8. Compose correct word combinations from both columns. Try to guess their meaning

lean –to shed couple couple-close collar double rafter purlin steeply-pitched flat

roof

9. Read the text. Find words characterizing types of roofs Roof

A roof is the topmost part of a building. It is a covering 'constructed over the enclosed space to keep out rain and wind and to preserve the interior from exposure to weather. A roof must be well framed, strong enough to resist winds and sustain snow loads, and serve as insulation to prevent transmission of heat. They should tie the walls and give strength and firmness to the structure.

Roofs are now built varying in inclination from the nearly horizontal to the steeply-pitched. The flat roofs are often used in buildings of cities not only as coverings but for play-grounds, tea-gardens, and such purposes, but in buildings where slates, tiles or stone slabs form the roof covering, the pitch should never be less than one-fourth of the span.

For utilitarian purposes, the inclination of the roof is made as flat as possible for the purpose of economising the timber and covering material.

The pitch of roof is governed, first by climatic conditions, secondly by the covering material used and by architectural requirements. For any given covering the milder the climate the flatter the pitch that may be given to the roof.

There are numerous forms among the wooden roofs, namely:

Lean-to or shed roofs are roofs formed with one slope only, and used for outhouses and for sheds.

Couple roofs are roofs composed of rafters with their feet fixed to wall plates, with their heads butting against a ridge piece; there is no tie, they depend for their stability upon the abutment afforded by the walls.

Couple-close roofs- for roofs about 12 feet in span;ties are used to prevent the walls being thrust out by the rafters. The ties are usually formed by fixing the ends of the ceiling joists to the feet of the rafters.

Collar roofs-in this type each pair of rafters has a collar ,a scanting similar to the rafters fixed abouthalf-way up the slope of the rafters. This tends to prevent the spread of the rafters, but it also subjects the rafters to considereable bending stress, which is at a maximum at the point where the collar is attached to the rafter.

Double rafter or Purlin roofs-Where the rafters exceed 8 feet in length it is more economical to introduce purlins than to employ scantling of an area greater than2 in 4 in.The purlins lie together and greatly stiffen the rafters.

Tasks after reading:

10. Choose correct titles to paragraphs. Add necessary sentences. Put them in order

1. Conditions and requirements for type of roof’s pitch. 2. Characteristics of roofs. 3. This type is formed with one slope. 4.This tends to prevent the spread of the rafters.5. Purpurse of the inclination.