All the boxes that you have prepared to be loaded in the moving truck should be prevented from an outside and inside influence.This means that you have to use a cover for them.Not only on the top but at the bottom too.Ask the mover if they can provide you big plastic or textlie sheets which will cover all your stuff.If they refuse you this kind of service you have to think for this matter by yourself.Ask your friends or neighbours of they have tarpaulin  to borrow you.If not you should buy one.On the moving day check the truck's floor.It happen to be full of dust which is not so bad-the point is to be dry and safe at the top.If you prefer you can use some cupboards under the boxes but this will cost you more money for packing supplies.When the movers finish with the loading ask them to cover the boxes.This will prevent them from dampness and some outside influence.