Historic Preservation - Technical Procedures
- Removing And Replacing A Clay Tile Roof
- Procedure code:
- Hspg Prepared For Nps - Sero
- Thermal And Moisture Protection
- Clay Tiles
- Last Modified:
- Removing And Replacing A Clay Tile Roof
- Last Modified:
REMOVING AND REPLACING A CLAY TILE ROOF
A. This procedure includes guidance on reroofing a clay tile
B. Clay tile roofs are extremely weather resistant due to
the low porosity of the tiles. The tile itself can last
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 option.
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 Precautions
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).
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
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
D. Greek pan--a tile system consiting of flat pans that
are capped by a gable-shaped top piece.
E. 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.
F. 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.
G. Shingle tile--also called flat tiles, are individual
pieces that are lapped and nailed like slate.
H. Spanish tile--also known as S tile or Pantile, is an
interlocking tile that provides a moderately undulating
I. Roman tile--is a tile system consisting of flat pans that
are capped by barrel-shaped top pieces. Also called a
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
variation. The range of shades is a prime
reason why a tile roof is so handsome.
c. Replace the material in its original
containers 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 waterproof coverings which will
not produce any condensation.
2. Power equipment is needed to deliver the tiles to
the roof level. Outside 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 important to save unnecessary
movement of heavy units.
4. 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
A. Environmental Requirements:
1. Do not apply new or repaired tile roofs in wet
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
A. Like slate, tile requires little ongoing maintenance: no
painting, no preservative coatings, waterproofing or
fireproofing, and almost no cleaning.
B. 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.
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.
A. Boston Valley Terra Cotta
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. Gladding, McBean & Co.
Clay roofing tiles and terra cotta pieces sold through distributors. Free
C. Ludowici Roof Tile Co.
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.
D. Midland Engineering Co.
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
E. Vande Hey Raleigh
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.
F. Hendricks Tile Manufacturing Co., Inc.
G. Monier Co.
Concrete tiles designed to imitate wood and terra cotta
are sold through distributors. Free literature.
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 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.
1. 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
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 (one) inch length but nail must NOT penetrate underside of
4. 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.
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
A. Rule or tape
B. Chalk line and chalk
D. Chipping hammer
E. Felt knife
F. Roof jacks
G. Mason's trowel and bucket
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
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, erosion, 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
E. 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
F. In addition to scheduled inspections, inspect after each
exposure to unusually severe weather conditions such as
strong winds, hail, or long continuous rains.
1. 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.
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-soled shoes that have non-slip
tread (preferably sneakers with a high top for
good ankle support). Avoid wearing loose
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
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
properly worn and secured with ropes of sufficient strength.
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.
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 windproof.
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 length, width, and thickness
2. When removing existing roofing, strip tiles down to
the roof deck.
3. 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.
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
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
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,
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, 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
2. Replace underlayment as required. 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
B. Reroofing with Clay Tile Shingles:
1. Installing Underlayment:
a. 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.
b. Lay parallel to ground level, lap 2"
horizontally 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.
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.
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
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
vertical walls not less than 6", thoroughly
g. All counterflashing 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
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
2) Use felt weighing 50 pounds per square
and fasten with lath nailed over embedded
3) Across lath apply horizontally 1" x 2"
wood strips spaced to accommodate tile,
and proceed as directed for a sheathed
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
b. Roof deck shall be clean, smooth and dry when
roof tiles are applied.
c. 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.
d. Lay tiles in straight lines parallel to ground
level, lapped according to manufacturer's
e. 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.
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
h. Cement ridges in laps and where they rest on
roof tiles. Fasten with 2" copper nails.
i. Cement hip rolls in laps and fasten with 2"
j. Where tiles join hip stringers, make
thoroughly 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
colored 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
END OF SECTION