Do you need to put varnish over stained wood?

New unfinished furniture can be finished many ways. the answer your question will be determined by how you want the furniture to look, how much protection will the wood need against weather exposure ( indoors or outdoors) and how much time you are willing to put into the finish work. Stain by itself usually will not be enough unless the product you choose is a finish that has stain included in the mix.