Removing And Replacing A Clay Tile Roof
- Procedure code:
- Hspg Prepared For Nps - Sero
- Thermal and Moisture Protection
- Clay Tiles
- Last Modified:
- This procedure includes guidance on reroofing a clay tile roof.
- Clay tile roofs are extremely weather resistant due to the low porosity of the tiles. The tile itself can last indefinitely.
- Premature failure of a clay tile roof usually results from failure of the metal flashing and fasteners (these do not last nearly as long as the tile), poor installation and/or the use of less expensive materials.
- If nails are driven too far prohibiting the tiles from hanging on the nail, the tiles will crack during thermal movement.
- If galvanized nails are used to fasten a tile, they will often corrode in 40 years or less.
- It is possible to replace just the flashing if the rest of the roof is sound, but if there is widely distributed failure, reroofing may be the best option.
- See 01100-07-S for general project guidelines to be reviewed along with this procedure. These guidelines cover the following sections:
- Safety Precautions
- Historic Structures Precautions
- Quality Assurance
- Delivery, Storage and Handling
- Project/Site Conditions
- Sequencing and Scheduling
- General Protection (Surface and Surrounding)
These guidelines should be reviewed prior to performing this procedure and should be followed, when applicable, along with recommendations from the Regional Historic Preservation Officer (RHPO).
- Abbey tile--is of the same type as the Spanish, but of a special design. the tiles are tapered and 16" long, the under one a true half-circle in section, the upper one being hog-backed, the combination making a handsome and sound roof. With a 3" lap, 200 tiles are required per square.
- English tile--a plain, flat tile that interlocks at the head and on one side.
- French tile--is a large interlocking shingle tile with deep grooves that give strong shadow lines and channel water.
- Greek pan--a tile system consiting of flat pans that are capped by a gable-shaped top piece
- Italian pan--a tile system consisting of a flat pan with short splayed-outward sections that act as a pan or when flipped over act as the cover between two pans.
- Mission tile--same thing as barrel tile. They do not interlock, but are lapped in courses. The convex pieces are laid on battens and cover the vertical joints between rows of concave tiles.
- Shingle tile--also called flat tiles, are individual pieces that are lapped and nailed like slate.
- Spanish tile--also known as S tile or Pantile, is an interlocking tile that provides a moderately undulating roof surface.
- Roman tile--is a tile system consisting of flat pans that are capped by barrel-shaped top pieces. Also called a pantile.
1.03 DELIVERY, STORAGE AND HANDLING
- Packing and Shipping:
- Field tile is generally shipped in pallets, and fittings in boxes.
- Acceptance at Site:
- Upon receipt of the shipment, pallets and boxes should be inspected for transportation damage.
- Examine the tiles for color by taking 10 field tiles at random from each of the pallets.
- Spread them out and observe the shade variation. The range of shades is a prime reason why a tile roof is so handsome.
- Replace the material in its original containers for storage. Pack any existing extra stock in similar manner.
- Storage and Protection:
- Store tile roofing materials in a dry location. When stored outside, place on platforms off the ground covered with waterproof coverings which will not produce any condensation.
- Power equipment is needed to deliver the tiles to the roof level. Outside storage is acceptable.
- Manufacturers should supply instructions for stacking tiles on gable and hip roofs so that loads are properly placed and the tiles located for minimum handling by the tile applicator. Proper job organization is important to save unnecessary movement of heavy units.
- DO NOT stack or store the roofing materials on the roof structure. Improper roof loads may cause the structure to fail.
1.04 PROJECT/SITE CONDITIONS
- Environmental Requirements:
- Do not apply new or repaired tile roofs in wet weather.
- Do not remove roofing from structures when rain is forecasted or in progress.
- If roofing is to be removed on a clear day, remove no more than can be replaced or repaired in one day.
- Like slate, tile requires little ongoing maintenance: no painting, no preservative coatings, waterproofing or fireproofing, and almost no cleaning.
- Tile's very low porosity makes it extremely weather resistant. The tile itself can last many years; 75 years is claimed for a thin flat shingle, and 350 years is not unreasonable for a barrel tile.
- Clay tile roofs are especially susceptible to mechanical damage from walking on tiles or from fallen tree limbs or other objects. Adjacent trees and landscaping should be kept trimmed and away from roof to avoid breakage. Heavy pads and ridge ladders should be used to equalize a person's weight whenever any work is done on the roof.
- Boston Valley Terra Cotta
6860 South Abbott Rd
Orchard Park, NY 14127
Manufactures custom-made roof tiles and architectural terra cotta for like replacement. Specialize in restoration projects, will match color, texture, and detail. Free literature.
Gladding, McBean & Co.
Lincoln, CA 95648
Clay roofing tiles and terra cotta pieces sold through distributors. Free roofing brochure.
Ludowici Roof Tile Co.
4757 Tile Plant Rd.
P.O. Box 69
New Lexington, Ohio 43764
Terra cotta pieces and clay roofing tiles in traditional patterns and imitation wood are sold direct and through distributors. Free product sheets on each style.
- Midland Engineering
South Bend, IN 46637
A major distributor for roofing products including German clay tiles and Vermont slate, sold through roofers and direct. Free brochures on all products - specify your interest.
Vande Hey Raleigh Mfg., Inc.
Little Chute, WI 54140
Manufactures a broad line of extruded concrete roofing tiles, including a simulated slate and a Mission tile. Also has a large stock of recycled slate, concrete, and clay tiles. Free literature.
Hendricks Tile Manufacturing Co., Inc.
Concrete tiles designed to imitate wood and terra cotta are sold through distributors. Free literature.
- Sheathing: Must be sound with no embedded metal or nails, no rotted ares, splits, cracks, or unevenness that would cause difficulty in laying tile or create potential for breakage of the brittle tile.
- Flashing: Use 20-oz. copper or lead-coated copper. Use 24 oz. material if bending is not complex. Line all valleys at least 20" wide for short valleys, 24" wide for long valleys, with 1/4" edge turned over and fastened with cleats. Lap joints a minimum of 4", do not solder.
- Nails for tiles and cleat (to fasten valley metal) shall be copper of sufficient length and holding power as recommended by the tile manufacturer. Roofing nails should have barbed or deformed shanks. They should be 11- or 12-gauge and have large heads of 3/8 to 7/16 inch diameter. The nails should be long enough to hold the tile and penetrate at least 3/4 inches into the deck lumber section.
NOTE: NAILS SHOULD NOT BE DRIVEN TIGHT AGAINST THE
TILE TO PREVENT DAMAGED AND ALLOW FOR MOVEMENT.
- Plywood deck - use ring shank nail, length for slight penetration through underside of deck.
- Board plank deck - use smooth shank nail at least 1 (one) inch length but nail must NOT penetrate underside of deck.
- Gypsum plank and nailable concrete decks use stainless steel or silicon bronze screw shank nail of length to penetrate 1/2 to 3/4 distance of deck. Never penetrate underside of deck. (Deck material should be fresh when tiles applied as old decking may be difficult.) If deck material is excessively hard use smooth shank nail.
- Sealant: Dow Corning Clear Silicone Rubber Sealant, or clear silicone sealant as manufactured by General Electric, or approved equal.
- Elastic Cement: Use only non-staining, non-corrosive cement as recommended by the manufacturer.
- Rule or tape
- Chalk line and chalk
- Chipping hammer
- Felt knife
- Roof jacks
- Mason's trowel and bucket
- Fox-tail broom
- Caulking gun
- Sheet metal shears
- Slate ripper
- Drill and glass drill bits
- Diamond blade masonry saw (water-cooled)
- Tile-setters blade saw with tub
- Whenever possible, make inspection from ground or from above if possible.
- Inspect for dirt build-up, biological attack, mold, fungus. Also inspect for buildup of debris and vegetation such as moss or lichen. Heavy coatings of any type form dams and stop natural drainage, resulting in various types of deteriorations.
- Inspect tile ridge details and starter courses for missing, loose, broken, or out of place tiles. Inspect for rust around nails (this will tell you if galvanized rather than copper nails were used), or nail pulling, excessive weathering or exposure, erosion, or staining indicating overall deterioration.
- Tile movement may be detected by unusually clean areas (lack of stains). Movement is often a sign of failed fastenings.
- Inspect the underside of the roof deck from the attic to detect leaks. Flashings are the most vulnerable points. Therefore, inspect the underside carefully at all flashing points for evidence of leakage such as water stains.
- In addition to scheduled inspections, inspect after each exposure to unusually severe weather conditions such as strong winds, hail, or long continuous rains.
- Establish rules for any foot traffic that may be required for the maintenance of the roof. Clay tile should be walked on as little as possible.
- Lay down heavy padding and then hang a self- supporting ladder over the ridge of the roof.
- Ladders to the roof should be secured at the top to prevent any sliding or fall-out from the building. The ladders should be set on an incline whereby the bottom of the ladder is approximately 25% of the height from the base of the building.
- Safety on the roof:
- Wear rubber-soled shoes that have non-slip tread (preferably sneakers with a high top for good ankle support). Avoid wearing loose clothing.
- Wear safety-belt or harness and secure to the chimney (if it's in good shape) or to a window on the opposite side of the building. Leave only enough slack so you can work comfortably in one area, and adjust the slack as you work on other sections of the roof.
- Be sure the roof is clear of debris and water. Avoid stepping on damaged or crumbling roofing materials.
- Steep roofs: On slopes where the roof is steeper than 4 inches rise per foot, special consideration must be given to footing and handling of materials.
- Chicken ladders or cleats shall be used on the roof as required for adequate footing.
- Safety lines, of an approved type should be properly worn and secured with ropes of sufficient strength. Rubber-soled shoes with grip-type bottom should be worn.
- Carrying and transporting of materials should be limited to a safe amount so that balance and footing are not impaired.
- Do not work on roof when wet or snow-covered.
- Remove only a quantity of old tiles which may be replaced on that same day. At the end of the day, use 15 pound roofing felt or polyethylene sheeting and insert under old tiles or lap junctions of new tile areas with existing and secure to make the roof watertight and windproof.
- Surface Preparation:
- Carefully examine, measure, and record existing tile patterns at edges, hips, ridges, and other special conditions. Measure the exposed dimensions and amount of lap of each type piece prior to removal, as well as length, width, and thickness after removal.
- When removing existing roofing, strip tiles down to the roof deck.
- If necessary, point up chimney joints and replace worn flashings. Clean, rebuild or replace gutters. After repairing of problem areas, clean debris from the roof surface.
- Be careful not to damage old metal wall and vent flashings that may be used templates for cutting replacements. If metal cap flashings at the chimney and other vertical masonry wall intersections have not deteriorated, bend them up out of the way so that they may be used again. Carefully remove tiles in these areas to avoid damaging reusable base flashing.
- For safety of the personnel, keep the deck clear of waste material as the work proceeds. Sweep the deck clean after old roofing has been removed.
- At this point, inspect the deck to determine whether it is sound. Make whatever repairs are necessary to the existing roof framing to strengthen, level and true the deck. Replace rotted, damaged, or warped sheathing or delaminated material plywood.
- Cover all large cracks, knot holes, loose knots and resinous areas of the deck with sheet metal patches nailed to the sheathing.
- Remove loose or protruding nails or hammer them down.
- Do not apply new materials over wet sheathing.
3.03 ERECTION, INSTALLATION, APPLICATION
- Replacing Flashing only:
- Remove tiles surrounding the valley flashing.
- If tile is to be salvaged and reused, carefully remove nails using either a slate ripper, or insert a hack saw blade under the cover tile and saw through the nail.
- If the tile is already broken, lightly strike the broken tile with a hammer to further break it into pieces for removal. Exert extreme care to avoid damage to any lightning protection system.
- Replace underlayment as required. Use minimum 40 lb. asphalt impregnated roofing felt.
- Cut and install new copper flashing and counter flashing as required. See (b)(2) below.
- Replace tiles matching original lap and general appearance.
- Reroofing with Clay Tile Shingles:
- Installing Underlayment:
- Cover all pitched roofs under tile with best quality asphalt impregnated roofing felt weighing not less than 40 pounds per square, 60 pounds on low slopes.
- Lay parallel to ground level, lap 2" horizontally and 6" vertically.
- Carry felt 6" up all vertical surfaces and 4" over gutter and valley metal.
- Double layer shall be applied at eaves.
- Fasten all edges with large headed galvanized nails on 6" centers.
- Install Flashing:
- Open Valleys: Line all valleys with 16 oz. copper, usually 20" in width for short valleys, 24" for long valleys (wider where necessary), with 1/4" edge turned over and fastened with cleats. Lap joints 4" (more where required), but do not solder.
- Closed Valleys: Flash between each course of tiles with 16" strips of same length as tiles.
- Rounded Valleys: Flash between each course of tiles with curved strips of same length a tiles. Extend strips 8" beyond tiles, 4" under tiles and at least 6" up wall.
- Underlay all valley metal with full width 40 lb. felt. Where gutter metal extends upon roof, it must be brought up to a point above gutter level.
- Extend flashing at dormers, chimneys and other side walls up the vertical surfaces not less than 6" and thoroughly counterflashed. Extend such flashing under tile not less than 4".
- Wood saddles and returns must be lined with 16 oz. copper extending upon sloping roofs not less than 12" (more where necessary) and up vertical walls not less than 6", thoroughly counterflashed.
- All counterflashing is to be plugged, pointed and made secure.
- Where tile and metal roofs intersect, extend metal up tile roof 12" or more.
- Extend gutter metal up roof to a point higher than outer edge of gutter.
- Wood Strips:
- Apply on hips and ridges 1" wood stringers of proper height to carry hip rolls and ridge. Also as required by the particular style of tile, cart strip at eaves, gable rakes and end bands, and for covers of mission tiles. See manufacturers instructions.
- If roof deck is poured concrete, embed from ridge 1" x 2" beveled wood strips, extending from eave to ridge, spaced 20" on centers.
- Concrete must be smooth and flush with strips.
- Use felt weighing 50 pounds per square and fasten with lath nailed over embedded strips.
- Across lath apply horizontally 1" x 2" wood strips spaced to accommodate tile, and proceed as directed for a sheathed roof.
NOTE: All strips to be supplied by general contractor and applied by his crew under direction of roofer.
- Application of Tile:
- Minimum roof pitch is determined by the type of tile used. Follow the manufacturer's instructions.
- Roof deck shall be clean, smooth and dry when roof tiles are applied.
- On vertical applications or extremely steep pitches where wind currents may cause lift, set the butt of each tile in a bead of plastic cement or sealant or install copper "hurricane clips" at intervals indicated by manufacturer. Use plastic cement or sealant carefully to avoid smearing exposed tile surface.
- Lay tiles in straight lines parallel to ground level, lapped according to manufacturer's instructions.
- Fasten each tile with 1, 2 or 3 nails as required in each tile or fitting. Fasten tiles overlapping sheet metal valleys with copper wire nailed into deck beyond flashing-- do not nail through metal.
- For open valleys the exposure of metal at th top shall be at least 6" and shall increase at the rate of 1" for every eight feet of flow down the valley.
- Cement gable rakes to field tiles and fasten with nails.
- Cement ridges in laps and where they rest on roof tiles. Fasten with 2" copper nails.
- Cement hip rolls in laps and fasten with 2" copper nails.
- Where tiles join hip stringers, make thoroughly waterproof with plastic cement.
- When hip starter and closed ridge end fittings have not been specified, the voids at ends of hips and ridges shall be filled with mortar colored to nearest match of tile color.
- When ridge angles and hip/ridge terminals have not been specified they shall be mitered of job, nailed or wired, and set in elastic cement.