The cabin should be completed to roof level with the roof boards and rain slats fitted. Do not fit the side, front or rear fascia boards yet.
You will have received extra materials as stated in your Insulation fitting instructions.
The pressure treated timbers are to provide a border down the front edge of the roof from ridge to eaves, down the rear edge from ridge to eaves, and all along the eaves. It sits on top of the roof boards.The timbers may need to be trimmed to length.
The horizontal member at the eaves is best fitted by screwing up from the underside of the roof boards. It should be positioned 20mm up the slope from the tips of the roof boards for a standard 19 degree roof slope (or 34mm for a 30 degree roof slope).
It is recommended that a vapour control barrier is laid on the roof below the insulation layer.
The insulation material is 50mm thick rigid urethane with a 6mm plywood facing. It lies within the borders, usually in portrait orientation, with the plywood upwards. The boards need to be screwed through into the main roof boards using 70mm screws. Each board simply buts up against the next. Some pieces will need to be cut and these may be laid in any direction. It is best to cut an angle on the uppermost boards so that the plywood meets at the ridge.
It is recommended that a breathable membrane is laid over the insulation before the shingles or other roof covering is fitted. This is usually included in the pack. It is essential to use such a membrane on roof pitches below 15 degrees but is generally good practice on all roof pitches.
Side fascia boards may be cut to the appropriate length of the building. They are fixed to the side of the pre-fitted border. The purpose of setting the margin timber slightly up the roof slope is to aid the positioning of the fascia boards vertically, rather than toeing inwards.
The roof is now ready for the roof shingles or other roof covering to be fitted.