By The Roofing Brief Team. Last reviewed: October 2026.
Clay tile roof installation follows a fixed sequence: verify the structure can carry the load, deck and dry-in the roof, lay underlayment, set battens (or plan a direct-nail layout), install field tiles course by course from the eave up, then finish hips, ridges, and flashing. Clay tile from Ludowici, Verea and Tejas Borja weighs about 800 to 1,025 pounds per square (8 to 10.25 psf) on the makers’ spec sheets, so the load check comes before anything else. IRC Section R905.3 sets the code floor: solid sheathing, a 2-1/2:12 minimum slope, double underlayment up to 4:12, and at least one fastener per tile on solid sheathing without battens.
Pricing and lifespan are covered in our companion guide on clay tile roof cost and lifespan; HomeGuide’s 2026 guide puts installed clay tile at $8 to $25 per square foot.
Tile roof installation rules at a glance: the decision table
Every step of a tile job hangs on slope, climate and sheathing. The thresholds below come from the 2021 IRC Section R905.3 (as printed in the Seattle Residential Code, Chapter 9) and the TRI/WSRCA Concrete and Clay Roof Tile Installation Manual for Moderate Climate Regions.
| If your roof is | Then | Source |
|---|---|---|
| Below 2-1/2:12 | Tile is not a permitted covering; use a low-slope membrane, or tile only as decoration over one per TRI | IRC R905.3.2; TRI manual |
| 2-1/2:12 to under 3:12 | Double underlayment; lugged tile on battens must sit on a counter batten system | IRC R905.3.2; TRI manual |
| 3:12 to under 4:12 | Double underlayment (19 inch starter, 36 inch sheets lapped 19 inches) | IRC R905.3.2, Table R905.1.1(2) |
| 4:12 to 7:12 | One layer of underlayment lapped 2 inches; direct-nail or battens | IRC Table R905.1.1(2); TRI manual |
| Steeper than 7:12 | 1 by 2 inch nominal battens required for positive anchoring | TRI manual |
| Solid sheathing, no battens, any slope | One fastener per tile | IRC Table R905.3.7 |
| In a snow area | At least two fasteners per tile | IRC R905.3.7 |
| Tile weighs under 9 psf installed | At least one fastener per tile regardless of slope | IRC R905.3.7 |
| Ultimate design wind speed over 130 mph, or roof more than 40 ft above grade | Attach per the tile maker’s instructions (high-wind manuals) | IRC R905.3.7 |
| January average daily temperature 25°F or lower, slope under 7:12 | Valley underlayment solid-cemented, or self-adhering polymer-modified bitumen | IRC R905.3.8 |
Can your roof structure carry a clay tile roof?
Before any tile goes up, the framing has to be rated for the dead load. The maker data below runs from 800 pounds per square (Verea flat tile) to 1,025 pounds (Ludowici French), and Ludowici says its Shingle tile ranges from 1,300 to over 2,200 pounds per square. The TRI manual notes that one square can take from 75 to over 400 pieces depending on size and exposure, and tells designers to add the weight of underlayment, fasteners and hip and ridge treatments. On new construction, engineered trusses or rafters are specified for the tile load from the start. Lighter options are compared in our guide to composite roof tile weight.
For a re-roof from a lighter material to clay, have a structural engineer check rafter or truss size, spacing and span against the tile maker’s weight per square before you order tile. Reinforcement can mean sistering rafters, adding purlins, or upgrading trusses. Ask the engineer for the design dead load in psf and compare it to the table below, because the fix after 9 to 10 psf of tile is loaded costs far more than the fix before.
| Tile (maker) | Profile | Weight per square (100 sq ft) | Approx. psf | Pieces per square | Source |
|---|---|---|---|---|---|
| Ludowici French | Interlocking | 1,025 lb | 10.25 | 133 | Ludowici spec |
| Ludowici Italia | Two-piece mission | 950 lb | 9.5 | 148 | Ludowici spec |
| Ludowici Spanish 13″ | One-piece barrel (S) | 900 lb | 9.0 | 171 | Ludowici LRT-518 sheet |
| Tejas Borja Mission C-50.21 Celler | Clay barrel | About 810 lb | 8.1 at 3 in headlap | Not stated | ICC-ES ESR-2111 |
| Verea flat tile | Flat clay | 800 lb | 8.0 | Not stated | Verea products page |
| Ludowici Shingle tile | Flat shingle | 1,300 to over 2,200 lb | 13 to 22+ | Varies by exposure | Ludowici Shingle Tile Installation Manual |
| Concrete flat tile (for comparison) | Flat concrete | 950 to 1,200 lb | 9.5 to 12 | Varies | Verea products page |
What roof slope does clay tile require?
Clay and concrete roof tile installs on slopes of 2-1/2:12 or greater under IRC Section R905.3.2. Below that pitch, tile is not a code-approved covering because water moves too slowly to shed reliably through the laps. From 2-1/2:12 up to 4:12, the same section requires double underlayment, because the underlayment does more of the waterproofing work at those pitches.
Slope also sets the fastening and batten rules. Under IRC Table R905.3.7, tile on battens below 5:12 needs no fasteners (the anchor lugs hold it), from 5:12 to under 12:12 it needs one fastener per tile in every other row, and spaced sheathing without battens from 12:12 to under 24:12 needs one per tile. The TRI manual adds that battens are required above 7:12 and must sit on counter battens below 3:12.
Step-by-step clay tile roof installation process
Tiling a roof with clay tiles runs in a set order from deck to ridge, and the code sections and TRI figures below apply at each stage. Have the dry-in inspected before tile is loaded, because the underlayment is what keeps water out.
- Prepare and inspect the deck. IRC R905.3.1 requires solid sheathing (spaced lumber is allowed only in Seismic Design Categories A, B and C). The TRI manual calls for at least nominal 15/32-inch plywood or 1-inch lumber. Replace rotted decking and sweep the surface clean.
- Install drip edge and dry-in. Set metal drip edge at eaves and rakes, with underlayment over it at the eaves and under it at the rakes. The IRC R905.1.2 eave ice barrier list (asphalt shingles, metal shingles, roll roofing, slate, wood) does not name clay tile, so in cold regions follow the TRI Alliance cold and snow design manual or the local code for an eave membrane.
- Lay the underlayment. On 4:12 and steeper, one layer applied shingle fashion, lapped 2 inches, with 4 inch end laps offset 6 feet. From 2-1/2:12 to 4:12, two layers: a 19 inch starter strip, then 36 inch sheets lapped 19 inches. IRC Table R905.1.1(1) lists ASTM D226 Type II (No. 30 felt), ASTM D2626 Type I or ASTM D6380 Class M roll roofing for tile.
- Install flashing at valleys, walls and penetrations. IRC R905.3.8 calls for metal flashing of at least 0.019 inch (No. 26 galvanized gauge); valley metal extends 11 inches each way from the centerline with a 1 inch splash-diverter rib, lapped 4 inches at ends, over an extra 36 inch underlayment strip on slopes of 3:12 and up.
- Snap layout lines and set battens (if used). Chalk courses to a 3 inch minimum headlap (TRI). Nail 1 by 2 inch nominal battens with 8d corrosion-resistant box nails at 24 inches on center, leaving a 1/2 inch gap at batten ends every 4 feet for drainage (TRI).
- Install field tiles course by course. Start at the eave and work up and across. Fasten with corrosion-resistant nails of at least 11 gauge with a 5/16-inch head, long enough to penetrate the deck 3/4 inch or go through it (IRC R905.3.6), driven snug but not tight so the clay does not crack.
- Finish hips and ridges. Set hip and ridge tiles over a raised nailer or a mortar or foam closure, lapping away from prevailing weather. The perimeter fastening zone covers three tile courses but not less than 36 inches from hips, ridges, eaves and rakes (IRC R905.3.6), and perimeter tiles get at least one fastener each.
- Detail edges and clean up. Cut and fit rake, valley and penetration tiles with a wet saw, fasten or clip every cut piece, and check each fastener and 3 inch headlap before the crew leaves.
Clay tile roof underlayment: what to use and when to double it
Underlayment is the real waterproofing layer on a clay tile roof, because tile sheds most water but is not watertight on its own. Water that gets under a tile in wind-driven rain runs on the underlayment to the eave. The TRI manual lists ASTM D226 Type II (No. 30 felt), ASTM D4869 Type IV or ASTM D1970 self-adhering membranes meeting ICC-ES AC150, and a felt underlayment can wear out while the tile above it is still sound.
The IRC sets one layer on 4:12 and steeper and two layers from 2-1/2:12 to 4:12. Self-adhered (ASTM D1970) membranes are common in high-wind and high-heat regions because they seal around fasteners, and IRC R905.3.8 requires self-adhering or solid-cemented valley underlayment where the January average is 25°F or colder on slopes under 7:12. Because the underlayment can outlast the tile only rarely, many owners re-lay the same tiles over fresh underlayment mid-life, a lift-and-relay job covered in our guide to tile roof replacement. Compare membrane options in our guide to roof underlayment types and when each is required.
Battens vs direct-nail: how tiles attach to the roof
Tiles attach one of two ways: nailed directly through the tile into the deck (direct-nail), or hung on and nailed to horizontal wood battens. Battens are 1-inch by 2-inch nominal wood strips run across the roof at the tile’s headlap spacing. Slope sets the outer limits (IRC Table R905.3.7 and the TRI manual), and climate and tile profile decide within them.
The TRI manual requires battens on slopes steeper than 7:12, where they give the tile a positive anchor and stop it sliding. Direct-nail is common on moderate slopes in dry climates. Counter battens at least 1/4 inch tall (vertical strips under the horizontal battens) create a drainage and ventilation gap that helps the underlayment dry. Fastening counts scale with exposure: tiles under 9 psf need at least one fastener each, and snow areas require at least two fasteners per tile (IRC R905.3.7).
| Factor | Direct-nail | Battens |
|---|---|---|
| Typical slope | 2.5:12 to 7:12 | Above 7:12 (required by TRI); counter battens below 3:12 |
| Fasteners (IRC Table R905.3.7) | One per tile at any slope | None below 5:12; one per tile every other row from 5:12 to under 12:12 |
| Underlayment drainage | Water sits closer to deck | Gap aids drying (with counter battens of 1/4 inch or more) |
| Fastener path | Through tile into deck | Tile nose hooks/nails to batten |
| Best for | Dry climates, moderate pitch | Steep pitch, wet/freeze-thaw climates |
| Underlayment penetrations | More holes in the membrane | Fewer holes in the field membrane |
Installing field tiles, courses, and exposure
Field tiles install from the eave upward, course by course, each overlapping the one below by at least 3 inches of headlap (TRI). The first (starter) course sets the exposure for the whole roof, so it is snapped to a chalk line and checked for straightness; on Ludowici French tile, for example, the exposure is 8-1/8 by 13-3/8 inches and a square takes 133 pieces.
Headlap (the vertical overlap of one course onto the next) runs 3 inches minimum unless the tile design precludes it, per the TRI manual, and Tejas Borja’s ESR-2111 weights assume that 3 inch headlap. Side laps interlock on profiled tiles (S-tile, barrel) or butt on flat tiles. Each tile fastens through its pre-formed nail holes with corrosion-resistant nails or screws, driven snug but not tight, because over-driving cracks clay. Cut tiles at rakes, valleys, and penetrations are trimmed with a wet saw and fastened or clipped so no cut edge is left loose.
Finishing hips, ridges, valleys, and flashing
Hips and ridges are capped with matching ridge tiles set over a raised nailer or a mortar or foam closure, lapped away from prevailing wind, with the end tiles mechanically fastened. In the TRI manual’s higher-wind attachment schedule, which also covers mean roof heights of 40 to 60 feet, the noses of ridge, hip and rake tiles are set in roofer’s mastic and eave-course noses are clipped. Valleys use preformed metal flashing with the IRC’s 1 inch splash-diverter rib, with cut tiles held back to leave an open waterway.
Wall and chimney transitions need headwall and sidewall flashing woven into the underlayment and the tile courses, plus counter flashing let into masonry; the TRI checklist calls for at least 3 inches of flashing coverage over tile at roof-to-wall joints and recommends a Z-bar or surface-mount reglet counter flashing. Pipe penetrations get a deck flashing plus a malleable metal tile flashing dressed over the profile. Ludowici backs its terra cotta with a 75-year limited material warranty, but flashing and underlayment are the parts that get renewed, which is a core theme in ongoing tile roof maintenance and underlayment care.
DIY or hire a pro? Clay tile labor realities
Clay tile installation is a specialist trade, not a typical DIY project. A square of 800 to 1,025 pounds has to be loaded onto the roof in stacks, every cut piece needs a wet saw and a fastener, and the flashing details above are where leaks start. The TRI Alliance installation guides cover moderate climate, high wind, and cold and snow regions, each with its own fastening schedule. Our roof replacement timeline by material shows how many days a tile job usually takes.
Labor is a large share of a tile roof budget: HomeGuide’s 2026 guide prices clay tile at $8 to $25 per square foot installed against $2.50 to $18.00 per square foot for the tile alone. When you vet installers, ask three things: which TRI manual (moderate climate, high wind, or cold and snow) they install to, how they fasten at your slope under IRC Table R905.3.7, and for references on your tile profile. Our tile roofing company vetting guide walks through the questions that separate a real tile specialist from a generalist, and the broader learn about roofing hub covers adjacent decisions.
Frequently asked questions
What is the correct order of steps to install a clay tile roof?
The order is: confirm the structure can carry the load, prepare the solid deck, install drip edge and dry-in, lay underlayment (two layers from 2-1/2:12 to 4:12), set valley and wall flashing, snap layout lines at a 3 inch minimum headlap and install battens if used, lay field tiles from the eave up course by course, then finish hips, ridges and penetrations. The dry-in and flashing steps happen before tile and do most of the waterproofing.
Do clay roof tiles need battens or can they be nailed directly?
Both are valid. Direct-nail through the tile into solid sheathing takes one fastener per tile at any slope under IRC Table R905.3.7 and is common from 2-1/2:12 to about 7:12 in dry climates. The TRI manual requires 1 by 2 inch nominal battens on slopes steeper than 7:12, and counter battens under them below 3:12.
What underlayment goes under a clay tile roof?
The IRC lists ASTM D226 Type II (No. 30 felt), ASTM D2626 Type I or ASTM D6380 Class M roll roofing, and the TRI manual adds ASTM D4869 Type IV and ASTM D1970 self-adhered membranes. Use one layer lapped 2 inches on 4:12 and steeper, and two layers (19 inch starter, 36 inch sheets lapped 19 inches) from 2-1/2:12 to 4:12.
What roof slope is required for clay tile?
Clay and concrete tile installs on slopes of 2-1/2:12 or greater under IRC Section R905.3.2. Below 4:12, double underlayment is required; above 7:12, the TRI manual requires battens. Below 2-1/2:12, tile is not a code-approved roof covering because water sheds too slowly through the laps.
How heavy is a clay tile roof and will my house support it?
Maker spec sheets put clay tile at 800 pounds per square (Verea flat) to 1,025 pounds (Ludowici French), or about 8 to 10.25 psf, and Ludowici’s Shingle tile at 1,300 to over 2,200 pounds per square. Many existing structures framed for lighter roofs need reinforcement, so have a structural engineer check the framing against your tile’s weight before a conversion.
Can I install a clay tile roof myself?
It is not recommended for most homeowners. A square weighs 800 pounds or more, the fastening schedule changes with slope, snow and wind under IRC R905.3.7, and flashing errors are expensive to fix after the roof is loaded. HomeGuide’s 2026 installed range of $8 to $25 per square foot reflects how much of the cost is skilled labor.