Clay and concrete tile roof installation field guide

What a tile roof is, and the layer that actually keeps water out

A clay or concrete tile roof is a covering of overlapping fired-clay or molded-concrete tiles laid in courses on a sloped roof, where the tiles shed the bulk of the rain and take the sun, the hail, and the wear for decades. The tile is the part everyone sees and the part everyone thinks of as the roof. It is not the waterproofing.

The waterproofing is the underlayment under the tile. Water gets under tile. It blows in sideways at the headlap, it wicks back up a low course, it finds the gap at a cut tile, and it runs down the underlayment to the eave. The tile is the rain shield and the wear surface. The membrane beneath it is the barrier that keeps the building dry, which is why a tile roof that leaks almost never failed at the tile. It failed at the underlayment or at a flashing.

So the real work of a tile roof is four things, and the tile is arguably the easiest of them. Verify the structure can carry the weight, because tile is heavy. Install a first-class underlayment, because that is the actual waterproofing. Fasten the tile for wind and seismic so it stays on the deck. And detail the flashings and valleys, because that is where the leaks start. This guide walks those in order. The shingle system that competes with tile is covered in the steep-slope asphalt shingle guide, and the membrane itself is covered in the roofing underlayment guide. Read both alongside this one.

Clay or concrete: which tile?

Clay tile is fired earth, and the color is baked through the body, so it holds its color for the life of the tile and reads as the premium product. Concrete tile is molded from sand, cement, and pigment, costs less, and carries most of the volume in the trade today. The pigment in concrete is a surface or through-color coating, and it can fade or chalk over the years where clay does not.

Weight is the first practical split. Concrete tile is generally the heavier of the two, commonly running 8 to 12 pounds per square foot, while clay is often somewhat lighter, in the rough range of 6 to 10 pounds per square foot for standard profiles. Both are far heavier than asphalt shingles, and both push you to the same structural check. Lightweight versions of each exist, and the only number that counts is the published weight for the specific tile you are installing.

Clay is harder and more brittle, so it breaks differently underfoot and at the cut, and some clay tile is pre-drilled or wants a specific fastener. Concrete is a little more forgiving to handle and cut but absorbs more water, which is part of why it weighs more wet. Neither is the universal right answer. Match the tile to the structure that will carry it, the climate, the look the job wants, and the manufacturer's data, and confirm the actual weight, water absorption, and freeze-thaw rating against that manufacturer's published sheet rather than a rule of thumb.

Tile profiles: flat, low, high, and interlocking

Profile is the shape of the tile, and it sets both the look and how the tile channels water. Flat tile is exactly that, a flat slab that reads like slate or shake and stacks with a clean low line. Low-profile tile has a gentle S or a small barrel and a modest rise. High-profile tile is the deep barrel, the S-tile, the mission and Spanish look with a tall water channel and a strong shadow line.

The other split is interlocking versus overlapping. Interlocking tile has a formed side lock and a head lock that engage the neighboring tiles, which controls the exposure, resists wind-driven water at the joint, and speeds the field because the tile self-aligns. Overlapping tile, the classic two-piece barrel mission with a pan and a cover, laps loosely and relies on the lap and the underlayment more than on a mechanical lock. Most modern concrete and clay tile is single-piece interlocking. The two-piece mission look is still made and still wanted on the right building.

Profile drives the rest of the system. A high barrel needs bird stops and closures at the eave to seal the open ends, and it needs the right hip and ridge tile to cap a deep channel. A flat tile needs a clean weatherblock at the head and at the rake. The manufacturer's installation manual is tied to the exact profile, so the closure pieces, the trim tiles, and the fastening pattern come from that book, not from another tile that looks similar.

How much does a tile roof weigh?

A tile roof commonly weighs 6 to 12 pounds per square foot or more, which is roughly three to five times the weight of an asphalt shingle roof. Said another way, a square of tile, the 100 square feet roofers price by, runs in the rough range of 600 to 1,100 pounds installed, against 200 to 350 pounds for shingles. That weight is the single biggest issue on any tile job and it is the one that gets skipped.

Concrete is usually the heavier material, often 8 to 12 pounds per square foot, and it gets heavier wet because concrete absorbs water. Clay tends to run a little lighter, but it is still in a different league from shingles. The exact figure belongs to the specific tile, so pull the manufacturer's installed weight for the profile and the underlayment and batten system you are actually building, not a category average.

This is a dead load the building carries for fifty years, not a live load that comes and goes. A roof framed and engineered for a 2 to 4 pound shingle was never designed to hold a 10 pound tile, and the difference does not announce itself the day you finish. It shows up as deflection, sagging ridgelines, and cracked finishes months later, or worse in a seismic or snow event when the dead load is the thing the design assumed was light. Treat the weight as a structural question first and a roofing question second, and put the load number to the structural engineer and the building official before the tile is on the order.

Verify the structure carries the load

Before a tile roof goes on a building that did not already carry one, the structure has to be verified for the added dead load, and that verification belongs to a structural engineer, not to the roofer's judgment. This is the part of a tile job that is genuinely dangerous to guess at. The framing, the rafters or trusses, the deck, the connections, and the walls all carry the load, and a system sized for shingles can be well short of what tile needs.

The reroof-over-shingles trap is the classic failure. A house has an asphalt roof, the owner wants the look and the life of tile, and somebody loads 10 pounds per square foot onto framing that was engineered for 3. It passes the eye, it passes the first winter, and then the rafters deflect, the ridge sags, the drywall cracks, and in a snow region the margin that was supposed to be there for live load is gone. Do not assume the structure is adequate because the roof looks stout. Assume it needs checking until an engineer says otherwise.

The honest hedge here is hard and it is not legal cover, it is how the job is actually run. The structural adequacy for tile dead load is the structural engineer's call, confirmed against the manufacturer's installed weight and the adopted building code, with the building official signing off on the load path. If the existing structure is short, the engineer specifies the reinforcement, the new framing, or the lighter tile that brings the load within what the building can carry. Get that done before the tear-off, because finding out the framing is undersized with the deck open and the tile on a pallet in the driveway is the expensive way to learn it.

The underlayment is the waterproofing

The underlayment under a tile roof is the actual waterproofing, and that is the one idea to carry off this whole guide. The tile sheds the bulk of the water, but a meaningful amount gets under the tile in every rain, and the membrane on the deck is what catches it and runs it back out to the eave. A tile roof is, in waterproofing terms, an underlayment roof with a heavy, durable, good-looking rain shield over it.

Because of that, the underlayment is not a place to save money. It is common, and it is a real mistake, to spec a premium fifty-year tile and then roll a cheap felt under it that will not last twenty. When the underlayment fails, the roof leaks even though every tile is intact, and the fix means pulling all that tile to get at the membrane. The membrane choice deserves at least as much attention as the tile choice, and the full type-by-type breakdown lives in the roofing underlayment guide. Read it for the comparison between felt, synthetic, and self-adhered membrane.

The places water gets under the tile are predictable. Wind drives rain up the headlap. Water wicks back at a low course or a flat profile. Snow melts and refreezes and backs up at the eave. A cut tile at a valley or a hip leaves a gap. Capillary action pulls water sideways at a tight lap. In every one of those cases, the underlayment is the layer standing between the wet and the deck, so it has to be detailed to shed, lapped the right way, and sealed at every fastener penetration and flashing.

Spec the underlayment high-temp

Tile gets hot, so the underlayment under it has to be a high-temperature product, not the same sheet you would run under shingles. Air moves under tile and the tile itself radiates heat down, and the membrane on the deck can sit at temperatures that cook a standard self-adhered ice-and-water shield until the asphalt flows and the sheet slumps or loses adhesion. Use an underlayment the manufacturer rates for tile and for the service temperature you will actually see.

Across the trade the spec has moved well past a single layer of 30-pound felt. Common tile underlayments now are a high-temperature self-adhered membrane, a heavy two-ply felt application, or a tile-rated synthetic, and the choice tracks the slope, the climate, and the warranty the owner is buying. On a fifty-year tile, a long-life membrane is the right match, because the whole point is to keep the underlayment alive as deep into the tile's life as you can.

Slope drives coverage. On lower slopes the underlayment carries more of the load because water sits longer and backs up further, so the manufacturer and the code call for enhanced coverage, commonly a doubled or fully self-adhered application below the standard slope and down to the minimum the tile allows. The exact membrane, the number of plies, and the lap come from the tile manufacturer's installation manual and the adopted code, hedged to the climate, and on a high-wind or high-temperature job that spec is stricter than the general one.

What is the minimum slope for a tile roof?

Clay and concrete tile is commonly installed on slopes of 2.5:12 and steeper, but the underlayment requirement changes with the slope. The widely referenced figure, carried in the Tile Roofing Institute installation manual and the model codes, is a 2.5:12 minimum, with standard single-underlayment application generally starting around 4:12 and an enhanced or doubled underlayment required for the lower slopes between 2.5:12 and 4:12.

The reason is the same physics as any shed-style roof. The flatter the slope, the longer water sits on the surface and the further it backs up under the tile in wind and at the eave, so more of the waterproofing job falls on the membrane. Below the minimum, tile is the wrong covering, and you switch to a true waterproof roof built to hold standing water rather than shed it. Putting tile on too flat a roof is a leak you build in on day one.

Do not treat any of these slope numbers as universal. They vary by the specific tile profile, the manufacturer, and the adopted code edition with local amendments, and an interlocking tile may carry a different minimum than a two-piece barrel. Confirm the minimum slope and the matching underlayment application for the exact tile against the manufacturer's manual and the building official before you commit the covering to a low-slope plane.

Battens versus direct-to-deck

Tile is set either directly on the underlayment over the deck, hooked or fastened through it, or on horizontal battens, which are wood or composite strips run across the slope that the tile hangs on and fastens to. Both are valid, and the choice tracks the tile, the climate, and the manufacturer's manual. Battens are typically a nominal 1 by 2 of decay-resistant exterior-grade material, fastened over the underlayment to the deck.

Battens raise the tile off the membrane and create an air space and a drainage plane under the tile, which lets any water that gets under the tile run down to the eave instead of pooling, and lets the assembly breathe and dry. The trap is that a plain horizontal batten can dam water at each course if it is laid solid across the slope, so the better detail is a counter-batten or a raised batten system, where vertical battens run up the slope under the horizontal ones to keep the drainage path open, or the horizontal battens are notched or shimmed to let water pass.

Direct-to-deck eliminates the damming risk and is common in foam-set and some interlocking systems, but it puts the tile tight to the membrane, so the underlayment has to be the real drainage surface and the detailing has to be clean. Whichever you run, the batten size, spacing, material, and the drainage detail come from the tile manufacturer's installation manual, because the batten gauge is what sets the exposure and the headlap for that profile.

Fastening the tile: nails, screws, clips, wire, and foam

Tile is held to the roof by some combination of nails or screws through the tile or batten, clips at the nose or the side for uplift, wire-tie systems on older and seismic work, and foam adhesive that bonds the tile to the one below or to the deck. The method is not a free choice. It is set by the slope, the wind zone, the seismic zone, and the manufacturer's and code's fastening schedule, and on a tile roof the attachment is what keeps the heavy covering on the building in a storm.

Mechanical fasteners are corrosion-resistant nails or screws, stainless or hot-dip galvanized, sized to penetrate the batten or deck per the schedule. Screws hold better than nails because they do not back out, and they are common on hip, ridge, and high-uplift areas. Clips add hold at the tile nose against uplift and are standard in coastal and high-wind work. Wire-tie or mortar-and-wire systems are the historic method, still seen on two-piece mission tile and on seismic retrofits, where the wire ties the tile into a continuous net.

Foam adhesive, a two-component polyurethane, bonds the tile in a pattern and is widely used in high-wind regions because it makes full-surface contact, flexes, and resists uplift well when applied to a Miami-Dade or equivalent approved pattern. The catch is that foam is unforgiving of a dirty or wet surface and of a sloppy bead pattern, and even where foam carries the field, the code commonly still requires the perimeter and the first course to be mechanically fastened, because the perimeter is where uplift concentrates. The fastener type, the count per tile, and the pattern come from the manufacturer's listing and the adopted code, and on a high-wind job they come from the engineer.

Wind uplift and seismic

Wind uplift is the governing load on a tile roof in a hurricane zone, and the fastening schedule that resists it is engineered, not eyeballed. The corners and perimeter of a roof see the highest uplift, the field sees less, and the schedule reflects that with more attachment at the edges. In high-wind regions the design is driven by the local code, the wind speed, and a tested, approved tile-and-fastener system rather than by a generic nail pattern.

In Florida and the rest of the high-velocity hurricane zone, the controlling documents are the Florida Building Code, the FRSA/TRI Florida high-wind tile installation manual, and the Miami-Dade Notice of Acceptance for the specific system, with field bonding verified to the Testing Application Standard, TAS 106, on adhesive and mortar-set tile. A combination of foam and screws is a common high-wind detail because it builds in redundancy at the ridges, perimeters, and valleys where the tile is most likely to lift first.

Seismic loads are a different problem and they matter most in the West. The heavy dead load of tile is itself a seismic liability, because mass times acceleration is force, and a heavier roof drives a larger lateral demand on the walls and connections below. That is one more reason the structural engineer has to be in the loop on a tile job in seismic country, both for the load path and for how the tile and any mortar are tied down so a quake does not shed tile off the roof. The wind and seismic attachment requirements come from the adopted code, the tested system, and the engineer, and they are not the place to improvise.

Flashings and valleys: where tile roofs leak

Tile roofs leak at the flashings and the valleys far more than in the field of the tile, so the metalwork is where the roof is won or lost. The valley is the highest-volume water path on the roof, and on tile it is an open metal valley: a wide formed metal channel, usually with a center rib or a hemmed edge to keep water from crossing under the tile, with the tile cut to a clean line and held back off the metal so water runs down the metal, not under the tile.

The other failure points are the headwall and the sidewall, where the tile field meets a vertical surface. A headwall, where the slope runs into a wall above it, needs a continuous metal flashing turned up the wall and counterflashed, sized to carry the water the slope delivers. A sidewall, where the slope runs alongside a wall, needs flashing woven or stepped against the wall and lapped onto the underlayment, with the tile profile closed at the wall so wind-driven water cannot run behind it. The deep channel of a barrel tile makes these details fussier than they are on a flat profile, because the metal has to seal against a contoured tile.

The principle under all of it is that the flashing ties into the underlayment, the real waterproofing, and the tile laps over the flashing as the shed surface. Get the lap direction wrong, or rely on a smear of sealant where a formed metal pan belongs, and the flashing leaks regardless of how good the tile is. Use the right metal for the climate and the tile, lap it to drain onto the membrane, and treat sealant as a supplement to a flashing that already sheds on its own, never as the flashing.

Hip and ridge

The hip and the ridge are capped with trim tiles that close the top of the roof where two planes meet, and how they are set has changed. The historic method is mortar-set: the ridge and hip tiles bedded in mortar, which looks traditional and is still done, but the mortar cracks and lets water in as the roof moves and ages, and it adds weight and rigidity that does not flex with the building.

The current method is a dry, mechanically fastened ridge and hip, built on a ridge board or a metal ridge riser with a weatherblock or a flexible closure under the trim tile, and the trim tile screwed down rather than buried in mortar. The dry system flexes, drains, and lets the ridge breathe, and it does not depend on mortar that will crack. Where mortar is used for the look, the better detail backs it with a mechanical fastener and a flexible closure so the mortar is cosmetic and the attachment and the seal do not depend on it.

The ridge is also the natural exhaust point for a vented roof. A vented ridge detail, with the closure formed to pass air while blocking water and pests, lets the air space under the tile breathe out at the top, which helps the assembly run cooler and dry. The trim tile, the closure, and the fastener all come from the tile manufacturer for the matching profile, because a hip and ridge tile is profile-specific and a mismatched cap is both a leak and an eyesore.

Eave, starter, and bird stop

The eave is where the roof starts and where water leaves it, so the first course gets special detailing. The starter course or a raised eave closure lifts the nose of the first tile to the right plane and angle, because a high-profile tile laid flat at the eave would tip the wrong way and let water run back. Setting that first course right is what sets the plane for every course above it.

On a barrel or high-profile tile, the open ends of the tile at the eave are sealed with a bird stop, also called an eave closure: a formed metal or molded piece that fills the gap under the curved tile so birds, rodents, and wind-driven rain cannot get up under the field. Skip it on an open-profile tile and you have built a row of nesting cavities along the eave and an open path for water and pests under the whole roof.

Two more eave details matter. Anti-ponding metal, or an eave riser, at the eave keeps the underlayment and the first course from sagging into a low spot that holds water at the most vulnerable line on the roof. And the drip edge or eave metal carries the water that runs down the underlayment off the deck and into the gutter, not behind it. The eave is a small length of roof that does an outsized amount of work, and it is a common place to find a tile roof leaking back into the fascia because one of these pieces was left out.

Penetrations

Every pipe, vent, and curb that comes through a tile roof is a hole in the waterproofing, and it gets a flashing that ties into the underlayment and sheds onto the tile. A plumbing vent or a flue is flashed with a lead or a formed metal pan, a flange that laps onto the underlayment and turns up the pipe, dressed so the tile above laps over the flange and the tile below laps under it. Lead is traditional on tile because it dresses to the contour of a barrel and works around the pipe by hand.

The detail that makes a penetration work is the same as a valley or a headwall: the flange sheds onto the underlayment, the upslope tile covers it, and the tile is cut and shaped around the penetration so water runs over the flashing, not into the cut. The tile cut around a pipe is fussy on a high profile, and the gap left by the cut is sealed and closed so wind-driven water cannot drive into it.

The mistake is treating a penetration as a caulking job. A bead of sealant around a pipe on top of the tile is not a flashing and it does not last, because the tile moves, the sealant fails, and the water goes straight into the hole. Flash it with metal or lead that laps the membrane, and use the manufacturer's flashing for the profile where one exists.

Can you walk on a tile roof?

You can walk a tile roof, but tile breaks underfoot if you step wrong, and broken tile is both a leak risk and an ongoing service cost. The rule is to walk where the tile is supported, which means stepping on the lower third of the tile, at the headlap where the tile below carries the load, not on the unsupported nose or the center of the span where the tile flexes and cracks. Clay is more brittle than concrete and breaks more readily, so the same step that survives on concrete can crack a clay tile.

Breakage happens during the install and for the life of the roof. During the install, the crew walks the roof constantly, and a foreman who lets the crew walk noses and centers will be replacing tile before the job is even done. After the install, every trade that comes up to service a vent, a dish, a solar array, or a chimney walks the tile, and a roof that gets a lot of rooftop service will shed broken tile steadily unless the people up there know how to walk it.

Plan for access. Stage walk paths, keep replacement tile from the original lot on hand, and on a roof that will see regular rooftop equipment service, consider walkways or designated paths so the foot traffic is not landing on tile that was never meant to be a floor. The fragility of tile is not a defect, it is a property of the material, and the way you manage it is by controlling where feet land, not by hoping the tile holds.

Field layout, headlap, and exposure

The field of a tile roof is laid to a layout that fixes the headlap and the exposure before the first tile goes down. Headlap is how far each course laps over the one below it, the overlap that keeps water from getting under the joint, and exposure is how much of each tile is left to the weather, the part you see. The two are linked: more headlap means less exposure, and the manufacturer sets the minimum headlap and the resulting exposure for the profile.

On a battened roof, the batten gauge, the spacing between battens up the slope, is what locks the exposure in, so getting the batten layout right is getting the coursing right. The crew strikes the layout off the eave and the rake, sets the gauge so the courses land evenly and the top course meets the ridge cleanly without a sliver, and works the coursing so the cut tiles fall where they are least conspicuous and least vulnerable. A field laid to a loose gauge wanders, the headlap shrinks in spots, and the roof leaks at the courses where the lap went short.

Plan the cuts at the rakes, the valleys, the hips, and the penetrations as part of the layout, not as an afterthought tile by tile. A half tile or a cut piece at a valley still has to lap and shed like a full tile, and a cut that leaves too little tile to lap is a leak. The minimum headlap, the exposure, and the allowable cut come from the manufacturer's manual for the profile, and the field is held to that gauge from eave to ridge.

Cutting tile

Tile is cut with a wet saw or a dry diamond blade at the rakes, valleys, hips, and penetrations, and the half tiles and field cuts are part of every tile roof. A wet saw with a diamond blade gives the clean, controlled cut tile needs, and the water keeps the dust down, which is the real reason to run wet rather than dry.

Cutting concrete and clay tile releases respirable crystalline silica, and silica dust is a serious health hazard regulated under the OSHA silica standard. Dry-cutting tile on a roof without controls puts a cloud of silica into the air the crew breathes. Wet-cutting, on-tool dust collection, and respiratory protection are the controls that keep the exposure down, and the respirable crystalline silica requirements and the exposure limit are covered in the silica safety guidance by topic. The short version is do not dry-cut tile in the open without dust control.

Beyond the dust, a cut tile has to perform like a full tile. The cut edge still has to lap and shed, the cut piece still has to be fastened, and a sliver too small to fasten or lap is not a usable tile, which is why the layout plans the cuts so they land at a workable size. Keep the cut tile from the same lot so the color matches, and seal and close the cut where it sits at a valley or a penetration.

How long does a tile roof last?

The tile itself lasts 50 years and well beyond, with clay commonly going 50 to 100 years or more and concrete 50 years or more, which is the headline that sells tile. The roof, as a watertight system, does not last that long on the original underlayment, because the underlayment and the fasteners wear out long before the tile does. That gap is the most important and most misunderstood fact about tile roof life.

Asphalt felt underlayment commonly lasts 20 to 30 years, sometimes less in a hot climate, and even upgraded synthetic and self-adhered membranes are generally rated in the 25-to-50-year range, not the century the clay might reach. So a tile roof built to last 50-plus years will, in most cases, need its underlayment renewed at least once partway through the tile's life, and the metal flashings and the fasteners are on a similar clock. The life of the watertight roof is set by the underlayment and the metal, not by the tile.

The practical answer is the relay, sometimes called a lift-and-relay or a renew-and-reuse. When the underlayment reaches the end of its life, the tile is carefully removed and stacked, the old underlayment and flashings are stripped, a new first-class underlayment and new flashings go on, and the original tile is reset, with broken pieces replaced from matched stock. Done right, a relay gives the building another full underlayment cycle on tile that still has decades left, which is exactly why spending up front on a long-life underlayment and breakage-resistant detailing pays off. The tile is the durable part. Plan the roof around the parts that are not.

Maintenance

A tile roof is low-maintenance, not no-maintenance, and the maintenance is mostly inspection plus targeted repair rather than recoating or resealing. Inspect on a regular cadence and after any major wind or hail event, and the things to look at are the flashings, the valleys, the ridge, and any cracked, slipped, or missing tiles, because that is where the trouble starts.

Replace broken and slipped tile promptly, because a single broken tile exposes the underlayment to direct sun and water and accelerates the failure of the layer that is actually keeping the building dry. Keep the valleys and the eaves clear of debris, leaves, and the windblown junk that dams water and forces it sideways under the tile. In wet and shaded climates, moss and lichen grow on tile, hold moisture against it, and lift the courses over time, so keeping growth off the roof matters more than it looks.

The long-term maintenance item is the underlayment, and the maintenance plan should name the year it is expected to come due so it is a planned relay, not an emergency. A tile roof that gets its broken tiles replaced, its flashings watched, and its underlayment renewed on schedule will deliver the long life the tile is capable of. One that is installed and forgotten will leak at a failed flashing or a worn-out membrane while every tile on it still looks new.

Cost and value

Tile costs more up front than asphalt shingles, both in material and in labor, and the weight adds a structural cost on any building not already built for it. The return is the long life, the appearance, the fire resistance, and the curb appeal and resale value that a genuine clay or concrete tile roof carries, especially in the Southwest, Florida, and the Mediterranean-style markets where it is the expected roof.

The honest way to weigh it is the whole-life cost, not the install price. A tile roof that gets one underlayment relay over 60 or 80 years can beat two or three full shingle replacements over the same span, provided the structure carried the weight without an expensive upgrade and the underlayment and flashings were done well enough to reach the relay. The weight tradeoff is the swing factor: on a building designed for tile, the value case is strong, and on a building that needs heavy structural reinforcement to carry it, the math gets harder and the lighter alternatives deserve a look.

Where tile roofs actually fail

Tile roofs fail in a short list of predictable ways, and almost none of them are the tile itself failing. The biggest is not verifying the structure for the weight, which shows up as deflection and sagging months or years after a tile roof goes on framing that was sized for shingles. Next is a cheap underlayment under a long-life tile, where the membrane wears out decades before the tile and the roof leaks while every tile is intact.

After those come the detail failures. The wrong slope for the tile, too flat for the profile and the underlayment, lets water back up and leak at the laps. Poor valley and flashing detailing, the open metal valley done wrong or a sidewall relying on sealant, leaks at the highest-volume water paths on the roof. Inadequate wind or seismic fastening lets the heavy covering lift or shed in a storm or a quake. And walking the tile wrong, on the noses and the centers, breaks tile during the install and for the life of the roof, exposing the underlayment one tile at a time. Every one of these is preventable on the front end and expensive on the back end.

What to document

A tile roof is a fifty-year system, and the record of what went on under the tile is what the next roofer, the relay crew, and the inspector rely on years out. Capture the load verification, the underlayment spec, the fastening schedule, and the flashing details, because the tile hides all of it and nobody can see it once the roof is finished.

The table below is the short version of what belongs in the record. Tie each element to the requirement it has to meet and the source that set it, the manufacturer, the engineer, or the code, so the next person can check the roof against what it was supposed to be.

Field checklist

Common mistakes

• Loading tile onto framing sized for shingles without an engineer verifying the structure carries the weight.
• Spec-ing a cheap underlayment under a fifty-year tile, so the roof leaks while every tile is intact.
• Running tile on too flat a slope for the profile and the underlayment.
• Treating valleys and flashings as a sealant job instead of formed metal lapped onto the membrane.
• Under-fastening for the wind or seismic zone, especially at the perimeter and the first course.
• Walking the noses and centers of the tile and breaking it during the install and after.
• Using a standard underlayment that cooks under the heat tile traps against the deck.
• Laying solid horizontal battens that dam water with no drainage path.

Standards and references

The two authorities that govern a tile roof are the tile manufacturer and the structural engineer, and neither is optional. The manufacturer's installation manual controls the underlayment, the slope minimum, the batten and fastening schedule, the closures, and the trim, because all of it is tied to the specific profile and is the basis of the warranty. The structural engineer owns the load question, the verification that the framing and the building carry the tile dead load, and the engineer's call is confirmed by the building official.

For the system standards, the Tile Roofing Institute, in partnership with the Western States Roofing Contractors Association, publishes the concrete and clay roof tile installation manual that the trade and the codes lean on, and in Florida the FRSA/TRI Florida high-wind tile installation manual covers the hurricane-zone requirements. The model building codes, the IBC and the IRC, set the slope, underlayment, and fastening framework, and high-wind work runs to the Florida Building Code, the Miami-Dade Notice of Acceptance for the tested system, and the field-bonding standard TAS 106. Silica exposure from cutting falls under the OSHA respirable crystalline silica standard.

Hedge the numbers correctly. The weight, the slope minimum, the underlayment spec, and the fastening schedule all come from the manufacturer's manual, the structural engineer for the load, and the adopted code edition with local amendments, confirmed with the building official. The three things to hold firm on are these: verify the structure carries the weight before the tile is ordered, spec the underlayment high-temperature because it is the actual waterproofing, and fasten for the wind and seismic zone while detailing the flashings, because that is where tile roofs leak. The exact figures are the manufacturer's and the code's, and the load is the engineer's.

Units and terms

Tile work carries its own vocabulary, and the same idea reads differently across a manufacturer's manual, an engineer's load calc, and a code section.

Weight is given in pounds per square foot for the load calc and in pounds per square, per 100 square feet, for the roofer's takeoff. Slope is given as a ratio of vertical rise to 12 units of horizontal run, so 4:12 and 2.5:12, and sometimes as a percentage. The terms below cover the pieces that show up most on a tile job.

Clay vs concrete tile

Clay tile is fired earth with color baked through; concrete tile is molded sand, cement, and pigment, usually heavier and prone to fade

Tile profile

The shape of the tile, flat, low, or high (S-tile, barrel, mission), interlocking or overlapping, which sets the look and the water channel

High-temp underlayment

A tile-rated membrane that holds up to the heat tile traps against the deck, where a standard ice-and-water shield would flow

Battens

Horizontal strips the tile hangs on and fastens to, raised on counter-battens or notched so water drains under the tile

Headlap and exposure

Headlap is how far a course laps the one below; exposure is the part of the tile left to the weather; more lap means less exposure

Wind clip

A metal clip at the tile nose or side that resists uplift, standard in coastal and high-wind work

Bird stop

A formed eave closure that seals the open ends of a high-profile tile against birds, pests, and wind-driven rain

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