Clay interlocking, the past, present and future

Sarah Jackson, marketing product manager at Marley Eternit, discusses the history and evolution of clay interlocking tiles and why build time, cost and skills challenges are encouraging more contractors to turn to this easy to lay option

Interlocking clay roof tiles are certainly not a new invention; in fact they have been used on our roofs for hundreds of years.  The idea of joining clay tiles together by overlapping them was first brought to the UK by the Romans in the form of the under and over Tegula and Imbrex tiles, which have  evolved to become the Roman single and double roll tiles that we see today. 

After the departure of the Romans the art of making clay tiles was lost until around the 12th century but it wasn’t until the 16th century that overlapping clay tiles were re-introduced to the UK from the Netherlands.  These new tiles linked together with an S-shape rather than relying on the vertical overlaps to prevent water penetration and became known as pantiles, which are considered as one of the oldest single lap tiles in the country.  As a result of these influences, the roof tile has left a lasting legacy in certain parts of the country and planners will often insist on replacing like with like.

Unlike today’s modern equivalent, early roman tiles and pantiles were fairly irregular and not very efficient at keeping out water.  So in the first half of the 20th century, rather than simply overlapping individual tiles, some UK and European manufacturers began to design larger clay tiles with raised weatherbars, so that they could be interlocked from one tile to the next, improving performance, coverage  and water tightness. 

Before the 1940s, clay was a very popular material for the UK roofing market but the demand for the tiles during the post war reconstruction effort in the 1940s and 1950s far outstripped the supply from British companies.  This led to large quantities of cheap imports flooding the market and giving clay tiles a bad reputation at the same time as they faced stiff competition from an exciting and cost effective new roof tile – concrete.   From the 1950s to the 1970s, concrete tiles all but obliterated clay in UK roofs because they were bigger, cheaper and easier to fit.

From the 1970s, there was a steady recovery in clay tiles and by the beginning of the 21st century, there had been major investment in modern and efficient new clay tile factories in the UK.   This led to the next stage in the evolution of clay interlocking tiles and in the early 2000s, a new type of tile was developed which looked like clay but fitted together like a concrete interlocking tile with high coverage rates.  Whereas traditional clay interlocking tiles often had a fixed gauge, this modern large format version had a more open or flexible gauge which eliminated the need to cut tiles or use special shortened tiles.  Until then, the cost of clay tiles had been seen as prohibitive to some building projects but for the first time, these tiles brought about true competition to the large format concrete tiles, which dominated the UK since the end of World War Two.

To date, there has been very little competition in the large format clay interlocking tile market and roofing contractors have been able to choose from only a handful of products.  In recent years, other large format clay tiles have been launched but haven’t been accepted by the UK market because they were too technical and complicated to fit.  That’s the reason why, at Marley Eternit, we have taken the decision to introduce two very easy to lay large format interlocking clay roof tiles in popular profiles, double roman and a clay single pantile, to give contractors  more choice and availability in this market. 

As well as having a flexible or open gauge, our new Maxima and Melodie tiles have been designed to work with our standard concrete segmental ridge tiles and third round hips, as well as our universal fittings and accessories.  This not only keeps the cost of the roof down but also ensures contractors don’t need to carry any complicated extras.  The modern interlocks and weather bars offer new levels of weatherproofing and are capable of achieving extremely low roof pitches whatever the UK weather throws at it. 

Whereas traditional interlocking clay tiles could only be used at roof pitches of around 20 to 30 degrees, both of our new tiles can be used on low pitch roof designs.  In fact, the Melodie, our new interlocking clay pantile, has one of the lowest minimum pitches in the roofing industry at a market leading 12.5 degrees, so it can be used on projects where roofers may not have been able to use clay tiles before. 

We’ve taken the decision to launch the products because there is noticeable growth in the clay interlocking tiles market, which we estimate has grown from about 1% to 6% in the last ten years.  Although this is still a relatively small part of the market at the moment in the UK, in some European countries clay interlocking tiles make up 50-70% of the market.  We believe there is an opportunity for growth in this country as well.

Prior to the recession there was an indication that clay was starting to challenge the concrete interlocking market.  Now the housing market is growing again, with the Construction Products Association estimating a growth of 16% in private new housing starts this year, we are already seeing a noticeable surge in the sales of clay plain tiles and expect this to follow though to the clay interlocking market  for a number of reasons.  

Firstly, building and roofing contractors need to balance rising tender costs brought about by an increase in both labour prices and inflation.  Large format clay interlocking tiles are the perfect product for roofing contractors to offer as a way of getting the clay aesthetic quickly and cost effectively because they have the high coverage rate of a large format single lap interlocking tile, cutting installation costs by up to 30%.  

Secondly, clay interlocking tiles help to address the increasing skills shortage seen in the roofing and wider construction industry because they give the clay aesthetic but are as easy to fix as a concrete tile.

Finally, availability is also another factor driving the growth in this market as the housing resurgence has highlighted some supply concerns, but the new Maxima and Melodie tiles are available with little lead time. 

They may have been part of our roofing history for hundreds of years but the development of modern large format clay interlocking roof tiles has revolutionised the clay market, making clay tiles more affordable and opening up new markets, as well as helping contractors to meet today’s time, cost and skills challenges. 

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