Roof Penetrations for Solar: Attachments and Flashing

What a roof penetration means in plain terms

Your roof is a waterproof skin. Anything that goes through it, such as a vent pipe, a chimney or a bolt, is a penetration. Roofers seal every one so water cannot follow it inside.

A solar array sits on rails, and the rails sit on small feet called mounts. On most shingle roofs, each mount is held by a lag bolt driven through the shingles and the roof deck into a rafter below. That bolt hole is the roof penetration.

The DOE notes that PV arrays must be mounted on a stable, durable structure that can support the array and withstand wind, rain, hail and corrosion over decades ⁶. The penetrations are where that structure meets your roof, so they matter more than their size suggests.

How a flashed mount keeps water out

Water runs down a roof. Shingles overlap so each row sheds water onto the row below. Flashing is a thin metal plate that joins that pattern. Its top edge slides up under the shingles above the mount, so water flowing down passes over it, not under it.

The bolt then passes through the flashing. IronRidge's GF-1 guide says the flashing's grommet and the L-foot combine to form a watertight seal. Sealant fills the pilot hole, and a rubber (EPDM) washer bonded to the bolt presses down on top.

The guide is specific about the lap: regardless of shingle height, the top edge of the flashing must sit under the third course. It also says the rubber washer will begin to push out at the sides when the bolt is fully seated, and calls that the most effective visual sign of a watertight seal.

Sources: [1]

What good installation looks like

This is the sequence from IronRidge's GF-1 installation guide (revised January 2026), one current flashing product for asphalt shingle roofs. It is here so you know what good work looks like, not as instructions. Roof work belongs to a licensed contractor.

1. Mount rows are marked and the rafter under each mount is located.
2. The shingle above the mount is lifted; nails in the way are removed and their holes filled with approved sealant.
3. The flashing slides between the first and second shingle courses until its top edge sits under the third course.
4. A pilot hole is drilled into the rafter and filled with sealant compatible with the roof type.
5. The L-foot and lag bolt go through the flashing into the rafter, until the bonded washer bulges slightly at the edges.

The point to take away: the flashing is lapped under the shingles above, like another shingle. Sealant alone, without that lap, is the shortcut that leaks.

Types of solar roof attachment

Example: the parts in one flashed mount

Parts listed in the IronRidge GF-1 installation guide, revised 21 January 2026 ¹:

The guide lists a TAS 100(A) wind-driven rain test rating and Florida Product Approval for GF-1. Other brands use different parts; ask for the guide for the product on your plan set.

Where penetrations show up on your paperwork

The permit plan set shows each mount on the roof plan, and the structural pages give the spacing between mounts. Charleston County lists a fastening design to roof members among its solar permit requirements ³.

The spec sheets in the plan set name the mount and flashing product. That tells you which installation guide applies. The contract or warranty documents should say who is responsible for roof leaks at the mounts.

Benefits of flashed mounts, and their limits

Limits: an old roof under new panels

Penetrations can only be as good as the roof they sit in.

If the shingles are near the end of their life, the array may need to come off for a re-roof within a few years.

DOE guidance says a replaced roof means the installer removes the system, then reinstalls it after the new roof is done ⁷.

That is why many installers suggest re-roofing first. Our re-roof before solar guide and roof-before-solar check help you decide.

What drives cost, lifespan and warranty

We do not quote dollar prices here. These are the drivers for the roof-attachment part of a job. See solar cost for current figures.

• Number of mounts. More panels and tighter wind spacing mean more mounts and more labor.
• Roof type. Tile and some metal roofs take special hardware and more time than shingles.
• Roof repairs first. Damaged decking or old shingles add cost before any mount goes in.
• Removal and reinstall. A future re-roof means paying to take the array off and put it back; see removal and reinstall.
• Warranty. DOE guidance says a workmanship warranty of up to 10 years may come with a system, and that major parts typically carry 25-year warranties ⁷. Check what your contract says about roof leaks.

The process: from design to inspection

A licensed contractor does all roof work. You review the plans and check the results.

1. The site survey checks rafter size, spacing and roof condition.
2. The designer sets mount spacing from wind and load design, and marks each mount on the roof plan.
3. An engineer signs the structural letter where the jurisdiction requires it ².
4. The building department reviews the plan set, including the fastening design.
5. The crew installs flashed mounts into rafters, then rails and panels.
6. The inspector checks the work. In the City of Charleston, the required inspections include an electrical rough, an electrical final and a building final ².

Maintenance: what to check, and when

Warning signs of a leaking mount: when to call a pro

Call your installer first; their workmanship warranty usually covers the holes they made. See a roof leak after solar.

• Water stains or drips on the ceiling or attic wood under the array.
• Damp or dark spots around a bolt seen from the attic.
• Shingles lifted, cracked or missing near the array.
• Rails or panels that move, rattle or sit out of line after a storm.
• Mounts that are visibly not lined up with rafters in install photos.

Safety

Rules, licenses and roof warranties

Local building codes govern how mounts are attached. South Carolina has the 2021 building codes in force, and the 2024 International Residential Code is scheduled for local use from 1 January 2027.

Your local building department applies the wind design for your address. We do not cite code section numbers here because we could not load the adopted text.

Who installs the racking matters. City of Charleston guidance says a contractor licensed only as a Solar Panel Installer may install the panels and electrical system but not the roof mounting or framing.

That work needs a Residential Builder, a Residential Specialty Contractor with a Roofer classification, or a General Contractor with a roofing license. The state's registration package splits the work the same way.

Three different warranties can touch the same hole: the shingle maker's, your roofer's workmanship warranty and the solar installer's workmanship warranty. Manufacturers set their own conditions for solar on their roofs, so ask yours in writing before installation. See our guide to the solar workmanship warranty.

Sources: [2] [5] [4]

Roof penetrations in SC, GA and VA

Roof penetration compared with related terms

Common misconceptions

Myth Solar panels always cause leaks.

Reality A flashed, lapped mount sheds water like the shingles around it. Leaks usually trace to a missed rafter, a hole left unsealed, or flashing that is not under the course above.

Myth Fewer penetrations is always better.

Reality Mount spacing is set by wind and load design. Stretching it to save holes can overload the attachments.

Myth A dab of sealant is enough.

Reality Sealant alone ages and cracks. The lap of flashing under the shingles above does most of the work.

Myth Any solar contractor can do the roof part.

Reality In South Carolina, a solar-only registration does not cover roof mounting ².

When roof penetrations matter to you

Use these rules:

• If your roof is near the end of its life, re-roof before solar.
• If your roof is metal or tile, ask which attachment the design uses and whether it penetrates.
• If you have a roof warranty, ask the maker about solar in writing before you sign.
• If you want proof of good work, ask for photos of mounts before panels go on.
• Next step: run the solar hazard check for wind exposure, and read about panel weight and roof loading.

Related terms

Solar Mounting System

A solar mounting system, also called racking, is the set of attachments, rails, clamps and bonding hardware that secures solar panels to a roof or the ground and holds them at a fixed angle against wind and snow.

Solar Design

Solar design is the engineering step that turns a site survey into a specific system: which panels go where, how they are wired and attached, and how they connect to the home's electrical service, documented in a plan set submitted for a permit.

Solar Site Assessment

A solar site assessment is an inspection of a property to decide whether, where and how solar panels can be installed, covering sunlight, shade, roof direction and angle, roof condition and structure, and the home's electrical service.

Solar Panel

A solar panel, called a solar module in the industry, is a weatherproof assembly of photovoltaic cells wired together behind glass in a frame, which turns sunlight into direct-current electricity.

Solar Array

A solar array is the complete set of solar panels in one installation, wired together so their combined direct-current output feeds the inverter as a single source.

Solar Inspection

A solar inspection is the check of a finished solar installation against the approved permit and the adopted codes, carried out by the local building department's inspector.

Solar Permit

A solar permit is the approval a local building department, the authority having jurisdiction, issues before a solar system can be installed.

Also referenced from: Solar Shingles, Solar Site Assessment, Solar Design, Solar Mounting System, Ballasted Solar Mount