Does Spray Foam Really Void Your Roof Warranty? Here's What the Manufacturers Actually Say

If you've spent much time talking about spray foam on roof decks, you've probably heard some version of this:

“You know that's going to void the roof warranty, right?”

It gets repeated often enough that it has basically become spray foam folklore. Foam the underside of the roof deck, kill the ventilation, void the shingles. End of discussion.

Except it isn't that simple.

I went through the current guidance from several of the major asphalt-shingle manufacturers, and the answers are all over the place. Some manufacturers really do take a hard line against spray foam directly beneath the roof deck. Others leave their manufacturing-defect warranty intact but exclude damage they believe was caused by the unvented assembly. Another reduces the warranty period. Some make a distinction between their basic product warranty and the premium extended warranty the homeowner may have paid extra to receive.

So yes, spray foam can affect the shingle warranty. But the blanket statement that spray foam automatically voids every roof warranty is wrong.

More importantly, the warranty itself probably deserves a little less drama than we tend to give it. The bigger questions on a roof-deck job are still whether the assembly can manage moisture, whether leaks can be detected and repaired, whether the roof is already near the end of its useful life, and whether the foam is appropriate for the climate and construction. The warranty matters, but it is one part of a much bigger roof.

Still, if we're going to change the way a roof assembly works, we ought to know what the company whose name is printed on the shingle bundle has to say about it.

First, What “Roof Warranty” Are We Even Talking About?

Before getting into the manufacturers, it helps to clear up something that gets muddled almost immediately.

There usually isn't one single “roof warranty.”

The shingle manufacturer may provide a limited warranty against manufacturing defects. The roofing contractor may provide a separate workmanship warranty. A homeowner may also have an enhanced or system warranty that was purchased or earned by using a certified installer and a specific combination of roofing products.

Those are different things.

For this article, we're primarily talking about the shingle manufacturer's warranty. If a roofer gives the homeowner a ten-year workmanship guarantee and that contractor's agreement says modifying the attic ventilation voids their guarantee, that is a separate issue and needs to be handled with the roofer.

The manufacturer's warranty is also not a promise that a “lifetime” shingle will perform perfectly for the rest of the homeowner's life. These warranties are generally centered on manufacturing defects, with varying periods of non-prorated and prorated coverage and plenty of exclusions for things outside the manufacturer's control. IKO, for example, explicitly says its warranty periods are not guarantees of the useful life of the shingles and limits its basic coverage to manufacturing defects that significantly affect water-shedding performance. Owens Corning likewise describes its standard warranty as product-defect coverage.

That makes the real question a little different.

It isn't simply, “Do I still have a warranty?”

It is, “If something happens to this roof later, what will the manufacturer actually agree to cover?”

That answer is much more useful.

Is This Really Something Contractors Need to Worry About?

Yes—but probably not for the reason the warning makes it sound like.

If you're spraying underneath a fifteen-year-old roof with a basic prorated shingle warranty, the practical value of that warranty may be very different from a brand-new roof where the homeowner just paid for a premium roofing system and an enhanced warranty.

The warranty question matters most when there is something meaningful to preserve.

It also matters because roof problems get expensive quickly, and nobody wants to find out after a problem occurs that the homeowner, roofer, builder, and foam contractor all had different assumptions going into the job.

Imagine a roof develops premature shingle problems several years after the attic was converted to an unvented assembly. The shingle manufacturer says the problem was related to the roof assembly. The roofer points at the spray foam. The homeowner says nobody ever mentioned the warranty.

At that point, whether the foam actually caused the failure is only part of the argument. Your work is now sitting right in the middle of somebody else's roofing claim.

That is the reason contractors should care. Not because a shingle warranty should dictate every insulation decision, but because if you're changing the roof assembly, it is better to know about the manufacturer's position before the foam is stuck to the decking.

Code-Compliant and Warrantied Are Two Different Things

This part is important because the warranty discussion sometimes gets twisted into an argument that spray foam simply does not belong under a roof deck.

That isn't true either.

Unvented conditioned attics with spray foam installed at the underside of the roof deck are recognized building assemblies. DOE's Building America guidance specifically discusses both open-cell and closed-cell spray foam used this way and describes properly designed unvented conditioned attics as potentially resilient, durable, and efficient across climate zones.

The fact that a shingle manufacturer may dislike that assembly does not suddenly make the assembly illegal or bad building science.

The building code answers one question.

The shingle warranty answers another.

A roof can be designed correctly, meet the adopted code, manage moisture properly, and still fall outside a particular manufacturer's preferred warranty conditions.

The manufacturer gets to decide what it wants to warranty. That does not make its warranty document the building code.

So What Do the Manufacturers Actually Say?

This is where the blanket answer falls apart.

GAF: No, the Warranty Does Not Automatically Disappear

GAF is probably the easiest place to show why the word void is so often misleading.

Its current technical bulletin asks the question directly: Will sprayed-in-place foam insulation void the warranty?

GAF says no. Its Shingle Limited Warranty against manufacturing defects remains in effect.

But there is a pretty important second half to that answer: GAF excludes damage to the shingles that it attributes to spray foam applied directly to the roof deck or to a lack of ventilation.

So if the shingles themselves have a legitimate manufacturing defect unrelated to the attic assembly, the existence of spray foam does not automatically erase the warranty.

If GAF believes the damage resulted from the foam or from the unvented roof, that damage is outside its responsibility.

That's considerably different from saying, “Your warranty is void.”

It is also considerably different from saying, “Don't worry about it, your warranty is fine.”

Both answers leave out the part that actually matters.

Owens Corning: The Basic Warranty May Survive, but the Better Warranty May Not

Owens Corning takes a somewhat similar position with its standard coverage, but there is an extra wrinkle.

Its current technical bulletin says the Standard Limited Warranty and Total Protection Roofing System Warranty do not cover damage caused by improper or inadequate ventilation, unvented attics, or enclosed rafter assemblies. If Owens Corning determines that the shingle damage was caused exclusively by a manufacturing defect unrelated to the ventilation issue, full warranty coverage can still apply.

Then you get to the extended warranties.

Owens Corning says its System Protection, Preferred Protection, and Platinum Protection extended warranties require a fully ventilated roof system. Unvented attics, enclosed rafter assemblies, and sealed decks with spray foam or other insulation applied directly against the underside of the deck do not qualify.

That distinction matters much more on a new roof.

A homeowner may still have basic protection against a manufacturing defect while losing eligibility for the enhanced roofing-system warranty they thought they were getting.

That's worth knowing before the foam goes in.

Malarkey: You Still Have a Warranty

Malarkey may have the most refreshingly simple answer of the group.

Its own FAQ asks what happens if spray foam is installed between the rafters directly against the underside of the sheathing. Malarkey explains that this creates an unventilated roofing assembly if no ventilation cavity is provided, but then says plainly that the homeowner still has a warranty.

Problems resulting from the lack of ventilation are excluded.

Again, the warranty did not disappear.

The manufacturer's responsibility simply became narrower.

Atlas: This Is the One Everyone Is Thinking Of

Atlas is different.

Atlas says directly that it does not warranty its shingles when spray foam is applied against the underside of the roof deck. Its installation instructions are even less ambiguous: spray foam insulation applied directly to the bottom of the decking will void the warranty.

So if somebody tells you that spray foam can void a shingle warranty, Atlas proves the point.

But even Atlas doesn't say that no roof containing spray foam can ever be warrantied. Its guidance allows assemblies where continuous airflow is maintained directly beneath the roof deck. The key is that the actual roof deck remains ventilated rather than having foam bonded directly to it.

With Atlas, the distinction is pretty straightforward: direct foam against the deck is the problem.

TAMKO: The Exclusion Is Written Right Into the Warranty Language

TAMKO also takes a firm position.

Its technical notice acknowledges that spray foam under roof decks is a recognized method of constructing an unvented roof assembly and even discusses using baffles when a contractor wants to maintain soffit-to-ridge ventilation. But when it gets to the warranty, TAMKO cites its exclusion for shingles installed over roof decks with polyurethane foam applied to the underside.

That's not something a foam contractor should try to explain away.

If TAMKO shingles are on the roof and the warranty matters to the owner, TAMKO's position is the one that matters.

Whether another manufacturer is perfectly comfortable with the assembly is irrelevant.

IKO: This Is Why You Read the Whole Warranty

IKO is probably the messiest example, which makes it one of the more interesting ones.

Its current U.S. warranty says shingles installed on insulated, underventilated, or unventilated roof decks have their warranty period reduced to 10 years, with five years of Iron Clad Protection. That reduction specifically includes situations where insulation is installed immediately beneath an acceptable roof deck.

So far, that sounds simple enough.

Then you keep reading.

Elsewhere in the same warranty, IKO excludes damage arising from applications where spray insulation has been applied in the attic space.

That means I would not tell a customer, “IKO gives you a ten-year spray-foam warranty.” That is cleaner than the actual document.

IKO does provide reduced terms for insulated and unventilated roofs, but damage arising from the spray-insulation application can still fall into an exclusion.

This is exactly the kind of thing that gets mangled when a warranty is reduced to one sentence on a Facebook group.

CertainTeed: Be Careful Not to Invent a Rule

CertainTeed is a good example of why I don't like making the manufacturer's position stronger than the manufacturer does.

CertainTeed's current public warranty table says shingles installed on an inadequately ventilated roof deck receive a ten-year warranty and no SureStart coverage.

What that does not automatically tell us is that every properly designed unvented spray-foam roof is considered an “inadequately ventilated roof deck” under CertainTeed's warranty.

Those are not necessarily the same thing.

So rather than turning that language into “CertainTeed voids your warranty if you spray the deck,” the responsible answer is to identify the specific shingle and assembly and get clarification from CertainTeed if preserving the warranty is important.

Sometimes the correct answer really is, “Ask the manufacturer.”

That's better than confidently making one up.

But Doesn't Spray Foam Cook the Shingles?

This is probably the most common explanation given for why shingle manufacturers care about ventilation.

The basic idea makes sense. When you move the insulation and air barrier from the attic floor to the roofline and eliminate traditional attic ventilation, the roof operates somewhat warmer.

The part that gets exaggerated is how much warmer.

Building Science Corporation's guidance says asphalt shingles over an unvented attic typically experience an average temperature increase of only around 2°F to 3°F. Based on the available research, BSC estimates that the change could result in roughly a 10% reduction in useful shingle service life.

Ten percent is worth acknowledging.

It is also a long way from the picture you sometimes hear painted of shingles baking themselves to death because spray foam touched the other side of the plywood.

BSC points out that shingle color and roof orientation have roughly double or triple the effect on durability that vented versus unvented construction does.

In other words, that black west-facing roof may care a lot more about being black and west-facing than it does about whether there is a ridge vent underneath it.

That does not invalidate Atlas's warranty. It does not override TAMKO's exclusion. Manufacturers are allowed to set the conditions under which they will stand behind their products.

It simply means we should separate the warranty policy from the science instead of treating them as the same thing.

The Bigger Roof-Deck Issues Are Somewhere Else

This is also where I think the warranty conversation can distract us from the issues that deserve more attention.

When we spray directly against a roof deck, we are changing how the entire assembly handles heat, air, and moisture. Leak detection becomes different. Drying potential changes. The foam type matters. Climate matters. Indoor humidity matters. The condition of the roof before we spray matters.

DOE's guidance for existing roofs actually recommends inspecting the roofing for deficiencies before installing foam and repairing any existing leaks first. If the roof is at or near the end of its service life, DOE says replacement should be considered before the underside is foamed.

That is a much bigger practical concern to me than whether a fifteen-year-old shingle warranty loses another exclusion.

If the roof already needs replacement, don't bury the underside of it under thousands of dollars' worth of spray foam and pretend the warranty paperwork is the big issue.

Fix the roof first.

For the same reason, whether open-cell or closed-cell belongs against the roof deck deserves far more attention than a generic warranty warning. We covered that in depth in Should You Use Open-Cell Foam on Roof Decks? Here's What Building Science Says.

The warranty matters. The assembly matters more.

What About Leaving a Gap Above the Foam?

This idea comes up often when somebody wants the benefits of insulating the roofline without giving up the manufacturer's ventilation requirements.

It can work—but only if you actually create a ventilated roof assembly.

Leaving an inch or two of random dead space above the foam is not the same thing.

Atlas, for example, requires full flow-through ventilation directly beneath the decking when using this approach. Air needs an intake, an exhaust, and a continuous unobstructed path between them.

That generally means properly installed ventilation baffles or a vented nail-base assembly designed to maintain airflow from the eave to the ridge.

A little hollow space trapped between spray foam and plywood is just a little hollow space trapped between spray foam and plywood.

It does not magically become ventilation because we gave it a name.

Open-Cell vs. Closed-Cell Does Not Automatically Change the Warranty

Foam contractors naturally want to know whether closed-cell gets treated differently from open-cell.

From a building-science standpoint, absolutely. Open-cell and closed-cell foam handle vapor very differently, and that can have major implications at a roof deck.

From the shingle manufacturer's standpoint, not necessarily.

Atlas refers broadly to spray foam applied directly beneath the decking. TAMKO refers to polyurethane foam. GAF's bulletin addresses sprayed-in-place foam insulation. Owens Corning addresses spray foam or other insulation applied directly against the deck.

So switching from open-cell to closed-cell does not automatically solve the shingle-warranty question.

It may solve a vapor-control problem.

That's a different problem.

Existing Roof? Make Sure You're Reading the Right Warranty

There is one more thing that is easy to overlook on retrofit work.

The current warranty on the manufacturer's website may not be the warranty that applies to the roof you're standing underneath.

IKO's current U.S. warranty, for example, specifically says it applies to shingles installed on or after February 1, 2025 and that the warranty in effect when the shingles were installed is the one that applies. Owens Corning similarly tells homeowners that coverage is based on the warranty in effect when their shingles were installed and provides a process for requesting older warranty documents.

So if you're foaming a ten-year-old house, don't necessarily grab the 2026 warranty and call the issue settled.

Figure out what shingles are actually on the building and roughly when they were installed.

If preserving that warranty really matters, look up the correct document.

What Should the Foam Contractor Actually Do?

This does not need to turn into a three-hour research project on every estimate.

On new construction, ask the builder or roofer what roofing product is being installed. If the manufacturer has a known restriction against direct-applied spray foam, deal with it before the insulation goes in.

On existing homes, ask the age of the roof. If it is near the end of its service life, that deserves attention regardless of what the warranty says. If the roof is new enough that meaningful warranty coverage may remain, identify the manufacturer before telling the customer anything definitive.

And most importantly, don't guarantee somebody else's warranty.

A foam contractor cannot promise that GAF, Owens Corning, Atlas, TAMKO, IKO, CertainTeed, Malarkey, or the roofer will honor a future claim. That decision belongs to whoever issued the warranty.

There is nothing wrong with telling the customer:

“Spray foam at the roof deck can affect roofing warranty coverage depending on the manufacturer and roof assembly. If maintaining that warranty is important to you, let's verify it before we spray.”

That is accurate, fair, and a whole lot better than either “Don't worry about it” or “You're going to void your roof.”

Final Thoughts

So, does spray foam really void your shingle warranty?

Sometimes.

Atlas says direct-applied foam will void its warranty. TAMKO specifically excludes shingles installed over decks with polyurethane foam underneath. Owens Corning allows standard manufacturing-defect coverage to survive in certain circumstances but excludes direct-foamed unvented assemblies from its extended warranties. GAF and Malarkey leave their basic warranties in place while excluding problems they attribute to the unvented assembly. IKO reduces coverage for insulated and unventilated roofs while separately excluding damage arising from spray-insulation applications. CertainTeed's published language on inadequate ventilation needs more care than simply calling every foamed roof “void.”

That's the real answer.

Not very catchy, but much more useful.

And after digging through all of this, I would not let the shingle warranty be the thing that decides whether a roof deck should be sprayed. There are bigger questions to answer first: Is the existing roof sound? Is it likely to need replacement soon? Is the unvented assembly appropriate for the climate? How will it handle moisture? Which foam are we using? Can the roof dry? What happens when it leaks?

Get those things wrong and a piece of warranty paperwork is going to be pretty far down the list of problems.

But once you decide that foam at the roofline is the right assembly, take the extra few minutes to see whose shingles are sitting on top of it.

We already spend plenty of time reading the technical data sheet on the foam we're about to install.

It probably isn't a bad idea to read the paperwork on the other side of the plywood too.

by Gage Jaeger, Owner and Founder of Foambid