Vinyl tiles require an extremely smooth surface, because any flaws and imperfections will show through as bumps and indentations in your floor. Usually the best subfloor is a layer of well-sanded plywood.
Most manufacturers do not recommend laying new vinyl over more than one layer of existing vinyl, and in fact will not guarantee the flooring if there is more than one layer of vinyl beneath. Another problem with laying over existing vinyl is that if the lower layer is patterned, the texture will eventually show through your top layer.
Vinyl flooring can be laid on top of concrete, but again, uniformity and smoothness can be a problem. Also, a plywood layer will give you a better feel under foot.
Some manufacturers offer do-it-yourself installation kits, but many homeowners choose to use a contractor in order to achieve a smooth, professional look.
If you feel a vinyl flooring option will be the best for your home, contact Jim’s Floors and request a visit to assess your needs and provide a quote.