Ice & Water Barrier or Underlayment

I am getting a new roof and want it to be extremely durable, lasting a long time.
The roof size is 26 SQ and about 10 SQ require an Ice & Water Barrier product, such as Certainteed Winterguard.

If I would like the most watertight roof possible, would it make sense to put Ice & Water Barrier on the entire roof area?
After all, it would be watertight, self-sealing around nails, etc. versus an underlayment that is only water-resistant.

What is the upcharge for Ice & Water barrier products over underlayment - how much more would it cost to do the remaining 16 SQ with Ice & Water barrier (i.e. Certainteed Winterguard) instead of underlayment (felt or synthetic)?

What Ice & Water barrier products do you recommend?

Thanks for your help and recommendations!!

The Ice Guard is about $50.00/sq, less to your roofer. Make sure you have roof vents if you completely cover your roof with that product. Yes, it does give you a long lasting underlayment that will protect your roof for many, many years. I recommend MFM Wind and Water Ultra.

If your going to use a granulated product like winterguard, you should cover it with another layer of synthetic or felt.
The problem with the granular ice and water is that the shingles stick to it, so when your roof eventually has to be replaced, there’s little they can do but either scrape it or replace all the wood.
The second layer of underlay will prevent that.

Full ice and water will not extend the life of your roof, so unless you live in a hurricane zone it isn’t really beneficial.


3 to 4 hundred dollar difference. (For me)
Good felt- 100$
Best felt - 200$
Synthetic - 100$
Best synthetic 200$
Ice and water shield 500$

Nice piece of mind for a small roof.
And can really make up the difference if there is any sloppy workmanship roofers on the crew.

Absolutely full ice and water shield will extend the life of your roof. It is a secondary water barrier.

My favorites are Atlas, resisto, polyglass ir-x,
Tarco m300.
These are my favorite because they tend to have the least wrinkling And also easy removal of its release film/plastic.
Resisto and polyglass being most favorite.

I agree that ice and water shield presents big problems for the next roofer.
And installing a cheap synthetic over it solves the issue.
I will be charging big money to remove roofs in the future that have full ice and water shield
Or refuse to do the job at all.

Patchup, which ones are you comfortable with,
That you think the shingles wont permanently stick?
The Owens Corning is smooth but it wrinkles terribly. I do like its multi direction installation
But it doesnt like to stay flat…

Now if the decking doesnt have to be renailed
And you can leave the existing underlayment
Installing ice and water shield over the old underlayment is great.
No problems for the next roof removal.

Whenever I’m stripping ice and water, it seems that some brands stick sometimes and other times they don’t.
I think the smooth surface stuff should be better, but I have had to strip shingles off grace that were stuck as bad as the cheap stuff.
I don’t think there’s a good solution other than cover it up.
I don’t think full coverage of I/w will extend the life of the roof,most roofs I replace aren’t leaking theyre either blowing off or the shingles are rotting away. Most leaks occur around details,where Ice and water is less effective

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Another issue I’ve seen with full I+W coverage is moisture damage to the underside of the decking from sweating. Mostly on homes where there was inadequate venting due to design (hip roof) or blocked intake vents.


While it won’t make the shingles last longer it does give you continuing protection against leaks IF your shingles blow off or are damaged by the environment. Once again, DO vent your roof. It is not only good for this system, but it is good for any pitched roof system.


IMO full self adhered ice and water shield is a mistake. Eventually all roof decks need renailing/repair/replacement and this makes it extremely difficult to find rafters for removal and repair of new decking. Can also create moisture retention problems even on properly vented roofs depending on the configuration. Def not a compensation for poor workmanship and does nothing to extend the life span of any roofing material IMO. Ice and water shield at eaves(12” past inside wall minimum depending if in snow/ice area and local codes) and in all valleys and put any other money into a quality shingle/underlayment and even more so a knowledgeable installer.


No one said ice and water shield extends the life of your shingles.
It does extend the life of your roof.
A roof is a system together, not just Shingles.

If it doesnt work, why do you put it at your eves and valley?

Why do government codes demand it??

It is not code to put it in the valley!!!
So why do you do it?
Hahahaha. I know why…

Why do insurance companies give you a major discount on your home owners insurance for installing it?
You think they like giving up thousands of dollars for nothing?
It is because they know their investment is
Better protected.

IMO ice & water shield over the entire roof is a complete waste of resources with the exception of metal and tile roofs.

There is absolutely no need for Ice & water shield in warm climates at all, not in the valleys, the eaves or anywhere else.

It is code because of politics.

IMO a roofer that is recommending ice & water shield over the entire roof is inexperienced and doesn’t truly understand their trade.

Provided there is adequate functioning ventilation full ice and water shield will cause no harm.

If the ventilation system is non-existent or not functioning properly there may be big problems with condensation, mold, & rot.

Using ice and water shield with electro galvanized nails accomplishes nothing in a situation where the ice & water shield is actually needed, the cheap nails rust out in 5-7 yrs of constant ice damming.

Do these advocates for full ice & water shield also use hot dipped or better fasteners?

If they don’t that again demonstrates that they just don’t fully grasp their trade and what is important and what is not.


Ice/water shield is not ice/water shield when installed any way other than direct deck. I agree it is wasteful in many applications and just a gimmicky selling point but why even install over existing underlayment? It won’t even seal the nails.
One area I do think it is useful in any climate is valleys with potential leaf debris, especially if owner isn’t maintaining the roof.

@ Northstar99

Appreciate your advice!
If I should use the best shingles and underlayment instead of ice&water barrier, which products would you recommend.
I plan on using Landmark Pro and Certainteed Diamond Deck.
Are there alternatives that would be a step up regarding durability? (My contractor is Certainteed certified, so I would prefer using Certainteed shingles).

Oh you are so right Axiom.
It IS politics!!
I agree no ice and water shield is necesary anywhere.

Shingle companies Warranty shingles down to a 2/12 if certain conditions are met.
The government And the shingle companies demand that under a 4/12 must have ice and water shield or two plys of d.226 underlayment…
And then the government goes even further and demands that the d.226 underlayment has 10 million fasteners in it.

Well trust me, full ice and water shield with no fasteners through it
Is ten times more water tight than 2ply d.226 undetlayment with 10 million fastenerss blown through it.
Especially on 1x decking roofs!!!
Its almost suicide especially with these guys putting on 2 ply synthetics.
They cant figure out why their roofs are leaking.

the government demands i do one or the other.
It is not my choice.
Yes, it should be repealed!!!
How dare the government tell us how to do our job!!!

By the way, i always talk the homeowner out of using ice and water shiled over a 4/12.
And never is there used on any eve, valley.

But under 4/12 is different.
And i happen to agree that extra measures have to be taken!.

The problem is… the ten million fasteners i am required to penetrate the 2/ply by the government.
They have forced my 2/ply into shit with the ten million fasteners hitting into splits sides of wood, hitting air spaces everywhere.

Before the law, i always hand nailed the underlayment.
We would know we missed the wood and correct the issue on the spot.
But now with the law…
You will wear your wrist out hand nailing ten million fasteners.
So we have to use a gun
And it is impossible to tell you hit an air space with the simplex gun…

So for these reasons, i use full ice and water shield below 4/12s
Because i want my customers roofs water tight.
No guessing and sleepless nights about how many of the ten million fasteners hit into air spaces.

If YOU were subject to this law,
You would do the same thing.
You are not subject to this law.

Simonsays, What is the exact pitch of your roof?
Critical information when discussing which underlayment to use.

Sorry - the roof pitch is 8/12.
Also, if it’s relevant: We are in a spot that gets pretty high winds.

Thank you

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Landmark Pro is a great shingle and will work just fine. As far as an underlayment goes any decent synthetic will do just fine. A higher quality one is preferable on roof slopes that require better traction and any slope that has to be left exposed overnight but this will be an installer preference. Dont have the Diamond Deck available here and Nova Seal by Intertek is the best ive come across. Expensive though.

Once the shingles are installed the quality of the underlay is a non issue IMO. Roofs have been installed with just #15 felt for a 100 years with no issues. Make sure the intake/ventilation setup is adequate and you will have no problems.
Good luck with your project.

High wind nailing (6 nails per shingle) would also be a good idea in a wind location. Proper sealing of the shingles is also very important. Hard to accomplish this time of year depending where your located. -32 celsius here this morning!

I recomend GAF tiger paw for an 8/12.