Before we get into the key differences between clay and concrete tiles, let’s take a look at what these tiles are and what they’re made of:
Overview of Clay and Concrete Tiles
Clay tiles are produced by baking moulded clay. The density of the clay is determined by the length of time and temperature at which it is heated. New Zealand tiles are generally formed of local terracotta clays, fired with a clear or coloured glaze on the outer surface for weather protection and left unglazed on the lower surface. The purpose for not glazing the lower surface is so to allow the tile to breathe. Colours of clay tiles range from shades of white, yellow, orange and brown.
In general concrete tiles are made of a coarse cement/aggregate mix with a slurry finish. The slurry was usually a mixture of cement, sand, silica, and coloured ochre. Depending upon the manufacturer, the cement mix may be compacted or gravity fed, air or force dried. Concrete tiles are manufactured from sand, cement and water which are molded under heat and high pressure. The exposed surface of a tile may be finished with a paint like material. Concrete tiles have additional water locks, or interlocking ribs on the edges that prevent water infiltration.
While the two may bear resemblances aesthetically, there are plenty of important differences one must understand when considering a new roofing project.
See also our comprehensive Clay and Concrete Tile Roof Guide.
To help you when selecting your roofing tiles, here are 7 key differences between clay and concrete tiles:
1. Water Absorption
Concrete roofing tiles have a water absorption of about 13%, while clay roofing tiles have a water absorption of about 6 %. Consequently, this higher rate of water absorption can lead to the development of mildew and stains on concrete tiles. The extra water will also put additional weight pressure on the roof. However, water absorption can be minimised by adding an extra coating.
Concrete tiles weigh almost 40% more than clay tiles. Concrete tiles can weigh anywhere from 820 to 1.100 pounds per square (100 sq. ft.), depending on the style, while most clay roofing tiles weigh only 600-650 pounds per square. As a result, it is more difficult for the roof structure to adequately support the heavier weight of concrete tiles. In some cases, concrete tiles are not recommended for use on buildings, unless the roof framing is reinforced to support the added weight.
3. Propensity to Crack and Shatter
In colder climates, clay tiles have a tendency to crack or shatter due to freezing and thawing cycles. As a result, clay tiles are mostly found in warmer climates.
Conversely, concrete tiles are not as susceptible to damage due to freezing temperatures, and therefore can be used in almost any climate.
Heavier weight, higher rate of water absorption, and formation of mildew makes concrete tiles more challenging to maintain than clay tiles, which are almost free of these issues.
5. Appearance Colour and Longevity
Concrete tiles are naturally grey but can be produced in many different colours to match the appearance of other existing tiles or materials. Clay tiles come in a variety of rich and attractive natural shades but aren’t available in as many different colours, shapes, or textures as concrete tiles.
Since clay is a naturally occurring material, clay tiles maintain their original colour for years despite weather conditions. On the other hand, concrete tiles can fade over time. Due to their porous nature, concrete tiles are also more prone to stains than clay tiles. Also, because concrete tiles are dried not baked, they can have a more uniform shape than clay tiles and are dimensionally stable.
Both concrete and clay tiles outperform a lot of other roofing materials in durability. Concrete tiles may last 30 to 50 years or more, while clay tiles have been known to last well over 100 years.
You can expect to pay around 20% less for a concrete tile as opposed to a standard machine-made clay version. However, spread out over the lifetime of the roof (as clay has a longer lifespan), the difference may work out to be negligible. Clay tiles can also add more value to your property.
Clay tiles are often seen as a more environmentally friendly product, as opposed to concrete, but when looking at the whole manufacturing approach and comparing the entire process, concrete is in reality more sustainable.
- Compared with traditional clay roof tiles, concrete tile manufacturing requires considerably less energy usage during production. This is largely because of the extensive power required for clay tiles, in a 1,000-degree kiln for up to 48 hours.
- Concrete tiles are cured at a much lower temperature and for only a short amount of time. This means an energy saving of up to 30% on the energy used producing clay tiles.
- A study in 2008 showed that during its entire lifecycle, a concrete roof tile only creates around 45% of the greenhouse gases triggered by a clay roof tile during its lifetime.
Clay titles and concrete tiles both have their advantages and disadvantages and both remain popular choices.
Check out our Clay and Concrete Tile Roof Guide for more information.