Lay ridge caps from the opposite end of the roof to the direction of prevailing winds. Each cap should be overlapped by the next cap in the run by a minimum of 150mm.
We usually recommend ridge caps are fixed using self-drilling TEK type stitching screws to the high point of each profile they cover and through the appropriate ridge filler if one is being used. This helps ensure a robust weather resistant joint as well as keeping out birds and vermin.
Top tip - When constructing your purlin support structure consideration should be given to the need for additional purlins to support your ridge caps and other flashings.