When you look at a finished roof, you see shingles.
But the shingles are only the top layer.
One of the most important protective components can be completely invisible after installation:
Ice and water shield.
IKO describes ice and water protector as a self-adhering waterproof underlayment membrane installed directly on the roof deck in vulnerable locations.
It is designed to give your roof another line of defence when water gets somewhere shingles alone may not be enough.
Why Do Ontario Roofs Need Extra Protection?
Ontario roofing has to deal with:
- Snow
- Ice
- Wind-driven rain
- Freeze-thaw cycles
- Heavy storms
Shingles are designed to shed water downward.
But unusual conditions can force moisture in directions it normally would not travel.
For example, ice dams can cause water to back up underneath shingles.
IKO and GAF both identify self-adhering leak barriers as additional protection against ice dams and wind-driven rain.
Where Is Ice and Water Shield Installed?
Common vulnerable areas include:
- Eaves
- Valleys
- Rake edges
- Around chimneys
- Around roof penetrations
- Around skylights
- Low-slope roof areas
IKO specifically identifies these areas because they experience higher water-intrusion risk.
Local code requirements and roofing-system specifications also matter.
Why Put It at the Eaves?
Ice dams typically form near the colder lower edge of a roof.
Snow melts higher up.
Water travels downward.
Then it refreezes near the eaves.
As the ice builds, additional meltwater can back up underneath shingles.
Ice and water membrane helps protect the roof deck beneath that vulnerable area.
Why Are Valleys Important?
Valleys receive runoff from two roof slopes.
That creates concentrated water flow.
GAF identifies valleys as one of the roof areas where a leak barrier can add protection beneath the shingles.
This component matters even though homeowners never see it once the roof is finished.
Is Ice and Water Shield the Same as Regular Underlayment?
No.
Both sit beneath roofing.
But self-adhering ice and water membranes are specifically designed to create more robust moisture protection in vulnerable areas.
IKO notes that these membranes bond directly to the roof deck and are designed to seal around nail penetrations when properly installed.
Should the Whole Roof Be Covered?
Not automatically.
In some situations, entire-roof coverage may be specified.
But full coverage can also change moisture movement through the assembly, which means attic ventilation becomes particularly important.
IKO specifically cautions homeowners to consider ventilation when using full-roof ice and water membrane coverage.
This is why roof-system design matters more than:
“More waterproofing must always be better.”
Ask What’s Under the Shingles
When comparing roofing quotes, don’t compare only:
- Shingle brand
- Shingle colour
- Price
Ask:
- What underlayment is included?
- Where will ice and water membrane be installed?
- How are valleys protected?
- How are penetrations handled?
- How does the system address Ontario winter conditions?
A Roof Is a System, Not Just a Shingle.
Planning a roof replacement? Envirotech Exteriors can explain the layers beneath your shingles and how the complete system protects your home.