Old House Journal Magazine

December 2003

Crowns of Clay
Unlike feet of said material, clay roofs can be trusted to last, with just a bit of attention.

By Paul Kelsey Williams

From left: French; Provincial, a rustic flat-slab single tile especially appropriate to French provincial and Tudor dwellings, popular since the early 1900s; Spanish; Classic tile, an interlocking tile with a surface that varies from smooth to sanded. Photo Courtesy of Ludowici Roof Tile

Clay tiles make an appealing roof because of their varied styles, colors, patterns, and profiles. The fact that they've been used to cover abodes since the Neolithic age, or about 12,000 years ago, is testament to both their durability and their adaptability to changing architectural styles.

A properly maintained clay tile roof can easily last 100 years or more, which gives it one of the longest life expectancies for roofing materials used today. However, tile roofs are also inherently fragile when not maintained. That means inspecting the roof annually, perhaps with high-power binoculars or from a friendly neighbor's upstairs window, and replacing or repairing any tiles that are loose or broken. Tiles can easily break when an inexperienced homeowner or contractor takes a stroll on the roof or a tree drops a large branch during a winter storm. Before you can begin to search for replacement tiles through architectural salvage or new manufacturers, you should determine not only what shape and type of tiles you have, but also their glazes, colors, and finishes.

Traditional Types, Shapes, and Colors

Generally, there are two types of clay roofing tiles: interlocking and overlapping. Interlocking tiles are designed in pairs so that an extrusion or "lip" on one of the tiles hooks over another, thereby locking or securing two together. They are then nailed onto the roof structure. Overlapping tiles, which can also function in pairs, generally do not have any sort of lip and are simply nailed in place.

There is a variety of clay tile shapes, but essentially two types: pan tiles and flat tiles. Pan tiles are perhaps most common. They have a half rounded or S shape, are laid face up and face down, and are often referred to as Spanish or Barrel Mission tiles. Flat tiles can be completely plain and flat and, like roofing shingles, can overlap one another with variations on a slight center ridge or other adornment. Any of the standard tile shapes may be known by regional names, which makes it important to bring or send samples to your potential supplier. Other materials produced to simulate clay add to the confusion of what tile you may have on your roof. They include stamped metal and dyed concrete, which tends to be much thicker than clay and more susceptible to fading.

As with floor or wall tiles, those that cover most of the flat surface of the roof are called field tiles. Specially shaped tiles for valleys, eaves, along dormers, and the ridge of the roof are finish tiles. Birdstops are often used at the roof edge to prevent birds and bats from nesting in the rounded opening of the tiles.

Terra cotta is the color most commonly associated with historic clay tile roofing. Its reddish color comes from the large amount of iron oxide found in the clay but can vary a lot, with shades of orange, black, and brown brought out during the firing process. Lighter colors can also be produced depending on the clay source, and all were often carefully mixed to create a roof surface with varied colors. When a more uniform color was desired, glazes were applied to the clay before firing, which produce colors ranging from yellow and green to solid glossy black.

Studying Your Roof

If you're contemplating removal of a few or all of your clay tiles, it helps to have a basic understanding of reasons they might have failed. Clay tiles are heavy and require more structural support and underlying sheathing than average shingle or metal roofing. They fail most often due to a breakdown of either the wood sheathing on which they are laid or their fastening system. Start by looking at how they were originally attached to the roof structure. Generally, all clay tiles are laid on continuous wood sheathing and nailed along vertical or horizontal "nibs," laths, or battens.

Early clay roofs were laid directly on laths and battens secured to the rafters so that the tile is visible from the attic space, and some later applications utilized a copper wire tied from the tile to the wood battens. Holes in the tiles allowed for a copper nail or hanger to protrude, leaving the tile hanging loosely and vulnerable to breakage in freeze/thaw cycles. Carefully examine the nails holding the tiles onto the roof to determine if they are corroded by tannic acids common in oak sheathing or battens. As with any type of roof, properly maintained downspouts and gutters are essential to keep water and ice from seeping under tiles. Clay tiles, especially early handmade examples, can vary greatly in quality. For instance, efflorescence of soluble salts on the surface may indicate that a tile is excessively porous as a result of under-firing during the manufacturing process.

Immediately replace badly chipped, cracked, or broken and missing tiles to prevent moisture from penetrating the roof's structure, which can lead to a costly renovation job requiring total tile replacement.

Repairing Broken and Missing Clay Tile

Once you've targeted tiles for removal or replacement, you need to avoid breaking neighboring tiles or nearby roof parts. While a careful roofer can generally walk on flat tiles, high-profile pan tiles are more fragile. Lay sheets of plywood, planks, or even burlap bags filled with sand to distribute weight so you can move about the roof without breaking additional tiles. You may need to remove many tiles in a path leading up to a problem area and number and map them for reinstallation. It's also not unusual for an entire roof to be stripped of its tiles while new battens and fastening systems are installed for the reinstallation of the original tiles.

Remove individual tiles with a slate ripper or hacksaw blade inserted under the tile to cut the nail or nails holding it in place. The nail holding the tile is usually not driven all the way to the surface so the tile hangs on the nail and can be easily lifted. If the nail is tight to the surface or its head is wider than the tile hole, you may be able to grind off the head. Don't use the tile itself as a fulcrum to remove the nail, since the force can easily break the tile. Reinstall tiles with copper nails. To reanchor tiles that have damaged nail holes, use a copper strip or "tingle" that is nailed onto the roof sheathing and bent around the edge of the tile, much like hangers you may have used to fasten antique plates to a wall.

When repairing a clay tile roof, you should always re-use as many of the original tiles as possible in the most highly visible places in order to achieve a close match in color and shape. You may be able to relocate tiles from less prominent portions of the structure, such as the sides and rear, or behind chimney stacks or dormer windows, to create an authentic front roof, then replace them in these areas with newer tile that might not exactly match the original.

Sources for Replacement Tiles

Many late 19th- and 20th-century tiles are marked on the underside with their manufacturer and the size and name of the particular tile shape. Some of the companies producing tiles today (notably Ludowici and Gladding, McBean) were selling tiles more than 100 years ago and are a good source for exact matching. Many of these companies, as well as architectural salvage yards, maintain stockpiles of used tile, while others will manufacture a matching customized tile when sufficient quantities are requested. You should order extra tiles to compensate for breakage during installation or transport.

New tiles produced today have even more variations in size, color, texture, and thickness, and not all are appropriate for a historic structure-especially tiles of a bright color with a high-gloss glazing. On the other hand, today's clay tile manufacturers are producing tiles for specific weather conditions, from arid regions to wet and frequently freezing locations, so you may be able to balance your climatic needs with historic authenticity.


Paul Kelsey Williams is president of Kelsey & Associates, Architectural Historians,
(202) 462-3389, washingtonhistory.com.

A Helpful Reference Historic and Obsolete Roofing Tile by Vincent H. Hobbs and Melvin Mann was written to help professionals match old tiles. It contains 254 pages, 700 color photos, a reference section, and a guide to troubleshooting. A graphic arts scale allows for a more precise match.