Following on from the one week erection of my Castle Hill bach the builders have completed the counter batten and purlins fixing.
This type of roof assembly is called above sheathing ventilation. This protects the roof structure and the roofing from water damage.
Running down the roof pitch are 45x20mm thick counter battens. This allows drainage and drying of the roof.
Any moisture build up can drain down and out at the eaves.
Air enters at the eave with behind fascia ventilation and exits at the top through ridge vents under the ridge capping.
The counter battens are generally fixed @ 600mm crs.
They reduce to 300mm crs within 1200mm of the gable ends as this is an area of higher wind load.
At the ridge there are 300mm long counter battens between the full length counter battens to give more fixing to the top purlin. This purlin is located down from the solid timber plate in the ridge of the SIP so is only fixed to the SIP OSB skin.
The bottom purlin is fixed into the solid timber within the eave of the SIP.
Intermediate purlins fix through the 20mm counter battens (which are structurally fixed to the SIP) and the 11mm OSB skin to the SIP.
This fixing arrangement is SED and will vary depending on site location.
If you are interested in SIP PREFAB come talk to me.
Builder Irving Builders
SIP by Formance
Wrap and tapes by Pro Clima NZ Ltd
