Intro
| The Tile-Making Process | Historical
Background | Ceramic Floor Tile Types | Laying
Ceramic Tile Floors | Historic Ceramic Floor Tile: Preservation and
Maintenance | Historic Ceramic Floor Tile: Damage and Deterioration
Problems | Historic Ceramic Floor Tile: Repair and Replacement | Summary | Some Sources for Replacement Tiles
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 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.
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 tile-setter 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 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 subfloor 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.
*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 ¼" to 5/8" as the
setting bed for the tiles.
