5.2 Evaluation of experiences

14 questionnaires were scrutinized with regard to roof structure and installation of FC elements.

Roof structure

Most respondents build gable roots, usually with trusses and purlins. A few prefer rafters to trusses. No material other than timber is used. There is little information available on truss assembly. Two participants mention bolts, otherwise nails are used.

The span of the trusses, or width of building varies from 5 to 10 m, the distance between rafters, or trusses, from 0.8 m to 2.5 m; minimum required roof pitches mentioned are between 14° and 26°.

Protection against insects and decay

Only halt of the participants think that some sort of protection Is necessary. Usually, waste engine oil is applied.

Structural demands towards the roof

There is little awareness of the necessity to build a strong roof. Three of the questionnaires mention wind speed of 120-200 km/in. One participant thinks that the roof has to support only the self weight of FCR tiles; another one mentions earthquakes in his area. One mentions, that the roof should be able to support the weight of people installing or repairing the roofing elements.

FCR: sheets or tiles?

Ten participants make sheets, four make tiles. If given a choice, six would continue with sheets, but eight would prefer tiles.

How do the elements overlap?

Only five participants give a clear answer. For sheets the normal end overlaps are 6”, and side overlaps probably according to the available asbestos moulds. For tiles the overlaps are as per standard I.T.W. specifications.

Method of fixing the elements

For sheets, two participants install J-hooks, two others fix them with nails, another one uses screws. Fixing through cast-in wire loops is used for both sheets and tiles.

Ridge tiles

Except three participants who install either galvanized iron sheet ridges, concrete ridges or clay tiles, all the others manufacture their own V-shaped FCR ridge tiles.

By whom are the elements Installed on the roof?

Eight participants say that the elements are installed by an experienced work group, in five instances this group being identical with the producers’ team. Five others go along with “do-it-yourself” methods. As for guidance, practical on-the-pb training as well as written guidelines are applied.

Repairs

Ten participants claim that it is fairly easy to carry out repairs. Four participants, working with sheets, maintain that repairing is difficult. Commonly used repair methods are:

- very fine cracks are sealed with paint or cement slurry

- on small cracks, first paint with PVC glue (white carpenter’s glue), then apply a strip of FC mortar, approx. 1/4” thick
- if cracks are large the element has to be replaced.

Maintenance

Five participants claim that no maintenance is needed. The others mention checking of the wooden structure, e.g. sagging or badly warped purling. The fixings need to be checked, and cracks may need repairs. The roof cover should be kept clear of leaves, accumulated dirt, etc.