Can you re-stain over old stain?

You are being misinformed if another contractor tells you that you can’t re-stain over old stain. Solid stains will adhere to old stain perfectly well. These old stains are already deep into the pores of the wood and they still provide protection. However, you must still sand the floor of the deck to open the pores to insure adhering. Why would you remove stain from the deck only to put more on? Contractors will often advise the customer to remove the old stain. This is a common way to charge the customer for more material and labor.