schedule, and back the work with real warranties.
About the author
IK Ideals Contractor has installed and replaced roofs across Brooklyn rowhouses, multifamily walk-ups, and mixed-use buildings. Our field team reviews every technical article for accuracy against manufacturer install guides and local code practices.