First is the growth in wood flooring. It is exciting to see the proliferation of species and colors. Strip flooring volume is still high but the development of planks and with random sizes, plus distressed wood flooring has fueled the acceptance by the average homeowner. Imports from the far east with products such as bamboo and teak, plus the imports from Canada and South America have contributed to the growth.
Now for the downside; there are at least 12 problems and 20 causes with wood floors. Many of the problems are related to moisture being present; for we know that wood is organic (from living material) and its worst enemy is water. Some of these problems are: water from above, below, and even from the glue used to form a bond. Wood expands and contracts, perhaps minutely, but it does so every day.
Some of the causes of problems: old asphalt adhesive left on concrete, concrete curing compound left on concrete, contamination on concrete, moisture, incorrect trowel sizes, non-acclimated wood flooring, poor and inadequate nailing, uneven substrates, and improper application of finishes.
Now that we have identified the causes, let's identify some of the problems: mold, cupping, hollow sounding, crowning, cracking (normal - abnormal), squeaky floors, uneven floors, finish peeling, and disbonding.
At this point let's review the causes of the flooring problems and why they are in most instances predictable and preventable prior to the flooring installation.
1. Excessive moisture vaporizing through the slab will cause cupping.
2. Top side moisture may cause crowning.
3. Buckling caused by moisture and no room for expansion
4. Abnormal cracks from prior exposure to moisture; consequent shrinkage and or panelization
5. Disbonding through expansion
6. Splinters caused by expanding and edge crush
7. Mold is a more and more serious problem. Mold only needs moisture, a food source (wood) and a warm environment. The first sign is when (black) staining becomes apparent.
Asphalt adhesive: Creates a poor bonding surface as it is susceptible to movement weakness and alkali attack.
Curing compound: Another source of bond weakness, preventing a full mechanical bond between the bonding material and the concrete substrate; in reality it is a contaminant.
Trowel size: A worn or incorrect trowel size can lead to a weak bond and/or hollow sounding spots due to inadequate transfer.
Uneven substrates: May cause hollow sounds after installation is complete. If flooring can flex even slightly then it is probable that the subfloor is uneven and high and low spots exist. Levelness varies; one manufacturer requires 1/8-inch in 8 feet, while another requires 1/8-inch in 6 feet, so be aware.
Squeaky floors: Improper nailing and/or inadequate nailing. This will result in squeaky floors and sometimes will result in weakening of the bond.
Installation errors: At the risk of alienation, I must say that many of the above problems are not unavoidable. There are too many installers, inexperienced untrained, and placed in a pressure situation to get the job done. Many necessary precautions are neglected.
I have not put the cart before the horse in this article. Everyone speaks or writes about the problem first and the causes are not presented in total. In this article, I hope that by presenting the causes first it can be seen that practically all are preventable before actual installation. As I have said many times, an installer only has so many hours in the day/week/year to make a living. Make the most of this time by knowing how to eliminate call-backs. Perhaps using this article as a check list will also eliminate problems.
I also apologize for making this sort of a thumbnail presentation. Every cause presented above deserves its own chapter. More thorough information is available from many sources and easily downloaded from the Internet.