When installing new flooring, as a Home Inspector, I cannot stress enough the importance of having your subfloor inspected first.
A thorough inspection from the crawlspace is of utmost importance when assessing the condition of a subfloor. Removing an existing floor covering can reveal problems such as dry rot, termite damage, dips or humps, water damage, or even mold. Any of these conditions need immediate attention prior to installation of any floor covering.
On a recent Home Inspection, I noticed the flooring in a particular room had soft, bouncy spots. The existing flooring was a cheap laminate flooring material, and at first glance it may have seemed that the floor covering material was the cause. However, once I inspected the crawlspace I noticed a good portion of the subfloor had been replaced in the same area with the soft spots.
When subfloor is replaced, it is important to ensure that the subfloor is the proper thickness. This measurement will depend on the spacing of the floor joists; the wider the floor joists are, the thicker the subfloor should be. Always have a qualified flooring specialist install or replace any subfloor to make certain that it is installed properly with no issues that could affect the floor covering installation. A solid subfloor will give you a solid floor covering.
A squeaky, wavy, soft floor is not attractive and can lead to bigger problems later on. If you don't have time to do it right, when will you have time to do it over?