Housing in Southern Africa October 2015

Exposed trusses

Reinforcement

Roof tiling

tile should be opened or closed to achieve the desired overhand. It may be necessary to fix a cut tile at each end of the roof. Once the overhang has been achieved, it will thenbe pos- sible to lay a course of tiles that are true and straight both horizontally and vertically. When this has been established, the battens at the gable end can be cut and verge counter bat- tens (50 x 38 mm) installed. Tiles in each course, or in each alternate course, should be set out in vertical alignment so that the tiling presents a regular and even appear- ance. All starters, finishers and full tiles at the end of each course at a gable should be mechanically fixed. The cutting of tile ridges, hips, verges and valleys shouldbe neat and present a straight line. Tiles at ridges and hips extend under the capping by a sufficient distance to be weather- proof. Similarly, tiles should overlap valleys by a sufficient distance to be weatherproofed. ■

the finished work. Plaster should be firmly trowelled onto walls and executed in one operation. Plaster should be pushed onto the wall or ceiling using pressure to compact the plaster and to ensure full contact with the substrate. Once applied the plaster should stiffen. It is important that the plaster does not dry out too quickly and should be dampened or sprayedwith a light spray for a period of not less than three days. Successive coats should not be applied during this time. Once the substrate coat has hardened sufficiently another coat can be applied. INSTALLATION OF CLAY AND CONCRETE ROOF TILES Mechanical fixing systems may com- prise either singly or in combination,

mechanical fixings such as clips, nails, screws and cement mortars. Mortar for bedding and pointing comprises one part common cement and three parts sand and mixed in accordance to specifications. Fixing nails should penetrate battens to a depth of not less than 25 mm. Damage due to excessive gusting occurs at eaves, verges and ridges. Mechanical fixing systems prevent tiles from being lifted off. All tiles should be aligned vertically, hori- zontally and diagonally and overlap each other by the minimum amount specified by the manufacturer, but not less than 50 mm. At the beginning of the tiling operation, a course of tiles should be laid along the roof from right to left at the eaves and along the ridge. This procedure will ensure that the overhang of both verges, is equal. If the tiles do not provide the desired overhang at each gable end or do not fit, the lock tolerance on each

19