Reusing 1978 Clay Tile on Skip Sheathing Near the Coast
A 3,200 sq ft Spanish clay tile roof on a 1978 house three miles from the coast is scheduled for re-roofing. The assembly is tile over two layers of 30-lb felt on 1x6 skip sheathing at 10 in. o.c.; there is no solid decking. The signed contract calls for removal of tile and underlayment, installation of a 40-year synthetic underlayment, and reinstallation of the owner's existing tile. The owner, to save money, insists that "at least 70 percent" of the tile be reused. On the pre-job walk you count roughly 25 percent broken or previously mastic-repaired tiles, find rusted valley metal the owner says was replaced two years ago, and note that the tile manufacturer lists 2.5:12 as the minimum slope for this profile; the roof is 4:12. The job is a $48,000 lump sum with a 10 percent mobilization draw already paid.
1. The owner wants 70 percent of the tile reused. What is your professional judgment, and what must change in the contract before work starts?
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Reuse is workable; a 70 percent guarantee in a lump sum is not.
- Removal breakage on 45-year-old clay that is already ~25 percent broken or mastic-repaired typically runs 15–30 percent, so a 70 percent net reuse rate is optimistic, not a production assumption you can bank.
- The percentage should become a measured outcome, not a promise: credit the owner a stated dollar amount per square (or per piece) of tile actually salvaged and reinstalled, and state in writing that new matching tile will be purchased for the visible field, all valleys, hips, ridges and edge courses.
- Sequence salvage from the least visible slopes first so the best stock goes to the front elevation.
- Photograph and log the existing broken/repaired tile and get the owner's signed acknowledgment of the pre-existing condition before tear-off.
- Confirm lead time and price on matching new tile before demolition; a supply gap mid-job with an open roof is the real risk here.
Tear-off should not begin until the reuse credit language and the new-tile responsibility are executed as a written change order.
2. Evaluate the underlayment selection and fastening for this specific assembly.
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- Skip sheathing changes the fastening problem. Fasteners only hold where they hit a board; lay out chalk lines over the 1x6s and expect a higher fastener count than a solid-deck job. Do not let the crew nail between boards and rely on the felt.
- A generic synthetic underlayment may not be listed for spaced sheathing. Use only a product the tile manufacturer lists for use beneath that tile profile over skip sheathing, and install at the manufacturer's spacing with cap nails or button caps.
- Temperature matters under tile. Tile roofs run hot; if the approved product line offers a high-temperature version, that is the correct choice over a 4:12 field.
- Corrosion: three miles from the ocean, electro-galvanized or plain steel fasteners will bleed rust onto tile and stain the fascia. Use hot-dip galvanized or stainless (Type 304) fasteners and replace the rusted valley metal with a heavier gauge.
- Verify support. Confirm with the tile manufacturer that 1x6 at 10 in. o.c. meets the required support for this profile; if not, the fix is battens or added purlins, not a heavier underlayment.
The spec should be revised by written supplement naming the approved underlayment, fastener type, and any battens - not left as "40-year synthetic."
3. The rusted valley metal was reportedly replaced two years ago. Who pays for its replacement now, and how do you handle it?
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- This is a pre-existing condition discovered in the field, not work you performed, so the default is a change order to the owner.
- But read the scope first: if the contract says "replace flashings as necessary" or similar, the cost is already inside your lump sum and you absorb it. If it says "reuse existing valley metal," the replacement is extra.
- Do not simply install new underlayment over rusted metal and hope - perforated valley metal guarantees a callback inside your warranty period.
- Practice: photograph the condition, price the item (linear feet of new metal, plus the labor to work it into the tile field), and issue a written change order for signature before the area is covered. Note it in the daily log with the date and the owner's decision.
- If the owner declines, get that refusal in writing and exclude the valley metal from the workmanship warranty in writing. A verbal refusal will not survive a leak claim.