Repair and reattachment of clay roof tile

Technical procedures are supplied by GSA only as a reference. All procedures have been reviewed for general consistency with federal standards for rehabilitating historic buildings. Specifications should only be applied under the guidance of a qualified preservation professional who can assess the applicability of a procedure to a particular building, project or location.

References to products and suppliers serve as general guidelines and do not constitute a federal endorsement nor a determination that a product or method is the best alternative or compliant with current environmental regulations and safety standards.

Part 1 – General

1.01 Description

1. This specification provides guidance for the repair and reattachment of clay roof tiles.
   1. This specification has been developed for use on historic properties (defined as any district, site, building, structure, or object that is listed in or eligible for listing in the National Register of Historic Places) and provides an overview of accepted practices. Site-specific specifications, when appropriate, will be provided by the Architect.
   2. All work described herein and related work must conform to the Secretary of the Interior’s Standards for the Treatment of Historic Properties.
   3. The Contractor shall provide all labor, material, equipment, and operations required to complete the rehabilitation work indicated herein.
   4. All work described herein and related work must have the approval of a Cultural Resources Manager, Conservator, Historic Architect, or other professional who meets the standards outlined in the Secretary of the Interior’s Standards – Professional Qualifications Standards pursuant to 36 CFR.

1.02 Section includes

1. Removal and reattachment of loose tiles
2. Replacement of damaged tiles

1.03 Related sections

1. Section 01100-07-S for general project guidelines to be reviewed along with this procedure. These guidelines cover the following sections and should be reviewed prior to performing this procedure and should be followed, when applicable, along with recommendations from GSA Historic Preservation:
   1. Safety Precautions
   2. Historic Structures Precautions
   3. Submittals
   4. Quality Assurance
   5. Delivery, Storage and Handling
   6. Project/Site Conditions
   7. Sequencing and Scheduling
   8. General Protection (Surface and Surrounding)
   9. Historic Building Treatment Procedures

1.04 Quality assurance

1. The contractor performing the work described in this section shall have a minimum of five years experience in repair and installation of historic clay tile roofing and shall have successfully completed at least three projects of similar scope within the previous five years. He/she shall demonstrate a working knowledge of The Secretary of the Interior’s Standards for the Treatment of Historic Properties with Guidelines for Preserving, Rehabilitating, Restoring & Reconstructing Historic Buildings.
2. Warranty: The contractor shall provide a written warranty for the clay tile roof repairs against failures in materials and workmanship for a period of five years after the date of substantial completion.

1.05 Submittals

1. The contractor shall submit to the architect or GSA Approving Official:
   1. A detailed description and schedule for repair of clay roof tiles including annotated drawings and/or photographs of areas to be repaired. A complete external and internal inspection is required prior to submittal. The inspection will also aid in determining a future maintenance plan. Prepare a narrative description of procedures to be used for protection of the existing roof, removal of tiles and installation/reinstallation of roof tiles.
   2. The manufacturer’s product literature for all proprietary products specified for clay tile roof repairs including replacement tiles, cements, mortars and metal fabrications. Product literature shall include specification data, Safety Data Sheets (SDS), and instructions for storage, handling, and use.
   3. A project safety plan to include at minimum: any personal protective equipment to be used by the contractor’s staff such as disposable clothing, gloves and safety glasses, procedures for emergencies and accidents, documentation of staff training in use of equipment and/or chemical products as required by the manufacturers.
2. The contractor shall submit samples of the following items to be used in the repair work.
   1. Replacement roof tiles: Submit samples of replacement roof tiles. Samples shall illustrate the full range of color variation to be expected. Salvaged or replacement clay tile that matches existing tiles should be used for replacement. Modern tiles or cement-based tiles are not an appropriate substitute for historic clay tile.
   2. Fasteners: Submit samples of nails, bibs, clips and other metal fasteners to be used in the attachment of the new roof tiles.

1.06 Testing and mockups

1. Contractor, at inconspicuous locations designated by the Project Team and GSA Historic Preservation, shall perform small test patches (no larger than 6 inches by 6 inches) for all products to be used. Testing will determine the best method(s) to perform the work and ensure that the chosen products do not cause harm.
2. Following testing, mockup panels shall be created (mockup panels may incorporate successful test patches) using the chosen methods. Size and location of mockup panels shall be determined by the project Team and GSA Historic Preservation.
3. In the presence of the architect, all personnel to be assigned to the project shall demonstrate their ability to complete the required work in an acceptable manner. Each mechanic shall remove and replace one clay roof tile at locations designated by the architect. Personnel not completing the sample work in an acceptable manner shall not be permitted to work on the roofing repairs.
4. The methods used, their application, etc. shall be in accordance with manufacturer’s instructions.
5. The mockup shall include an evaluation of the materials and techniques proposed for the protection of surrounding areas and materials.
6. Approved mockups shall become part of the work and shall serve as the quality standard for all similar work.
7. Any testing, demonstrations, or mockup that is rejected by the project team shall be removed in its entirety without damage to the surrounding masonry and a new demonstration/mockup shall be performed for the project team’s review.

1.07 Delivery, storage, and handling

1. The Contractor shall:
   1. Deliver clay roof tiles and accessory materials to the site in manufacturer’s original unopened packaging with identification information visible thereon.
   2. Store field tiles on pallets away from general construction operations until ready to begin installation. Special shapes must be stored in manufacturer’s original packaging. Store roof tiles in such a manner as to avoid unnecessary handling.
   3. Store accessory materials such as mastic, adhesives, membranes, etc., off the ground in a dry, secure location where ambient temperatures are within the manufacturer’s recommended range.
   4. Provide power equipment as required to safely move tiles to the roof in preparation for installation.  Outside storage is acceptable for power equipment.
   5. The contractor shall dispose of all packaging, waste materials and construction debris in accordance with local, state and federal environmental regulations. All wood scrap shall be kept separate for recycling. No burning of debris, waste material or trash will be allowed on site.
   6. Where possible, clay tiles removed from the roof shall be salvaged for reinstallation. Stockpile salvaged tiles in a location designated by the owner’s representative. Store salvaged tiles on pallets, off the ground. Do not stack pallets.

1.08 Safety

1. The contractor shall only use chemical products whose safety data sheets (SDS) have been reviewed and considered acceptable by the government. Any project surfaces containing lead-based paint, as disclosed by the government, shall be handled by the contractor in accordance with OSHA (29 CFR 1926.62), EPA (40 CFR 261) and state regulations. Any lead-based paint or coating that is removed in a project resulting from this scope shall undergo Toxicity Characteristic Leaching Procedure (TCLP) testing by the contractor. The contractor shall dispose of any lead waste as hazardous if it fails the TCLP.
2. The contractor shall isolate the work area with cones, tape or similar means as possible for the duration of the project, to prevent unauthorized individuals from entering. At least one entrance must remain accessible during the course of the work.
3. For any work required on elevated surfaces (4 feet or more above the ground) the contractor shall install and use any ladders, scaffolding or platforms in accordance with OSHA regulations (29 CFR Subpart M).

1.09 Project/site conditions

1. The contractor is responsible for protecting existing adjacent materials during the execution of the work. Provide all necessary protection and work procedures to avoid damage to existing material assemblies not a part of the work of this Section. At a minimum, the contractor shall:
   1. Provide sturdy, weather-proof protection at all areas exposed during clay tile roof repairs and installation. Do not leave interior spaces exposed to the elements overnight. The contractor shall maintain adequate supplies of protective materials on site at all times in the event of sudden weather changes.
   2. Protect roof framing during clay tile installation by distributing materials in such manner as to avoid overloading.
   3. Protect new and existing clay tile roofing by limiting foot traffic over installed tile and ensuring the use of proper soft-soled footwear by all roofing personnel. Use sand bags, planks, suspended ladders and/or platforms where possible to avoid damage to roof surfaces.
   4. Protect roofing and gutters from damage by ladders or work platforms. Keep gutters clear of debris from clay tile repair work.
2. The contractor shall coordinate roofing work with the work of other trades to minimize delays in the construction process. Coordinate roofing with other work including, but not limited to, structural framing, exterior finish carpentry, flashing and gutter work and chimney restoration. Schedule roof work to avoid traffic by other trades over newly installed areas.
3. All contractor personnel performing treatment operations shall be provided by the contractor with gloves, respirators, protective clothing and any other personal protective equipment (PPE) as recommended by the manufacturer of the products used during the work and required by local, state, and federal regulations. Rubber sole shoes with non-slip tread shall be worn on the roof.

Part 2 – Products

2.01 Manufacturers

1. The tile product and manufacturer must be pre-approved by the project team.
2. For repair projects, the contractor shall have the option of providing salvaged roof tile, subject to approval of submitted samples, if this provides a better match to the existing roof materials.
3. Where necessary, tiles may be removed from inconspicuous areas of roof and relocated to patch more visible areas to ensure the best match. Areas for tile removal must be pre-approved by the project team and/or GSA Historic Preservation.

2.02 Materials

1. Tile:
   1. Salvage tile to match existing in good condition.
   2. Incombustible, vitrified tile manufactured from shale and fire clays, having less than two percent moisture absorption when tested in accordance with ASTM C 67, and meeting Grade 1 freeze/thaw resistance requirements when tested in accordance with ASTM C 1167. No substitute materials such as pigmented concrete, metal, or plastic shall be accepted.
   3. Historic tile roofs often incorporated variations in tile exposure and size to compensate for the effects of perspective when viewed from the ground. When attempting to match existing tiles, the contractor shall note variations in size and exposure in the historic tile and procure replacements to fit accordingly.
2. Shapes and Fittings:
   1. Supply special shapes and fittings of same material and finish as adjacent field tile, factory-formed before firing, as indicated on drawings or specified in manufacturer’s instructions for project conditions including, but not limited to, the following: Hip caps, ridge caps, rake edges, detached gable rake edges, eave edges, valley edges, termination caps, half tile, end bands.

2.03 Accessory materials

1. New sheet metal for forming clips shall be 26 gauge Type 304 dead soft stainless steel coated with 50 percent zinc and 50 percent tin alloy to a thickness of 20 microns (TCS II).
2. Underlayment: Where sheathing is present, asphalt-saturated organic felt conforming to ASTM D 226, Type II, non-perforated. Nominal weight 30 pounds per 100 square feet (1.5 kg/sq m); two layers required.
3. Wood:
   1. Wood Stringers: S4S, maximum 19 percent moisture content, nominal one inch (25 mm) thick, of height required to support tile.
   2. Wood Nailers and Cant Strips: Preservative-treated wood.
4. Flashing: As specified by project architect and approved by GSA Historic Preservation.
5. Tile Fasteners: Corrosion-resistant; types and sizes specified in manufacturer’s instructions for indicated uses and conditions.
6. Mortar Materials
   1. Mortar or grout is not a substitute for weatherproof tile repairs. Sometimes a dab of mortar is added for extra stability or to deter wind-blown rain.
   2. Mortar for setting tile and grout for finishing rake and eave edges, if used, shall have comparable flexibility and always be lower in strength and permeability than the tile itself. Mortar mixes must be approved by the Architect.
7. Sealants and adhesives: Waterproofing compounds are not appropriate for use on clay tile.

2.03 Equipment

1. Rule or Tape
2. Hammer
3. Chipping Hammer
4. Sponge
5. Fox-tail Broom
6. Caulking Gun
7. Slate Ripper
8. Drill and Glass Drill Bits

Part 3 - Execution

3.01 Examination

1. Examine all existing tile prior to the start of work. Note any tile that can remain or be reinstalled.
   1. Whenever possible, perform inspection from ground or from above if possible. Inspect for:
      1. Biological growth: 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. This is more apt to occur on north slopes.
      2. Individual tiles: Inspect tile ridge details and starter courses for missing, loose, broken, or out of place tiles.
      3. Wear: Excessive weathering, spalling or staining indicating weathering and age. Tile movement may be detected by unusually clean areas (lack of stains). Movement is often a sign of failed fastenings.
      4. Leaks: 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 and along the downhill side of any roof penetrations for evidence of leakage such as water stains.
2. Examine all framing, sheathing and lath, where applicable, for any conditions that may affect the repair and reinstallation of the clay tile roofing. Notify the architect if any framing and/or decking is found to be unsuitable for roofing. The absence of sheathing is not necessarily unsuitable. If sheathing was historically absent on the roof, the repairs should be conducted in the same manner.

3.02 Preparation

1. Roofing contractor to coordinate roof repairs with chimney restoration, carpentry, flashing and gutter work if required to ensure that structural repairs are completed and eave configurations and tile projections are suitable to receive new gutter work and that flashings and other items may be installed prior to tile installation.
2. The roofing contractor shall transport and stage tiles in such a way as to avoid overloading the roof framing during installation.
3. Protect roof tiles to remain using sandbags, planks, or padded ladders as required to distribute the weight of personnel required to access the roof. Do not walk over roof tiles unnecessarily.
4. Where roofing to remain is too fragile for foot traffic, remove tiles as required to create a path to the repair area. Salvage all sound tiles for reinstallation.
5. 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 the removal, as well as length, width, and thickness after removal.

3.03 Removal of existing roof tiles

1. Salvaging a Broken or Loose Tile: If the shingle tile is broken at the nail hole, salvage the tile by carefully drilling a new hole with a carbide-tip drill and nailing the tile in place with a hammer so that the tile “hangs” on the nail.
2. Remove slipped or mismatched tile(s) using a hacksaw blade or slate ripper to cut the nails or wire ties. Gently remove the tile(s) without damaging the edges of adjacent tiles to remain. Broken tiles may be cracked with a mallet to facilitate removal.
3. Where flashing and/or gutter replacement is required, remove all tiles covering the full extent of the metalwork to be replaced.

3.04 Replacement tile installation

1. Sound all tiles prior to installation by tapping lightly. All tiles should ring clear. Tiles that rattle or produce a muffled sound when tapped are likely defective and shall not be used.
2. Nails shall not be driven so as to produce strain on tiles. Nails shall be driven so that the head protrudes slightly from the surface of the tile. The tile shall be loose when fully nailed. If this is not executed properly, building movement could crack the tile.
3. Some early tiles utilize only their hook shape to secure themselves to the roof lath or battens. The original installation should be used unless the architect confirms that the method is causing roof damage. If the architect deems appropriate, spot replacement of damaged, missing or non-matching tile may be done by one of the following methods:
   1. Clip Method
      1. A noncorrosive sheet metal strip is nailed in place underneath the location where the replacement tile will be installed. The strip shall be long enough to protrude several inches below the bottom edge of the replacement tile. Fold the exposed portion of the strip to double thickness.
      2. Slide the replacement tile into position. Hold in place by folding the doubled sheet metal strip and crimping tight to the bottom edge of the tile.
   2. Hook Method
      1. A pre-formed wire or non-corrosive sheet metal hook is placed over the top edge of the course beneath the tile to be replaced.
      2. Slide the new tile into position under the course above, bending the bottom of the sheet metal/wire hook up and over the bottom edge of the tile.
   3. Nail and Tie Method
      1. Where multiple tiles are removed, reinstall using nails or wire ties fastened to nails driven directly into the roof deck or battens.
4. Replacement ridge tiles shall be laid in to match the pattern of the remaining tiles.
5. Entire surfaces of all roofs, except as noted, shall be covered with tile in a proper and weatherproof manner. Upon completion, all tiles must be sound, whole and clean. The roof must be left watertight and neat in every respect, and subject to the Architect’s approval. 

3.05 Final report

1. The Contractor Shall:
   1. Provide a final report of completed work, including all approved submittals and photographs of the areas cleaned that were taken before, during, and after the work.
   2. Provide a written summary of the project and results upon final inspection and approval. The summary shall include a discussion of steps taken or new findings not specified in the initial documentation. Summary should also include any applicable ongoing care, repair and warranty requirements.