Do I need a moisture barrier or vapor barrier to be used before installing wood flooring?

Answered by Brett Kulina ~ August 2, 2010 ~ Comments

My house is 20 years old. Do I need a moisture barrier or vapor barrier to be used before installing wood flooring? I've heard a million different opinions. I want to use Boston's Best, I've been assured that is all I need.

Brett Kulina

When gathering information for a DIY home improvement project, it can be frustrating when there does not seem to be a clear answer to a simple question, and conflicting opinions from seemingly qualified people can make the task all the more difficult. Your question about the need for a moisture barrier under a wood floor is definitely one of those dilemmas which will illicit several different opinions, usually based on the specifics of your home, but sometimes those differing opinions are simply based on what has worked for others. The important thing to realize is that wood floors are effected by water, and you need to do whatever you can to keep your wood floors moisture free. Remember, wood can shrink and expand because of changing humidity levels in the air, and wood flooring can buckle, warp or even split if it comes into contact with more significant amounts of water.

That being said, you need to evaluate the conditions in your home in order to choose the right moisture barrier to install under your new wood floors. I believe that all wood flooring should have some type of moisture barrier between the floorboards and the sub-floor. I have used both red rosin paper and 15-pound roofing felt as a moisture barrier under wood floors which were installed over an above-grade plywood sub-floor, and both of these products have a proven track record for these types of installation. If you are installing a wood floor over a cement sub-floor or in a basement, then you will need to increase the level of moisture protection. For these types of installation I would recommend a 8-millimeter plastic sheeting be installed as the moisture barrier. For areas in your home that have excessive moisture, or the possibility of standing water, then I would avoid a solid wood floor product all together.

Undoubtedly you will find differing opinions on the subject, but don't let the abundance of opinions cloud the fact that you need to take whatever steps are necessary to keep your wood floors as moisture free as possible. Good luck with your project!

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