Details

The concrete interlocking tile has long dominated the British domestic roofing scene: Double Roman, Ludlows, Mendips, Bold Roll and most successful of all, Redland’s Grovebury. The attraction of providing a roof covering for no more than £12/m2 supplied and fixed, compared with over £20/m2 for the next cheapest option, has made it the preferred choice of new housebuilders.

The products themselves do tend to look much of a muchness. For a touch of class you could step up to a small format plain tile but, even if you keep to concrete rather than clay, you need to lay 60 typical plain tiles to cover a square metre as opposed to just 10 for a Grovebury, so not only do materials costs expand but, inevitably, labour costs do as well. The other traditional mass produced roof covers, slate and pantile, also suffer in both cost and coverage comparison with the concrete interlocker, though their cost penalty is less exacting.

The concrete interlocking tile is a visual deceit, based on the looks of the pantile or the Mediterranean rolled tiles (hence Double Roman). Functionally, they could just as well be flat - there are some large format flat tiles but the eye doesn’t take easily to such a featureless mass of concrete laid on a roof. Introducing vernacular bumps and curves into the profile of each tile does just enough to make them acceptable, but they are never attractive in their own right.

Now manufacturers have begun to reassess the possibilities of large format tiles and to look at other ways of softening their visual impact. The best known of these new designs is Forticrete’s Gemini which tricks the eye into thinking it is two plain tiles by the simple device of having a groove planted down the centre of one large format (330 x 270 mm) tile. Geminis do not actually sit like a plain tile - the tell-tale camber is missing, the tile lies completely flat - but from the ground it is hard to notice and at a coverage of 19/m2, the laid tiles come in at under £20/m2 as opposed to £25-30/m2 for a plain tile.

There are now two more largish format interlocking plain tiles to choose from besides the Gemini. One is HF’s Beauvoise, which, like the Gemini, mimics two plain tiles with a central vertical groove. The other is a new tile from Sandtoft called the 20/20: this does not have a central groove but does introduce a slight cross camber which makes the tile sit better on a roof. Both the Beauvoise and the 20/20 have a coverage of 20/m2, and their laid cost should be very similar to the concrete Gemini. Yet they are also both clay tiles, giving housebuilders the option of clay plain tile at much lower prices.

Nick Oldridge, marketing manager at Sandtoft comments: “We see the 20/20 as a great way to grow the market for clay roofing. There is a lot of interest from both housebuilders wanting something different and housing associations having to re-roof but wanting to stay with clay.”

The other area where these tiles gain is that they can be laid at pitches as low as 22º whereas a traditional small format tile needs a roof pitch of at least 35º.