• Hardwood flooring should be staggered between courses.hardwood floor texture image by GoodMood Photo from Fotolia.com
  
  Hardwood flooring is milled with tongue-and-groove edging that makes the boards fit tightly together, giving you that flat, unbroken surface. But it's not as simple as snapping them together and nailing them in. Wood is a natural product that expands and contracts more than most building materials, and the course-by-course layout can create problems if you don't plan it all out properly.
  
  

Acclimation

• If you simply start installing your hardwood floor on the day it's delivered, you will almost certainly be re-installing it within a year. Wood flooring moves throughout its life with environmental changes, but moves most when it's initially set in a new environment. It's crucial that the flooring be opened up and stacked around the room for at least a week (preferably longer) after it arrives, so it will do most of the expanding and contracting it's going to do before you nail it down. Buy a moisture meter with a pin that sticks into the wood so you can tell when the moisture level in the flooring is the same as the moisture level in the plywood underlayment.
  
  

Layout

• Hardwood floors are generally laid in courses starting alongside one wall and building across to the other. It's important to know from the start how wide that last course is going to be, so you don't end up having to cut a sliver of floorboard there; it's better to split the difference. Mark parallel lines ¼ inch out from the starting and ending walls (to allow for floor expansion), then measure between the lines. Divide that measurement by the width of your floorboards. Add whatever remains to the width of a floorboard and divide in half to get your starting and ending width.
  
  Example: For 4-inch boards, with 1 inch of space leftover, your starting and ending widths will be 2-1/2 inches (5 inches, divided in half).
  
  

Installation

• Lay the first course of floorboards with the grooved side facing the wall. If you have to length-cut the first course on a tablesaw, cut off the grooved side and put the cut toward the wall. You'll install most of the flooring with a floor stapler that drives the staples through the sides of the boards at an angle, hiding them, but the first course has to be top-nailed with a nail gun to hold it all in place. Make sure the ends of the boards don't line up between courses. Trim will cover the expansion gaps by the walls.