Additional Design Considerations

New houses constructed under the control of the National House-Building Council must further conform to the requirements of the Registered House-Builder's Handbook, Volume 2 of which sets out the technical requirements for the design and

Fig. 3.18a Trimmed opening for dormer. For trimmer numbers required see Fig. 3.18b.

Cut 1 or 2

Add 2

One each side

= Additional rafters

NB Check trimmer size for span on all openings

Cut 3 or 4

Add 4



Two each side t r

Fig. 3.18b Trimming construction rules.

construction of dwellings. The reader is directed particularly to the section on carpentry, Chapter 7.2.

Chapter 8 of this book concerns itself with the many other aspects of roof construction which apply to all roof forms. The items covered are as follows:

(1) Storage and handling of timber;

(2) Preservative treatment;

(3) Wall plates and straps;

(4) Gable ends, straps and gable ladders;

(5) Water tank platforms;

(6) Ventilation of roof voids;

(7) Roof bracing;

(8) Eaves details;

(9) Trimming small openings.

This chapter has dealt with the construction of new attic roofs. Chapters 9-12 explore the possibilities, problems and solutions when converting loft spaces to form attic rooms.

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