Concrete Tile Roofing
Ice-ball testing gives concrete tile two very different numbers depending on its shape. Flat concrete tiles begin to fracture at around an inch and a quarter of hailstone diameter — barely above the one inch at which the National Weather Service calls a storm severe. High-profile S tiles, with their arch carrying the load down into the tile below, hold out to roughly two inches. Same material, same roof, a difference you would never guess from a color sample. That is a fair introduction to concrete tile generally: it is a tough covering with specific limits, and the limits are worth knowing before you buy rather than after a spring storm. APC Roofing sets and maintains concrete tile roofs in Florida, Colorado, Missouri and Kansas, where it is an everyday covering in the first and an exception on a street of shingles in the other three.
Concrete tile is cast from sand, cement and water, pressed into shape and cured — a manufactured product rather than a fired one, which is why it comes in profiles clay cannot easily match. High-profile S tiles, low-profile pans, and completely flat tiles that read as slate or shake from the street all come out of the same process. Color is typically a surface finish applied over the gray body of the tile rather than running through it, and that is the important difference from clay. Surface color weathers. Over many years a concrete roof softens in tone, and a chipped tile shows gray underneath. It is usually the more affordable route into tile, and it is the heavier one.
Weight is the first question, not the last. Concrete tiles are heavier than clay of a comparable shape, and heavier still when saturated, since the material takes on a small amount of water in prolonged rain. On a structure built for tile that is a non-issue. On a building currently wearing shingles it settles the project: rafters, connections and walls all have to be confirmed capable of carrying the finished roof before anyone opens a color chart. Anywhere winters cross freezing, ask what freeze-thaw performance the tile is certified to as well — the same absorbed water that adds weight expands about nine percent when it freezes, and tile made for a warm market spalls and delaminates in a cold one.
Two early cosmetic surprises catch owners out. Efflorescence is a white bloom of lime that works its way to the surface of new tiles and fades on its own with weathering. Some color variation between production batches is normal. Neither affects performance. Over time, shaded northern slopes may pick up moss or algae, which is cleaned carefully and at low pressure — a pressure washer aimed at concrete tile strips the surface finish and breaks tiles underfoot.
What actually fails on a concrete tile roof is rarely the tile. Far more often it is the underlayment beneath it, the flashing at a valley or wall, or the mortar and fastening at hips and ridges. A leak on a concrete tile roof is therefore not evidence that the roof is finished. In many cases the tiles are lifted and stacked, the membrane underneath is renewed over a repaired deck, and the same tiles go back down. The tile roof repair page explains how that work runs.
