Turf

Turf roofs represent one of the oldest known forms of roof covering in the northernmost parts of Europe, and are still in wide use. In towns and cities in central Europe there is a renaissance of the turf roof and roof gardens. Turf has also been used as insulation in walls. In Iceland, the construction of turf walls with structural properties was widespread right up to the twentieth century.

Ordinary grass turf used for a building should preferably be taken from old mounds or fields to ensure that it is well bound with grass roots. If the grass is relatively young (three to four years old) the root system will be undeveloped, so the turf may break up when removed. Turf should not be taken from a marsh.

Modern turf roofs often start as loose earth that is then sown with grass seed. A recommended mixture consists of 70% sheep's fescue (Festuca ovina), 10% timothy grass (Phleum pratense) and 20% creeping bent grass (Agrostis stolonifera). In dry areas, generous amounts of house leek (Semper vivum) and rose root (Sedum roseum) - which are very resistant during dry periods - should be added. The Sedum can be sown and the Semper vivum planted, because it will spread through a rapidly developing root system. Semper vivum contains a lot of sap and therefore has a certain

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|Table 10.7 Climbing plants

Species

Maximum height (m)

Growth conditions

Self climbers:

< ft

Climbing hydrangea (Hydrangea anomala and H. petiolaris)

4-8

Sun and shade

lb

Ivy (Hedera helix)

30

Shade

Virgina creeper 'five-leaved ivy' (Parthenocissus quiquefolia)

20

Sun and shade

Virginia creeper 'Lowii' (Parthenocissus tricuspidata)

20

Sun and shade

Trellis climber:

Blackberry, bramble (Rubus fruticosus)

2-3

Sun

Chinese wisteria (Wisteria sinensis)

6-10

Strong sun

Climbing rose (Rosa canina)

3-4

Strong sun

Common hop1 (Humulus lupulus)

10

Sun and shade

Common Virginia creeper (Parthenocissus vitacea)

10

Sun and shade

Honeysuckle (Lonicera pericymenum)

10

Sun

Winter jasmine (Jasminum nudiflorum)

2-5

Strong sun

1 Plant withers In winter.

1 Plant withers In winter.

degree of fire resistance. When turf roofs were common in towns, laws ensured the use of Semper vivum on the roof.

Redcurrants, gooseberries and blackcurrants thrive in roof gardens and on flat roofs with a deep layer of earth. Trees planted on roofs should have a very shallow root system, e.g. birch.

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