Best Roof Types for Solar (And When to Re-Roof First)

“What’s my roof going to do for solar?” is the second question every homeowner asks (right after “how much does it cost?”). The honest answer is: most roofs work, some work better, and a few should be re-roofed before the array goes up. Here’s how we evaluate each material.

Asphalt shingle — the most common, the easiest

About 80% of NJ homes have asphalt shingle roofs. The reason solar fits these so easily is that the installation industry has spent 20 years perfecting the mounting hardware for shingle. Flashed feet from IronRidge, Unirac, EcoFasten, and Quick Mount PV all provide a watertight seal at every penetration that’s tested to outlast the shingle itself.

Best for solar? Yes — provided the shingle is in the first half of its useful life. A 25-year architectural shingle 5 years in is the ideal substrate. A 25-year shingle 18 years in is a re-roof conversation, because we don’t want to put a 25-year array on a 7-year-of-life roof.

Re-roof + PV bundle considerations: When a homeowner is already 12+ years into a shingle roof and considering solar, bundling the re-roof with the install is usually the cheaper, cleaner answer. Reliant carries GAF Master Elite certification specifically so we can do both jobs under one warranty document.

Standing-seam metal — the best solar substrate, period

If you have a standing-seam metal roof, it is the single best surface to mount solar on. Here’s why:

• No penetrations needed. Standing-seam mounting hardware clamps to the seams (S-5! clamps and similar). The roof never gets penetrated, so there’s no flashing, no caulk, no risk of leaks.
• 50+ year roof life. A good standing-seam will outlast two solar arrays.
• Reflectivity. Cool-coated metal roofs reduce the heat load on the panels above them, which preserves panel efficiency in summer.

Best for solar? Absolutely. If you’re building new and considering solar, standing-seam metal is the substrate to specify.

Caveat: Trapezoidal-rib (or “R-panel”) metal roofs are not the same as true standing-seam. They have exposed fasteners and require penetrations for the racking, which means the mounting math is closer to shingle than to standing-seam.

TPO / EPDM single-ply (commercial flat)

The two most common commercial roof systems. TPO (thermoplastic polyolefin) is the white membrane you see on warehouses and retail buildings. EPDM is the black rubber membrane more common on older commercial buildings.

For solar, both work — but the mounting strategy is different.

Penetrated mounting. Stanchions through the membrane down to the structural deck, properly flashed by the membrane manufacturer’s spec. Works, but every penetration is a future leak risk if not detail-flashed perfectly. Reliant does this kind of work when the deck geometry requires it.

Ballasted (no penetrations). Racking sits on the membrane and is weighed down with concrete ballast blocks. No holes in the roof. Industry-standard ballast designs from PanelClaw, IronRidge, and Unirac come with engineering calcs for snow + wind loads. This is our default approach for commercial flat roofs whenever the structural capacity supports it.

Best for solar? Yes, both — but ballasted is preferred when the structure handles it. We always do a structural review before specifying.

Re-roof + PV consideration: Single-ply membrane roofs typically have a 20-year life. If the roof is more than 8–10 years old, we recommend a tear-off + new membrane before the PV install. The cost of re-roofing under an existing array later is roughly 4× the cost of bundling.

Tile (clay, concrete)

Mediterranean tile is common in older NJ housing stock and parts of the suburbs. Solar on tile is possible but more expensive and requires specialty mounting hardware.

The challenge: every tile under a mounting foot has to be replaced with a flashed “shoe” (a metal tile-replacement that supports a rail mount). The labor is roughly 2–3× the labor on shingle for the same array size, and you need to source replacement tiles to match the rest of the roof for aesthetics.

Best for solar? Possible. Not ideal. If the budget supports the additional labor, sure. If the tile roof is also approaching end-of-life, we recommend re-roofing to shingle or metal under the array and either selling the tiles or keeping them for accent walls.

Slate — handle with care

Authentic slate roofs (real Vermont or Pennsylvania slate, not synthetic) are 75–100-year roofs. Mounting solar on slate without breaking tiles requires specialty hardware and a slate-trained installer. Most solar contractors won’t touch real slate, and the ones that will charge a premium.

The right answer for slate: standing-seam metal sections specifically added under where the array will sit (cutting the slate and patching the perimeter), or a ground-mount alternative.

Wood shake

Wood shake roofs are rare in NJ commercial work but show up in some upscale residential. Solar on wood shake is not recommended. Shake roofs have inherent fire-risk concerns, and the mounting penetrations are difficult to make weather-tight without flashing approaches that change the look of the roof.

If your home has a wood-shake roof and you want solar, the conversation is usually: re-roof to a Class-A material first, then install solar.

The decision matrix

Here’s how Reliant ranks roofs for solar fit, all else equal:

Roof type	Solar fit	Notes
Standing-seam metal	★★★★★	Best substrate. No penetrations.
Architectural shingle (mid-life)	★★★★	Easiest install. Most common.
TPO / EPDM (ballasted)	★★★★	Commercial standard. No penetrations.
TPO / EPDM (penetrated)	★★★	Works. Demands tight flashing.
Architectural shingle (late-life)	★★	Re-roof + PV bundle recommended.
Trapezoidal metal	★★★	Penetrated, but predictable.
Tile	★★	Expensive specialty install.
Slate	★	Specialty contractor required.
Wood shake	☆	Re-roof first.

What we tell every prospective homeowner

Before any solar quote, we want to know two things about your roof:

1. Material and approximate age. Type of shingle, when it was last replaced, any known leaks.
2. Pitch and orientation. South-facing roofs with 25–35° pitch are optimal in NJ. North-facing roofs produce 60–70% of south-facing, which still works for many systems but changes the math.

If the roof is approaching end-of-life, we’ll tell you to re-roof first (or bundle it with us). The cost of installing solar on a roof that fails in 5 years and has to be taken down and reinstalled is roughly 3× more than doing the roof first.

That’s not the answer most contractors want to give. It’s the answer that protects your investment.

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Want us to look at your roof? Send photos (drone shots or just a few cell-phone pictures from the yard) and the address. We’ll tell you honestly what’s going to work, and what should be re-roofed first. Send your roof →