Principios Metodológicos de la Enseñanza AICLE

For less grand buildings local materials have been used right up to the 19th century. The coming of the canals, followed by the railways eventually made it economic for brick, slate and tile to be transported more widely so that Welsh slate would be used to cover London’s Victorian terraces.

Modern bricks came into use in about AD1300, having lapsed since Roman times, and the earliest brick building which survived into the 20th century is Little Wenham Hall in Suffolk (AD1260). The pre-dominance of brick for domestic construction dates from the reign of William and Mary and it remains the most economic and universally acceptable material for the external facing to residential buildings.

Half-timbering as in Lancashire, Cheshire and the West Midlands dates mainly from the 14th to 16th centuries. Terracotta was used in Essex in the early 16th century and in localities with chalky soils flint was used and is still common in Norfolk, Suffolk and Hertfordshire.

In these areas the flints are split (or knapped) to provide a flat face and the wall is built using flints as random rubble set in lime mortar with the knapped faces providing an attractive weathering surface. Lots of churches in Hertfordshire and East Anglia together with village houses are built this way. The flints are extracted from gravel pits or harvested from the surfaces of the fields after ploughing, and is good cheap local material, easy to collect and transport.

In both ecclesiastical and secular buildings the earliest periods likely to be encountered are:

1189 to 1272 Early English 1307 to 1377 Decorated 1377 to 1558 Perpendicular

These three periods feature the Gothic style in Britain which survives generally in the form of ecclesias-tical buildings.

The Renaissance period commended at the start of the 16th century after the Wars of the Roses and during the suppression of the monasteries (1536–1540). During this period we saw the conversion of some ecclesiastical buildings into mansions, the endowing and building of grammar schools, and during the Elizabethan period a great increase in the building of country houses such as Longleat in Wiltshire and Haddon Hall in Derbyshire.

The Jacobean period saw such mansions as Holland House in Kensington and Bolsover Castle in Debyshire built. These and the preceding Elizabethan mansions were principally of brick and stone but timber construction was still employed in Cheshire, Lancashire and Shropshire. Emmanual College Cambridge and Jesus College Oxford were built during this period.

The Anglo-Italian period began during the reign of Charles I who employed Inigo Jones (1573–1653) to design complex structures of classic grandeur. The Great Fire of London (1666) presented an

Dates and periods

43 to 450 Roman Britain 450 to 613 Coming of the English 613 to 1017 Division into Kingdoms 1017 to 1066 Saxon and Danish

1066 Saxon techniques replaced by Norman

1066 William I

1087 William II

1100 Henry I

1135 Stephen

(Continued)

Dates and periods (Continued)

1154 Henry II

1189 Richard I 1189 to 1272 Early English

1199 John

1714 George I 1714 to 1837 generally referred

to as Georgian

1727 George II

1760 George III

1820 George IV 1810 to 1820 also as Regency

1830 William IV

1837 Victoria 1837 to 1901 generally referred

to as Victorian

1901 Edward VII 1902 to 1914 generally referred

to as Edwardian

1910 George V

1914 to 1918 Virtually no construction during First World War

opportunity for the redesigning of the city and the genius for construction of Sir Christopher Wren (1662–1723).

From here there was a logical progression of construction methods and styles to the 18th century which is split into two periods: Queen Anne (1702–1714) and Georgian (1714–1837) including the period of the Regency (1810–1820). Dwelling houses from the Queen Anne period were typically fairly to plain and functional but in well-proportioned facing brickwork and now much appreciated and sought after. Castle Howard and Blenheim Palace were designed during the Queen Anne period in the Anglo-Classical style whilst during the Georgian period Robert Adam (1728–1792) was probably the most famous exponent of the Georgian style (witness the Adelphi Terrace in London and Keddleston Hall, Debyshire). Columns, vaulting and sprawling plans again became fashionable with a strong emphasis on facades. This prompted the classical revival with ambitious pseudo-Greek models such as the Bank of England (1788) and St George’s Hall, Liverpool by H. L. Elmes (1815–1847).

An upsurge in church building in the 19th century brought us the Gothic Revival with Augustus W. N.

Pugin (1812–1852) as the apostle of ecclesiastical work in this style. The most impressive buildings of

Ridge purlin tier. The upper arch brace is carried to the back of the hammer beam

A: True hammer beam with vertical tenon B: Pendentive hammer beam with much weaker horizontal tenon

C: Pendentive hammer beam with advantage of strength from vertical tenon, and decorative pendant

Fig. 15.1 Typical hammer-beam construction used mainly in churches and cathedrals. Detailed knowledge of this type of construction is essential before an accurate assessment of strength may be made.

this time are, however, not churches but the Houses of Parliament designed by Sir Charles Barry with Pugin’s help and the New Law Courts designed by G. E. Street (1824–1881), who was a pupil of the famed Sir Gilbert Scott. Further notable buildings of this period include Keble College, Oxford, Truro Cathedral and Manchester Town Hall.

Towards the end of the 19th century we had the Arts and Crafts movement, which influenced the design of small-scale residential development including the furniture and decoration. A good example of this is the Bedford Park Estate in Chiswick, West London, designed by Norman Shaw as an enclave for artists and writers where the distinctive style of the houses with brick and hanging tile elevations, bal-conies and fenestration are much appreciated now and where – at the time of writing – good examples sell for £1 million or more to the well-heeled London house-hunter looking for a characterful family home.

This then brings us up to the 20th century and the substantial and well founded works of architects such as Sir Edwin Lutyens RA whose Castle Drogo in Devon, completed in 1930, was the last great country house to be built in Britain.

The defects

Elizabethan and Jacobean

Generally walls are not plumb and vary in construction from timber lath and plaster via porous brick-work and eroded freestone to disintegrating cob. Roof timbers typically include cruck from which the bark has not been stripped and will be heavily infested with furniture beetle. Lots of oak and other hard-wood used in the construction will be in contact with damp masonry and thus prone to fungal attack and deathwatch beetle.

Floors consist of stone flags or herringbone brickwork laid directly on the earth, with both floors and the base of walls prone to rising damp and damp penetration. In the case of cob walled cottages, how-ever, the dampness is necessary, for if the walls dry out they disintegrate to dust, having then no moisture content to make the cob filling cohesive.

Queen Anne, Georgian and Regency

These are attractive in appearance, especially the front elevations, but the facade generally hides a multi-tude of defects. Walls may be in brickwork using a soft lime mortar with a considerable amount of tim-ber built into the walls in the form of bressumers, lintels, wall plates and especially bonding timtim-bers.

Bonding timbers, usually 100
50 mm softwood, were built into the walls replacing a whole course of brickwork on the internal face and intended to add strength and stiffness. Walls subject to damp penetra-tion from leaking parapets and the like will often show signs of alarming bulging and leaning due to rot and beetle attack to built-in timbers. The remedy, more often than not, is complete rebuilding of the wall.

Solid walls are frequently not thick enough to keep out the weather, for example, the 150 mm ashlar stonework used in the bath area for classical terraced housing. The stonework is often battened and lined internally and covered with lath and plaster or other material to cover up the damp.

The outside space to basement houses below pavement level is known as ‘the area’ and usually gives access to storage vaults (originally for coal) under the pavement.

Watch out for basements and ground floors with timbers laid directly on the earth and a general absence of damp-proof courses (dpc) or damp-proof membranes and inadequate ventilation, making an ideal breeding ground for wood boring weevil, furniture beetle and both wet- and dry-rot.

Traditional queen post and king post roof trusses may be found in this period with roof timbers gener-ally better than in the earlier Elizabethan and Jacobean buildings.

On the following page there are examples of designs for Rate Houses from London typical of the period.

Following the Great Fire of London in 1666 a Building Act was passed by Parliament in 1667, fol-lowed by another in 1774 specifying four sizes of houses permitted to be built in towns and cities: First Rate and its accompanying mews, Second Rate, Third Rate and Fourth Rate.

This standardisation of style and height gave rise to the homogeneity of Georgian London and the house types continued to be used through the Victorian period – with embellishments – as may be seen in South Kensington.

Victorian and Edwardian

Too much fussy detail to elevations and roofs gives rise to damp penetration and resulting timber defects.

Parapet gutters often become blocked at the outlet, especially if there are trees nearby dropping leaves in

Principal rafter

Tie beam 225
100 mm

Principal rafter

King post

Beam Queen posts

Straining sill

9750 mm Queen posts

Mansard Pole

plate

King post

Strut Strut

130
100 mm

140
100 mm

150
100 mm

100
100 mm

280
100 mm 150
100 mm

75
50 mm 100

100 mm

Fig. 15.2 Early timber trusses, variations of which will be commonly encountered in older buildings.

autumn. Typical roof layout are either the centre valley (or butterfly) type with parapet at the front drain-ing to a hopper head at the rear, or with a central ridge draindrain-ing to parapets at front or sides. Roof tim-bers beneath the parapet gutters and centre valleys should be carefully checked during survey since these are invariably problem areas. A variation in some parts of London includes an internal lead-lined gutter running inside the roof space from front to rear draining the front parapet gutter in order to obviate any need for a down pipe at the front. A blockage to the rear outlet to one of these results in all the front roof slope rainwater overflowing above the top floor ceiling with disastrous consequences.

The outside space to basement houses below pavement level is known as ‘ the area’ and usually gives access to storage vaults (originally for coal) under the pavement

Fig. 15.3 First Rate house and its mews.

(a) (b) (c)

Fig. 15.4 (a) Second Rate, (b) Third Rate and (c) Fourth Rate.

Inter-war

There was very little new building during either the First World War or the Second World War. Most builders were called up to fight. Construction began in about 1919 and ended in 1939 so during this period we had the growth of the inter-war suburbs.

Depending upon the part of the country, walls were either solid or cavity brick. If cavity watch out for signs of rusting wall ties. Slate dpc and suspended timber ground floors are common. Watch out for high ground levels bridging dpc and blocked sub-floor ventilation. Generally very little trouble is experienced with buildings from this period provided that they have been well maintained during their lifetime.

Nineteen-fifties and -sixties

A system of government licences was in force until 1953 and a licence was required for any private house building so as to divert maximum resources into the huge local authority building programme. Private house building generally dates from 1953 onward, typically simple solid construction. Because timber was imported (much from Canada) and Britain was short of dollars every effort was made to minimise the use of timber. Ground floors were normally solid concrete. Minimal architraves and skirting boards were used with simple flush-faced doors filled with stramit. Watch out for perished felt dpc, settlement of floor slabs and inadequate damp-proof membranes in solid floors. Also leaking Finlock gutters and brittle sarking felt which tears easily. Exterior painted softwood all suffered badly from wet-rot attack.

During the 1960s we found an increasing use of flat roofs surfaced in mineral felt, often on poor-quality decking of stramit or chipboard with no vapour barrier and poor insulation.

A

B B _York

Slab

C

F F

Sections Plans

Enlarged section at BB

Internal elevation

E E

D D

C A

Fig. 15.5 Nineteenth century flue construction. During inspection it is wise to count the chimney pots and trace the flues within the building. The bringing together of flues to the chimney is called ‘gathering’.

Nineteen-seventies, -eighties and -nineties

Design and construction improved gradually over this period. Thermal insulation increased. The need to encourage the development of more ‘brownfield’ and poor quality sites led to some foundation problems, however, and the problems associated with the action of tree roots in clay soils were highlighted in a drought in 1976 which led to a general tightening up of site investigation procedures and foundation specification with an increasing use of bored piles on shrinkable clay sites.

Local characteristics

When carrying out a Building Survey on an older building one should beware of any structure which appears to be out of keeping with its locality. So if we find a building constructed of materials which are not indigenous to its location we should be looking for defects. Buildings using traditional materials and construction methods may be the result of 300 or 400 years of trial and error.

London

In London we generally find most of the construction to be in brick.

Few residential or small-scale buildings dating from before the Great Fire (1666) remain. The city and the east was developed first so that the older buildings here are generally Georgian or later with the attractive residential squares following the uniform pattern of the Rate Houses. The main problems are at the bottom in the basements and cellars which are not tanked in the modern manner and which invari-ably suffer dampness, and at roof level due to leaks at parapets. Structural movement in the form of lean-ing and bulglean-ing walls is common with lots of tie bars used to restrain outwardly bulglean-ing brickwork, especially to the tall flank walls at the end of terraces. Except at basement level the internal walls are invariably stud partitions clad in willow laths and lime plaster, with soft plaster often held together by the lining papers. Extensive use was made of bonding timbers and other woodwork built into the walls and prone to rot and beetle attack.

The west was developed later with much of Kensington and Chelsea very late Georgian or Victorian.

These developments followed the pattern of the Rate Houses with whole areas laid out to a grid as in Pimlico, built by Thomas Cubit around 1860. Much stucco rendering used with increasing use of Italianate decoration in stucco from 1860 to 1900 as may be seen in South Kensington and Bayswater.

Most of what looks like stonework is in fact stucco including the ornamental columns and pilasters to the entrances. When the frost gets behind the stucco and it falls off the columns are found to be of brickwork, often using broken brick and snapped bricks as an infilling.

The later Victorian buildings tend to be better constructed than the Georgian with better foundations and thicker walls, suffering less from structural movement but still prone to the usual problems induced by dampness at basement and roof level.

Many of the basements have been converted into flats. Sometimes also the vaults at the front extend-ing even below the pavement. I hardly ever find one of these, that is, totally free from damp. In general if you want a dry basement you have to construct a swimming pool inside out. Anything less than this will not work in the long run.

The regions

In addition to local brick we find a great deal of construction in stone. We also find a great variety of roof coverings including not only local slate and tile but also materials such as stone slabs and shingles.

In relation to stonework some notes on the weather qualities of the commoner building stones may be useful.

Building stones

Bath stone. A mined stone, fairly soft and easy to work and responds well to cleaning. Varies in colour from cream to light cream with a more open texture than Portland stone. Poor weathering qualities in industrial atmospheres and attacked by acid rain.

Beer stone. Fine-grained white limestone from east Devon. Poor weathering qualities but commonly found in many churches in the west of England and, in particular, Exeter Cathedral. The quarries had to be specially re-opened to find matching replacement stone for Exeter Cathedral when badly weathered stonework needed matching replacement.

Clipsham stone. Coarse-grained light brown limestone from the Rutland area used for restoration work on the Houses of Parliament and for general building in the Midlands and Oxford area.

Darley Dale. Derbyshire sandstone, fine-grained and light grey to buff colour. Good weathering qual-ities but difficult to clean.

Doulting. Soft, coarse-grained limestone from Somerset, coloured grey to light brown, with a crys-talline structure containing shell fragments. Very poor weathering especially in industrial atmospheres and generally unsuitable for exposed parapets and cornice work.

Forest of Dean. Gloucestershire sandstone, varying in colour from blue to grey to green, often used for paving, monumental work and exposed facings as it weathers very well and is fine grained.

Ham Hill. A soft Somerset limestone containing shells, rich yellow-brown colour. Cleans well but unsuitable for city atmospheres.

Hopton Wood. Derbyshire limestone, cream colour and containing fossils. Can be polished to give a marble-like appearance, however, it has poor weathering qualities in city atmospheres.

Kentish Rag. Commonly used in London area, a grey-white limestone which cleans well and is often used for rubble walling.

Portland stone. White stone commonly used in towns and cities for classical detailing. Quarried in Dorset. Probably the best limestone for city atmospheres.

Wootton stone. Red sandstone from Cheshire and south-west Lancashire, sometimes called Runcorn stone. Durable and fine-grained but best used inland as it weathers badly in marine atmospheres.

York stone. Very durable grey-brown Yorkshire sandstone, fine-grained and very hard. Commonly used for paving, sills and external dressings to buildings. Difficult to clean.

Granite. Hard stone varying in colour from pink to grey to brown. Considerable variation in quality depending upon source. The best comes from Aberdeen or Dartmoor (Devon). Ideal for most applications including engineering works. Beware of soft brown granite from west Cornwall, however, as some of this has poor weathering qualities and is in the first stages of conversion into

Granite. Hard stone varying in colour from pink to grey to brown. Considerable variation in quality depending upon source. The best comes from Aberdeen or Dartmoor (Devon). Ideal for most applications including engineering works. Beware of soft brown granite from west Cornwall, however, as some of this has poor weathering qualities and is in the first stages of conversion into

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