Period character guide: Cladding

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Helping a friend clad an extension with timber weatherboarding made me realise the impact that cladding has on a building. When I wander village streets of tile-hung or timber-clad cottages I now imagine how bland they would seem without their warm hued clay coats, painted boarding and surfaces indented with shadows of broken sunlight.

Cladding is found chiefly in the east and south east of Britain. Mainly it provides protection from the weather although it has also been used to bring buildings in line with prevailing fashions. Tile cladding appeared towards the end of the 17th century, often covering the upper half of earlier timber frames. Clay roofing tiles were frequently used, although tiles with a shaped lower edge were introduced to create decorative effects. Slates were used in a similar way but their smooth greyness gives a very different look.

Weatherboarding was originally restricted to agricultural or industrial buildings. Early cladding was of oak or elm but later softwood boards were used and it became more fashionable for domestic buildings in Georgian times. Some rural cottages and farm buildings were treated with tar, pitch or creosote; more often weatherboarding is painted.

Towards the middle of the 18th century, the fashion for brick buildings resulted in the development of mathematical tiles. These are made of clay and hung with nails like tile cladding to simulate bricks, often so successfully that it is hard to distinguish the difference.

From tree to board
At the sawmill run by English Woodlands Timber in Hampshire, traditional timber cladding is made using sweet chestnut, oak and western red cedar from local plantations. Jules Easton, sawmill manager, explained that the timber is freshly felled and selected by the sawyer to ensure that it does not have too many knots or imperfections.

The first stage is to manoeuvre the log or ‘round timber’ on to the saw bench using a winch and giant pincers known as ‘dogs’. I watched as a log was lowered and then pushed against the ‘fence’ of the saw bench with ‘pry bars’. The fence, a steel plate, acts as a guide as the hydraulically driven bench carries the timber towards the saw, enabling the round timber to be cut square.

Jules told me that their band saw is 60 years old and has a 7m blade which passes round two large wheels, one beneath and one above the bench. He explained that a sharp blade ‘rings’ as it passes through the timber but it can quickly become blunt if it hits stones embedded in a log.

The next stage is to cut the timber into planks known as slabs or blanks. Once again the fence is used as a guide and, on this occasion, it was set so the slab ended up being 32mm thick. Like the proverbial knife through butter the saw sliced the timber into slabs. The aroma of newly cut timber pervaded the air as deliciously as fresh coffee.

To produce feather-edge cladding from the slabs a second, smaller band saw is used. Again it has a fence but Jules showed me how it is set, this time, at an angle so each slab produces two boards tapering in thickness from 25mm to 5mm – 2mm is lost in the saw cut. Care and repair Timber and tile cladding often provides protection against the elements so think carefully before altering or removing it. In areas where new materials are needed, replace like with like.

Care is needed at corners and where cladding meets frames to avoid the creation of channels that will direct water into the building. Old structures need to ‘breathe’ so beware of fixing non-breathable sheeting beneath cladding materials.

Gentle prodding with a penknife is a good way to check the extent of a rotten area of weatherboarding. Where replacement is necessary you may need specially milled boards to get an exact match. The most common types of boards are feather-edge, square-edge or waney-edge but some have moulded edges.

While moulded cladding is air-dried and stable, other boards are cut ‘green’ so will shrink and are best fixed in the spring or autumn when temperatures are not extreme. With any type of cladding stainless-steel annular nails or screws should be used to prevent rusting and any reaction between the metal and the timber.

Not all timber needs to be finished and any finish you choose will depend on what has been used previously. When painting weatherboarding a flexible vapour-permeable type will allow for movement and the escape of moisture. Where new timber is being painted give it at least one coat before it is fixed so that unpainted areas are not revealed if the timber moves.

In the case of tiles and slates, they are either nailed to laths fixed to the wall or, on masonry walls, are fixed directly into the mortar between the bricks. In some cases the top edge is also bedded into lime mortar.

Problems can be caused by rusted nails or because the laths have rotted so repair work can vary from removing a few damaged tiles to fixing laths. Replacement tiles are available new or from salvage suppliers.

ABOVE (clockwise from top left): Shiplap weatherboarding with special attention paid to junctions between cladding, window frames and doors; Weatherboarding on a Surrey watermill; Waney-edged cladding.
BELOW (clockwise from left): In certain areas, tile hanging using decorative shapes became a popular finish; Mathematical tiles are made of clay to simulate bricks and are fixed with nails or a bedding of mortar. As with bricks, their joints are pointed in mortar; The fashion for brick buildings resulted in the development of mathematical tiles in the 18th century.

Word for word: A glossary of cladding-related terms
Sawyer: Somebody who saws wood for a living.
Shingles: Tapered slices of wood that are used to cover walls in much the same way as tiles or slates. Oak shingles are usually between W10cm and W15cm and from L20cm to L30cm.
Shiplap cladding: Weatherboarding with rebates cut on each edge to enable neighbouring boards to fit over one another.
Waney-edged boards: A board with bark left on one edge – these have long been a traditional finish for agricultural buildings.

Visit Roger Hunt's website at huntwriter.com

WORDS ROGER HUNT PHOTOGRAPHS ROGER HUNT
Featured in the October 2009 issue of Period Living