Concrete Tile Uplift in a High-Wind Zone
A 4,500 ft² concrete tile roof on a 6:12 gable is in a 130-mph basic wind speed zone, Exposure C. The assembly is one layer of 30-lb felt over 15/32-in. plywood, 1x4 wood battens at 24 in. o.c., and 16-in. concrete tiles fastened with two 1¼-in. electrogalvanized roofing nails per tile. Battens are nailed with 8d common nails at 24 in. o.c. There are no battens at the ridge or eave. After three years, tiles are slipping in the field, the underlayment is torn at the valley, and nails show rust at the eave. The tile manufacturer requires two fasteners per tile in the headlap and stainless or hot-dip galvanized fasteners for coastal exposure. The building is 4 miles from the coast.
1. Evaluate the fastening schedule against the wind zone and manufacturer requirements.
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The schedule is not adequate for a 130-mph Exposure C site. Key problems:
- Fastener length and type. A 1¼-in. electrogalvanized roofing nail is short for tile over a batten and is not the corrosion-resistant fastener the manufacturer requires near the coast. Electrogalvanized nails can rust through at the eave where moisture collects.
- Two fasteners per tile is only the minimum. In a high-wind zone, every tile in the field and at edges should be mechanically fastened per the manufacturer's wind-pressure design, not just two nails at the headlap.
- Batten attachment. 8d common nails at 24 in. o.c. may be adequate for gravity but not for uplift. The batten schedule must be designed for the wind pressure, with closer spacing at perimeter and ridge zones.
- Missing edge battens. No battens at ridge or eave leaves the tiles and underlayment unsupported at the highest-uplift locations.
A tile roof in this wind zone needs an engineered fastening schedule, not a generic two-nail-per-tile rule.
2. Diagnose the slipping tiles and torn underlayment.
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Slipping tiles are most likely caused by fasteners that do not engage the batten or tile headlap properly. If nails were driven above the headlap, through the overlap, or overdriven, the tile is not held. Short 1¼-in. nails may barely penetrate the batten, and cycling by wind and thermal movement works them loose. Missing edge battens allow the lower courses to creep.
Torn underlayment at the valley has a different mechanism. Valley tiles and battens concentrate load, and if the underlayment is a single layer of 30-lb felt with no valley protection, movement of tiles above it abrades the felt. A torn valley underlayment lets water reach the deck. The tear is likely at a batten end or where valley metal was omitted.
Rust at the eave confirms moisture exposure and inadequate fastener corrosion resistance. Rusted nails lose section and holding power, accelerating slip. The three symptoms are linked: water entry, fastener corrosion, and loss of mechanical restraint.
3. Recommend repair and re-roof details.
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Repair scope:
- Remove tiles and battens in affected field and valley areas. Replace any delaminated sheathing.
- Install a high-temperature ice-and-water or synthetic underlayment in the valley, with valley metal and correct laps.
- Replace battens with preservative-treated lumber, fastened at the engineered spacing for the wind zone; add eave and ridge battens.
- Fasten every tile with stainless or hot-dip galvanized fasteners of the length required to penetrate the batten. Place fasteners in the headlap per the manufacturer.
- Provide eave closure and ridge venting to resist wind-driven rain and uplift.
Quality control: pull-test a sample of fasteners, verify batten spacing at perimeter zones, and inspect from the eave for exposed or overdriven nails. In a 130-mph zone, the perimeter and ridge tiles are the first to fail, so do not accept a repair that only fixes the field.