Is waterproof underlay needed?

Hi, I am having a shingle roof installed, 2 companies use waterproof type underlay over the entire roof with ice shield at the eves and metal valleys, the other cheaper company is only using ice shield at the eves, no metal valley, shingles overlapping at valleys. Should I use one of the more expensive companies or is the cheaper one doing things correctly? I live in southern Ontario and our winters can be quite bad. I am a single female so any advice you could give me…Thanks

Most states in the U.S. underlayment is not required for new residential construction believe it or not. When you remove & replace an existing roof then it is require. Since you live in Canada well within the snow belt I’d have to recommend going with the better underlayments if you plan on keeping the home. B/T/W, What is the slope of your roof? Is it real steep or not so much? If its real steep 3 feet of ice & watershield should be proficient. Less steep go with 6 feet, walkable go with 9 feet or more.

Thanks for your input, it is a fairly steep roof

From what I gather in parts of Canada it is common practice not to use and underlayment.

From most manufacturers standpoint an underlayment is not required but is recommended.

A felt underlayment is what gives your asphalt roof it’s fire rating.

The underlayment protects the structure during the re-roofing process should it take more than a single day.

In the event that you have some strong winds or other incident that causes the loss of a few shingles or more the underlayment will keep water out of the structure until repairs can be made.

In most cold areas in America an ice & water shield membrane is required to be installed over heated portions of the structure by our building codes.

The code is usually 2’ beyond the interior wall line, many roofing companies just use 2 courses to achieve this, sometimes more is required.

So your roofing company should be using the ice & water shield on the eaves as described, in the valleys, and around skylights at a minimum.

They should at the minimum cover the remainder of the roof with at least a #15 felt underlayment, many have gone to a synthetic underlayment instead.

IMO to cover the entire roof with Ice & water shield is overkill and a waste of resources that could be better spent elsewhere.

Sometimes people refer to synthetic underlayments as a waterproof underlayment, so your question is unclear as to exactly what your roofers mean by “water proof” underlayment.

In short, yes good roofers use underlayments, there are different types for different areas of the roof.

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Hi, it is a synthetic underlay that is apparently waterproof

I do like the synthetic underlayment instead of felt/tar paper. You still need ice & watershield installed in the needed areas.

I roof in Canada, and we use underlay on every single job. Approximately 80% Felt and 20 % Synthetics.

Do you NEED synthetic underlay? NO
As Axiom said, it’s great for keeping a building dry during the roofing process.
Felt works just fine to stop any wind blown rain or snow. I am still pulling roofs off that have functioning felt underneath.
We put I&W on some roofs, but not many, it’s really not necessary in my area (Interior BC). It’s a great product to stop ice damming, which we don’t see here.
And you definitely don’t need I&W on your entire roof.

Regardless of the type of underlayment, once the shingles are installed and a million nail holes are put through the underlayment. NONE of it is “WaterPROOF”.

This fancy “waterproof” underlayment of the new modern era is nothing more than an extra product for roofing supply manufacturers to profit from.

But if your a really bad roofer then I guess it would be to your advantage since you can’t keep the water on TOP of the shingles!

The shingles, flashing, etc. all has to be done right irregardless of the underlayment.

I to roof in Canada and haven’t did a job without underlay for probably 20yrs. Before that it wasnt required on the whole roof just the eave. I mostly use felt,do to price, but have discovered a cheap synthetic,that is equal to 15#. and costs the same. Its made by Interwrap,you should check it out boys. “RhinoRoof Synthetic Roofing Underlayment”

Definitely go with the underlayment. We use the ice shield too here in Westchester NY, great product we get from GAF. It is a little bit of an upgrade over the tar paper, but worth the money in areas where there is a cold climate. Definitely use an underlayment even if its just the traditional black roof underlayment. If you have any questions you can contact us

Thanks for everyone’s input, I really appreciate it and needed it. I am going with the mid priced roofer that uses underlayment

Hi underlayment was used when shingles were organic. It helped preserve the shingle as the shingle would accept moisture that would wick up from condensation and curl, thus it prolonged the life of the shingle and gave extra warranty. Nearly all shingles put on today as of 2017 are synthetic.
In Alberta we need to be 18 inches inside wall measurement with ice Shield. There are other minimum code applications but not many use them.
For the last few years I have been applying CertainTeed shingles. I always apply six nails per shingle and have never had a blow off. We have had huge wind storms I’ve done many many repairs with other types of shingles and every single one of them had underlayment on them. Scam artists will try to sell underlayment and say that it’s for a fire rating which sort of his true and it is a secondary waterproofing element this is crap. Most of the times in a windstorm this underlayment comes off with the shingle that came off or shingles that came off. You see the shingles stick to the underlayment they don’t stick to the deck of the roof. so if you kind of put your hand on your shirt on your belly and put the shirt between your fingers and lift, that’s the effect of shingles sticking to underlayment. if you had glue on your hand it would pull off the shirt. if you had glue on your hand and no shirt it would stick to you belly. right. same thing as your roof.
Soooo, buy the best quality shingles, for me Certainteed brand. Have applicator 6 nail ice Shield ice exposed areas. And don’t underlayment above a 3 pitch. You will have a great roof. Also have them caulk under leading edges of venting.

And don’t underlayment above a 3 pitch. You will have a great roof"

Hahaha, no you wont.