What fittings and accessories should I use?
Below is some practical advice on how to get the perfect finish for your fibre cement roof. This includes a step by step ridge fixing guide as well as advice on choosing the right accessories for eaves and verges.
RIDGES
While there is no reason why clay or concrete ridges can’t be used on a fibre cement roof, specially designed fibre cement ridges give the best finish. Fibre cement duo pitch ridge units and stop ends are designed with a socket for a simple fix by drilling and screwing to an additional ridge fix batten at the apex.
Recommended screws are 60mm x 6.3mm self-sealing wood screws. An alkali resisting, non-oil based 6mm diameter butyl strip should be used to seal across the socket, 50mm from the end.
FIXING THE RIDGE
Step 1 and 2
- Fix the underlay along the roof apex to overlap opposite roof slopes by 300mm
- Fix the top batten to suit the gauge of the slate
Steps 3 and 4
- Fix an additional ridge fix batten downslope to enable the self-sealing screw to penetrate the ridge unit 50mm up from the bottom edge of the ridge unit
- Head nail the top slate course to the top batten.
Steps 5 and 6
- Apply 6mm butyl diameter strip across the socket, 50mm from the end
- Locate successive ridge units along the roof apex, drill and screw to the ridge fix battens, ensuring a level ridge with joints bedded on butyl strip
Step 7
Locate the starter ridge stop end at one end, drill and screw the end of the ridge to the ridge fix battens. Drill 125mm from the effective ends 50mm up, i.e. ignore the socket
VENTILATED RIDGE ROLL
Despite some popular misconceptions, fibre cement roofs do need to be well ventilated for the removal of stagnant moist air which would otherwise be trapped in the roof apex. Ventilated ridge roll goes underneath the ridge before it is screwed in and can provide 5000mm2/m ventilation to the roof apex.
EAVES
Eaves must be ventilated in accordance with BS 5534 and BS 5250. One way of doing this is to use a universal eaves vent system. A tilting fillet is not required when using the eaves ventilator. The tilt is formed by raising the fascia board 11-18mm above rafter level. The eaves vent unit is placed on the fascia providing the required tilt, removing the need for an eaves underlay protector. An eaves vent system provides continuous 10mm or 25mm free vent areas to roof voids for roof pitches up to 55 degrees.
VERGES
Rather than using a traditional dry verge system, an aluminium slate verge trim can be used to create a professional finish on a fibre cement roof. An aluminium slate verge trim provides the benefits of a dry verge and can be used with or without bargeboard but is not suitable for raking verges. Sheet metal cutters should always be used to cut the trim. Use protective gloves when handling to avoid injury from sharp edges.
