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Historic Preservation - Technical Procedures

Spectitle:

Removing And Replacing A Clay Tile Roof

Procedure code:

0732101R

Source:

Hspg Prepared For Nps - Sero

Division:

Thermal And Moisture Protection

Section:

Clay Tiles

Last Modified:

02/24/2012

Details:

Removing And Replacing A Clay Tile Roof



REMOVING AND REPLACING A CLAY TILE R= OOF


PART 1---GENERAL

1.01 SUMMARY

    A.   This procedure includes guidance on reroofing a clay tile
         roof.

    B.   Clay tile roofs are extremely weather resistant due to
         the low porosity of the tiles.  The tile itself can last
         indefinitely.  

    C.   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.

         1.   If nails are driven too far prohibiting the tiles
              from hanging on the nail, the tiles will crack
              during thermal movement.  

         2.   If galvanized nails are used to fasten a tile, they
              will often corrode in 40 years or less.

    D.   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 optio= n.

    E.   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 Precaution= s

         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).

1.02 DEFINITIONS

    A.   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.  

    B.   English tile--a plain, flat tile that interlocks at the
         head and on one side.

    C.   French tile--is a large interlocking shingle tile with
         deep grooves that give strong shadow lines and channel
         water.

    D.   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 vertic= al joints between
         rows of concave tiles.

    E.   Shingle tile--also called flat tiles, are individu= al
         pieces that are lapped and nailed like slate.

    F.   Spanish tile--also known as S tile or Pantile, is an
         interlocking tile that provides a modera= tely undulating
         roof surface.

    G.   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
         
    A.   Packing and Shipping:

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

    B.   Acceptance at Site:

         1.   Upon receipt of the shipment, pallets and boxes
              should be inspected for transportation damage.

              a.   Examine the tiles for color by taking 10 field
                   tiles at random from each of the pallets.  

              b.   Spread them out and observe the shade
                   varia= tion.  The range of shades is a prime
                   reason why a tile roof is so handsome.  

              c.   Replace the material in its original
                   conta= iners for storage.  Pack any existing
                   extra stock in similar manner.

    C.   Storage and Protection:
   
         1.   Store tile roofing materials in a dry location.
              When stored outside, place on platforms off the
              ground covered with water= proof coverings which will
              not produce any condensat= ion.

         2.   Power equipment is needed to deliver the tiles to
              the roof level.  Out= side storage is acceptable.

         3.   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 impor= tant to save unnecessary
              movement of heavy units.<= br>
         4.   DO NOT stack or store the roofing materials on the
              roof structure.  Imp= roper roof loads may cause the
              structure to fail.

1.04 PROJECT/SITE CONDITIONS

    A.   Environmental Requirements:

         1.   Do not apply new or repaired 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 repla= ced or repaired in one
              day.

1.05 MAINTENANCE

    A.   Like slate, tile requires little ongoing maintenan= ce:  no
         painting, no preservative coatings, waterproofing or
         fireproofing, and almost no cleaning.  

    B.   Tile's very low porosity makes it extremely weathe= r
         resistant.  The tile itself lasts indefinitely; 75 years
         is claimed for a thin flat shingle, and 350 years is not
         unreasonable for a barrel tile.

    C.   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.


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.  Slate from Vermont,
         Africa, and China, recycled and imported clay tile.
         Letterhead inquiries.

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

         Clay roofing tiles sold through distribu= tors.  Free
         roofing brochure.

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

         Clay roofing tiles in traditional patter= ns and imitation
         wood are sold direct and through distrib= utors.  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 throu= gh 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.   Hendricks Tile Manufacturing Co., Inc.
         P.O. Box 34406
         Richmond, VA  23234

         Concrete Tiles.

    H.   Lifetile
         3511 No. Riverside Ave.
         Rialto, CA  92376
         714/822-4407

         Extruded concrete roof tile in several shapes, including
         Mission tile and simulated cedar shake.  Free literature.

    I.   Marley Roof Tiles
         14 Orchard Park Rd. #24
         Madison, CT  06443
         800/521-5382 or (203)245-8057

         Concrete tiles designed to resemble clay tiles.  Free
         literature.

    J.   Monier Co.
         P.O. Box 5567
         Orange, CA  92667
         714/538-8822

         Concrete tiles designed to imitate wood and terra cotta
         are sold through distributors.  Free literature.

    K.   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.

2.02 MATERIALS

    A.   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.

    B.   Flashing:  Use 20-oz. copper or lead-coated copper.  Use
         24 oz. material if bending is not comple= x.  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.

    C.   Nails:  

         1.   Nails for tiles and cleat (to fasten valley metal)
              shall be copper of suffic= ient 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.

         2.   Plywood deck - use ring shank nail, length for
              slight penetration through underside of deck.

         3.   Board plank deck - use smooth shank nail at least
              1=AB" length but nail must NOT penetrate underside of
              deck.

         4.   Gypsum plank and nailable concrete decks - use
              stainless steel or silicon bronze screw shank nail
              of length to penetrate =AB 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.

         5.   Sealant:  Dow Corning Clear Silicone Rubber
              Sealant, or clear silicone sealant as manufactured
              by General Electric, or approved equal.

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

2.03 EQUIPMENT

    A.   Rule or tape

    B.   Chalk line and chalk

    C.   Hammer

    D.   Chipping hammer

    E.   Felt knife

    F.   Roof jacks

    G.   Mason's trowel and bucket

    H.   Sponge

    I.   Fox-tail broom

    J.   Caulking gun

    K    Sheet metal shears

    L.   Slate ripper

    M.   Drill and glass drill bits

    N.   Diamond blade masonry saw (water-cooled)

    O.   Tile-setters blade saw with tub


PART 3---EXECUTION

3.01 EXAMINATION

    A.   Whenever possible, make inspection from ground or from
         above if possible.

    B.   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.

    C.   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, erosio= n, or staining
         indicating overall deterioration.

    D.   Tile movement may be detected by unusually clean areas
         (lack of stains).  Movement is often a sign of failed
         fastenings.

    E.   Inspect the underside of the roof deck from the attic to
         detect leaks.  Flashings are the most vulnerable points.
         Therefore, inspect the underside careful= ly at all
         flashing points for evidence of leakage such as water
         stains.

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

3.02 PREPARATION

    A.   Protection:

         1.   Establish rules for any foot traffic that may be
              required for the maintena= nce of the roof.  Clay
              tile should be walked on as little as possible.

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

         3.   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.

         4.   Safety on the roof:  

              a.   Wear rubber-sol= ed shoes that have non-slip
                   tread (preferably sneakers with a high top for
                   good ankle support).  Avoid wearing loose
                   cloth= ing.

              b.   Wear safety-belt or harness and secure to the
                   chimn= ey (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
                   mater= ials.

         5.   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
                   prope= rly worn and secured with manila rope.
                   Rubbe= r-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.

         6.   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 windp= roof.

    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
              removal, as well as lengt= h, width, and thickness
              after removal.  

         2.   When removing existing roofing, strip tiles down to
              the roof deck.  

         3.   If necessary, point up chimney joints and replace
              worn flashings.  Cle= an, rebuild or replace gutters.
              After repairing of problem areas, clean debris from
              the roof surface.

         4.   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.  

         5.   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.

         6.   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.  <= br>
         7.   Cover all large cracks, knot holes, loose knots and
              resinous areas of the deck with sheet metal patches
              nailed to the sheathing.  

         8.   Remove loose or protruding nails or hammer them
              down.  

         9.   Do not apply new materials over wet sheathing.

3.03 ERECTION, INSTALLATION, APPLICATION

    A.   Replacing Flashing only:

         1.   Remove tiles surrounding the valley flashing.  

              a.   If tile is to be salvaged and reused,
                   caref= ully remove nails using either a slate
                   rippe= r, or insert a hack saw blade under the
                   cover tile and saw through the nail.  

              b.   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
                   prote= ction system.

         2.   Replace underlayment as requir= ed.  Use minimum 40
              lb. asphalt impregnated roofing felt.

         3.   Cut and install new copper flashing and counter
              flashing as required.  See (b)(2) below.

         4.   Replace tiles matching original lap and general
              appearance.

    B.   Reroofing with Clay Tile Shingles:

         1.   Installing Underlayment:

              a.   Cover all pitch= ed roofs under tile with best
                   quali= ty asphalt impregnated roofing felt
                   weigh= ing not less than 40 pounds per square,
                   60 pounds on low slopes.

              b.   Lay parallel to ground level, lap 2=AB"
                   horiz= ontally and 6" vertically.

              c.   Carry felt 6" up all vertical surfaces and 4"
                   over gutter and valley metal.

              d.   Double layer shall be applied at eaves.

              e.   Fasten all edges with large headed galvanized
                   nails on 6" centers.

         2.   Install Flashing:

              a.   Open Valleys:  Line all valleys with 16 oz.
                   coppe= r, usually 20" in width for short
                   valle= ys, 24" for long valleys (wider where
                   neces= sary), with 1/4" edge turned over and
                   faste= ned with cleats.  Lap joints 4" (more
                   where required), but do not solder.

              b.   Closed Valleys:  Flash between each course of
                   tiles with 16" strips of same length as tiles.

              c.   Rounded Valleys:  Flash between each course of
                   tiles with curved strips of same length as
                   tiles.  Extend strips 8" beyond tiles, 4"
                   under tiles and at least 6" up wall.

              d.   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.

              e.   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".

              f.   Wood saddles and returns must be lined with 16
                   oz. copper extending upon sloping roofs not
                   less than 12" (more where necessary) and up
                   verti= cal walls not less than 6", thoroughly
                   count= erflashed.

              g.   All counterflas= hing is to be plugged, pointed
                   and made secure.

                   1)   Where tile and metal roofs intersect,
                        extend metal up tile roof 12" or more.

                   2)   Extend gutter metal up roof to a point
                        higher than outer edge of gutter.

         3.   Wood Strips:

              a.   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
                   manuf= acturers instructions.

              b.   If roof deck is poured concrete, embed from
                   ridge 1" x 2" beveled wood strips, extending
                   from eave to ridge, spaced 20" on centers.

                   1)   Concrete must be smooth and flush with
                        strips.  

                   2)   Use felt weighing 50 pounds per square
                        and fasten with lath nailed over embedded
                        strips.  

                   3)   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.

         4.   Application of Tile:

              a.   Minimum roof pitch is determined by the type
                   of tile used.  Follow the manufacturer's
                   instr= uctions.

              b.   Roof deck shall be clean, smooth and dry when
                   roof tiles are applied.

              c.   On vertical applications or extremely steep
                   pitch= es 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.

              d.   Lay tiles in straight lines parallel to ground
                   level, lapped according to manufacturer's
                   instr= uctions.

              e.   Fasten each tile with 1, 2 or 3 nails as
                   requi= red in each tile or fitting.  Fasten
                   tiles overlapping sheet metal valleys with
                   copper wire nailed into deck beyond flashing--
                   do not nail through metal.

              f.   For open valleys the exposure of metal at the
                   top shall be at least 6" and shall increase at
                   the rate of 1" for every eight feet of flow
                   down the valley.

              g.   Cement gable rakes to field tiles and fasten
                   with nails.

              h.   Cement ridges in laps and where they rest on
                   roof tiles.  Fasten with 2=AB" copper nails.

              i.   Cement hip rolls in laps and fasten with 2"
                   copper nails.

              j.   Where tiles join hip stringers, make
                   thoro= ughly waterproof with plastic cement.

              k.   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
                   color= ed to nearest match of tile color.

              l.   When ridge angles and hip/ridge terminals have
                   not been specified they shall be mitered on
                   job, nailed or wired, and set in elastic
                   cemen= t.

                         END OF SECTION