►First of all, we should know that the problem of rotten is due to fungi. However, fungus can not be reproduced without water. Therefore, we should better avoid  the water close to construction beam, don't store it in damp place. The storage area needs to be ventilated and it is better if use the dampproof mat.
 

►Second, we want to avoid this phenomenon by applying a preservative to their surfaces. May be it have more costly, but has very good results.