Welcome back to our exciting Professional Roofers blog all about the important technical components that make up a roofing system. We, at Professional Roofers, want all of our clients and potential clients to feel as though they are on equal footing with us, and to understand all that technical ‘jargon’ we construction professionals tend to throw around, which is why we decided to focus our last few blogs and new few to all the important components that make up a roof. If you’ve missed our last few blogs, check them out, as there is certainly some great information in there!

This time, we have decided to discuss ‘underlayment’, an important component in any roofing system. The underlayment on a roof is a membrane that is applied to the plywood or ‘deck’ of your roof as an extra layer of water penetration protection before your shingles are installed. Think of it like saran wrap, just one more layer of protection. Underlayment looks an awful lot like a long thin tarp that is placed beneath your shingles; however, it is traditionally made of heavy black felt paper that has a layer of asphalt on its surface, which is placed there to help bond your shingles to it. With that said, just like any technology in the past several decades, underlayment has made advancements as well. These days, the black felt variety is no longer your only option, with several advanced synthetic variations available as well. These synthetic membranes can have a much higher performance than the felt variety in severe weather conditions, or can be matched to work better with specific roofing materials.


There is also another form of underlayment on the market that is particularly important in the Toronto region, where ice, snow, and severe rainstorms are common occurrences – ice and water protectors. This rubberized variety will be used along with the regular felt variety to provide great protection against ice and water. It is an extra-tough membrane that should be used around ‘critical’ areas of your home, where it is more likely that ice may form dams or water may penetrate in like your roof valleys, around skylights, or around chimneys.

Underlayment isn’t always necessary, but should be applied to low-sloped roofs, as well as specific high water risk areas of your home. It can also help improve the fire resistance of your home. If you have a low-sloped roof that requires a layer of underlayment, the membrane will be applied in long, overlapping strips that act as a secondary barrier against water penetration to your roof. These strips not only protect the joints and seams between plywood pieces on your roof decking from water damage, but they also form a seal around nails that are used during shingle installation, preventing leaks in that respect. Ice and water protector shields are sticky and cannot be moved once applied, unlike the regular felt variations. The membrane strips are also breathable, allowing your decking to release internal moisture and condensation that may have built up from within the home as well.

In short, underlayment is another key component of your Toronto roofing system. We hope you’ve enjoyed our latest Professional Roofers blog, and can’t wait to share a new technical component with you next time!

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