In Pennsylvania, the residential code calls for an ice barrier at the eaves in areas with a history of ice forming along the eaves and backing up water, and in western Pennsylvania you should expect that to apply to your house. The barrier has to run from the lowest edge of the roof to a point at least 24 inches inside the exterior wall line. That is the legal minimum. A well built roof also gets ice and water shield in the valleys and around chimneys, skylights, sidewalls and low slope sections.
What does the Pennsylvania code say about ice and water shield?
Pennsylvania does not write its own residential roofing rules from scratch. The Uniform Construction Code adopts the International Residential Code, with state amendments. As of January 1, 2026, the UCC is based on the 2021 International Codes, including the 2021 IRC.
The ice barrier rule is IRC section R905.1.2. In plain terms, it says:
- It applies in areas where there has been a history of ice forming along the eaves causing a backup of water, as designated in the code’s local climate table.
- The ice barrier is either two layers of underlayment cemented together or a self adhering polymer modified bitumen sheet, which is what most people call ice and water shield.
- It runs from the lowest edges of all roof surfaces to a point at least 24 inches inside the exterior wall line of the building.
- On roofs with a slope of 8 in 12 or steeper, it also has to extend at least 36 inches along the roof slope from the eave edge.
- Detached accessory buildings with no conditioned space, such as many sheds and detached garages, are exempt.
The same requirement shows up for asphalt shingles, metal roof shingles, mineral surfaced roll roofing, slate and slate type shingles, and wood shingles and shakes.
Whether the ice barrier box is checked is set in the climate table that each jurisdiction fills in. With our freeze thaw winters, you should plan on it applying here. If you want to be certain, ask your municipal code office. Our guide to roofing permits in Pennsylvania explains how local permits and inspections work.
How far up the roof does the ice barrier have to go?
The key phrase is “24 inches inside the exterior wall line.” The point is measured from the wall line of the house, not from the edge of the shingles, so your overhang counts against you.
Here is why that matters. A standard roll of ice and water shield is about three feet wide. On a house with a 12 inch overhang, one course at the eave usually comes up just short of the line. On an older Pittsburgh home with deep 18 or 24 inch eaves, or a steep pitch, one course often falls short and a second course is needed.
| Situation | What the code looks for |
|---|---|
| Typical pitch, short overhang | Barrier reaches at least 24 inches past the inside of the wall |
| Deep overhang or steep pitch | Often two courses at the eave to reach the line |
| Pitch of 8 in 12 or steeper | The 24 inch rule plus at least 36 inches up the slope from the eave |
| Detached shed or detached unheated garage | Exempt from the ice barrier rule |
A roofer who rolls one strip along every eave without measuring may be under the minimum on your house. Ask how they figured the coverage.
Where else should ice and water shield go?
The code only addresses the eaves. Water gets into houses in plenty of other places, and good roofers protect those spots even though the code does not list them.
- Valleys. Two roof planes dump water into one channel. Valleys carry the most water on the roof and are where leaves from oak and maple trees pile up in the fall.
- Chimneys. Membrane under the step and counter flashing gives a second line of defense. Our article on chimney flashing leaks shows what fails first.
- Skylights. Manufacturers supply flashing kits, and a membrane collar around the curb adds protection.
- Sidewalls and dormers. Where a roof meets a wall, wind driven rain finds the gaps.
- Low slope sections. Porch roofs and transitions near the bottom of the range shingles allow shed water slowly and are prone to backup.
- Penetrations. Pipe boots and vents benefit from a small patch of membrane underneath.
Some homeowners ask for full coverage over the whole deck. That is rarely needed on a properly vented roof, and it can trap moisture if the attic does not breathe. Proper attic ventilation matters as much as the membrane for stopping ice dams.
Do shingle warranties require ice and water shield?
Shingle manufacturers publish installation instructions, and their warranties generally depend on the roof being installed according to those instructions and local code. In cold climates, those instructions call for an ice barrier at the eaves. If a required layer is skipped, a later leak claim may be denied.
Enhanced system warranties usually go further and require the manufacturer’s own accessory products, including its underlayment and ice and water barrier, installed by a certified contractor. Bella is an Owens Corning Platinum Preferred contractor, and we install the full system the warranty calls for. The exact terms vary by manufacturer and warranty level, so read the published warranty for the product you choose.
What should I look for on a roofing estimate?
A good estimate spells out the ice barrier instead of hiding it in “underlayment.” Look for:
- The product name for the ice and water shield
- Where it goes: eaves, valleys, chimneys, skylights, walls
- How far up from the eave, or a statement that it meets the 24 inch rule
- What covers the rest of the deck, usually synthetic underlayment
- Drip edge at eaves and rakes
Our guide on synthetic underlayment vs felt covers the field layer. In Bella’s typical replacement pricing, ice and water shield at eaves and valleys is part of the base scope, not an add on. For a 2,000 square foot home with architectural shingles, most of our jobs land between $14,000 and $19,000, and every home is different.
Frequently Asked Questions
Is ice and water shield required on a reroof in Pennsylvania?
Generally yes. The code’s reroofing section requires a replacement roof covering to meet the same roof assembly rules, so the ice barrier applies where the jurisdiction requires it. A tear off is also the only chance to install it properly on the bare deck.
Can I use felt instead of ice and water shield?
The code allows two layers of underlayment cemented together as an ice barrier. Almost no one does it that way now. A self adhering membrane is faster, seals around nails and is what manufacturers expect.
Does ice and water shield stop ice dams?
No. It keeps water that backs up behind an ice dam from getting into the house. Stopping the dam itself takes good insulation and ventilation in the attic.
Does my detached garage need it?
The code exempts detached accessory buildings without conditioned floor area. We still recommend it at the eaves and valleys, since the cost is small compared with a rotted deck.
Can it be added without replacing the roof?
Not really. The membrane bonds to the deck under the shingles. For a leak at one spot, a roofer can remove a section, install membrane and relay shingles.
If you are not sure what is under your shingles, Bella can take a look. Call (724) 515 5163 for a free inspection or estimate, or learn more about our asphalt roofing work. Schedules fill up before winter, so the sooner you book, the better your odds of getting done before the first hard freeze.