Building Code For Sistering Rafters
A building code (3) for sistering rafters, or any building code in general, specifies minimum standards (2) in the design and construction of rafters (1) and not their maintenance or reinforcement.
For this reason, there is not a building code for sistering rafters as this activity is considered as a reinforcement of a roofing structure. Therefore, only industry standards of the structural engineering practice (10) apply in regards to sistering rafters. Building codes, such as the Residential Building Code, that does not apply in Wisconsin (11) (12), do not refer to sistering rafters. Likewise, some states consider them directly incorporated by law and adopted by reference (4). The US remains as one of the few advanced countries without a uniform building code (5), but finally now all states utilize the International Building Code. This is different from the European Union (6), whose codification is being adopted also outside the EU (7), such as EFTA countries (8) and has overwhelming adoption in Asia Pacific (9).
There is not a building code for sistering rafters as it is a reinforcement of an existing roofing structure while codification entails directives for design and construction standards.
Nonetheless, and without a related building code, industry standards fos sistering rafters have to be observed, such as the recommended utilization of a board of the same dimensional number and that the longitude of the sistered rafter must prolong for a minimum of 4’ past the affected surface so the subsequent nailing can be 4’. The reason for this is so that nailing can be staggered across the boards without splitting the wood.
The rafter is attached through the sistered rafter with an adhesive substance and then, without any building code as reference, standards indicate that the rafters must be permanently fastened with 3-1/2-inches long nails (16d nails) plus a coach bolt or carriage bolt every 15”.
