CONCRETE ROOF TILES

Concrete tiles were first produced in Europe in the late nineteen century and their advantages soon

became apparent. The versatility of concrete makes it capable of producing strong, easy to use and

most importantly, extremely weather resistant roof tiles. Tiles are produced in a varity of sizes, profiles,

colours and finishes. Modern mass production methods of concrete roof tiles have resulted in tiles with

consistent size and quality at an economical cost. When choosing tiles for a roof, consideration has to

be given to the roof pitch and how the tiles will be fixed. As the pitch decreases so the roof tile becomes

 more reliant on its design and surface finish to effect rain water run off. Roof tiles are designed for and

tested to a minimum rafter pitch for a certain headlap. Tiles can be divided into two groups- variable lap

and fixed lap. Variable lap tiles are the most common and easiest tiles to be used. The headlap can be

adjusted to suit different rafter lengths. Fixed lap tiles are laid with a strict headlap and may require cutting

to suit rafter lengths. A standard specification would call for roof tiles to be fixed in alternate courses with

 aluminum alloy nails to 25x50mm tanalized battens fixed over BS 747 1F roofing felt.

Prior to any work at the eave consideration should be given to installation of a

 ventilation system. The roofing underlay should drain any rainwater into

the gutter. Any water traps behind the fascia should be avoided. The first tile

 batten is positioned so that the roofing tiles drain water into the centre of the

 gutter. Prior to fixing any tiles eave filler combs if required are fixed to the

 top of the fascia. These are used when the roof tiles are profiled and prevent

 access of birds and vermin into the roof space. The first course of tiles can

then be laid and should fixed with an eave clip.

The ridge tiles are usually the last part of a roof to be completed. The last

course of tiles should be fixed with nails or clips. If the tiles are profiled then

 dentile slips should be used in the pans of the tiles. These reduce the

amount of mortar used to bed the ridge tiles and therefore the risk of the

mortar cracking due to shrinkage. The ridge tiles are then bedded into a

mortar which can be coloured to match the colour of the roof tiles and

pointed to give an even appearance. Ridge tiles should not be solid

 bedded. The tiles should only be bedded at the edges of the tiles to

prevent shrinkage of the mortar.

The roof battens should extend on to the outer wall. A fibre cement undercloak is inserted between the top of the wall and the battens. The purpose of the undercloak is to close of the cavity wall and to support the bedding material. The undercloak should extend over the wall between 38-50mm. Verge clips are now fixed to the roof battens. The roof tiles can be bedded in a sand cement mortar that should be coloured to match the colour of the roof tiles. Upon completion the excess mortar can be struck off and pointed for a neat finish.