Plain tiles are the widely-seen flat form of roof tile, which, in practice is usually gently cambered. Being ‘double-lap’, the tail overlaps two courses below. Unlike the uniform, mass-produced plain tiles from Victorian times onwards, earlier hand-made ones were hung not by protruding nibs but wooden pegs and possessed greater individuality. Sizes of these ‘peg tiles’ range from just 229 x 152 mm in Kent, to 305 x 203 mm in York. Most are a shade of red, although soft, variegated colours are associated with Cambridgeshire.

This depends on the extent of deterioration. Consideration should normally be given to retiling when repairs are no longer cost effective. This is typically after one-fifth of the tiles have been reinstated. The condition of gutters and ancillary items, such as flashings will also influence the course of action. Repair or retiling should be entrusted to a reputable roofer, and the SPAB may be able to advise on suitable contractors in your area.

New tiles should usually match the type, colour, texture, size and thickness of existing ones. Avoid using second-hand plain tiles from other buildings. Substitution with concrete tiles is undesirable as, generally, is replacement of hand-made plain tiles with machine-pressed ones (or vice versa). When completely re-covering a roof, the maximum number of old tiles should be re-used. Depending on the circumstances, new tiles can be mixed with old ones across the roof or reserved for less prominent slopes.

The emphasis should be on matching existing details. The detailing of hips, valleys, ridges, dormers, eaves and abutments should therefore be recorded. Details such as tile-and-a-half rather than cut-tile verges may be inappropriate for pre-Victorian buildings and the lime mortar fillets found on many old roof abutments usually deserve retention rather than replacement with lead flashings. Bedding mortar for hand-made tiles should normally be lime-based (without cement).