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Foam Set vs Mortar Set Tile Roof: Which Holds Up in Florida Wind?

In a foam set vs mortar set tile roof, foam set tile is stuck down with polyurethane foam paddies and mortar set tile is bedded in cement mortar. After Hurricane Charley, investigators found mortar set roofs lost far more tile than foam or fastened roofs. Foam still fails when too little is used, so workmanship matters.

By Josh Hildebrand, owner of Coastline Roofing · Florida license CCC1331076 ·

Your tile roof is only as secure as whatever glues or fastens each tile down. Here is how foam, mortar and fasteners compare, and what to ask a roofer.

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The basics

What is the difference between foam set and mortar set tile?

Foam set tile is stuck down with paddies of polyurethane foam adhesive. Mortar set tile is bedded in cement mortar. A third method uses nails or screws through holes in the tile.

Every tile on a roof has to be held down. The Florida Division of Emergency Management describes the three main systems this way. Mortar set tile sits in paddies (blobs) of mortar that glue it to the underlayment. Adhesive set tile sits in paddies of foam adhesive that glue it to the underlayment. Mechanically attached tile is fastened to the deck with nails or screws through holes cast into the tile.

The FRSA-TRI Florida High Wind Concrete and Clay Tile Installation Manual (7th Edition, effective December 31, 2023) is the main trade guide here. It says field tile can be secured with nails, screws, foam adhesive or mortar. It requires factory premixed, bagged mortar with a Florida product approval, and says job site mixed mortar may only be used for looks and for weather blocking (sealing the edges). Foam systems also need a Florida product approval, so the roofer must follow the foam maker's instructions.

Who this affects: anyone with a tile roof, especially an older one. The state agency says older installations typically used mortar at the hips, ridges and eaves. When it matters: before a re-roof, after a storm, and when a roofer quotes a new tile roof. Where: wind decides it, and Florida's Gulf Coast gets hit by hurricanes. For a bigger picture, see wind lifted roof tiles in Florida.

Not sure how your tile is attached?

Josh usually flies a drone over a tile roof first, so you can see the hips, ridges and eaves in a written photo report without anyone walking on the tile. Coastline Roofing works all over Florida (license CCC1331076).

Call (941) 896-7793 or text your town and a photo.

Side by side

Foam set vs mortar set tile roof: how do they compare?

Mortar set did worst in the storm studies. Foam and fasteners did better when done right. All three can fail from bad workmanship.

Foam set, mortar set and mechanically attached tile compared
QuestionFoam set (adhesive)Mortar setMechanical (nails or screws)
How it holdsPolyurethane foam paddies bond tile to underlaymentMortar paddies bond tile to underlaymentFasteners go into the deck through the tile
Storm recordAfter Charley, roofs installed after the 1997 code revisions with foam or fasteners had a much higher survival rate (JLC and FEMA)Largest blow off areas after Charley and the other 2004 storms (NRCA's Professional Roofing)Better survival, but too few or the wrong fasteners caused failures (JLC)
Common failureToo little foam or foam in the wrong placeBond breaks between mortar, underlayment and tileToo few fasteners, wrong type, or tile working off the nail head
Florida manual rulesNeeds a product approval. Fasteners also needed on steeper slopesPremixed, bagged mortar with product approvalNail and screw sizes and corrosion rules in the manual
Effect of walking on the roofTile can still crack under footWalking can break the mortar bond (Florida Division of Emergency Management)Tile can still crack under foot

The same state agency says investigations of hurricane damage suggest mortar set systems perform worst, while the other systems perform better as long as the maker's high wind instructions are followed, hip and ridge tiles are attached to ridge boards, the eave tiles have better anchorage and the roof is not hit by debris.

FEMA's 2005 Home Builder's Guide to Coastal Construction recommends mechanical attachment instead of mortar in all high wind areas, JLC reports, and the Institute for Business and Home Safety has never approved a mortar set roof for its Fortified program. These are recommendations from agencies and industry groups, not rules every roof must follow.

Where tile lets go

Where do tile roofs fail first, and why?

Wind finds the edges, then the field. Mortar ages. Foam depends on the person who set it.

Hips and ridges

The Florida Division of Emergency Management says older roofs often used mortar here, and those tiles blow off first, as gusts exceed about 80 to 90 mph. Mortar here can crack or leave a hollow cavity. NRCA's Professional Roofing found hip and ridge tiles failed often, even in lower wind areas.

The first row at the eaves

The same agency says widespread damage to the first row of tiles at the eaves tends to occur as gusts pass about 100 mph. Eave tiles can get extra anchorage with a second fastener or a larger foam paddy.

Too little foam

JLC reports that some foam roofs failed because installers used too little foam or placed it in the wrong spot. Foam is not magic. A good roof depends on paddy size, position and a clean bond to the underlayment.

Mortar that has aged

Mortar weakens over time, and tile set in it can blow off, JLC reports. A roof that looks fine from the ground may have cracked or empty mortar beds under the edges.

Flying debris

The FRSA says broken tile usually results from debris impact rather than wind uplift, and that its two inch lift figure is not a code rule for replacement. See cracked roof tile: repair or replace.

Mixed systems

The FRSA-TRI manual warns against mixing systems, because mismatched attachments and weather blocks can shorten the life of a tile roof. A tile roof repaired by different crews over the years may have several systems on one slope.

What to check

How can you tell if your tile roof is foam set or mortar set?

Look under the edge of a tile and in the attic. A roofer can tell you more safely, and a drone helps because walking on tile can crack it.

  1. Look at the hips, ridges and eaves from the ground

    Look for mortar and see whether it fills the space under the tile or leaves a hollow. Look for cracked mortar and for metal clips at the eaves, advises the Florida Division of Emergency Management. Clips are not required, just a sign of extra care.

  2. Check the attic on a clear day

    Nails or screws sticking through the deck in straight lines about every 12 inches are probably tile fasteners. Lines every 3 feet are usually the underlayment nails. If you see no tile fasteners, the tile may be foam or mortar set.

  3. Peek under a tile edge from a ladder

    The agency says you may be able to see foam or mortar paddies under the edge of a tile. Stay off the roof. It warns that walking on tile can break a mortar bond or crack tile. Our guide on walking on a tile roof explains why.

  4. Ask a roofer for a photo report

    A roofer can fly a drone, photograph the edges and tell you which system you have. Josh usually flies a drone over a tile roof first.

  5. Ask what changes on a re-roof

    If a roof is replaced or a section is lifted and relaid, the new attachment follows the tile maker's product approval and the FRSA-TRI manual. Eagle Roofing says a lift and re-lay can suit roofs installed before full mechanical or adhesive attachment was required. See tile roof lift and relay and underlayment replacement.

Choosing a method

Which is better for a Florida tile roof?

Mechanical fasteners and foam have the better storm record. Mortar set is the one both FEMA and the Florida agency steer away from. Workmanship decides the rest.

There is no perfect system. Mechanically attached tile depends on the number, type and head size of the fasteners. Foam depends on paddy size and placement. Mortar depends on the bond between mortar, underlayment and tile, and on how the mortar ages. The Florida agency says the uplift resistance of mortar and foam systems depends on the installer placing a large enough paddy in the right position.

The FRSA-TRI manual also sets rules for foam on steeper roofs. On slopes from 2:12 to 6:12, extra fasteners are not required with the foam. Above 6:12, up to 7:12, every tile in the first course and every third tile in every fifth course get fasteners in addition to the foam. Above 7:12, every tile gets one. With battens and tiles with lugs, extra fasteners are not required. A slope is written as rise over run: 6:12 means 6 inches of rise for every 12 inches of run.

When you get a quote for a tile replacement or a repair, ask three things in writing: which attachment method will be used, which product approval or maker's instructions it follows, and how hips, ridges and eaves will be anchored. Compare answers across bids. For costs, see our tile roof cost guide. For storm prep, read hurricane roof prep.

Coastline does tile roof repair and replacement and leak diagnosis. We do not tell you what your insurance policy covers. Your insurer and your policy decide that.

Not a promise

No attachment system makes a roof hurricane proof. Roofs with each attachment method lost tile in the 2004 hurricanes, and the Florida agency says tile can become windborne at wind speeds starting at 120 to 130 mph.

Reviews

What homeowners say about working with Coastline

★★★★★
"From beginning to end the roof was done in 2 days. One night the crew stayed until 8:00. Each evening before leaving the crew ensured the yard was cleaned. We are so happy, and our roof is beautiful!"
Sharon T.Roof replacement
★★★★★
"Russell was great to work with. He was prompt in coming out to assess our roof and very knowledgeable. ... The job was complete in 2 days once work began."
Bryan S.Roof replacement
★★★★★
"Josh was especially amazing. He was professional, patient, and took the time to explain everything clearly so I felt comfortable and informed throughout the entire process. You can tell he genuinely cares about his customers and takes pride in his work."
Madison T.Roofing customer
Keep reading

Related guides

Tile Roofing

Tile roof repair and replacement in Palmetto and nearby counties.

See our tile roofing →

Wind Lifted Roof Tiles

What to do when wind has lifted or moved tile on your roof.

Read about lifted tile →

Hurricane Roof Prep

What to check on your roof before a storm.

See the prep list →

Also see tile roof lift and relay and wind speed and roof damage.

FAQ

More questions

Is foam set tile better than mortar set?

Storm studies favor foam and mechanical attachment. FEMA's team found mortar set roofs lost much more tile after Hurricane Charley, JLC reports. Foam roofs still failed when installers used too little foam or placed it badly. The FRSA-TRI manual allows foam, fasteners and mortar, with approval rules for each.

Is mortar set tile still allowed in Florida?

The FRSA-TRI manual still lists mortar as a way to secure field tile, with factory premixed, bagged mortar that has a Florida product approval. FEMA's 2005 coastal guide recommends mechanical attachment instead of mortar in high wind areas. Ask your local building department and the tile maker's approval for your roof.

Can foam adhesive be added to a mortar set roof?

The Florida Division of Emergency Management describes having a roofer remove hip, ridge and eave tile and reinstall it with two part expanding foam and a board. That is a retrofit idea for edges, not a full redo. Have a licensed roofer check what fits your roof and what the permit requires.

How long does foam adhesive last on a tile roof?

We did not find a published lifespan from the foam makers or a standards group, so we will not give a number. The FRSA-TRI manual says foam must meet listed material standards and a Florida product approval. An inspection of the paddies and edges tells you more than a guess.

Do I need extra fasteners with foam set tile?

On steeper roofs, yes. The FRSA-TRI manual says no extra fasteners are needed on slopes from 2:12 to 6:12. Above 6:12 and up to 7:12 it calls for fasteners in the first course and on every third tile every fifth course. Above 7:12, every tile gets one. Battened roofs with lugged tile are an exception.

Sources

  1. FRSA and TRI Alliance: Florida High Wind Concrete and Clay Tile Installation Manual, 7th Edition (12/31/2023)
  2. Florida Division of Emergency Management: Tile roofs guidance for homeowners
  3. Journal of Light Construction: Tile Roofs for Hurricane Zones (FEMA Charley findings)
  4. Professional Roofing (NRCA): The hurricanes of 2004, Thomas L. Smith (Sept. 2005)
  5. FRSA (Florida Roof magazine): Post-storm considerations for repairing damaged concrete and clay tile (Nov. 2022)
  6. Eagle Roofing: FAQ on lift and re-lay (roofs installed before full attachment was required)

Find out how your tile is really held down

Coastline can inspect your tile roof and send a written photo report that shows the hips, ridges, eaves and any cracked or loose tile, so you know where you stand.

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