Ice and water shield on a roof is the one layer most homeowners never see and the one layer that decides whether a Pittsburgh winter ends with a dry ceiling or a stained one. It is a self adhering, rubberized asphalt membrane that sticks directly to the roof deck under the shingles at the eaves, in the valleys and around every chimney, skylight and vent. We install it on every roof replacement in Pittsburgh because the North Hills, the river towns and the city itself all share the same problem: snow that melts, refreezes at the roof edge and backs water up under the shingles. This guide covers what it is, where it goes, what Pennsylvania code requires, how it compares to regular underlayment and when the whole roof should be covered.
What Is Ice and Water Shield?
Ice and water shield is a peel and stick roofing underlayment. The bottom face is a rubberized asphalt compound that bonds to the wood decking; the top face is a smooth film or a granular surface that gives the crew traction. Manufacturers call it a leak barrier or ice barrier, and Pittsburgh roofers call it ice guard, moisture guard or simply ice and water. It is all the same category of product.
Two properties set it apart from felt or synthetic underlayment. It is waterproof rather than water resistant, so it stops water that sits on it, which is exactly what happens behind an ice dam. And it seals around every shingle nail that passes through it, so nail holes do not become leak paths.
On a complete Atlas roof system we use Atlas ice and water underlayment with Atlas shingles and ventilation, which is what lets us offer the Atlas 50 year warranty as an AtlasPro+ Platinum Select contractor. Specifications are on the Atlas ice and water underlayment page.
Why Ice Dams Are a Pittsburgh Problem
An ice dam forms when heat escaping from the house melts snow on the upper roof. The meltwater runs down to the eave, which hangs past the heated wall and stays below freezing, and it refreezes there. Each cycle adds ice until a ridge forms along the gutter line. Water from the next melt pools behind it, climbs under the shingles and finds the nail holes and seams in ordinary underlayment.
Pittsburgh gives this process everything it needs. Our winters rarely stay frozen for weeks. We get snow, a few days above freezing, rain on snow, then a hard freeze, over and over from December into March. Add the local housing stock and the risk goes up again:
- Older homes with shallow attics. Brick foursquares in Bellevue, Ben Avon and Observatory Hill and the frame homes in West View and Ross Township often have little insulation at the eaves, so the roof edge is the coldest part of the roof and the ridge is the warmest.
- Low slope additions and porch roofs. Many Pittsburgh homes have a 2/12 or 3/12 pitch over a back addition or a front porch. Water drains slowly on these roofs and ice dams form fast.
The damage shows up as brown stains on the ceiling near an exterior wall, wet insulation, rotted fascia and eventually rotted decking at the eave. Our roof repair crews see it every spring on roofs installed with felt only.
Where Ice and Water Shield Goes on a Roof
On a standard shingle roof it goes where water is most likely to sit or be driven uphill:
- Eaves. From the drip edge up the slope far enough to pass the exterior wall line by at least 24 inches. On a home with a deep overhang or a low pitch that usually means two courses of membrane rather than one.
- Valleys. A full width run centered in every valley before the field underlayment is lapped over it.
- Penetrations. Around chimneys, plumbing vents, attic fans, skylights and satellite mounts, lapped so water runs over the seam rather than into it.
- Sidewalls and headwalls. Where a roof meets a vertical wall, such as a dormer or a second story wall, the membrane turns up the wall behind the step flashing.
- Pitch changes. Where a steep slope drops onto a shallow one, as on a gambrel or a porch roof.
Synthetic underlayment covers the rest of the deck, lapped over the top edge of the membrane so every seam sheds water downhill.
What Pennsylvania Building Code Requires
Pennsylvania enforces the International Residential Code through the Uniform Construction Code, and Allegheny County municipalities issue roofing permits under it. Section R905.1.2 of the IRC requires an ice barrier wherever there is a history of ice forming along the eaves and causing water to back up. The barrier must be either two layers of underlayment cemented together or a self adhering polymer modified bitumen sheet, and it must run from the lowest edge of the roof to a point at least 24 inches inside the exterior wall line of the building. You can read the section text at the International Code Council.
The code sets a floor, not a ceiling. Valleys and penetrations are not covered by that sentence, so a contractor who installs ice and water shield at the eaves only is meeting code while leaving the most common leak points unprotected.
Manufacturer warranties add a second layer of requirements. Atlas, Owens Corning, GAF and CertainTeed all call for a leak barrier at the eaves and in the valleys in their installation instructions. Skip it and the shingle warranty may not pay a claim.
Ice and Water Shield vs. Synthetic Underlayment vs. Felt
| Underlayment | How it handles water | Seals around nails | Where we use it |
|---|---|---|---|
| Ice and water shield | Waterproof, stops standing water | Yes | Eaves, valleys, penetrations, walls, low slopes |
| Synthetic underlayment | Water resistant, sheds running water | No | The open field of a shingle roof |
| 15 or 30 pound felt | Water resistant, absorbs and wrinkles when wet | No | Not used on our installations |
Felt is what we find under most Pittsburgh roofs installed before about 2010. It tears in wind, buckles when wet and offers nothing at the nail holes. Synthetic underlayment is a real improvement in the field of the roof, but it still only sheds water. Ice and water shield is the only one of the three that keeps water out when the water is not moving.
Types of Ice and Water Shield
There are three common types, and the right one depends on the roof surface above it.
- Granular surface. The most common type. The gritty top face gives the crew footing and lets the shingle adhesive bond. We use it at eaves and valleys under asphalt shingles.
- Smooth surface. Thinner and more flexible, easier to form around pipes and corners, and used for full coverage on low slope sections.
- High temperature. Built to stay stable under standing seam and metal roofing, which runs much hotter than shingles in summer. Standard membrane can soften and bleed under a metal panel, so the high temperature product is required under metal on every roof we install.
Should You Put Ice and Water Shield on the Entire Roof?
This is the question we hear most often, and the honest answer is that it depends on the roof.
Full coverage makes sense when:
- The pitch is 4/12 or lower. Water drains slowly on shallow roofs and shingle manufacturers call for a fully adhered underlayment on anything under 4/12.
- The roof is small and chopped up, with many valleys, dormers and penetrations, so that the protected areas would cover most of the deck anyway.
- A metal roof is going on, since high temperature membrane is already required under the panels.
- The attic cannot be insulated or ventilated properly, as with a finished attic bedroom under a 1920s roof, and ice dams are a yearly event.
Standard coverage makes sense on a simple gable or hip roof at 6/12 or steeper with balanced soffit and ridge ventilation, where water moves fast and the field of the roof is not where leaks start.
One detail matters here. Ice and water shield is a vapor retarder, so a fully covered deck can no longer dry to the outside and attic ventilation has to be right. We check soffit intake and ridge exhaust on every estimate and will not recommend full coverage on a roof that cannot breathe.
Ice and Water Shield Only Works With Good Ventilation
Ice and water shield keeps backed up water out of the house, but it does nothing to stop the ice dam from forming. That job belongs to attic insulation, balanced intake at the soffit and exhaust at the ridge, and gutters that drain. New vented soffit and fascia is often the missing piece on older North Hills homes, and our 5 and 6 inch seamless gutters are sized to the roof so meltwater moves instead of sitting. When those are right the membrane is rarely tested. When one is wrong, the membrane is what saves the ceiling.
How Ice and Water Shield Affects the Cost of a New Roof
We do not quote prices in a blog post because every roof is different, but the underlayment portion of an estimate is driven by the linear feet of eave and valley, how many courses the eave needs to clear the 24 inch wall line, the number of penetrations and sidewalls, whether metal roofing requires high temperature membrane and whether any low slope sections call for full coverage. On our estimates the ice and water shield is a standard line, not an upgrade. If you want to spread the project over time, our financing options are explained on the site.
Frequently Asked Questions
What is ice and water shield on a roof?
It is a self adhering, rubberized asphalt membrane that bonds directly to the roof deck under the shingles. Unlike felt or synthetic underlayment it is fully waterproof and seals around every nail that passes through it. It is installed at the eaves, in the valleys and around chimneys, skylights and vents, the places where water backs up or is driven under the shingles.
Is ice and water shield required in Pennsylvania?
Yes at the eaves. Pennsylvania adopts the International Residential Code, and section R905.1.2 requires an ice barrier from the roof edge to at least 24 inches inside the exterior wall line in areas with a history of ice dams, which includes all of Allegheny, Butler and Beaver counties. Valleys and penetrations are covered by manufacturer instructions rather than the code sentence, and we protect them anyway.
Can you put shingles directly on ice and water shield?
Yes. It is designed to sit directly under asphalt shingles, and granular surface products let the shingle adhesive strip bond to them. What you cannot do is leave the membrane exposed as a finished roof. It is not rated for sunlight and breaks down within weeks unless it is covered by shingles, metal or another roofing material.
Should ice and water shield cover the whole roof?
Not on most Pittsburgh shingle roofs. Full coverage is the right call on pitches of 4/12 and lower, under metal roofing and on roofs with so many valleys and dormers that the protected zones already cover most of the deck. On a simple, steeper roof with balanced ventilation, ice and water shield at the eaves, valleys and penetrations with synthetic underlayment in the field is the better system.
How long does ice and water shield last?
As long as the roof above it. The shingles protect the membrane from sunlight, so it does not weather the way the roof surface does. When the shingles are replaced, the old membrane comes off with them and new membrane goes down on the deck. Installed in the right places, it should not need attention for the life of the shingles.
Does ice and water shield stop ice dams?
No. It stops the water behind an ice dam from getting into the house, which is a different job. Ice dams are prevented by attic insulation, balanced ventilation and gutters that drain. The membrane is the backup that protects the decking and ceilings when the ice dam forms anyway, which in a Pittsburgh winter it eventually will.
Get a Written Estimate for a Roof That Is Ready for Winter
Malick Brothers Exteriors is a family owned roofing company founded in 2022 by Ryan Malick, based at 500 Perry Highway in West View, BBB A+ accredited and registered with Pennsylvania as home improvement contractor PA174918. We install ice and water shield at every eave, valley and penetration on every roof we replace, and we roof all winter. If you have seen stains along an exterior wall after a thaw, we will check the eaves and attic and give you a free written estimate with every layer spelled out. Contact Malick Brothers Exteriors to schedule your roof inspection.
