40 PRESERVATION 

BRIEFS 

Preserving Historic Ceramic Tile Floors 

Anne E. Grimmer and Kimberly A. Konrad 

U.S. Department of the Interior 

National Park Service 

Cultural Resources 

Heritage Preservation Services 

Figure 1. Minton encaustic tile floor, 3rd floor, Patent Office Building 

(now the National Portrait Gallery), Washington, D.C. Originally constructed between 1836-40 under the supervision of Robert Mills, the 

upper floors of this portion of the building were restored and redecorated in 

1877 in the "Modern Renaissance style" by Cluss & Shulze, Architects, 

after a disastrous fire. Photo: Jack E. Boucher, HABS Collection. 

With a tradition that dates to ancient civilizations, ceramic* 

tile flooring can be found in a variety of settings in diverse 

cultures and structures, including residential buildings 

ranging from large apartment buildings to small private 

houses, institutional buildings such as government offices 

and schools, and religious buildings such as cathedrals and 

mosques. Historically, its widespread use may be attributed 

to the fact that a readily available natural material-claycould be converted by a relatively simple manufacturing 

process-baking or firing-into a very durable, long-lasting 

and attractive floor tile that is easy to maintain. Ceramic 

floor tiles exhibit a versatility of colored glazes and 

decoration, and they range from the plainest terra cotta tiles 

to highly decorated individual ceramic tiles and elaborately 

patterned tile floors. Their modularity, as standardized 

units, make them easy to fit into different sized spaces which 

also explains much of the popularity of ceramic floor tiles 

throughout history (Fig. 1). 

This Brief begins with an overview of ceramic tiles as a 

traditional flooring material. It includes an explanation of 

the various kinds of historic floor tiles used in the United 

States and how they were made. General guidance is given 

on preservation treatments, focusing on maintenance, and, 

when necessary, selective replacement of damaged floor 

tiles. The Brief is intended to provide owners and managers 

of historic properties with an understanding of the 

significance and historical background of ceramic floor tiles, 

and a basic awareness of maintenance techniques and 

various deterioration problems to which tile floors are 

especially prone. In the case of significant historic ceramic 

tile floors, a professional conservator of ceramics should be 

consulted to advise in matters of repair, restoration or 

conservation. Historically, ceramic tiles were used on walls 

as wainscotting, on fireplace hearths and fireplace 

surrounds, and even on furniture, as well as for flooring. 

However, because floor tiles are subject to greater damage 

and deterioration, they are the primary emphasis of this 

Brief. Highlights include: a short history of ceramic floor 

tiles; a description of ceramic tile types; a summary of 

traditional installation methods; maintenance techniques; 

and guidance on repair and replacement. 

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The Tile-Making Process 

Clay is an earthen material, moldable or plastic when wet, 

non-plastic when dry, and permanently hard when baked 

or fired. It is widely distributed geographically, and often 

found mixed with sand in soils of a loam type-a mixture 

of clay, silt and sand. Relatively pure clay is not usually a 

surface deposit, although, in some cases, it may be exposed 

by erosion. Clay types vary throughout the world, and 

even within a region. Each type of clay possesses a unique 

combination of special properties such as plasticity, 

hardness and lightness, as well as color and texture, which 

makes some clays better suited for one kind of ceramic than 

another. The correct clay mixture needed for a particular 

purpose can be created by blending clays and adding other 

materials, but using the wrong type of clay can result in 

expensive production problems such as crazing (the 

formation of tiny cracks in a tile glaze) or warping of the 

tile itself. Traditionally, chalky clays have been preferred 

for many kinds of ceramic tiles, in part because they 

produce, when fired, a white body which is desirable for 

decorating. Other materials can be added, including grog 

(or ground-up fired clay) that helps aerate the clay and 

prevents warping, speeds firing and reduces shrinking, or 

calcined flint, to harden it. 

There are several methods used for making ceramic tiles: 

extrusion; compaction or dust-pressing; cutting from a sheet 

of clay; or molded in a wooden or metal frame. Quarry 

tiles are extruded, but most ceramic floor tiles, including 

traditional encaustic, geometric and ceramic "mosaic" tiles 

are made from refined and blended ceramic powders using 

the compaction method, known as dust-pressing. 

Encaustic tiles, which were made by dust-pressing, are 

unique in that their designs are literally "inlaid"into the tile 

body, rather than surface-applied. Once formed, tiles are 

dried slowly and evenly to avoid warpage, then fired in a 

special kiln that controls high, even heat at temperatures up 

to 1200·C (or approximately 2500·F) for 30-40 hours. 

Higher temperatures produce denser tiles with harder 

glazes. Most ceramic tiles require only one firing to achieve 

low porosity and become vitrified or glasslike, but some, 

especially highly decorated tiles, are fired more than once. 

Non-vitreous and semi-vitreous tiles are fired at lower 

temperatures and are much more porous. 

Historical Background 

Historically, the use of ceramic floor tiles goes back to the 

fourth millennium B.C. in the Near and Far East. The 

Romans introduced tile-making in Western Europe as they 

occupied territories. However, that art was eventually 

forgotten in Europe for centuries until the 12th century 

when Cistercian monks developed a method of making 

encaustic floor tiles with inlaid patterns for cathedral and 

church floors. But, this skill was again lost in the 16th 

century following the Reformation. Except for finely 

decorated wall tiles made in Turkey and the Middle East, 

and Delft tiles made in Holland in the 17th century, ceramic 

floor tiles were not made again in Europe until almost the 

mid-19th century. 

The modern tile industry was advanced by Herbert Minton 

in 1843 when he revived the lost art of encaustic tilemaking in England. The industry was further 

revolutionized in the 1840s by the" dust-pressing" method 

which consisted of compressing nearly dry clay between 

two metal dies. Dust-pressing replaced tile-making by 

hand with wet clay, and facilitated mechanization of the 

tile-making industry. Throughout the rest of the 19th 

century, dust-pressing enabled faster and cheaper 

production of better quality floor tiles in a greater range of 

colors and designs. In the 1850s encaustic tiles were 

selected for such important structures as the new Palace at 

Westminster in London, and Queen Victoria's Royal 

Residence on the Isle of Wight. By the latter part of the 19th 

century, despite the fact that encaustic tiles were still quite 

expensive, they had become a common flooring material in 

many kinds of buildings. 

Development of the Tile Industry in America. Although 

plain, undecorated ceramic tiles were traditionally a 

common flooring material in many parts of the Americas, 

especially in Latin and South America, ceramic floor and 

roof tiles were probably not made in the North American 

Colonies until the late-16th or early-17th century. It was, 

however, in the Victorian era that ceramic tile flooring first 

became so prevalent in the United States. The production 

of decorative tiles in America began about 1870 and 

flourished until about 1930. 

Like so many architectural fashions of the day, the 

popularity of ceramic tile floors in America was greatly 

influenced by the noted architect and critic, Andrew 

Jackson Downing. In his book The Architecture of Country 

Houses, published in 1850, Downing recommended 

encaustic floor tiles for residential use because of their 

practicality, especially in vestibules and entrance halls. 

The 1876 Philadelphia Centennial Exposition, with its 

European and even a few American exhibits of decorative 

floor tile, was a major factor in popularizing ceramic tile 

floors in the U.S. Initially, most ceramic tiles-other than 

purely utilitarian floor tiles-were imported from England, 

and their relatively high cost meant that only wealthy 

Americans could afford them. However, when English tile 

companies realized the potential for profitable export, they 

soon established agents in major U.S. cities to handle their 

........... "'~:" ~ ~ . ~ 

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Figure 2. In the 19th century, Minton tiles were sold from this catalogue 

to American clients-including the Architect of the Capitol-by Miller & 

Coates, 279 Pearl Street, New York. Photo: David W. Look, AlA. 
.ey 

TO 

SfCTO< 

American business (Fig. 2). The English near monopoly 

actually stimulated the growth of the U.S. tile industry in the 

1870s resulting in sharply decreased English imports by 1890. 

The location of potteries and ceramic tile factories is 

dependent upon the ready availability of suitable ball clay 

(clay that balled or held together), kaolin (a white clay used 

as a filler or extender), and feldspar (a crystalline mineral), 

and an accessible market. Since the cost of shipping the 

manufactured products tended to restrict profitable sales to 

limited areas, this usually determined whether a factory 

would succeed. Although the United States Pottery in 

Bennington, Vermont, is known to have made encaustic 

tiles as early as 1853, the Pittsburgh Encaustic Tile 

Company (later the Star Encaustic Tiling Company), was 

the first successful American tile company, and is generally 

considered the first to manufacture ceramic tile in the U.S. 

on a commercial basis beginning in 1876. 

At least 25 ceramic tile companies were founded in the 

United States between 1876 and 1894. In the East, several 

notable tile firms that were established in this period 

flourished in the Boston area, such as the Chelsea Keramic 

Art Works, the Low Art Tile Works, and the Grueby 

Faience Company. Other East Coast companies organized 

in the late-19th and early-20th century included the 

International Tile & Trim Company, in Brooklyn, New 

York; the Trent Tile Company, Providential Tile Company, 

Mueller Mosaic Tile Company, and the Maywood Tile 

Company, all in New Jersey; and the Moravian Pottery and 

Tile Works in Doylestown, Pennsylvania (Fig. 3). 

Many factories were also established in the Midwest-in 

Indiana, Michigan, and, especially, in Ohio. In the last 

quarter of the 19th century, the town of Zanesville, Ohio, 

was the largest center for pottery and tile-making in the 

world. Some of the factories in Zanesville included: Ohio 

Encaustic Tile Company; Mosaic Tile Company; Zanesville 

SECTION A-A 

---'-[ 

: i 

Figure 3. (a) The Moravian Pottery and Tile Works, a National Historic 

Landmark in Doylestown, PA, was designed in the Spanish Mission style 

and constructed by Henry Chapman Mercer over a period of years from 

1911-1917. Tiles were manufactured primarily by hand in keeping with 

Mercer's Arts and Crafts ideals. (b) Mercer's tiles, seen here in the 

library, were used throughout his house, Fonthill. (c-e) One of Mercer's most important commissions was the floor of the Pennsylvania State 

Capitol in Harrisburg. if) The factory closed in 1930 after Mercer's 

death, but resumed tile-making in 1974. New tiles are dated and made in 

the traditional way. (a) Drawing: Leslie S. Claytor, Benita C. Welch, 

Isabel C. Yang, HAER Collection; (b) Photo: Jack E. Boucher, HABS 

Collection; (c-e) Photos: Courtesy, Mercer Museum, The Bucks County 

Historical Society; (j) Photo: Anne Grimmer. 

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Figure 4. The tiled Presidential Seal in the courtyard of the Pension 

Building (now the National Building Museum), Washington, D.C., was 

installed in honor of President William McKinley's second inauguration in 1901. The"heavy Damask design," resembling fabric, that was used to 

decorate the tiles, indicates they were probably manufactured by The Mosaic Tile Company, Zanesville, Ohio, which first introduced this design. Photo: Kimberly A. Konrad. 

Figure 5. Geometric tiles made by the American Encaustic Tiling 

Company, also in Zanesville, were installed in the corridors of the Pension Building in 1888, several years after the building's completion. Photo: Kimberly A. Konrad. 

Figure 6. The Los Angeles Union Passenger Terminal features ceramic 

tile floors in the Art Deco-style. Photo: HABS Collection. 

Majolica Company; and J.B. Owens Pottery, later to become 

the Empire Floor and Wall Tile Company (Fig. 4). The 

American Encaustic Tiling Company, established in 1876, 

was one of the first, and most successful manufacturers in 

Zanesville (Fig. 5). In the early 1930s it was the largest tile 

company in the world, producing large quantities of floor 

tile, plain and ornamental wall tile, and art tile until it 

closed about 1935, as a result of the Depression. The United 

States Encaustic Tile Company, Indianapolis, Indiana; 

Rookwood Pottery, Cincinnati, Ohio; Cambridge Art Tile 

Works, Covington, Kentucky; and Pewabic Pottery, Detroit, 

Michigan, were some of the other well-known potteries in 

the Midwest. 

Around the turn of the century, the industry began to 

expand as tilemakers moved West and established potteries 

there. Joseph Kirkham started the ceramic tile industry on 

the West Coast in 1900 when he set up the Pacific Art Tile 

Company in Tropico, California, after his company in Ohio 

was destroyed by fire. In 1904 the company became the 

Western Art Tile Company, surviving for five years until it 

went out of business in 1909. During the early-20th 

century, other companies were founded in Southern 

California, in and around Los Angeles (Fig. 6). Batchelder 

& Brown, in particular, of Pasadena (later BatchelderWilson in Los Angeles), was well-known for its Arts and 

Crafts-style tiles in the teens and 1920s. By the early 1940s 

California had become one of the leading producers of tile, 

especially faience, in the U.S. (Fig. 7) . 

Ceramic engineers, potters and artists not only moved 

frequently from one pottery to another, but often struck out 

on their own and established new factories when 

dissatisfied with a former employer. Also, it was not 

uncommon for one company to reuse a defunct factory or 

purchase another pottery business, change the name and 

increase the product line. As a result, many of the 

companies in existence today are descendants of the early 

pioneering firms. 

Changes in the Tile Industry. The majority of ceramic floor 

tile made in the U.S. before 1890 was encaustic, but various 

factories gradually began to develop and produce other 

kinds of tiles. The Trent Tile Company, among others, 

started to manufacture both white and colored ceramic 

mosaic tiles by the mid-1890s (Fig. 8). White vitreous wall 

tile became available, as well as more decorative tiles with 

colored glazes, such as the variegated faience glazes 

intended to give a more hand-crafted appearance that were 

originated by the Grueby Faience and Tile Company in 1894, 

and soon adopted by other potteries (Fig. 9). 

In the 19th and early-20th century, many ceramic tile firms 

had their own engraving departments, while some used 

commercial designs supplied by professional printers. 

Well-known designers were often commissioned to work 

on specific product lines for a particular firm. These 

designers worked for one firm after another which resulted 

in similar designs being produced by different companies. 

(Historic ceramic floor tiles were usually identified by a 

manufacturer's or designer's mark on the back, if they were 

marked at all.) By the latter part of the 19th century readymixed glazes and colors were also available. This was a 

great advantage for potters who, prior to this, had to mix 

their own colors and glazes. 

During the 20th century, the floor tile industry continued to 

evolve as much as it had in the previous century. Modern 
Figure 7. "Scott/IS Castle" in Death Valley, California, was built over a lO-year period, beginning in 1922. Many of the rooms, the salon (a), as 

wel~ as t~e kitchen. (b), have tile floors. Some are composed of both local, 

Califorma-made tiles, and Spanish tiles. Photos: Jack E. Boucher, HABS 

Collection. 

Figure 8. The Trent Tile Company advertised its "Ceramic Mosaic 

Floor" tiles in the 1906 edition of "Sweet's" Indexed Catalogue of 

Building Construction. Photo: Sharon C. Park, AlA. 

Figure 9 .. Beginning in the late-19th century, a decorative frieze with a relief.deslgn, such as thIs clas~lcal egg and dart motif, was often added to 

hIghlight plam ceramIc wall tile. Photo: Kimberly A. Konrad. 

methods of production employed sophisticated machinery, 

new materials and decorating techniques. In the years 

following World War II, there were many advances in the 

industry. Commercially manufactured dust-pressed tiles, 

which had previously required more than 70 hours just in 

the kiln, could be made in less than two hours from the raw 

material stage to finished tiles, boxed and ready to ship. 

Dried, unglazed tiles were sprayed with colored glaze 

evenly and automatically as conveyors carried the tiles into 

the tunnel kilns, and the extrusion process ensured that the 

tiles were cut to a uniform thickness and size. The changes 

and developments in the production of floor tile brought 

forth a wide range of shapes and sizes, along with new 

colors, glazes and decorating techniques. 

After the turn of the century, fewer encaustic floor tiles 

were used, particularly in residential architecture. The 

introduction of ceramic mosaic floor tiles was a factor in 

their decline (Fig. 10). The development of rubber 

interlocking floor tiles in 1894, along with other, more 

resilient, flooring materials, was instrumental in the 

decreased popularity not only of encaustic tiles, but also 

other ceramic tile flooring. These new materials were not 

only cheaper, they were not as fragile; they were also lighter 

and thinner, and easier to install. 

Ceramic mosaic tiles remained in common use through the 

1930s in part because an innovative development had made 

laying such small tiles easier. The tiles were pre-mounted 

in decorative patterns on 12" x 12" sheets of paper, and sold 

ready to lay in cement. This greatly simplified the tile 

setter's work, and no doubt was a significant factor in the 

increased popularity of ceramic mosaic tiles. Sophisticated 

mosaic floor designs became common in entrance foyers of 

public and private buildings (Fig. 11). Small, white, 

unglazed tiles in round, square, octagonal or hexagonal 

shapes were promoted for their sanitary qualities, 

particularly for bathroom floors, while larger, rectangular, 

white, glazed tiles were used for bathroom walls or 

wainscotting. Colored tiles were also popular, especially 

for bathrooms, and even kitchens (Fig. 12). Quarry tile, 

which was larger and thicker than other ceramic floor tile of 

this period, was often used in public buildings, as well as 

for entrance halls, small studies, libraries, dining rooms and 

even living rooms in private homes. But, by the 1930s, the 

fashion for art tile had diminished to the point where floor 

tiles were, for the most part, generally regarded as 

primarily utilitarian, as opposed to important decorative 

elements. 

Ceramic Floor Tile Types 

The thickness of historic ceramic floor tiles varied 

considerably according to their intended use and when they 

were made. Floor tiles were thicker and harder than wall or 

ceiling tiles. Stove tiles, meant to retain the heat of the 

stove, were sometimes as much as several inches thick. 

Medieval floor tiles were usually one inch thick; encaustic 

tiles of the Victorian era tended to be slightly thinner. 

Modern, 20th-century tiles, with the exception of some art 

pottery tiles, are the thinnest, as a result of modern 

Figure 10. Ceramic mosaic tile floors were practical for structures like this 

Bath House, Hot Springs, Arkansas (1914-1915). Photo: Jack E. Boucher, HABS Collection. 

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manufacturing methods. The backs of most, but not all, 

ceramic floor tiles are covered with raised (or sometimes 

recessed) ridges, circles or squares which help to increase 

the bonding capability of the tile. 

Unglazed and Glazed Tiles 

Ceramic floor tiles can generally be divided into two types: 

unglazed and glazed. Unglazed tiles include: quarry tiles; 

encaustic and geometric tiles; and ceramic mosaic tiles, 

which can be either glazed or unglazed. Most other ceramic 

floor tiles are glazed. 

Unglazed Tiles 

Quarry tiles are the most basic type of historic ceramic floor 

tile (Fig. 13). Originally made from quarried stone, they are 

machine-made using the extrusion process. Quarry tiles are 

unglazed, semi-vitreous or vitreous, and essentially are 

square or rectangular slabs of clay baked in a kiln. The 

colors of quarry tiles are natural earthen shades of gray, red 

and brown determined by the clay and, to some extent, the 

temperature and duration of firing. Quarry tiles, which 

range from 1/4" to 1 / 2" in thickness, are available in square 

and rectangular shapes in sizes that include 3", 4-1/4", 6" 

(one of the most common sizes), 9" and 12" squares; 6" x 12", 

6" x 9", 4-1/4" x 9", 3" x 6", and 3" x 9" rectangles; and 4" x 8" 

hexagon shapes. (Pavers or paver tiles are a simpler, and 

tend to be somewhat cruder, version of quarry tiles. Like 

quarry tiles, they are usually unglazed, but slightly thicker. 

Machine-made pavers are either semi-vitreous or vitreous, 

and generally formed by dust-pressing, although 

sometimes are extruded. Hand-made pavers which are 

common in Mexico and southern Europe are non-vitreous.) 

Encaustic tiles are a type of traditional unglazed-yet 

decorative-floor tile, manufactured by the dust-pressed 

method. Whereas most ceramic tiles are surface-decorated 

or decorated with impressed or embossed designs created 

by a mold, encaustic tiles are unique in that their decorative 

designs are not on the surface, but are inlaid patterns created 

as part of the manufacturing process. First, a thin, 

approximately 1/4" layer of fine, almost powder-dry, clay 

was pressed into a mold with a relief design at the bottom 

which formed a depreSSion in the face of the tile. A second, 

thicker layer of coarser clay was laid over the first layer, then 

covered with another layer of fine clay. This "sandwich" 

helped prevent warping and ensured that the body of the 

tile was strong and had a fine, smooth surface. The layers of 

clay "dust" were compacted by presses, after which the 

mold was inverted and the die removed, thus producing a 

tile with an indented or intaglio pattern on top. After the tile 

dried, colored slip (liquid white clay colored with dyes), was 

poured to fill in the intaglio pattern. Each color had to dry 

before another color of slip was added. The recessed area 

was overfilled to allow for shrinkage, and after drying for 

several days, and before firing, the excess slip was scraped 

off the surface by a rotating cutter that created a flat, 

although not completely smooth, face. Problems might arise 

during the firing. Due to the dissimilar rates of contraction 

of the different clays, the inlaid clay could shrink too much 

and fall out of the tile recesses; or, the tile could be stained 

by the different pigments used for the design if impure or 

unstable (Fig. 14). 

By the 1840s, encaustic tiles were made entirely with almostdry clay using the dust-pressed method. This served to 

Figure 11. Ceramic mosaic tiles were used decoratively on the entrance 

floor of this early-20th century school building. Photo: Kimberly A. 

Konrad. 

eliminate the possibility of staining the body of the tile with 

other colors and permitted the use of more colors on a 

single tile. Thus, an encaustic tile can sometimes be dated 

according to the complexity and the number of colors in its 

pattern. Red tiles with white figurative patterns were 

generally the earliest, followed by brown and buff colored 

tiles. In the 1860s, blue tiles with yellow or buff patterns 

were popular, succeeded by more subtle color schemes 

featuring a "chocolate" red with a soft grey. By 1860, up to 

six colors were used in a single tile to form a pattern. 

Toward the end of the century, white encaustic tiles with a 

black or gold design were common, as well as tiles with 

complicated color patterns of white, black, gold, pink, green 

and blue. Encaustic tiles were decorated with traditional as 

well as original designs. Some, particularly intricate, 

designs were painted on the surface of the tile with opaque 

colored glazes, instead of being inlaid (Fig. 15). Most major 

tile manufacturers sold many of the same pre-formed 

encaustic floor tile patterns through catalogues. Encaustic 

tiles were produced in a variety of sizes, mostly square or 

octagonal in shape, and almost any design could be custommade for a special purpose or to fit a particular space. 

Historic, 19th-century encaustic tiles were generally slightly 

less than 1" thick, about 15/16." Cheaper tiles of lesser 

quality were also made of clay or cement. These designs 

Figure 12. These colorful (yellow, black and white), and boldly patterned 

Art Deco-style ceramic tiles were made in France. Ernest Hemingway's 

wife, Pauline, brought them back to the U.S. in the 19305 and had them 

installed in a bathroom in their house in Key West, Florida. Photo: 

Susan Escherich. 
Figure 13. Quarry tiles were used in the corridors on many of the upper 

floors of the U.S. Department of the Interior Building (1935-1936). They 

were laid in a pattern identical to the more expensive marble floor tiles 

that were used in the public spaces. Photo: Brooks Photographers, HABS 

Collection. 

resembled those commonly found on encaustic tiles but 

applied as a transfer printed pattern, or using a multi-color 

lithographic or silkscreen process. These are still manufactured and popular in many parts of the world (Fig. 16). 

Smaller, single-colored versions of encaustic tiles that, 

when assembled together form a geometric pattern, are 

called geometric tiles in England. However, in the United 

States they are generally not differentiated from encaustic 

tiles. Based on the geometric ~egments of a six-inch square, 

they were typically rectangular, square, triangular or 

hexagonal in shape, and about the same thickness as 

patterned encaustic tiles (Fig. 17). Geometric tiles were 

especially well suited for decorative borders, and a wide 

variety of floor designs could be created with their many 

shapes, sizes and colors-either alone or combined with 

patterned encaustic tiles. The cost of producing geometric 

tiles was much less than of encaustic tiles because each tile 

involved only one type of clay and one color. By the end of 

the 19th century, over 60 different shapes and sizes of 

geometric tiles were available in up to ten colors, including 

buff, beige or tan, salmon, light grey, dark grey, red, 

chocolate, blue, white and black. 

Ceramic mosaic tiles are essentially smaller versions of 

geometric tiles (usually no larger than 2-1/4", and no 

thicker than 1 / 4") ranging in size from 1 / 2" to 2 3 / 16", in 

square, rectangular or oblong, hexagonal, pentagonal and 

trapezoidal shapes. Both vitreous and semi-vitreous 

mosaic tiles were available, unglazed in solid or variegated 

colors with a matte finish, or glazed in unlimited colors. 

Single, one-piece tiles were also fabricated to give the 

appearance of multiple mosaic pieces. This was achieved 

with a mold, which gave the appearance of recessed 

mortar joints separating individual "mosaics" (Fig. 18). 

Glazed Tiles 

With the exception of quarry tiles, encaustic tiles, and 

some mosaic tiles, most ceramic floor tiles are decorated 

with a glaze. While unglazed tiles derive their color solely 

from the clay, or from oxides, dyes or pigments added to 

the clay, the color of glazed tiles is provided by the glaze, 

either shiny or matte. Some potteries specialized in certain 

kinds of glazes and were famous for them. The earliest 

and most common method of clay tile decoration made use 

of tin-glazes which were essentially transparent lead 

glazes. Tiles were either dipped into the glaze or the glaze 

was brushed on the tile surface. Glazes were generally 

made with white lead, flint, or china clays ground up and 

mixed with finely ground metallic oxides that provided 

the color. Colored glazes were commonly known as 

"enamels". Colors included blue derived from cobalt, 

green from copper, purple from manganese, yellow from 

antimony and lead, and reds and browns from iron. An 

opaque glaze was created by adding tin oxide. 

Laying Ceramic Tile Floors 

19th Century Techniques. Aside from the use of 

improved tools and modern materials, installation 

methods have changed little since the mid-19th century. 

M. Digby Wyatt, an architect for one of the major 19th 

century encaustic tile manufacturers in Britain, Maw & 

Co., described this procedure for laying encaustic and 

geometric tiles in 1857: 

First, either an even layer of bricks, a 2-1/2" bed of 

concrete of quicklime and gravel, or a mixture of Portland 

cement and clean sharp sand was laid to prepare a solid 

foundation for the tiles. If the tiles were to be laid over an 

existing wooden floor, the floor boards had to be pulled 

up, sawn into short lengths and fitted between the joists. 

Concrete filled in the spaces and made the base flush with 

the upper face of the joists, and created a level surface 

finished within 1" of the finished floor line. A layer of 

Figure 14. Making encaustic tiles. When finished, a reproduction encaustic tile resembles a historic tile, but the reproduction process is quite different from the 

traditional method. Designs for reproduction tiles are recreated by a computer from drawings of the original tile. (a) The computer image of the design is transferred 

to, and machine-cut into, a Plaster of Paris mold. Plastic, buff-colored clay is pressed into the mold to form the main body of the tile, and left to dry for 24 hours. (b) 

Colored slip, or liquid clay, is poured into the indented portions of the tile to create the pattern. (Each color of slip must dry before another color can be poured.) (c) 

After drying, and before firing, excess slip is scraped off, leaving the surface of the tile smooth, but the slip-filled areas still slightly recessed. (d) A side view of the 

19th-century tile at the top of the photograph clearly shows the 3-layer clay "sandwich," as well as the 2 colors of slip that form the inlaid design. The new tile, be/ow, 

is slightly thinner and is made from only 1 layer of clay. Photos: (a-b) H&R Johnson Tiles Ltd.; (c-d) Wayne Firth, Office of the Architect of the Capitol. 

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Figure 15. The detailed features of the portrait on this round tile in the U.S. Capitol were painted on the surface of the tile rather than inlaid. 

Photo: David W. Look, AlA. 

cement mortar was then laid on top. This allowed the tiles 

to fit in the same amount of space as the floorboards they 

replaced.* 

Before laying the tiles, skirting boards or shoe moldings 

were to be removed, and replaced after the tiles were laid. 

This eliminated having to cut the outer tiles to fit exactly, 

and resulted in a neater appearance. 

Next, the floor design was marked off with mason's string 

or chalk lines which divided the space into equal quadrants. 

The first section to be laid out was defined by two parallel 

strips of wood, or guide pieces, about 4" wide. A level 

thickness of cement was spread between these strips. The 

tiles, thoroughly soaked in water, were laid in the cement 

and leveled with a straight-edge. The foundation had to be 

kept wet while the tiles were being laid. Small strips of 

wood temporarily placed at right angles to the guide pieces 

helped keep elaborate patterns straight. 

When the bed was hard, the joints were filled with pure 

cement mortar-sometimes colored with lamp black, red 

ochre or other natural pigments-mixed to the consistency 

of cream. Excess mortar was wiped off the tiles with a 

piece of flannel or sponge. 

*The traditional practice of sawing the original floor boards and fitting 

them between the joists, still used today to maintain a low finished floor 

profile, has resulted in numerous cracked tiles and other failures. Instead, a better approach is to leave the existing floor boards, if they are in good 

shape, and install a cementitious backer board (CBU) available in 

thicknesses ranging from 114" to 5/8" as the setting bed for the tiles. 

~ • ~ 

~. • • .~ 

~ • • ~ • • ~ ~ 

~ • ~ 

~. • • .~ 

~ • ~ 

Figure 17. Shown here are typical geometric tile patterns popular in the 

late-19th century, as illustrated in Decorative Tile Designs in Full 

Color. Selected and arranged by Carol Belanger Grafton. NY; Dover 

Publications, Inc. , 1992, pp. 73, 83. 

Figure 16. Historic cement floor tiles in a house at 103 Calle San Jose, Old 

San Juan, Puerto Rico, feature a design intended to resemble wood parquet. 

(Note the mismatched repair.) Photo: Jack E. Boucher, HABS Collection. 

A newly-laid tile floor could not be walked on for 4-6 days 

until the cement hardened properly. Occasional washing 

would remove the saline scum that often appeared on the 

surface right after the tiles were laid. 

20th Century Techniques. Almost 50 years later, in 1904, 

the Tile Manufacturers of the United States of America 

published Suggestions for Setting Tile with the intent of 

bringing tile-laying up to a uniform standard. This 

guidance was very similar to that given by Wyatt. But, 

there were some differences, such as using hollow clay tile 

as a foundation material and heavy tar paper when laying 

tile over a wooden floor to protect the floor boards from the 

moisture of the mortar mix. Emphasis was placed on using 

the best quality cement, sand, and purest water to obtain a 

durable tile floor. Soaking the tiles before setting was no 

longer necessary, but using stiffer mortar was suggested to 

prevent it from rising up between the tiles. 

Tile-laying methods changed somewhat more later in the 

20th century, mostly due to the availability of new materials 

and techniques. By the 1920s small ceramic mosaic tiles 

were manufactured as 12" square sheets held together by a 

face-mounted paper "skin." This made it possible to lay the 

12" square of tiles as a unit rather than each of the small tiles 

individually. Mounting the tiles directly in the cement 

resulted in a very strong bond. But the face-mounted paper 

obscured the tiles from view making it difficult for the tilesetter to see if the tiles were being laid straight. The fact 

that the paper was not removed until after the tiles were 

firmly set in the cement bond coat further complicated 

Figure 18. One-piece tiles were made with a mold that created the 

appearance of mortar joints and individual mosaics, as illustrated in 

Decorative Tile Designs in Full Color. Selected and arranged by 

Carol Belanger Grafton. NY; Dover Publications, Inc., 1992, p. 87. 
Figure 19. Regular maintenance treatments for the historic quarry tile 

floors in the U.S. Department of the Interior, shown here in a side 

corridor, include: stripping and waxing once a year; weekly spraying and 

buffing with a commercial "floor finish revitalizerlcleaner" that is slip 

resistant; and dust mopping or damp mopping 4 times a week. Photo: Brooks Photographers, HABS Collection. 

realignment of crooked tiles. This paper "skin" was 

eventually replaced with a fabric mesh backing. This 

permitted the tiles to be aligned as soon as the moisture 

from the bond coat loosened the mesh from the back of the 

tile; it also allowed a single tile to be cut away from the 

mesh and repositioned immediately. Although the fabric 

mesh made tile setting faster, sometimes it also resulted in a 

weaker bond by reducing the contact area between the 

backs of the tiles and the bond coat. 

Following World War II, different methods of preparing a 

foundation for a ceramic tile floor were developed to be 

more compatible with new materials, such as reinforced 

concrete, expanded wire mesh, polyethylene and 

waterproof plywood. New adhesives and grouts also 

facilitated tile installation, and an increased variety of 

epoxy and cement mortars allowed for different setting bed 

thicknesses. But today, after half a century of practical 

application, some of these "new" materials, such as 

plywood, particle board, oriented strand boards and other 

wood panels, are no longer recommended for use with 

ceramic tile. 

Mortar beds are lighter, more flexible, and much thinner 

than they were previously, having shrunk from several 

inches to as thin as 3/32". A greater variety of materials are 

used for setting ceramic floor tiles, including bonding 

agents and waterproof membranes. Basic installation 

methods have not changed significantly, but they vary 

according to the type of sub floor on which the tile is to be 

laid. While the same concerns for level underlayment and 

strong adhesion exist, advancement has occurred mostly in 

the increased speed and ease of laying the tiles. 

Historic Ceramic Floor Tile: Preservation and 

Maintenance 

Before undertaking any work more complicated than 

regular maintenance or a very simple repair on a significant 

historic ceramic tile floor, or on any historic tile floor where 

serious damage has occurred, it is recommended that a 

professional conservator of ceramics, an historical architect, 

an architectural historian, or a chemist with particular 

knowledge and experience in this field be consulted. This 

will ensure that all future work, whether it be regularlyscheduled maintenance or more technical and specialized 

repair and restoration, is done in accordance with the 

Secretary of the Interior's Standards for the Treatment of 

Historic Properties. 

Cleaning Methods. Ceramic tiles are essentially a practical, 

low-maintenance flooring material. Yet, even glazed tiles 

are somewhat porous, and can get dirty and stained, 

especially in heavy traffic areas or where oil, fat, and grass 

stains are likely to occur. Although heavily soiled areas 

may be difficult or impossible to clean completely, in most 

instances, cleaning ceramic tile floors is relatively easy. 

Cleaning should always begin with the gentlest means 

possible, which may be as simple as warm water. Regular 

maintenance should include sweeping, or preferably dry or 

damp mopping or vacuuming to reduce grit. Tiles can 

usually be cleaned with a non-soap-based household floor 

cleaner, such as one of the commercial products intended 

for cleaning ceramic tile floors available on the market. 

All cleaning and stain-removal products should always be 

tested on a small, inconspicuous area before using. 

Abrasive cleaners (including powdered cleansers and even 

"mildly" abrasive creams) and mechanical equipment can 

damage and wear away the protective surface, as well as 

the decorative design on the tiles, and should not be used 

on ceramic tile floors. Generally, acid-based cleaning 

solutions should also not be used on ceramic tile floors 

because they can damage the complex silicates in a glaze. 

However, there are some acid-based cleaners specially 

formulated for cleaning and removing coatings from 

ceramic tile floors that may be acceptable, but even these 

must be used with caution. Sometimes an acid-based 

cleaner may, in fact, be needed to remove discoloration or 

staining caused by lime or cement mortar. But, it should be 

tested first, used with caution, and applied only to a 

thoroughly wetted tile floor from which excess water has 

been removed. Pre-wetting a ceramic tile floor before 

cleaning is a good policy to observe with all cleaners. The 

water saturates the porous tile and prevents chemicals or 

other cleaning agents from penetrating into the tile body. 

Floor tiles should be always rinsed thoroughly after 

cleaning. 

Figure 20. The surfaces of these 

late-19th century encaustic tiles 

have become worn and much of 

the pattern has been lost after more than 100 years of use. Photo: 

Anne Grimmer. 

Figure 21. These cracked 

geometric tiles may have been 

damaged by the repeated passage 

of heavy equipment over the floor. 

Photo: Anne Grimmer. 

9 
10 

Plastic pot-scrubbers may be effective in loosening and 

removing superficial dirt without abrading the glazed or 

vitrified surface of the tiles. Stubborn asphalt or oil stains, 

scuff marks, or soiling can sometimes be removed with 

ammonia or one of the household spray products intended 

for cleaning kitchen or bathroom tiles. If necessary, a 

solvent may be applied carefully to pre-wetted tiles, but it 

should not be left on the surface for an extended amount of 

time as it may cause discoloration. If possible, a stain 

should always be identified first in order to select the 

material best-suited to remove it. 

Organic growth, such as mold or mildew, can be eliminated 

with a dilute solution of household bleach and a neutral 

household detergent, or a dilute (5-10%) solution of trisodium phosphate (TSP). After applying either of these 

solutions, it may be necessary to scrub the floor with a 

natural bristle or nylon brush, and then rinse with clear 

water. Even a dilute bleach solution should not be left on a 

ceramic tile floor for more than a few minutes, since the 

alkali in the bleach can lead to the formation of a white 

efflorescent deposit. Efflorescence (a whitish haze of 

water-soluble salts) may stain and streak the tile, or may 

even cause minor spalling around the joints. 

Regular maintenance of a ceramic tile floor should always 

begin with vacuuming to remove loose dirt and grit. Then, 

a mild cleaning solution may be applied and left on the 

floor for 10-15 minutes, without letting it dry on the tiles. 

Heavily soiled areas may be scrubbed with a natural bristle 

or nylon brush to loosen dirt from the tile surface. Finally, 

the floor should be thoroughly rinsed with clean, clear 

water, preferably twice, and dried with terry cloth towels, if 

necessary. Any proprietary cleaning product should 

always be used in accordance with the manufacturer's 

directions (Fig. 19). 

Protective Coatings. In most instances, traditional ceramic 

tile floors probably would not have been treated or given a 

protective coating other than wax. In the 19th century, 

some encaustic tile floors were treated with linseed oil, but 

this is not a practice recommended today because linseed 

oil tends to attract dirt and discolors as it ages. Most 

historic ceramic tile floors simply acquired a natural 

"polish" or sheen through use. Because the surface of 

ceramic tiles is already protected with a fired skin or a 

glaze, an additional protective coating should generally not 

be needed. 

Opinions differ concerning the use of protective coatings, 

penetrating sealers, or waxes on ceramic tile floors, and, 

especially, on historic ceramic tile floors. If properly 

applied and regularly cleaned, a coating can sometimes be 

an effective maintenance treatment, but only on interior 

floors. However, if not adequately or properly maintained, 

rather than facilitating maintenance of ceramic tile floors in 

high traffic areas, such coatings may tend to emphasize 

traffic patterns as they wear away or become scratched. 

Some coatings may also peel in spots, or cause tile to appear 

hazy or cloudy if the coating is not applied in accordance 

with the manufacturer's specifications, or if the tiles are not 

perfectly clean when the coating is applied. Furthermore, 

applying such a coating may actually increase maintenance 

costs, since a coating requires periodic removal and 

renewal. The frequent removal of a coating can also 

damage a ceramic tile floor if it is carried out with harsh 

chemicals or abrasive mechanical equipment. If any coating 

Figure 22. Original section drawing of the 2nd and 3rd floors of the House of Representatives Wing of the U.S. Capitol shows how 

Montgomery C. Meigs ensured the durability of the encaustic tile floors 

that were laid in the 1850s. He specified that the 3/4" tiles be laid on top of1l2 to 3/4 " mud (or mortar), which, in turn, was to be laid over a coal 

tar membrane on top of 3" of brick over an air space of 4-6 ". Photo: Wayne Firth, Office of the Architect of the Capitol. 

is considered, a traditional coating, such as floor wax, may 

be the most suitable. Wax is easy to remove when it 

becomes worn, and does not impart a high, potentially 

inappropriate, gloss to the surface. 

On the other hand, a penetrating sealer, or impregnator, may 

be worth considering to protect patterned encaustic tiles, or 

painted or printed tiles featuring a design that might be 

worn off, particularly in public buildings with a high 

volume of foot traffic. For example, some manufacturers of 

new, reproduction encaustic tiles recommend applying a 

penetrating sealer to the replacement tiles, as well as to the 

historic tiles. Impregnators do not change the color of the 

tile surface and, unlike some penetrating sealers, are 

completely invisible after they have been applied. They can 

reduce the porosity or water absorption of the tile surface, 

and provide some protection for the tile (and the grout) 

against staining. This may be particularly useful on lightcolored floors. Whether to apply an impregnator to an 

historic ceramic tile floor, and what type or product to use, 

are decisions that should generally made in consultation 

with a conservator or ceramic tile specialist. It may also be 

necessary to comply with certain safety standards and friction 

requirements of the ADA (Americans with Disabilities Act). The 

ADA Guidelines recommend "a static coefficient of friction" of 

0.6 for level surfaces and 0.8 for ramps. This may require the 

application of a non-slip sealer or wax to historic ceramic tile 

floors in some public buildings. 
Despite the non-traditional shiny finish they may impart to 

a floor surface, two-part, acrylic-based coating systems are 

commonly used today on historic ceramic tile floors in 

many public buildings, primarily because they facilitate 

easy maintenance. If it is decided that a sealer is to be used, 

a product with a matte or dull finish may be preferable, or 

more appropriate, for a historic ceramic tile floor than one 

with a high-gloss. 

In some cases, temporary protection may be the best 

approach until a better solution is found. Non-permanent 

protection for an historic ceramic tile floor may be as simple 

as using floor mats at doors or in heavy traffic areas. 

Historic Ceramic Floor Tile: Damage and 

Deterioration Problems 

Loss of Tile Surface and Pattern. Ceramic tiles are among 

the most durable of historic flooring materials, but natural 

wear and a certain amount of deterioration or damage is 

inevitable. Some tiles, such as dense, close-textured quarry 

tiles and ceramic mosaic tiles, resist abrasion and stain 

absorption very well. But many others, especially patterned 

encaustic and geometric tiles, are extremely susceptible to 

abrasion. Heavy traffic can also result in uneven wear, or 

even cupping, in certain areas of tile floors that get more use 

than others, such as doorway entrances. The particular clay 

mix, or the dye or pigment used to color the clay, can also 

affect the hardness and durability of individual tiles or an 

entire ceramic tile floor (Fig. 20). 

Tile Glaze Failure. Occasionally some glazes can become 

pitted or powdery as they age. Lead glazes used in the 19th 

century, which were fired at low temperatures, deteriorated 

relatively quickly. Glazes have different physical properties 

from the fired clay tile body itself, and as a result may 

sometimes crack or craze. Unless the crazing visibly 

extends into the porous clay of the tile body beneath, this is 

not generally a serious material failure; however, dirt 

entering these cracks cannot be removed, and will discolor 

the tile. If the crazing penetrates through the glaze, it may 

increase the water absorption of the tile. 

Tile Breakage. Ceramic floor tiles are very susceptible to 

damage and breakage caused when something heavy is 

dropped. Repeated passage of heavy objects, or carts, over 

a floor can also crack and break ceramic tiles, as well as 

heavy vibration from outside traffic (Fig. 21). 

Moisture Damage to Tile. Ceramic tile floors have been 

traditionally viewed as highly waterproof systems that do 

not require protection from moisture. In reality, however, 

this is not true. Water-related problems are one of the most 

common causes for the deterioration and failure of historic 

tile floors, particularly in bathrooms and other rooms where 

there is a lot of moisture. Water that is allowed to sit in 

areas around shower stalls and bathtubs can eventually 

damage grout and mortar, and loosen tiles. Some of the 

more porous kinds of tiles that are not as hard-fired may 

actually begin to powder or spall if subjected to constant 

moisture. 

Loose, Cracked, Broken or Unbonded Tile due to Mortar 

Failure. The durability of ceramic tile floors depends to a 

great extent on a sound mortar bed and sound mortar joints. 

The wrong mortar type or mortar that is inadequately 

mixed can also spell trouble for a ceramic tile floor. Failure 

of a tile floor system laid over a subfloor is often the result 

of weakened or deteriorated grout or mortar which allows 

the tiles to become loose. Mortar may also be weakened or 

loosened by cleaning solutions that are too strong. 

Proper tile-laying technique includes the use of a material 

that will allow for some movement of the tiles. 

Traditionally, a layer of asphalt (replaced by a layer of 

plastic or building paper in more modern construction) was 

inserted to separate the base and the bedding underneath 

(Fig. 22). This prevents bonding between the base and the 

bed, and allows for some "relative" movement. It is 

intended to prevent the ceramic tile floor from arching or 

ridging, a condition in which single or entire rows of tiles 

can pop up to relieve tension and separate completely from 

the bed. When this happens, the condition will probably 

require taking up and relaying many or all of the tiles. 

Tile Damage or Loss caused by Systems Update. The 

installation of new plumbing, electrical and HV AC systems, 

or the attachment of new fixtures and furnishings, may be 

one of the most common sources of damage to an historic 

ceramic tile floor. Earlier remodeling projects to remove old 

pipes or to replace "out-dated" bathroom fixtures may have 

resulted in the loss of floor tiles (Fig. 23). Different shapes 

and sizes of new fixtures, equipment or pipes may have 

exposed previously untiled areas that have been 

inappropriately patched with cement. Careless workers 

and insensitive installations can also result in damage, 

breakage or removal of historic floor tiles. All of these 

conditions will require matching replacement tile. 

Historic Ceramic Floor Tile: Repair and 

Replacement 

The Secretary of the Interior's Standards for the Treatment of 

Historic Properties emphasize the retention and preservation 

of historic building material. Preservation and repair 

treatments are always preferable to replacement. 

Mortar Joint Repair. Deteriorated mortar joints and loose 

mortar or grout can generally be repaired. First, the entire 

floor should be checked for loose tiles that need to be 

regrouted. Damaged mortar should be carefully removed 

by hand and the joints wetted or a bonding agent applied in 

preparation for regrouting. When making mortar repairs, it 

is important to use grout that matches the old in color and 

consistency as closely as possible. 

Figure 23. These non-matching tiles are inappropriate replacements for 

original tiles that were damaged during bathroom remodeling. Photo: Anne Grimmer. 

11 
12 

(a-b) Above: By the mid-1970s, many of the patterns in the encaustic tile floors had become faint, and some had completely worn off in the most heavily 

trafficked areas. (c) Below left: Damaged areas of the floor had been patched with salvaged pieces of tile that fit, but did not match. Photos: Wayne Firth, 

Office of the Architect of the Capitol. 

Figure 24. U.S. Capitol Restoration Project. Restoration of the historic 

ceramic tile flooring at the U.S. Capitol is one of the most extensive on- going undertakings of this kind in the U.S. When the Office of the 

Architect of the Capitol contacted H&R Johnson-Richards, the man ufacturer of Millton Hollins tiles, regarding restoration of the tile 

floors in preparation for the American Bicentennial, the company was unaware of the extent of original Minton encaustic and geometric floor 

tiles in the U.S. Capitol building. Montgomery C. Meigs, Supervising 

Engineer, and Architect of the Capitol Extension, Thomas U. Walter, 

specified Minton encaustic tiles for the floors in the two wings that were added to the Capitol. The tiles were ordered from the factory in England 

through Miller & Coates, a Minton supplier in New York City, and 

installed in the 1850s. 

When the project was initiated, the intent was to replace only those tiles 

that were severely damaged or worn. Removing and replacing selected 

sections of the tile floor in their entirety was determined to be a better 

approach because of the difficulty of removing one tile without damaging 

adjacent tiles in good condition, in addition to the difficulty of matching new and old tiles which are slightly different in color, pattern and 

thickness. This means that sometimes tiles in good condition may have to 

be removed, but they are salvaged and stored for future reuse. 

Before ordering the reproduction tiles, each section of the Capitol floor was drawn and photo-documented. The condition of all the tiles was evaluated 

based on a ratillg of one to four (excellent, good, damaged, or, in need of 

replacement), and color-coded accordingly. Every tile that needed to be 

replaced was individually numbered and photographed with dimensional, 

color and grey scales. 

H 8< R 

JOHNSON 

=.:.:-_"=:"' ... ..:.==.. .. :.0:.:.:.:::-_ ~ • .:::.o:::." .. __ .... __ 
(d) Since the early-20th century, making 

encaustic tiles had, again, become a lost 

art. Thus, H&R Johnson-Richards not 

only had to learn how encaustic tiles had 

been made historically, but, also, how to 

reproduce them. After studying old 

records of the early tile manufacturers, the 

company began reproducing tiles using 

modern-day computer-assisted technology 

(CAD/CAM). Drawing: H&R Johnson 

Tiles Ltd.; Photo: Wayne Firth, Office of 

the Architect of the Capitol. 

(e) The top tile is a new reproduction of the historic tile below. (j) This design is identified as No. 84 in Miller & Coates' Minton Tile Catalogue (detail Figure 2). (g) What might appear to be an inappropriate repair with 

non-matching modern tile in the center of the star is, in reality, a neatly executed patch to serve as temporary 

in-fill for the reproductions that have been ordered. (h) Shown below is a restored section of the Capitol floor. 

Photos: (e,g,h) Wayne Firth, Office of the Architect of the Capitol; (j) David W. Look, AlA. 

13 
14 

Figure 25. This comparison of an original, historic encaustic tile (top) 

with a reproduction encaustic tile (bottom) reveals an obvious difference 

in thickness, but only a slight difference in the design. Photo: Wayne 

Firth, Office of the Architect of the Capitol. 

Tile Repair. Trying to remove one tile can endanger 

surrounding tiles. Thus, it may be better to preserve and 

retain an original historic tile that is only slightly damaged, 

rather than replace it. Sometimes cracks may be repaired, 

or a corner or piece of tile that has broken off may be 

reattached, using an epoxy glue, or grout. If a tile is 

chipped or a small corner or edge is missing, a carefully 

executed patch of epoxy-mixed with colored enamel, or 

mortar tinted to blend with the tile, may be less 

conspicuous than trying to replace every tile that has even 

the slightest damage. And, it is a better preservation 

treatment. 

In limited instances, glaze failure or surface powdering of 

ceramic floor tiles may sometimes be treated successfully 

by a conservator with a specially formulated, solvent-based, 

mineral densifying agent (such as silicic acid), followed by a 

siloxane sub-surface repellent, applied 24 hours later. 

Under the right circumstances, such a treatment can harden 

and bind the surface, and lower the absorbency of the tile, 

and still maintain the vapor transmission. But this is a 

highly complex undertaking and should only be attempted 

by a conservator after appropriate testing. Not only are 

these chemicals highly toxic and dangerous to handle, but if 

used improperly, they can cause greater damage to the tile! 

Tile Replacement. When an individual tile or a larger 

portion of an historic ceramic tile floor is missing or so 

severely damaged that it cannot be repaired, or if it has 

become a safety hazard, then it should be replaced. When a 

ceramic tile floor has deteriorated as a result of long term 

wear and abrasion, or from settlement or vibration damage 

to the setting bed, there are a number of factors that need to 

be considered before choosing a preservation treatment. If 

damage to tiles is the result of more than normal wear and 

tear, the source of the problem needs to be identified, and 

the problem corrected before replacing the damaged tiles. 

Successful replacement not only depends on the availability 

of matching tiles, but on the condition of the substrate on 

which the tiles are laid. Before installing the replacement 

tiles, any problems, such as settlement or vibration, will 

have to be addressed, and the height of the new setting bed 

may have to be adjusted for the thickness of the new tiles. 

Selective Replacement of Individual Tiles. This cautious 

approach, typically an attempt to replace only the most 

seriously damaged tiles, is often taken or considered when 

only a small number of tiles are involved. Unless old, 

matching tiles can be found and reused, replacement often 

requires specially fabricated reproduction tiles. In some 

instances, individual historic tiles that are damaged may be 

replaced with matching tiles salvaged from other, less 

prominent areas of the floor or from other buildings. This 

is most feasible if the tiles to be replaced are either plain, 

and easy to match, or decorated with a common historic 

floor tile pattern. 

In order to replace damaged tiles, it can be helpful to 

identify the manufacturer and the approximate date of the 

tiles, if possible. However, many mass-produced tiles are 

not marked and give little or no information as to their 

origin, although stylistic similarities with other marked tiles 

may sometimes provide a clue as to the manufacturer. 

Some decorating firms seldom signed their work, while 

many firms made bisque tiles (plain, unglazed, once-fired 

tiles) for other companies, as well as their own use. 

Identifying marks will generally be found on the back of 

the tile. A mark impressed or molded into the back of the 

tile may give the name or initials of the company which 

made the tile or the bisque; sometimes a printed or painted 

mark indicates if it was decorated by a different company, 

or artist. Historic building records and construction documents may provide information about the tile company or 

supplier. Catalogues of the period may also be useful in 

identifying the tile manufacturer of unmarked tiles. 

Replacing a single damaged tile is based on the ability to 

remove only the deteriorated tile without harming 

surrounding tiles. Attempts to remove one or several 

damaged tiles often fail because a hammer and chisel are 

used. The shock of the blows to the tile being removed 

travels through the grout into surrounding tiles and cracks 

them. To avoid damaging good tiles, all the grout around 

the tile must be removed. This is best accomplished by an 

experienced tile installer using a hand tool called a grout 

saw or, for grout joints wider than 3/8", a dry-cutting diamond blade, mounted in an angle grinder or circular saw. 

Other difficulties may be encountered when selectively 

replacing damaged tiles with reproduction tiles. New tiles, 

especially encaustic tiles, may be different in thickness and, 

sometimes, despite the attention to detail of the 

reproduction process, slightly different in color and design 

from historic tiles. This can cause both visual and physical 

problems, especially if the replacements are being laid in a 

piecemeal fashion. 

If the setting bed does not have enough mortar to grip and 

hold the tile, one new tile laid among the originals will 

eventually come loose. If the new and old tiles are different 

thicknesses, the setting bed in which the new tiles are laid 

must be at a different height to create a level finished 

surface. In addition, the two levels of setting beds may be 

of different composition; one may be harder, stronger and 

less flexible than the other. This may also lead to problems, 

since the setting bed foundation should act and respond as 

a unit to the load and stresses placed upon it. 

Sectional Replacement of Tiles. In some instances, the 

best approach may be to remove a complete section of 

damaged original tiles and replace that section of floor in its 

entirety with new reproduction tiles. Advantages of this 

method include the ability to lay a level setting bed, as well 

as achieving a finished product that is uniform in color and 

pattern match. Although this approach may involve 
replacing more original tiles with reproduction tiles than 

may be absolutely necessary, original tiles that remain in 

good condition can be saved to be reused in other sections 

where only a few tiles are damaged. This technique is 

generally most appropriate either when the section being 

replaced is the most damaged portion of the floor, or is in a 

relatively inconspicuous location and the tiles that are 

removed will supply enough salvaged pieces to permit inkind repair of a more visually prominent area (Fig. 24). 

When laying a section of reproduction tiles, it may be a 

good idea to use contemporary materials and installation 

methods such as expansion joints or flexible expansion 

material. One of the major causes of ceramic floor tile 

installation failure and cracked, broken or disbonded tiles 

is the lack of expansion joints. Expansion joints were 

sometimes used in laying historic ceramic tile floors, and 

these are frequently the ones that have survived in the best 

condition. Many preservation contractors hesitate to use 

conventional expansion joint filler materials because of 

their limited range of colors. However, there are new 

flexible sealants in a wide range of colors that are available 

in either sanded or unsanded textures to match the 

surrounding grout joints. As a result, the expansion joints 

are almost invisible. A bonding agent may also be 

considered-if recommended by the tile manufacturerand any drawings provided by the manufacturer should be 

used to guide the installation. 

Each preservation technique has advantages and 

disadvantages that the historic property owner or manger 

should take into consideration before deciding which one is 

best suited to the particular flooring problem. For example, 

slight differences in the shape, size, color and the pattern 

between the old and the new tiles are frequently 

encountered. If replacing an entire section, the slightest 

difference in size and dimension between the original tiles 

and the reproduction tiles, even if it is as small as 1/8" or 

1 / 16", can mean that the new section of tile will not fit 

inside an existing border (Fig. 25). Even though drawings 

and photos are provided to the manufacturer, there may be 

some variation in the design and pattern size on the new 

tiles. Thus, they may not align perfectly with the original 

tiles, and as a result the section of the floor that has been 

replaced may be quite conspicuous. 

Summary 

Historic ceramic tiles are a common flooring material in 

many different kinds of small, as well as large, private and 

public, structures throughout the United States. Whether 

plain, or decoratively patterned, traditional ceramic floor 

tiles are important in defining the character of historic 

buildings. Although ceramic floor tiles are a practical 

material, they are also fragile, and can be easily damaged 

by improper installation techniques, insensitive 

remodeling, harsh cleaning methods, and even regular 

daily use. Preserving them requires careful day-to-day 

maintenance. This should begin with using gentle, nonabrasive methods and materials to clean them, and, in some 

instances, using an appropriate coating or impregnator to 

protect them. 

Some historic ceramic tile floors, due to their manufacturer, 

their unique design, or their location in a certain room or 

within a particular building, may have greater significance 

than those that are purely utilitarian. Such floors should be 

accorded special care, and a ceramics conservator or 

preservation specialist should always be consulted to 

prepare responsible maintenance plans and to provide 

guidance concerning repair treatments and replacement 

techniques for them. 

Unless an historic ceramic tile floor is extensively damaged with 

many missing and broken tiles and, therefore, potentially 

hazardous, it may be preferable to leave it alone. An unevenly 

worn floor surface, worn colors or patterns on the tiles, or 

slight cracks, chips, or scratches in the tiles themselves does 

not necessarily mean that the tiles should be replaced. Such 

relatively minor imperfections seldom detract from the 

character of an historic ceramic tile floor. They may, in fact, 

impart character, and be less noticeable or obtrusive than 

replacement of a single tile or a larger section with new tiles 

that do not match the originals exactly. Each situation 

should be evaluated on its own basis before selecting the 

preservation approach best suited to the project. 

Selected Reading 

Austwick, Jill. The Decorated Tile: An Illustrated History of English Tilemaking and Design. New York: Scribners, 1980. 

Barnard, Julian. Victorian Ceramic Tiles. Greenwich, CT: New York 

Graphic Society Ltd., 1972. 

Bruhn, Thomas P. American Decorative Tiles, 1870-1930. Storrs, CT: 

William Benton Museum of Art, 1979. 

Byrne, Michael. Setting Tile. Newtown, CT: The Taunton Press, 1995. 

Decorative Tile Designs in Full Color. Selected and arranged by Carol 

Belanger Grafton. New York: Dover Publications, Inc., 1992. 

Fidler, John. "Protective Custody: John Fidler examines the options on 

caring for brick, tile or stone floors." Traditional Homes. (August 1989), 

pp.112-115. 

Furnival, William James. Leadless Decorative Tiles, Faience & Mosaic. 

Stone, Staffordshire: W.J. Furnival, 1904. 

Lavenberg, George N. Ceramic Tile Manual. Los Angeles: Building 

News, 1986. 

Massey, James C, and Shirley Maxwell. "Decorative Tile: Art for the 

Victorian and Arts and Crafts Home." Old-House Journal. Vol. XIX, No. 

2 (Marchi April 1991), pp. 54-58. 

Massey, James C, and Shirley Maxwell. "The Ceramic Circus." OldHouse Journal. Vol. XXIII, No.2 (Marchi April 1995), pp. 46-51. 

Riley, Noel. Tile Art: A History of Decorative Ceramic Tiles. London: The 

Apple Press, 1987. 

Rosenstiel, Helene Von, and Gail Caskey Winkler. Floor Coverings for 

Historic Buildings: A Guide to Selecting Reproductions. Washington, D.C: 

The Preservation Press, 1988. 

Taylor, Joseph A. "Ceramic Tiles in Commerce." BR Building 

Renovation. (Fall 1994), pp. 45-48. 

The Secretary of the Interior's Standards for the Treatment of Historic 

Properties with Guidelines for Preserving, Rehabilitating, Restoring and 

Reconstructing Historic Buildings. Kay D. Weeks and Anne E. Grimmer. 

Washington, D.C: U.S. Department of the Interior, National Park 

Service, Cultural Resource Stewardship and Partnerships, Heritage 

Preservation Services, 1995. 

Tunick, Susan. American Decorative Tiles. Sponsored by Assopiastrelle 

(Association of Italian Ceramic Tile and Refractories Manufacturers), 

and coordinated by D. Grosser and Associates, Ltd., New York (1991). 

Vandenburgh, Jayne M., mo. "Restoring the Ohio State Senate 

Building: An American Tile Classic Returns." Tile Design and 

Installation. Vol. 8, No.1 Ganuary 1995), pp.32-35. 

Wyatt, M. Digby. Specimens of Geometric Mosaic Manufactured by Maw 

& Co. of Benthall, near Broseley. 

London: M. Digby Wyatt, 1857. 

15 
16 

Some Sources for Replacement Tiles 

There are a number of companies that offer standard lines of 

reproduction tiles, while others focus on custom work. Some new 

lines of reproduction tile attempt to be exact replicas of original tiles 

from the late-19th and early-20th century, while others are modern 

interpretations or adaptations of traditional designs, and may not be 

appropriate as replacement tiles in a preservation or restoration 

project. For additional sources see: "Traditional Building's Ceramic 

Tile SourceList," Traditional Building, Vol. 9, No.4 (July / August 1996), 

pp.92-93. 

Designs in Tile 

P.O. Box 358 

Mt. Shasta, CA 96067 

Custom-made reproduction art tile. 

Fulper Tile 

P.O. Box 373 

Yardley, PA 19067 

Reopened factory reproduces historic tiles using original Arts and Craftsperiod glazes. 

H&R Johnson Tiles Ltd. 

Head Office: Highgate Tile Works 

Tunstall, Stoke-on-Trent 

England ST6 4JX 

U.s. Office: Johnson USA Inc. 

P.O. Box 2335 

Farmingdale, NJ 07727 

Stock and custom reproductions of Minton Hollins encaustic and geometric 

tiles. 

L'Esperance Tile Works 

237 Sheridan Avenue 

Albany, NY 12210 

Custom-made encaustic, geometric, mosaic and other traditional ceramic tiles. 

Moravian Pottery and Tile Works 

Swamp Road 

Doylestown, P A 18901 

Reproduction tiles based on Henry Chapman Mercer's original designs. 

Motawi Tileworks 

33 North Staebler Road, Suite 2 

Ann Arbor, MI 48103 

Reproduction tiles in Arts and Crafts, Art Nouveau and other styles. 

Native Tile and Ceramics 

4230 Glencoe Avenue 

Marina Del Rey, CA 90292 

Reproduction decorative tiles in Southern California tradition of Craftsman, 

Mission, Art Deco and other styles. 

Acknowledgements 

Anne E. Grimmer is Senior Architectural Historian, Technical Preservation 

Services Branch, Heritage Preservation Services Program, National Park Service, 

Washington, D.C. Kimberly A. Konrad is a Preservation Planner, Boston 

Landmarks Commission, The Environment Department, City of Boston, MA. The 

authors wish to thank the following individuals for providing technical review 

and other assistance in the development of this publication: Marc Tartaro, AlA, 

and William Allen, Office of the Architect of the Capitol, Washington, DC; Mary 

Catherine Bluder, Bucks County Historical Society, Doylestown, PA; Michael F. 

Byrne, Ceramic Tile Education Foundation, Clemson, SC; Milford Wayne 

Donaldson, FAIA, Los Angeles, CA; Gray LaFortune, CTC, Ceramic Tile Institute 

of America, Inc., Culver City, CA; Joseph Taylor, Tile Heritage Foundation, 

Healdsburg. CA; Susan Tunick, Friends of Terra Cotta, Inc., New York, NY; Anne 

Weber, Ford Forewell Mills and Gatsch, Architects, Princeton, NJ; Glenn 

Wharton, Wharton & Griswold Associates, Inc., Santa Barbara, CA; Charles E. 

Fisher, Sharon C. Park, AIA, and, especially, Kay D. Weeks, National Park 

Service, Washington, DC. 

This publication has been prepared pursuant to the National Historic 

Preservation Act of 1966, as amended, which directs the Secretary of the Interior 

to develop and make available information concerning historic properties. 

Comments about this publication should be directed to de Teel Patterson Tiller, 

Acting Manager, Heritage Preservation Services Program, National Park Service, 

P. O. Box 37127, Washington, D.C. 20013-7127. This publication is not 

copyrighted and can be reproduced without penalty. Normal procedures for 

credit to the authors and the National Park Service are appreciated. 

ISSN: 0885-7016 

Original Style 

Stovax Ltd. 

Falcon Road, Sowton Industrial Estate 

Exeter, Devon 

England EX2 7LF 

Reproduction ceramic tiles from 1750-1902. 

Pewabic Pottery, Inc. 

10125 East Jefferson Avenue 

Detroit, MI 48214 

Reopened factory reproduces original tile designs and glazes. 

Terra Designs Tileworks 

241 East Blackwell Street 

Dover, NJ 07801 

Mosaic tessarae experts, and reproduction of historic ceramic tiles. 

Tile Guild 

2840 East 11 th Street 

Los Angeles, CA 90023 

Reproduction of traditional Spanish, Portuguese, Dutch, Italian and English 

tiles. 

Tile Restoration Center, Inc. 

3511 Interlake N. 

Seattle, WA 98103 

Reproduction of Arts and Crafts-period tiles. 

Helpful Organizations 

The American Institute for Conservation of 

Historic and Artistic Works (AIC) 

1717 K Street, N.W., Suite 301 

Washington, DC 20006 

Ceramic Tile Institute of America, Inc. 

12061 Jefferson Boulevard 

Culver City, CA 90030-6212 

Friends of Terra Cotta, Inc. 

771 West End Avenue, 10E 

New York, NY 10025 

Tile Council of America 

P.O. Box 1787 

Clemson, SC 29633 

Tile Heritage Foundation 

P. O. Box 1850 

Healdsburg, CA 95448 

·Ceramic: Any product manufactured from a nonmetallic mineral (such as clay), 

by firing at high temperatures. 

Cover Logo: "Ceramic Mosaic and Vitreous Floor Tile." American Encaustic 

Tiling Company, Ltd., Zanesville, Ohio. "Sweet's" Indexed Catalogue of 

Building Construction. NY, NY: The Architectural Record Co., 1906. 

Photo: Sharon C. Park, AlA. 

October 1996