Panel count, closures, trim and cost for a retrofit metal roof, by eave run and rake length.
Estimates are planning aids, not a professional quote. Double-check quantities and product coverage — and any local code or permit requirements — before you buy.
⚠ Metal panels move with temperature far more than shingles do — fasten through slotted holes or floating clips exactly as the manufacturer specifies, and never bottom a screw out dead tight, or the panel will oil-can and split at the fastener within a few seasons.
⚠ Don't let steel panels or fasteners touch copper or lead flashing and vent stacks directly — dissimilar metals corrode each other galvanically wherever they're in contact and wet. Isolate the transition with compatible flashing or a paint/underlayment barrier.
⚠ Installing over an existing asphalt roof is common but not universal — most jurisdictions cap it at one existing layer and require battens for the airflow and drainage plane underneath the metal. Confirm with your local building department before skipping the tear-off.
| Roofing | $1,974–$2,671 |
| Fasteners & Hardware | $231–$313 |
| Lumber & Decking | $213–$288 |
| Siding & Trim | $95–$129 |
| Total | $2,513–$3,401 |
Excludes tools, delivery, tax and permit fees. Labor not included — this is a DIY materials estimate.
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About this calculator
Measure your existing roof's eave run and rake length, pick exposed-fastener or standing-seam panels, and the Metal Roofing Calculator turns that into a full retrofit takeoff: panel count cut to your exact rake length, foam closures at the eave and ridge, a high-temp slip sheet, ridge cap or vent, rake and eave trim, and either screws or concealed clips. It's built around what a re-roof crew actually measures on the roof, not a floor-plan footprint.
Switch on "over existing shingles" and it adds the battens code requires for drainage underneath the metal; turn it off for a bare-deck install instead. Advanced options add snow guards for cold climates, a premium Kynar finish, a vented ridge, and a waste allowance — every one of them moves the parts list and the cost, not just a label.
Step by step
A step-by-step walkthrough to go with your plan above. Follow the product instructions and any local code or permit requirements as you work.
Tape the eave run along the bottom edge and the rake length up the slope from eave to ridge on each plane, and confirm your local code allows going over the existing layer or requires a tear-off first.
Repair any soft or delaminated decking, and if you're going over shingles, pull any ridge vent and loose material and confirm the deck underneath is sound before covering it.
Install the high-temp synthetic underlayment over the whole deck, lapping each course over the one below it so water always runs over a seam, not into one.
Run 1×4 battens across the roof at the spacing your panel manufacturer specifies, screwed through to the rafters — this is what creates the drainage and airflow gap under the metal.
Fit foam closure strips along the eave to seal the panel's corrugation, then set and square the first panel dead straight — every following panel keys off this one.
Work panel by panel across the eave run, overlapping each panel's edge rib per spec, fastening with screws or clips as your system requires, and checking square every few panels.
Set ridge closures, cap or vent the ridge, then install rake and eave trim coil over the panel edges to shed water clean of the fascia and gable ends.
In snow country, fasten snow guard rows into the deck or battens per the spacing plan before calling the job finished — they're much harder to add correctly after the fact.
Equip the job
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Keep planning
Decks & Structures
Answers
Often, yes — it's one of metal roofing's biggest selling points over a full tear-off. Most codes allow it over a single existing layer, but require 1×4 battens run across the roof at spacing to create an airflow and drainage gap between the old shingles and the new metal, plus a compliant underlayment. Multiple existing layers, a soft or rotten deck, or local code can still force a tear-off, so confirm with your building department before you commit to skipping it.
Exposed-fastener panels are screwed straight through the face into the deck or battens, cost noticeably less, and are the more approachable DIY option. Standing seam panels lock together with concealed clips and no field-visible screws, cost more and usually need a seamer tool, but handle thermal expansion and long-term weathering better with nothing to eventually work loose or leak. Low-slope roofs, coastal wind exposure, or a highly visible roof plane all favor paying up for standing seam.
Exposed-fastener systems need self-tapping screws with a bonded neoprene washer, driven snug but not crushed — over-driving squeezes out the washer and the hole leaks within a season or two. Standing seam skips exposed screws entirely in favor of concealed clips fastened to the deck that let the panel float lengthwise as it expands and contracts. Either way, use the fastener length and spacing the panel manufacturer specifies, not generic deck screws.
DIY materials for exposed-fastener panels typically run $2–3 per square foot including closures, trim and fasteners; standing seam runs noticeably higher, often $4–7 per square foot in material alone, before factoring a premium painted finish. A basic re-roof of a modest single-story home can still land in the low thousands for exposed-fastener panels. This calculator totals materials only — installed pricing from a contractor runs several times higher because labor and equipment dominate the bill.
In snow country, yes, almost always. Metal sheds snow far more readily than shingles, and an unguarded metal roof can dump an entire roof's worth of snow and ice at once onto walkways, decks, cars, or anyone standing below. Snow guards or a continuous snow rail break that slab up into smaller, safer releases. They have to be fastened into the deck or battens rather than just the panel seam, so plan for them before the panels go on, not after.