Extending a Cottage - Design Solutions

ABOVE: A new conservatory and a two story rear extension to this 1930s cottage have added plenty of space but avoided interfering with the original. A timber-clad link has allowed the brick facing of the new extension to avoid having to match the original. Designed by Stone & Moon Associates (01423 528106)

Building Form

An important part of the appeal of the cottage is its proportions, and any new extension should seek to preserve this. The design of any new addition, therefore, should be subservient to the existing cottage.

Side extensions generally look best if they step back from the existing frontage and down from the roofline, although they can project back further than the existing building to form an Lshaped footprint.

Stepping extensions back and down also makes construction more straightforward, as different wall and roof materials, and the eaves and ridge will not have to intersect in the same plane, and differential movement can be accounted for more easily.

Rear extensions, too, tend to look best when stepped out of line with the side elevations of the existing property, and with a lower ridge height.

If lowering the ridge height restricts the potential for upper storeys within the extension – very likely given the low ceiling height in many cottages – it may be possible to create additional headroom by excavating and lowering the floor level of the extension and creating a split-level design. This solution works well if the change in level is a single step, or two at most, Building Form but can waste valuable space where stairs become a necessity. 

In terms of scale, it’s generally better to make several smaller additions than to build a single disproportionately large extension. However, it is possible to achieve the latter by placing the extension away from the original dwelling and designing it as an outbuilding, adjoined to the existing building by a single storey link. 

When it comes to roof shapes, a variety of intersecting roofs, often of differing materials, heights and pitches, is a key characteristic of cottage style and should be reflected in extension design.

New additions should generally aim to be of traditional form, which means the span of any duo-pitched roof should not exceed any more than 4-6m — this was limited by the length of timber rafters and joists traditionally available for use. The new roof should also be of the same or similar pitch to the original building, or a pitch suited to the chosen roofing material, be it slate, clay tile, stone or thatch. But it is generally accepted that 45° roofs should be avoided on traditional-style buildings — this angle never looks quite right.

The length of traditional roofs is less restricted, as they would have been supported by gable walls, roof trusses and purlins, so larger footprints can be achieved by careful orientation of the ridge.

For designs that require a wider roof span, two or more sections of intersecting roof at a traditional pitch and span should be used. Smaller additions can be sensitively covered by an outshot or catslide roof, or a lean-to roof.

Materials

The materials used to build cottages typically reflect the underlying geology, so whatever material was cheap or freely available in the ground was put to use, and other materials incorporated only if budget allowed. To get an idea of the local vernacular palette, simply take photographs of traditional buildings in the area. Look not just at the materials, but the way they are used and how they are combined.

Although you could extend in materials that match the existing building, the results are usually better if alternative, but complementary, materials are used whilst remaining within the vernacular palette. This will add to the character of the building and help any extension to blend in.

In areas with underlying clay and sand, walls were often built from cob or other forms of earth construction, bound together using straw. Cob walls would usually be covered in painted lime render, and built atop of a few courses of stone or brick to keep them dry. Lintels above openings would usually be timber. Extensions of these cottages could be in rendered cob, rendered blockwork, timber boarding or local brick or stone. 

In areas within the great limestone, sandstone, slate or granite belts that stretch across the British Isles, stone was the prevalent building material, used to build walls and, depending on what came out of the ground, to cover the roof, too. Where larger stone was not available, roofs may have been thatched, covered with clay tiles or, from the early 18th century, Welsh slate. 

Typically the stonework would be random rubble walling on simple cottages, or simple rough-coursed walling on better quality buildings, with cut stone or local brick quoins, and the same to form window or door reveals, with timber or stone lintels or brick arches. Extensions to stone cottages could be clad in stone, brick or timber boarding.

In Downland areas where there are clay, flint or chalk deposits, variously brick, napped flint or chalk block (clunch) were used, often with carved stone or brick around window or door openings. Lintels over openings would be timber, stone or brick arches. Roofs were often thatched or later covered with clay tiles. Extensions to these cottages could be clad in timber boarding, stone, brick or flint block.

In areas with large clay deposits, brick was the predominant material for cottages from the early 18th century onwards. The character and colour of the brick varies widely, depending on the colour of the clay deposits, the moulding process and the firing. Extensions could be in brick, render, timber boarding or half render on a brick plinth with hung tiles above. 

Oak was a widely used material for housebuilding up until the early 19th century and oak framed cottages can be found across many counties, especially the Welsh Border counties and the Weald area. It was supplanted by stone and brick construction because of the inherent fire risk. The post and beam frames may be infilled with wattle and daub panels (woven willow and earth), brick noggings or clad in timber boarding. In some areas they are clad in hung clay tiles, or in mathematical tiles which give the appearance of high-quality brickwork. 

Extensions to oak cottages could be oak frame with render infill, timber, brick or render.

Windows

Cottages are generally characterised by small window openings (glass was a relatively expensive commodity) and those of traditional solid wall construction, especially cob or stone, often had very deep window reveals — which bathe the interiors with a lovely soft light.

To maintain this character in an extension, walls need to be thicker than the standard 300mm modern cavity wall. This can be achieved by using traditional forms of solid wall construction, a 300mm cavity blockwork wall with stone cladding, or alternatively by using lightweight concrete foundation blocks in place of standard 100mm blocks. These are available in sizes 440mm x 215mm, in depths of 200-300mm. Aircrete blocks can be cut with a saw and so it is simple to shape them to create splayed or curved reveals.

Cottage-style windows are usually of the small-paned variety, made up of several rectangular or square panes held together in timber sashes and side hung, set in timber surrounds, or occasionally metal framed casements set in wooden or stone surrounds.

On older cottages, and those of some of the revivalist movements, such as the Gothic Revival of the mid 19th century, windows may be made up of small panes of ‘quarries’ held together with strips of lead, either in a rectangular, or sometimes a diamond pattern.

Larger window openings were formed by arranging two, three or more casement windows together, separated vertically by mullions or horizontally by transoms.

From the late 17th century onwards until the early 20th century, some larger and more refined cottages may have had vertical sliding sash windows.

As with external materials, the windows for an extension need not be identical in style to the existing cottage, which may well already incorporate a variety of different window types.

To meet today’s Building Regulations, new windows will almost certainly have to be double glazed, but there are specialist manufacturers who produce period-style double-glazed windows that are a very good match for period originals. Opt for a style that is later than the original building, so in most cases small-paned casement or sash windows, wooden or metal framed.

FURTHER READING:

• Design Masterclass: Extending a Cottage 
• A Self-built Cottage on a Remote Island
• Get The Look: Cottage Style