You can stop outdoor bamboo fencing from degrading due to weathering, but it will take a little time. When installing bamboo fencing, it's important not to use bamboo poles for the fence posts. Bamboo poles used for posts that you pound into the ground absorb moisture and are prone to bug infestations. Both water and bugs will quickly rot the posts.
Wire split bamboo fencing to existing fencing such as chain-link fencing. The bottoms of the bamboo strips should not touch the ground.
Leave the bamboo fencing to weather from six months to a year. The purpose of this is so the tough outer skin of the bamboo weathers, which will make it more porous. Watch for the bamboo to turn grey.
Coat the grey bamboo with an exterior waterproof sealant. Seal both sides of the bamboo and the top and bottom ends to deter absorption of water and bug infestations.
If you don't want to wait the six months to a year for the bamboo to weather, you can sand the tough outer surface of the bamboo and then stain, varnish or water seal. The sanded bamboo surface will be able to accept finishes and sealants. Before waterproofing the split bamboo, consider staining it with an oil-based stain or a coloured varnish.