we have bark in our back garden and are struggling to keep it weed free any advice...would rather have grass but we rent and have to keep it this way

it probably has no weed supressor under it,remove some of the chippings till you get to the bottom of them and see if any suppressor has been laid,if not,best thing to do will be to put all chippings to one side and lay a blanket above the bare earth,it will pay to put weedkiller on any growth before doing this,and ideally the chippings need to be about 2"deep to stop any light penetration.