Plain Tile Roofs
The two classic materials used on roofs in London early in the last century were Welsh slate and clay plain tiles. Whereas roofers are very reluctant to reuse old slate, no matter how in mint condition it might appear, plain tiles are another matter.
The wariness about using the client’s original slate is due to the difficulty of its removal from the old battening without splitting it, and the fact that it has to have a further two holes punched into the surface as the existing ones will invariably be too large. There hence is little chance of knowing the exact amount of recoverable material available, and any matching second-hand ones bought at a salvage yard tend to be mediocre and very over-priced.
Clay plain tiles are another matter entirely. For a start, the majority are not nailed into position but hang by lugs from the roof batons. This means no damage occurs in their removal.
The other point in their suitability for reuse is that an experienced eye can ascertain the percentage of recoverable tiles by merely putting a ladder up on the property’s guttering and closely inspecting the roof flanks from below.
The reason for this is because what the roofer is looking for is evidence of frost damage. For the most part frost damaged tiles delaminate from the bottom and not the top surface. This is because in the winter the margins underneath the tiles become wet as the rain cascades down the roof. It fans out and spreads 2 or 3 centimetres as it reaches the bottom edge.
Now, whereas the top surface may well dry off in the wind, the underside remains wet. Over the decades hard frosts attack the moistened surface and where the poor quality of the clay or the firing of the tiles has not been thorough, ice will push off the face of the material, exposing its more delicate centre. Once this happens the tile is compromised and will rapidly disintegrate from the bottom up. The tiles viewed from the road may appear intact, but on closer inspection, looking up from the gutter line, a proper estimation of quality and recoverable material can be accurately achieved. Frost damaged tiles will appear as a fragile delaminated shell.
This aside, the primary reason I encourage clients to reuse their clay plain tiles if they are largely undamaged is the beautiful colours and shapes you see in them that are not present in the dull mundane tiles you can buy today.
If cleaned with a caustic solution and wire brush, the plain tiles will come up as good as new. What is more, good quality second-hand machine made Rosemary or Acme plain tiles are readily available from most roofing or architectural salvage yards at a reasonable price. To make up the shortfall of tiles through frost damage or breakages, a roofer would have little difficulty finding replacements, if he is prepared to go the extra mile to achieve a roof of character.
To illustrate what can be done reusing the client’s own tiles, I have chosen a roof that at first glance was a complete write-off.
The badly maintained zinc valley at the front was a mess and the left hand party wall not only leaked but was about to fall apart. The one thing I did notice was the superb quality of the plain tiles.
I encouraged the client to let me clean and reuse them in conjunction with second-hand valley tiles I knew were available. The photographs before and after show what can be achieved using a little imagination and a lot of enthusiasm, much of which stemmed from a grateful client.
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In contrast, two photographs of frost damaged plain tiles show a roof not worth saving.