We are wanting to replace the flooring in a mobile home with sheet vinyl. Due to numerous other repairs, the budget is gone. There are no plans to ever sell this house. We removed all the carpet and took up the vinyl in the kitchen and one of the bathrooms since it had some problem areas. Laundry area was left alone since it was all adhered well. Original vinyl was applied directly to the subfloor. I know the bathroom vinyl was laid at a later date, and it was applied directly to the subfloor as well. Is it a MUST that we install some form of underlayment or can we get by with just using a leveler/patch where they pieces of subfloor meet? Or is that even needed? I can tell the vinyl used before was full spread glue. I believe the original subfloor is particleboard. We have repaired a few spots where a window air unit leaked and used plywood as the replacement material.