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Cembrit - How to Fix Fibre Cement Slates

Fibre Cement Slates - Roofing Materials - Slate Roofs - Pitched Roofs


The underlay should be fully supported behind the fascia to prevent sagging between the rafter feet. This is generally achieved with a tilting fillet. The underlay should finish by hanging into the gutter so that any moisture on the underlay will drain into the gutter. Eaves should not be sprocketed as this will affect fitting of the disc rivet at the tail of the eaves course.

Three courses of slates are required at eaves. The first under eaves course is cut and drilled so that it can be head nailed to the first batten. This first course acts as a base to support the tail rivet for the first full slate course.

(1) The first under eaves course is cut to the length of the batten gauge. Eaves overhang should be 50-55mm for 100mm gutters or to the centre line of the gutter if larger diameter gutters are used. Locate the centre point of the eaves and centre the first undereaves slate here. The first full slate will be laid over the top of this under eaves slate, this will mean that the slates on both verges will be cut to the same width. Work towards both verges with remaining under eaves slates.

The second under eaves course is cut from the same slate as the first under eaves course and its length will be the batten gauge plus the slate headlap. This second under eaves slate provides the double lap for the next but one full course of slates. It is installed to cover half the width of the first under eaves slate, allowing the shank of the tail rivet (which rests on the first under eaves slate) for the first full course of slates to pass between adjacent second under eaves slates. The second under eaves slate also oversails the fascia 50-55mm.

(2) The first full course of slates is nailed to the second batten (this batten also supports the head of the second under eaves slate) and is arranged so that the tail rivet passing between the two second under eaves slates protrudes through the hole in the tail of the full slate. The first full course of slates also oversails the gutter 50-55mm. The tails of all three courses of slate align and overhang the gutter.

(3) In order to provide the correct bond, the verge slate on alternate courses should be a slate and a half width cut from a double slate. These verge slates require pre-drilled holes for three nail and two rivet fixings, in addition to an extra hole (C) to allow the tail rivet for the course above to pass through the slate and a half.

Fibre Cement Slates - Conventional Fixing Method

The next single verge slate will also require an additional hole for the tail rivet of the subsequent slate and a half.

Tail rivets should always pass between two adjacent slates and through a hole in the tail of the slate they are holding. The protruding shank of the rivet is then bent down the slope.

Eaves-to-eaves ventilation can be provided either by soffit or over fascia ventilation. It works on external pressure differentials on different sides of the roof moving warm air out of the cold space. Whilst designing the eaves detail it is important to consider roof ventilation.

Condensation is caused when moisture bearing warm air from the occupied space within the building rises to come in contact with cold surfaces, which will generally be the underside of roof coverings or underlays, on the cold side of insulation. This is a particular concern with tight fitting fibre cement slates which do not allow significant leakage of warm moist air into the atmosphere. A spacer is used in the eaves so that the insulation can be installed over and beyond the wall plate without blocking the air path from eaves to ridge.

Where there is any doubt, ridge ventilation should be incorporated in the roof design. Continuous ridge ventilation will be the most effective solution.

Easy to fix fibre cement slates are cut and drilled with hand tools. No on site power is required for installation or dust suppression.

Fibre Cement Slates

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Studio 39
Thames Innovation Centre
2 Veridion Way
Erith, Kent
DA18 4AL

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