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Generally made of wood, the roof frame provides a roof’s load-bearing structure. A roof frame can come in widely different shapes and construction types. For example, the simplest type is a couple roof, where all loads are transferred via the inclined rafters placed against one another. In the case of a purlin roof, the rafters rest on two or more horizontal supporting timbers which join the two gable sides together. Purlin roofs are eminently suitable for integrating dormers or large-surface windows into roof surfaces. Screws have now completely replaced the wood connectors previously customary in roof frames, such as nails, steel brackets and rafter-purlin anchors, because screws have a higher load-bearing capacity and are more economical and easier to handle.
What else should be kept in mind?
Screws must be able to transfer strong forces on wood connections into roof frames. This applies especially when the rafters rest on the purlins. In this case, washer head screws with partial threads ensure that even twisted rafters are pulled close to the purlin so that the groove sits perfectly in position. When trimmer timbers are installed for structures such as chimneys or skylights, for example, full-thread screws fastened at an angle are assured to hold the timber joint together. Since wind pressure is less of a problem than wind suction on pitched roofs, screws with highly substantial pull-out resistance are definitely needed.
Discover now our screws for rafter insulation