To save precious hardwoods and create more affordable products, engineered floors and laminated panels have become very popular. Engineered floors consists of a relatively thin layer of hardwood glued onto a backing. The backing can be plywood or some type of fiberboard. Since the backing is invisible, inexpensive softwood or wood fibers are used. One of the first engineered wood was plywood. Plywood is a very stable panel manufactured by gluing several layers of veneer together and changing the orientation of the growth rings with each layer.
Stability: Laminated floors and panels are expected to be at least as stable as a solid piece of wood. And they often are very stable. However, being made from different layers of materials can present a new set of problems. These problems appear mainly, when the moisture is not right to begin with or when the planks are exposed to changes in moisture content.
If the top layer and the backing have the same shrinking tendencies, engineered floors will move just like solid wood floors. If the top layer and the backing shrink differently, then the panel is more moisture sensitive. More shrinking and warping can be expected.
When the top layer shrinks or expands and the backing does not follow at the same rate, the plank will curl or the panel will delaminate or surface checks appear.
Almost every piece of wood inside a home will endure some moisture movement in the course of a year. Weather and changing seasons affect the relative humidity inside a home and consequently the relative humidity affects the wood moisture in floors, panels or furniture. Small cracks appear and disappear with the changing seasons. This is true for solid and engineered wood. Operating an HVAC year round will stabilize the wood.
Changes of relative humidity are usually followed by changes in wood moisture: For example, when the EMC of air is lower than the wood moisture content (dry winter), the surface and eventually the entire piece of wood dries out until the moisture content has reached the EMC. (Click here for EMC and corresponding relative humidity and temperature.
Wood: When wood is drying out, the surface dries first and shrinks. The wetter core will follow later. Cupping and surface checking can occur. Stresses can build up near the surface and cause the wood to check (small surface cracks). If the deformations are severe enough, the structure of the wood can be broken and the defects are permanent.
Over time, the core will also dry out and the entire piece of wood will have a uniform moisture distribution again. Any cupping may disappear. What may still be noticeable is the overall shrinking and warping due to the change in moisture content. Small gaps between the floor planks may still be visible. Some wood species such as Oak, Sycamore and Beech are highly susceptible to defects from shrinking. Check the Internet for Shrinking Factors.
Engineered Products: When an engineered product dries out, the same drying process occurs as described above. The surface dries out first and shrinks. The hardwood used for the top layer will determine how much shrinking occurs. Since the core is usually very stable, the hardwood layer on top is responsible if any problems occur:
-When the top layer shrinks as little as the core, you have a very stable product (second drawing).
-When the top layer shrinks a lot more than the core, you have a product which will develop problems whenever the moisture changes. That engineered product (first drawing) will only be flat at the manufactured moisture content. The hardwood top will not fit the core at any other moisture content. >Dual-depth meters are ideal for engineered products.
-a problem floor
-a good floor
Click here to see what made the difference.
It is important to measure wood floors:
-at the time of delivery
-after job completion
As soon as floor packages are delivered, you should take a few moisture measurements. If you wait until the floor shows defects from shrinking and cupping it is often too late to fail a claim. Too much time has passed and the moisture content at the time of delivery cannot be determined. The supplier may not recognize any claims.
Measuring a cupped engineered floor after it has dried out, may show a perfectly good moisture content of 7%. The only indication that the top layer must have had a higher moisture content at some previous time, is the noticeable cupping.
Ideal for the floor installer dual-depth pinless meters:
The Ligno-Scanner SDM works great when checking multi-layered engineered products. The measuring depth can be selected to be 1/4 or 3/4 deep.
Engineered or laminated panels can be measured with the 1/4 depth for the top layer and the 3/4″ depth for the entire panel.
Installed floors can be measured with the 1/4″ depth without picking up any false readings from the sub floors and concrete underneath. Measurements for the stability test should be taken at the 1/4″ depth setting.
Click here for more info.