Composite decking usually spans around 400mm, however this varies from brand to brand. OVAEDAs composite decking can span 400mm between supports, however we recommend supporting it every 375mm. This means that a 50% stagger of boards will be created with even spacing throughout.
The best practice for overhanging decking is to try to keep it to 50mm. This will ensure you have as little movement as possible and mitigate any issues. However, if you have an area that is difficult to access with the support joist, it can overhang by up to 100mm. We advise that this is only in low traffic areas.
The above suggestions are for OVAEDA's composite decking – if you have already purchased your decking you would need to check with the manufacturer as to their recommendations.
If composite decking is overhanging too far, you will start to get a number of problems. The obvious one is that it will bend much easier, and even snap. This could cause unnecessary injury. Depending on the decking, it could also warp, as it is not held down on both sides. This can create inconsistent gaps and give your decking an unprofessional finish, just because the decking is not held down correctly. Finally, it may create a trip hazard, as some deck boards may rise of fall as they are not fully supported. Avoiding overhanging your decking too far is a great way to ensure that anyone lucky enough to enjoy your decking has no risk of injuring themselves.