One segment of the wood flooring market that is causing a lot of confusion is engineered wood flooring and the cores used to create those products. We've come a long way from the days when we were making engineered flooring in the U.S. by simply gluing three layers of hardwood veneer together. In today's complex market, how do customers and specifiers know which one is "best"? Can you even call some of them a "hardwood floor"? Here are some facts about the materials that are being used in today's engineered wood flooring market.
When I started in the industry here in the U.S., we would build engineered flooring by cutting our veneers, and as we graded them, the best ones would become the face veneers and the others would become the inner layers of the flooring (each turned to alternate 90 degrees). So those products had what we still call a "balanced construction" that was 100% hardwood. Over time we realized the species didn't necessarily have to be the same throughout the flooring from top to bottom—as long as we had the same species on the top and bottom and the other species in the cross direction, it worked. Today there are still engineered products that use this all-hardwood balanced construction; poplar is the product that is typically used for core layers because it is still a hardwood but is less expensive than other species.
HDF (high density fiberboard):
The next evolution of engineered flooring cores in the U.S. happened when a manufacturer started using a rotary veneer on the face and back but used an HDF core. HDF is actually harder than wood, so its resistance to dents was an improvement. However, standard HDF is susceptible to moisture, so it wouldn't stand up to exposure to water or a wet slab—it deteriorates with moisture.
You can put additives in the HDF to make it moisture-resistant, so some manufacturers started using that as a core material. A pitfall is that you can't tell by looking at it if it's the more expensive moisture-resistant HDF or not. For example, we imported a product in the early 2000s that was supposed to have a moisture-resistant core, but sometimes the supplier overseas would slip in some regular HDF instead. You couldn't look at the product and tell, but it would expand and contract in all dimensions. Expanding 3 percent across the width isn't very noticeable, but 3 percent across the length leaves you with a good crack at the ends of the boards. We eventually had to pull it from the market.
Today we use some products with the moisture-resistant cores, and they perform really well: You can boil them for an hour and they don't appreciably change. If you boil a regular HDF core, it will turn into oatmeal, so there's a big difference.
Baltic or Russian birch plywood:
Today, of course, we also have many engineered products built on Baltic birch plywood. Performance-wise it works well—it's stiff enough to support the hardwood veneers, and in some cases you can glue a sawn face or sliced face to it without having a back on the other side to counterbalance it. That all depends on the thickness of the face, because generally the thicker the face the thicker the core has to be or you have to use a balancing back on the product.
Baltic or Russian birch is all the same species and is sourced from either Europe or Russia, and one concern about it, depending on where it's sourced, is legality. You need to be sure it has the correct certifications to ensure you aren't violating the Lacey Act by buying illegally sourced plywood.
From a cost perspective, HDF has the lowest cost of the typical engineered flooring cores, followed by Baltic birch and then a hardwood core like poplar. However, in recent years, there are some new cores that are in our wood flooring market:
SPC (stone plastic composite):
SPC is basically made of stone dust and plastic, and for wood flooring we glue a wood veneer to its face. According to the definitions by both the National Wood Flooring Association and the Decorative Hardwoods Association (formerly HPVA), flooring that has real wood on its wear layer is considered "wood flooring." SPC is very, very hard, and it's heavy.
SPC is a hot category right now because "waterproof" seems to be all you hear about. SPC is affected dimensionally by temperature but not moisture (it will expand to some degree as it gains heat). You can submerge it in water for a week and it won't show any signs of being affected by moisture. When it has a real wood veneer, that face must be encapsulated with waterproof coatings.
Because it's so hard, SPC flooring resists dents better than traditional engineered flooring cores. The downside is that it's heavy, and you can't resand it because the veneers are so thin. If you have too thick of a veneer on an SPC core, the wood will overpower the core and the flooring won't stay flat.
WPC (wood plastic composite):
Although you hear about this core with vinyl flooring, I don't think it's stiff enough to hold wood flat, and I haven't seen a WPC composite wood floor.
At least one company offers a wood veneer product that is glued to a magnesium oxide core. It's unaffected by heat. It is affected by moisture in that it gains a little weight, but it doesn't expand and contract—it's basically like stone. The issue with magnesium oxide is that it is so brittle you can't put a click tongue and groove in it; it breaks off.
I think we're just starting to see the beginning of innovation with core materials in our flooring market; we'll see more and more types of cores coming out with all different chemical compounds and different minerals. There will always be a place for the traditional hardwood cores, but that isn't the sexy part of the market right now. No matter which core is used, though, the flooring will only be as good as the quality of the construction used to create it.