Plain or Flat Sawn vs. Quartered or Quarter Sawn
Flooring manufactured with grain or annual rings running across the width of the boards is called “plain,” or “flat” sawn. Flooring with grain running at right angles to the face or across the thickness is called “quarter sawn” or “quartered.” Both types of boards can be cut from the same log.
The difference in how the flooring behaves with change in moisture is significant since plain sawn expands and contracts across the width of the board, while quartered, in theory, gets thicker and thinner. Quartered has considerable more dimensional stability and does not respond to season or moisture changes as does plain.
Remember, wood floors and finishes are not waterproof. Movement from moisture (or humidity) will occur.
Wood, as a natural product, varies from piece to piece. It is not fabricated; it is milled from a tree and will have grain and color variances.