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Historic Preservation - Technical Procedures

Spectitle:

Replacing Loose, Broken Or Missing Clay Roof Tiles

Procedure code:

0732103R

Source:

Hspg Prepared For Nps - Sero

Division:

Thermal And Moisture Protection

Section:

Clay Tiles

Last Modified:

02/24/2012

Details:

Replacing Loose, Broken Or Missing Clay Roof Tiles



REPLACING LOOSE, BROKEN OR MISSING CLAY ROOF TILES


PART 1---GENERAL

1.01 SUMMARY

    A.   This procedure includes guidance on replacing clay roof
         tiles that are loose, broken, or missing.  GENERALLY,
         THIS WORK SHOULD BE ACCOMPLISHED BY A EXPERIENCED ROOFING
         CONTRACTOR.

    B.   See 01100-07-S for general project guidelines to be
         reviewed along with this procedure.  These guidelines
         cover the following sections:

         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)

         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).

    C.   For guidance on cleaning blackened clay roofing tiles,
         see 07321-02-R.

1.02 SYSTEM DESCRIPTION

    A.   A good roofing tile should be well and evenly burnt
         throughout, compact, hard yet tough, free from pinholes,
         lumps, or specks of unslaked lime, cracks or laminations,
         glazed or vitrified patches on the bed or underside, must
         not be warped or otherwise distorted, must not have
         broken edges or corners, and must not have high absorbent
         qualities.  It should also comply with ASTM standards for
         strength in resistance to compressive and tensile loads.

    B.   A dense well-burned tile will show a clean fracture when
         struck sharply with the edge of a trowel; a soft tile
         will crumble, and an overburnt tile will splinter or
         crack.

    C.   A clay tile roof in good condition is free of any loose,
         broken, or missing field tiles.  All starter tiles,
         circular cover starter tiles, eave closure tiles, top
         fixture pieces, ridge covers and other "special tiles"
         are also in place.  The roof surface is clear of all
         debris so that rainwater flow is not impeded.

1.03 DELIVERY, STORAGE, AND HANDLING

    A.   Storage and Protection:
             
         1.   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.

         2.   Field tile is generally shipped in pallets, and
              fittings in boxes.  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.

         3.   Power equipment is needed to deliver the tiles to
              the roof level.  Outside storage is acceptable.
              Manufacturers 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.

1.04 PROJECT/SITE CONDITIONS

    A.   Environmental Requirements:

         1.   Do not replace or repair tile roofs in wet weather.

         2.   Do not remove roofing from structures when rain is
              forecasted or in progress.

         3.   If roofing is to be removed on a clear day, remove
              no more than can be replaced or repaired in one
              day.

1.05 MAINTENANCE

    A.   Like slate, tile requires little ongoing maintenance:  

         1.   Clay tile requires no painting, no preservative
              coatings, waterproofing or fireproofing, and almost
              no cleaning.  

         2.   Its very low porosity makes it extremely weather
              resistant.  

         3.   Clay tiles can last indefinitely.  Thin, flat
              shingles can last at least 75 years.  Barrel tiles
              have been known to last 350 years.

    B.   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 to avoid breakage, and heavy pads and ridge
         ladders should be used to equalize a person's weight
         whenever any work is to be done on the roof.

    C.   In addition to scheduled inspections, inspect after each
         exposure to unusually severe weather conditions such as
         strong winds, hail, or long continuous rains.


PART 2---PRODUCTS

2.01 MANUFACTURERS

    A.   Boston Valley Terra Cotta
         6860 South Abbott Rd.
         Hamburg, NY  14075
         715/649-7490

         Manufactures custom-made roof tiles and architectural
         terra cotta for like replacement.  Specialize in
         restoration projects, will match color, texture, and
         detail.  Free literature.

    B.   Details
         P.O. Box 309
         Mill Valley, CA  94942
         415/568-5590

         Specialist in bringing together skilled artisans and
         sources of unusual high-quality building materials (much
         of it recycled), including roofing.  

    C.   Gladding, McBean & Co.
         P.O. Box 97
         Lincoln, CA  95648
         916/645-3341

         Clay roofing tiles sold through distributors.  Free
         roofing brochure.

    D.   Ludowici-Celadon Co.
         P.O. Box 69
         New Lexington, OH  43764
         614/342-1995

         Clay roofing tiles in traditional patterns and imitation
         wood are sold direct and through distributors.  Free
         product sheets on each style.

    E.   Midland Engineering Co.
         Attention:  Hubert Gockel
         P.O. Box 1019
         South Bend, IN  46624
         219/272-0200

         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.

    F.   Vande Hey Raleigh
         1665 Bohm Drive
         Little Chute, WI  54140
         414/766-1181

         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.

    G.   Dow Corning Corporation
         Box 0994
         Midland, MI  48640-0994
         517/496-4000

    H.   General Electric Silicone Products Div.
         Waterford, NY  12188
         518/237-3330

2.02 MATERIALS

    A.   Salvaged or replacement clay tile to match existing (see
         companies listed above in Section 2.01).

    B.   Nails:  Use 1-3/4" copper nails, or length and holding
         power as recommended by the shingle manufacturer.  The
         nails should be long enough to penetrate through the
         roofing material and at least 3/4 inches into the deck
         lumber section.

         NOTE:  STAINLESS STEEL TABS WITH STAINLESS STEEL NAILS
         MAY BE USED IF NO DANGER OF GALVANIC ACTION EXISTS.
         DIRECT CONTACT WITH, OR RAINWATER RUN-OFF FROM COPPER,
         ALUMINUM AND ALUMINUM ALLOYS, STEEL AND ZINC WILL CAUSE
         STAINLESS STEEL TO CORRODE.

    C.   Sealant:  Clear Silicone Rubber Sealant (Dow Corning
         Corporation) or clear silicone sealant (General
         Electric), or approved equal.

    D.   Elastic cement:  Use only non-staining, non-corrosive
         cement as recommended by the manufacturer.

2.03 EQUIPMENT

    A.   Rule or Tape

    B.   Hammer

    C.   Chipping Hammer

    D.   Sponge

    E.   Fox-tail Broom

    F.   Caulking Gun

    G.   Slate Ripper

    H.   Drill and Glass Drill Bits


PART 3---EXECUTION

3.01 EXAMINATION

    A.   Whenever possible, make 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 downhill side of any roof penetrations for
              evidence of leakage such as water stains.

3.02 PREPARATION

    A.   Protection:
   
         1.   Establish rules for any foot traffic that may be
              required during repair operations.

              a.   Ideally, clay tile should not be walked on.

              b.   Lay down heavy padding and then hang a self-
                   supporting ladder over the ridge of the roof.

              c.   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.

         2.   Safety on the roof:  

              a.   Wear rubber-soled shoes that have non-slip
                   tread (preferably sneakers with a high top for
                   good ankle support).  Avoid wearing loose
                   clothing.

              b.   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.

              c.   Be sure the roof is clear of debris and water.
                   Avoid stepping on damaged or crumbling roofing
                   materials.

         3.   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.
 
              a.   Chicken ladders or cleats shall be used on the
                   roof as required for adequate footing.

              b.   Safety lines, of an approved type should be
                   properly worn and secured with manila rope.
                   Rubber-soled shoes with grip-type bottom
                   should be worn.

              c.   Carrying and transporting of materials should
                   be limited to a safe amount so that balance
                   and footing are not impaired.

              d.   Do not work on roof when wet or snow-covered.

    B.   Surface Preparation:

         1.   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.  

         2.   For safety of the personnel, keep the deck clear of
              waste material as the work proceeds.  Sweep the
              deck clean after all loose or broken pieces have
              been removed.

3.03 ERECTION, INSTALLATION, APPLICATION

    A.   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.

    B.   Replacing Shingle Tiles:

         1.   Remove loose tile(s).  

              a.   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.  

              b.   If the tile is already broken, light blows
                   with a hammer to further break it into pieces
                   will facilitate removal.

         2.   Select a replacement tile of proper size to match
              existing, allowing a typical gap on each side.

              NOTE:  NOTHING LOOKS WORSE THAN UNMATCHED TILES
              NEXT TO EACH OTHER IN THE SAME COURSE.  TO BLEND
              THE NEW TILES IN WITH THE OLD, DON'T MIX THEM ON
              THE SAME ROOF PLANE.  PUT THE NEW ONES ON DORMER
              ROOFS, ON A CLIPPED GABLE, OR IN SHADOWS.

         3.   Slide the replacement tile into position.  

         4.   After aligning it carefully, drill a hole right
              below the slot of the two covering tiles.  

              NOTE:  MAKE SURE YOU DRILL THE HOLE ABOVE THE
              DOUBLE COVERAGE; YOU WANT A HOLE ONLY IN THE NEW
              TILE, NOT THE ONE BELOW IT.

         5.   Hold the new tile in place using a heavy gauge
              copper wire nail with a large flat head.  

              NOTE:  ITS LENGTH SHOULD BE TWICE THE THICKNESS OF
              THE TILES PLUS ONE INCH.  

         6.   Drive the nail between the covering tiles.

         7.   Cover the nailhead (also known as "making a baby"):

              a.   Bend a strip of copper about 2" wide and 6"
                   long into a slightly concave shape to make a
                   cover for the exposed nailhead.

              b.   After tile is secure, slide copper strip under
                   the tile positioned above the tile just
                   replaced until the bottom of strip is 2" below
                   nailhead.  

         -OR-

              a.   Secure with a 1" wide copper tab (20 oz).
                   Nail the copper tab into the deck between the
                   butt joint of the two tiles below.

              b.   Seal the nail hole with a nonstaining,
                   noncorrosive cement as recommended by the
                   manufacturer and suitable for use with copper.

              c.   Lay in the new tile and bend tab up and over
                   the end of the tile to hold it in place.  The
                   tab should be doubled at the bent end to
                   provide extra stiffness to the tab.  

    B.   Repair of Barrel Tile:  

         1.   Remove loose or broken tile and select replacement
              (see Section 3.03 A.1. and 2. above).  

         2.   Nail copper tabs with copper nails to supporting
              batten or sheathing.  For nails through sheathing,
              seal with a nonstaining, noncorrosive cement as
              described in Section 3.03 B.7. above.  

         3.   Bend tab as above to hold tile in place (see
              Section 3.03 B.7.c. above).  
   
                             END OF SECTION