The two questions we receive most frequently from customers concern solid versus engineered hardwood. "What's the difference between solid and engineered hardwood?" is usually followed by "How do I tell if I have solid or engineered wood floors in my house?" Today we'll shed some light on the first question for ya, paying particular attention to issues related to flooring in the Nashville area.
What is solid hardwood?
Solid hardwood flooring is simple enough to understand: each strip or plank is cut from one solid piece of wood without any visible layers. It can vary in thickness from 3/4-in. to 5/16"-in., but 3/4-in. is the most common option.
How is it installed?
Solid hardwood is usually nailed down (actually stapled, preferably), although in certain situations it can be glued or floated.
Where can it be installed?
Solid hardwood can be installed on grade or above grade. Grade is simply a way to define where things are in relation to ground level. As you can see from our fancy Photoshop image below, solid hardwood can be installed at ground level or higher. This rules out basements, sunken living rooms, etc.
Why can't I install solid hardwood in my basement?
Solid hardwood is au naturale, baby. Imagine if you went outside, cut down a tree, made it into boards, and brought it in your house. It would react to moisture inside your home just as it would if it were still outside as part of a solid tree. Any room below grade naturally has a lot more moisture issues than a room that's above ground, so when water or simply humid air comes into contact with solid wood flooring, it can cause cupping or other distortions to occur.
To see this in action, visit an older home with hardwood flooring in Nashville or elsewhere in the South. Even when moisture from below is not an issue, without air conditioning the humidity we all know and love makes for some pretty bad warping and distortion (not to mention lots and lots of sweaty glistening.) If the floor has not been restored, you'll be able to see the effects of moisture on the wood.
My house is on a concrete slab foundation. Can I install solid hardwood flooring?
Yes and no. Solid wood expands and moves slightly even after it's installed and is less stable than engineered wood. It must be glued down to a concrete foundation and traditionally adhesives have not worked well enough to warrant using them. The past few years have seen a boom in products marketed specifically to allowing installation of solid hardwood on concrete foundations.
The most well-known is Bostik's moisture cure polyurethane adhesive; the company also provides liquid moisture barriers to help prevent cupping and other problems associated with solid hardwood. Elastilon, a product of the Netherlands, has been popular in Europe for quite some time but has finally started making its way to the US. It's a "self-adhesive installation system" that acts as a vapor barrier and allows solid hardwood to be installed on concrete slabs. Another option is simply installing a plywood subfloor over a concrete slab to allow the hardwood to be nailed down.
The downside to all of these options is cost. Numerous engineered flooring options are now available, so the vast majority of customers can find a product they love without adding thousands of dollars to their budget.
Finally, despite being able to, installing solid hardwood on concrete is simply a method we do not recommend. There are too many problems unique to this method that can be avoided by using an engineered wood.
What are the advantages of solid hardwood flooring?
The main advantage of solid hardwood is that it can be sanded and refinished multiple times, greatly extending its life. That's why it's so common to see original hardwood floors in older homes; they can usually be salvaged by sanding and refinishing them until they're as good as new!