Surface materials

The main purpose of surface materials is to form a protective layer on a building's structure. Through their hardness and durability they must withstand wear and tear on the building, from hard driving rain on the roof to the never-ending wandering of feet on the floor. Sheet materials can also have structural and climatic functions such as bracing, wind-proofing, moisture control, noise protection, etc. Certain structures in brick, concrete and timber are in themselves surface materials and, therefore, do not need further treatment. Surface materials are otherwise used in roof covering, internal and external cladding, and on floors (Table 15.1).

Because surface materials are used on large exposed areas, it is important to choose materials that do not contain environmentally contaminating substances which may wash into the soil or ground water or emit unhealthy gases into the interior of the building. They should be both physically and chemically stable during the whole of their lifespan in the building or at least be easy to renew.

Exterior cladding and roofing are the building elements that are most exposed to the forces of the weather. They must therefore be chosen with local climatic conditions in mind. Especially critical are inelastic and porous materials used on facades exposed to driving rain and frequent freeze-thaw cycles. We should remember that weather conditions may change as a result of the ongoing climate change. This will lead to generally increased risks in Northern Europe, and possibly to reduced building stresses farther south (Noah's Ark, 2006). Along coastlines weathering due to salt spray is likely to increase.

Surface materials need a long aesthetic lifetime. They must withstand wear and dirt without becoming unattractive. A wood floor with good surface treatment will, even if highly worn, develop a fine patina over time, whilst an enamelled steel surface that is dented, or a plasterboard that is slightly cracked, will need to be replaced almost immediately. Since exterior claddings also function as protection for the structure, membranes and insulation materials, it is an advantage if any damage to these can be quickly noticed. Claddings of aluminium and polyvinyl chloride can conceal problems until they fail disastrously.

The roofing of the building is its hat; it must protect the building from everything coming from above, which sets requirements for how it is anchored, drained, and protected from frost, snow and ice. Most

Table 15.1 Surface materials in buildings

Material

Roofing

External cladding

Internal cladding

Flooring

Metals, sheets

Gu

Gu

Gu1

Lu

Cements/concretes; boards, sheets and tiles

Gu

Gu

Gu

Gu

Gypsum boards

Gu

Calcium silicate sheets

Gu

Plasters, cement based

Gu

Gu

Plasters, silicate based

Gu

Gu

Plasters, gypsum based

Lu

Gu

Plasters, sulphur based

Nu

Nu

Slate/stone

Gu

Gu

Lu

Gu

Fired clay; bricks and slabs

Gu

Gu

Gu

Lu

Ceramic tiles

Lu

Gu

Gu

Compressed earth slabs

Lu

Loam plasters

Lu

Lu

Bitumen products; sheeting

Gu

Lu

Plastic products; boards, sheets and tiles

Gu

Lu

Gu

Gu

Living plant surfaces, turf and climbers

Lu

Gu

Nu

Solid wood

Lu

Gu

Gu

Gu

Straw

Lu

Lu

Plant-based building boards, sheets and tiles

Lu

Gu

Gu

Building boards from domestic waste

Lu

Abbreviations: Gu: In general use; Lu: In limited use; Nu: Not in use. Empty spaces indicate that use is irrelevant. 1 Industrial buildings.

Abbreviations: Gu: In general use; Lu: In limited use; Nu: Not in use. Empty spaces indicate that use is irrelevant. 1 Industrial buildings.

roofing materials have a different material layer beneath them which helps to waterproof the building.

The external cladding has a similar task in many ways, but the demands are not quite as high, especially as far as waterproofing is concerned. However, in areas of hard rain and strong winds, very durable materials are required. Facades exposed to strong sun also need special attention.

The internal cladding has lower demands with regard to robustness in most types of rooms. The main factor is that damage can be caused by the use of the building, although the material in a ceiling does not need to have the same strength or resistance to wear and tear as that in the walls. Internal surfaces should have a higher level of finish, to give it a feeling of comfort and be pleasant to the touch. Cleaning should also be easier with these finishes. However, surface finishes should not block a material's ability to regulate indoor humidity. This is essential for a good indoor climate (see Chapter 14, page 245). This is a function that is as

Table 15.2 Washability of floor materials

Flooring material

Cleaning factor

Cork

7

Timber cubes

6

Timber

5

Concrete slabs

5

Asphalt

5

Bricks

5

Linoleum

4

Parquet

4

Terrazzo

3

Stone slabs

3

Ceramic tiles

2

Polyvinyl chloride PVC

2

Note: The lower the cleaning factor, the more easily the surface Is cleaned.

Note: The lower the cleaning factor, the more easily the surface Is cleaned.

important as robustness, and implies that hygroscopic materials should be preferred wherever there is no special risk of water spills or dirt.

The floor covering is the one surface in a building that is normally most exposed to wear. It is the part of the building with which the occupants have most physical contact, so comfort factors such as warmth and hardness must also betaken into account. Technical properties required in a floor material are that it should:

• possess a low thermal conductivity.

• demonstrate a low risk of electrostatic charge (Table 15.3).

• contain good acoustic properties.

• retain good moisture regulating properties.

• include mechanical strength to resist wear and tear.

• be resistant to water and chemicals.

Many floor coverings, such as linoleum and cork tiles, which are not load bearing as such, need to be laid on a stable floor structure. The amount of moisture in the structural floor and its ability to dry out are therefore critical: the quicker it dries out, the sooner the floor covering can be laid.

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