Concrete – Flooring Subfloor Condition How smooth it has to be

DriCore is a subflooring that is specifically designed for light or occasional moisture. The portion of the product that touches the floor is all plastic and it lifts the upper portion more than 1/2 inch away from the concrete floor. The joints are fairly tight (although not actually sealed). It is intended to allow water to accumulate in the open spaces under the plastic waffling and drain or seep away without reaching the upper layer.

The particle board that makes up the surface is impregnated with resin and is meant to be fairly impervious to moisture. If you have an actual flood that occurs which is high enough to reach and damage the surface, you have much bigger problems.

Vinyl isn't very thick, and it is quite plastic. This means that over time, it will conform to the shape of the floor beneath. This means that you will see grooves in the vinyl where there are gaps between the plywood sheets.

This means you want the sub-floor to be as smooth as possible. BUT!!!! you need gaps between the sheets to allow for expansion or else you risk having the sub-floor develop a slight buckle.

Here's what I would do under ideal circumstances:

• Spend some time screwing down the existing floor to the joists. This is likely the only opportunity you will have to do so.
• Get some 1/8" Hardboard, Lauan or birch plywood (one side smooth) and lay it down without gaps over the sub floor. At this thickness, you can staple it down.
• smooth any edges/fill any gaps.
• Lay your vinyl.

However, you need to make the call as to the quality of the existing floor the level of imperfection you are willing to tolerate. It may not be worth the extra expense and labour to do it this way. In which case, I would fill the worst gaps, sand down the worst edges, and lay down the vinyl.