A. Most likely, the problem you're dealing with is an uneven subfloor. A common problem among installers is not checking the subfloor for flatness. With all floors, and especially with a prefinished product, you need to check that the subfloor is flat and clean before the flooring goes down. Not checking the subfloor may save a little time up front, but it will cost you in the long run. Here are some other installation shortcuts I've seen that are not worth taking:
2: Not checking the nailing or stapling of the subfloor. Along with checking the subfloor for flatness, you need to check the fasteners in the subfloor. I've seen jobs where the building contractor missed the joist when he nailed the subfloor, or hit the joists but didn't use enough nails. This leaves you with up-and-down movement of the floor, which can appear as overwood or cause squeaks. Also, don't forget to check for fasteners sticking upout of the subfloor.
3: Laying over particleboard. Especially with a remodel, you may find the subfloor is covered with particleboard. Sometimes people are too lazy to pull it out and use plywood. That's a bad idea, because particleboard does not hold a nail. It's basically sawdust glued together. The nail may hold somewhat onto the plywood underneath the particleboard, but because there's not much holding power, the floor becomes loose over time. Even glued-down floors can pop up. They just pull up parts of the particleboard along with the flooring adhesive.
4: Not acclimating wood properly. Many times contractors don't give you the time (or you don't want to take the time) to let the wood sit on the job site. You can get away with this for years, but sooner or later, it will bite you. Not acclimating can leave you with too much movement in the floor — either it cups or shrinks. Take the time to acclimate the wood properly to normal living conditions. That means all wet trades are done, the building is closed in with window and doors, and the HVAC system is running. Use a moisture meter to check that the flooring is within 4 percentage points of the subfloor (plank should bewithin 2 percentage points).
5: Surface-nailing the last eight or nine rows. This is one that irritates me. Eighteen inches out from the wall where you can't use your regular nailer, some installers just go ahead and top-nail. No one wants to see all those top-nails. You should take the time to drill and hand-nail those rows. To make it even worse, sometimes installers top-nail and don't bother filling in those nail holes. That looks even worse.
6: Skip nailing. Those people who claim they lay 1,000 feet in a day aren't using a proper nailing schedule. They may use only a couple nails every board.
I've even heard of floors where only every other row is nailed. Every board needs to be secured to the subfloor. Use the right nailing schedule, with at least two nails in every board. If you don't, you'll have a loose, creaky floor that won't stay flat.
7: Not undercutting door jambs or moldings. I've seen this, but I can hardly believe it. When door jambs and moldings are already in, some people don't bother undercutting so the wood floor slides under for a nice fit. They leave it and notch the floor around it. It just looks unprofessional.
8: Using putty instead of replacing a board. Say you've got a big drill hole in the floor or a wide splinter. Some people just use a big gob of putty. That looks ugly. It takes a lot more time to replace the board than fill the hole in, but it's worth it.
9: Not using header boards. When installing at doorways or around fireplaces, it looks much better to use a header instead of letting all your floor ends go right into the other floor covering or hearth. A header isn't necessary structurally, but it looks more finished. Also along these lines, some installers don't finish under doorways properly. Instead of making sure the header goes halfway under the door, they just put it in wherever they think it's convenient.
10: Using wood flooring instead of real stair treads. This is another one I really hate to see. Real stair treads are 11/16 inch thick. Using wood flooring doesn't look as classy.
11: Not using spline. Over time, with seasonal changes in moisture, not using spline allows boards to pop up. All boards should be end-matched and side-matched. Spline is necessary with many borders, changes of direction, header boards and mitered corners. The best way to use spline is to glue and nail it.
12: Locking in appliances. If the dishwasher or other appliance is already installed or the job is a remodel, if you don't take the time to remove it and lay the floor under it, someone in the future will have a hard time doing a repair or removing it.