Wood Floor Resource Group is a registered provider with AIA/CES and, if you are interested, you can earn CEUs for attending this program. A sign-up sheet is circulating; please don’t forget to write down your AIA number if you want credit. Also, Certificates of Completion are available on request.
The name of this presentation is Essentials of Specifying Wood Flooring.
The presentation is protected by US and international copyright laws.
Here are the key learning objectives of this presentation.
Where does wood come from? Wood can be recycled, reclaimed, or salvaged. Many people use these terms interchangeably, but at WFRG we try to make clear distinctions between them. A strict definition of recycled products falls into one of two categories: post-consumer or pre-consumer (also called post-industrial). Post-consumer recycling means taking a product that has reached the end of its useful life and feeding it back into a process that makes more of the same product. This is what happens when we recycle paper or glass at home, but it is not at all common to recycle wood products in this fashion. The most common recycled wood products have pre-consumer content, meaning that the product incorporates wood or fiber that is a by-product of a different manufacturing process. This is very common with fiber-based products like particleboard and MDF which can use sawdust from sawmills. To us, reclaimed wood is a manufactured product that is being reclaimed from its original use. The most common example is deconstructing old buildings and remilling or reusing the reclaimed lumber. Finally, when we say salvaged wood, we mean that thing being salvaged is a log rather than a manufactured product. There are lots of sources for salvaged logs: urban street trees, orchards, and lake and river bottoms are a few.
But ultimately all wood –even recycled/reclaimed/salvage wood – comes from trees, and trees must grow in forests (complex ecosystems) or in plantations (generally monocultures). Some forests and plantations are managed carefully and responsibly, and some are not. If you want to learn more about responsible forestry, we have a separate educational program that focuses on this and other environmental issues. But this is not the purpose of this program, and we won’t say more about this topic today.
The purpose of this program is to better understand wood, and all wood is divided up into hardwoods and softwoods. Hardwoods come from broadleaf trees that are deciduous, meaning they lose their leaves in the winter. Softwoods come from coniferous trees, needle-bearing evergreens. Most hardwoods are harder than most softwoods, but there are soft hardwoods and hard softwoods. Red oak is the flooring industry standard and has a hardness rating (we will explain what “Janka hardness” means shortly) of 1290. Balsa is a broadleaf tree and hence is a hardwood but its Janka hardness is only 75. Meanwhile, Australian cypress is a softwood because it comes from a coniferous tree, but its Janka hardness is 1375, harder than oak!
Trees grow upward through budding from the ends of their branches. They grow in diameter as a result of the cells produced by the cambium layer. The cells that the cambium produces in an outward direction (towards the bark) form what is called the phloem tissue. Phloem is made up of tiny tubes that transport the sap downwards from the leaves, carrying the sugars produced by photosynthesis to the rest of the tree. The outermost phloem cells become the bark of the tree. The cambium layer also produces cells towards the inside, forming the xylem tissue, which is the tree’s wood. Xylem, too, is made up of tiny tubes, but these tubes carry the water, minerals, and other nutrients upwards from the root system to the rest of the tree. All trees have another physical feature called medullary rays that radiate from the center to the outside of the tree and allow passage of sap and nutrients horizontally, as well as providing a place for trees to store food.
Every year, the cambium produces new cells which form a ring around the trunk. In temperate climates where there are distinct seasons, more cells are added in the spring and summer – this is called “early wood.” But cell growth slows in the fall and winter, and the slow-growing cells – the “late wood” – create a visible “growth ring” that can be used to date the age of the tree: a tree with 100 growth rings is 100 years old. Growth rings also help create the grain pattern in milled wood products. Trees that grow in tropical climates with little seasonal variation often do not have visible growth rings. You can also tell something about the conditions surrounding the tree by the size of the growth rings. In warmer, moister climates, and/or when the tree has little competition for sunlight, it will grow quickly and the growth rings will be relatively large. By contrast, in colder, drier conditions, or when the tree is competing with many others for light, it will grow more slowly and the growth rings will be relatively tight. Slow-growing wood with tight growth rings generally is of better quality to fast-growing wood, being harder, more stable, and aesthetically superior.
All trees also have sapwood and heartwood, and the two are often sharply differentiated as in this log here. The sapwood is the phloem and the part of the xylem that conducts sap, as the name suggests. The heartwood is made up of xylem cells that die, losing their conductivity, hardening, and stiffening and forming the “skeleton” of the tree. For most species, the heartwood is desirable and architects and designers rarely see the sapwood because it is graded out, but in some species like maple and birch, it’s the opposite and the light-colored sapwood is desirable while the darker heartwood is usually graded out.
Now let’s look at how logs are converted into one of the two basic wood products that form the foundations of the wood products industry: lumber and veneer. The most efficient way to convert a round log into rectangles of lumber is to saw the log through and through, as in the picture to the bottom left. This is called plain-sawing the log. It is also possible to plain slice veneer, as in this picture here.
Another option is to quarter-saw the lumber. This term originated with the practice of cutting a log into quarters and then alternately sawing and flipping the log as in the diagram at the bottom so as to produce lumber whose growth rings are perpendicular to the face of the board (we’ll see why this is done). Veneer too can be quarter-sliced, as in this picture.
A third option for sawing is to cut the lumber a few degrees off the perpendicular 90 degree angle to the growth rings that you have in true quarter sawn. In the next slide we will see why this is done. It is also possible to rift slice veneer.
The reason that lumber and veneer is rift-sawn or sliced as opposed to being quarter-sawn or sliced is that, for certain species, the resulting difference in appearance is striking. This is because some species, such as the oaks, have exceptionally large medullary rays, the physical features we mentioned ealier that radiate from the center to the outside of the tree. When these species are quarter-sawn, the medullary ray is revealed as a pronounced ray/fleck figure as in the picture at the top. Some people want the clean, linear, straight-grained look, and in order to achieve this in oaks and some other species, you need to rift-saw or slice just off the perpendicular so as to avoid revealing the medullary rays. Note that all species have medullary rays, but in most they are so small that when revealed through quarter-sawing they don’t make much difference in the appearance of the wood, and therefore the distinction between quarter and rift-sawn is meaningless for most species.
The difference between quarter- and plain-sawn or sliced is also pronounced. Quarter-sawn faces generally have the linear, straight-grained appearance as seen on the left, and many people find this aesthetically desirable. Plain-sawn faces vary widely depending on which part of the log the lumber comes from. Because plain sawing is the most efficient way to produce lumber, the great majority of wood flooring on the market is plain sawn and hence the graining is somewhat wild and unpredictable – especially in species with pronounced growth rings.
Yet another option for producing veneer is to rotary peel it. In this process, the log is spun on a large lathe and then a long sharp knife engages it and unpeels it like an apple. Because the process is perfectly circular but the log itself is never perfectly round, the knife wanders in and out of the growth rings, producing a whacky, wild-grained look such as you see in construction plywood, lower grades of hardwood plywood, and lower-end wood flooring.
Now let’s talk about wood hardness. All wood will dent if sufficient force is applied – if, for example, you take a nail and pound it into the surface of the wood with a hammer. A woman’s high heel won’t exert as much force as a hammer and nail, but it’s not far off, especially where the rubber pad has fallen off the tip of the heel!
The standard measure of wood hardness is the Janka hardness test. This measures how many pounds per square inch of force are required to drive a steel ball bearing of a certain size and weight half of its diameter into a piece of wood. Harder woods require more pounds per square inch of force, and the resulting number is the Janka hardness of the wood.
As we saw in the beginning, the Janka hardness of oak is about 1290. There are many woods harder than oak, but most of them are tropical woods – as we see here, the hardest exotics are about three times as hard as oak! Woods softer that 800 or 900 are rarely used for wood flooring.
Now let’s look at a piece of wood under a microscope. If you cut a piece of lumber and look at the end grain, you will see the “tubes” of the xylem revealed. The xylem cells are like a big bundle of straws whose ends you see here. But note also how very much like a sponge this magnified piece of wood appears.
If wood looks like a sponge, it shouldn’t be a surprise that is acts like one, expanding as it absorbs moisture and shrinking as it loses it. The moisture content and the dimensions of wood constantly change with fluctuations in ambient humidity. All wood will always eventually reach equilibrium moisture content with the surrounding ait.
It would be one thing if wood moved equally in all directions, but it does not. Wood moves differently perpendicular to the grain (radial shrinkage) than it does tangentially to the grain (tangential shrinkage). Wood also moves in length, but so slightly that most people ignore the movement in this dimension. For most species, the ratio of tangential to radial shrinkage is about 2 to 1.
Now let’s take a typical, plain sawn piece of lumber. In this piecture, the heavy, longer arrows represent shrinkage in the tangential direction, while the lighter, shorter arrows are the direction of radial shrinkage. Shrinkage along surface A is more in the tangential direction than in the radial direction (i.e. surface A is more closely aligned with the dark arrow). Along surface B the shrinkage is mostly radial (surface B is closely aligned with the lighter arrow). Because wood moves nearly twice as much in the tangential direction as the radial direction, surface A will move more than surface B
For true quartersawn lumber, both faces will move evenly, and cupping will not occur. For any other grain pattern, the outer face (that which faced away from the center of the tree) will move more than the other face, which can cause the board to cup towards the outer face. Several factors can influence the severity of cupping in solid wood. The difference in shrinkage between the faces is greater as the lumber approaches a perfectly flatsawn piece. It is also greater when the lumber is sawn from areas closer to the center of the log. (Note: With smaller logs, a greater percentage of the lumber is close to the center of the tree. Hence, small timber has a greater tendency to result in more cupped lumber.)
For wood flooring, there are further implications for differential shrinkage in plain- and quarter-sawn material. Quarter-sawn wood moves twice as much in thickness (tangential to the rings) as it does in width (radial to the rings). But plain-sawn is the opposite: it moves twice as much in width as in thickness, and this is more likely to cause an entire wood floor to buckle.
Finally, there is a variation in movement and tendency to cup among species due to differences in tangential and radial shrinkage rates--the greater the ratio between tangential and radial shrinkage values (percent), the greater the tendency to cup. The most stable woods, like teak, are twice as stable as relatively unstable woods like maple. When dried for green to oven dry, a 6” wide piece of plain-sawn maple will shrink a full ¾ of an inch!
What does all this mean for wood flooring? Well, one obvious implication is that wood and water do not play nicely together. In fact, water is wood flooring’s worst enemy, whether it is water from below in improperly cured concrete slabs, or water from above from wet mopping or flooding.
Another implication is that big swings in humidity are challenging for wood flooring. Most wood flooring is designed to perform best when the relative humidity is from 35% to 65%, the range that is typical for the interior of most homes. Radiant heat sub-flooring, extreme heating or cooling of interior air, or simply big fluctuations in the weather can cause ambient humidity to go outside of the “safe” range and cause problems or failures.
Solid wood flooring is going to behave exactly according to the physical characteristics of the product: the species, the grain orientation, the shrinkage values, and the fluctuations in ambient humidity will govern changes that a wood technologist could predict if he knew all the variables.
This means that in exceptionally wet or dry conditions or in situations where changes in moisture may be extreme, it is generally a bad idea to specify solid wood flooring, especially in plain sawn, in wider widths, and in less stable species, and heaven forbid that you should combine all of them!
Another implication is that in such conditions, it is often a good idea to specify wood flooring in an engineered format. Engineered flooring tends to be significantly more stable than solid flooring for a number of reasons. One reason is that many engineered formats have central plies whose grain orientation is at right angles to the top and bottom layers, and this cross-ply construction tends to balance the movement of all the layers. Another reason is, where engineered products use a veneer face, the veneering process causes one face of the veneer to fracture extensively and this alters its physical characteristics, making it much more stable than solid lumber. This being said, engineered flooring can be less stable than solid wood in the lengthwise direction precisely because of the central plies. Solid wood moves very little longitudinally, but extreme conditions can cause the central plies in engineered flooring to move tangentially causing gapping or “end peaking” along the lengths of the floor boards.
The way that engineered flooring behaves as conditions change is complicated by the fact that there are many different formats of engineered flooring. But all engineered flooring has two basic components: a wear layer that is the wood you see and walk on and name the flooring after; and a substrate which supports the wear layer.
There are several options for producing wear layers. Sawn wear layers are made from lumber and are generally thicker. The sawing process is relatively inefficient and the physical properties are the same as solid wood. Veneering produces thinner wear layers, although somewhat thicker for a rotary process than a sliced veneer. Veneering is very efficient because there is no sawdust and little waste. Also, as described previously, the process causes knife checks on one face of the veneer which alters its physical characteristics and makes it more stable than sawn wood.
In terms of appearance, sawn and sliced wear layers have similar appearances to solid wood, while rotary veneer produces the whacky look we described earlier.
Now let’s look at the major engineered wood flooring formats and their relative pros and cons. 3-layer products have thicker, sawn wear layers, cross-slat cores made of small pieces of wood, and veneer backs. The great benefit of this format is that is least likely to cup. The big drawback is that in very wet or dry conditions, the small gaps between the core pieces can translate through the wear layer and become visible as a series of lines. This is called “telegraphing.”
Another common format for engineered wood flooring is 2-layer construction. Often there are more than two plies of wood because the bottom layer or substrate is plywood as you see here, but it is called 2-layer because there is a sawn wear layer on a plywood platform. Because there are no voids in the plywood, this format is not susceptible to telegraphing but it is more susceptible to cupping or end peaking.
Another format is multiply which is basically built like plywood with numerous thin plies, including a veneer wear layer. Many entry-level products are in this format, and the pros and the cons are the same as for two-ply.
A final, newer format is HDF core, where you adhere a veneer wear layer to a high-density fiberboard core. The advantage is that it is cheap, and the disadvantage is that it is cheap and less expensive HDF may fail if there is too much moisture.
There are a variety of different options for edge and end treatments, with bevels of various depths that are more forgiving if the milling of the tongue and groove vary somewhat, and square edge and true square edge treatments that replicate the look of solid, site-finished wood flooring but require absolute precision in the milling process in order to avoid “overwood” from one plank to the next.
There are also a variety of options for surface treatments, with smooth and handscraped being the main options, and for finishes, where it is possible to adjust gloss levels to achieve a variety of different looks.
Finally, there are two options for tongue-and-groove systems, with the regular T&G and then the more recent click T&G which allows for pieces of flooring to be fitted together without the use of glue on the edges, making the replacement of individual courses of flooring a possibility.
Next, there are a variety of different installation methods. Nailing or stapling is cheap and fast as long as there is something to nail into – usually plywood – but if you don’t have the right subfloor, then you need to install one adding significantly to labor and expense. Gluing down is solid and quiet, but relatively expensive and messy. Floating installations, which is only possible with engineered floors and in which each plank of flooring is glued to the next at the tongu-and-groove so that the flooring forms a panel that “floats” over (is not attached to) the substrate, are quick and inexpensive and hence increasingly popular, but they have the lease integrity and can have a “springy” feel, especially where the subfloor isn’t perfectly level.
No matter how good a wood flooring product is, an improper installation can cause problems or failure. The choice of the right installation method and the right wood flooring installer is crucial for project success. WFRG Director of Technical Services Bob Goldstein has 35 years of experience as a commercial wood flooring installer and is an NWFA certified trainer. He is available to consult with you and other members of the project team on all aspects of installation.
Job site conditions also really matter, and as discussed before, the biggest pitfalls to avoid are a too-wet concrete slab and improper heating and ventilation that creates too dry or too wet ambient humidity.
Another pitfall to watch out for is color change in wood. Almost all wood that isn’t stained changes color over time with exposure to air and light, and in some species the color change is significant. Educate your clients to expect these changes so that when they move rugs or furniture and see a light patch, they don’t think something is wrong with their flooring.
Another common pitfall to avoid, as we discussed earlier, is too much – or too little! – moisture.
How does engineered flooring compare to solid wood? Most people think that because solid wood flooring is thicker—3/4” is standard—it is higher quality than engineered flooring. But this isn’t necessarily so.
In comparing the two, you need to remember that solid flooring is not ¾” of useable material. This is because you can only use the wear surface that is above the T&G since you can’t sand down further, and typically this wear surface is no more than ¼” thick. The wear layer of the better quality engineered wood flooring products approach or match the wear surface of solid wood—1/8” is standard for most of our products, and we can make custom product that has ¼” wear layers. So the question now is, how thick is thick enough? You can sand and refinish a 1/8” wear layer at least twice while ¼” will another couple of sandings. How many times do you really need to be able to sand and refinish?
It’s also worth pointing out that engineered flooring makes much more efficient use of the high-quality wood that we choose and walk on in wood flooring. Solid flooring is made from lumber, and a single piece of 1” thick lumber will yield one piece of flooring, but that same piece of lumber will yield five 1/8” wear layers for engineered flooring. Solid flooring wastes precious, high-grade material as a “platform” to support the wear surface, while engineered flooring uses abundant and inexpensive woods in the platform and saves the quality wood for the part that counts.
Because it has to acclimate on site, the tongue-and-groove fit of solid wood can’t be milled very tight to allow for “play” as the wood expands or contracts. Thus, while solid flooring must be nailed down to a plywood subfloor, the T&G of engineered wood flooring can be milled to a very tight fit so that it can be floated over or glued directly to concrete, thus eliminating the cost—both financial and to the environment—of using all that plywood for the subfloor.
Here’s a comparison of costs of installing solid vs. engineered wood flooring. While you often pay more upfront for engineered wood, the installed costs are usually less than for solid.
Finally, with engineered flooring you get a factory-finish that is generally much higher quality than a finish that can be applied on-site.
Site-applied finishes rarely involve more than 3 coats, and because the finish must contain water or a chemical solvent for it to dry out, it is significantly less durable than a factory finish that is applied in highly controlled conditions and dried with ultraviolet light. Site-applied finishes also offgas – sometimes significantly. Our products have nine coats of UV-cured acrylic urethane on top of an aluminum-oxide subcoat which is practically impossible to wear through. The UV-cured finish is totally inert and will not offgas. The one drawback of many factory finishes is that, while they are durable, when they scratch they sometimes scratch white. There are a number of ways to mitigate or remove these scratches, which we will cover shortly.
We can’t overemphasize the importance of screening and top-coating. In most cases wear a factory-finished wood floor starts to look shabby, screening and top-coating is a relatively inexpensive and low-hassle way to return it to its oringinal condition. This involves chemically or mechanically abrading the surface of the factory finish so that a site-applied finish can adhere to it. that installers screen the factory finish and apply one or two top coats of a site-finish. This system can be repeated indefinitely, and if you always renew the finish, you never have to sand. Returning to the questions of “how much wear surface do you need” and “how many times do you need to be able to sand and refinish,” the answer may be zero – but two times should certainly be enough. Remember, you walk on the finish, not on the wood!
There are several factors that affect how well a wood floor will perform in a demanding commercial application. The first is your specification! It is extremely important to select the right product for the application. But it is equally important to choose the right installer and installation method, and last but not least, to properly maintain the floor over its life.
Clearly, you should specify harder woods at the top of the Janka scale for high-trafiic applications.
To care for your floor, we recommend operating a humidity control system at all times to keep relative humidity within acceptable ranges. Don’t allow standing water on the floor and use only recommended cleaners. To remove white scratches, you can use the BonaKemi fill stick and marker touch-up kit.
We are happy to share our care and maintenance guidelines with you in either electronic or printed form.
There are a number of other considerations in any project, not the least of which is the budget. Generally, the most economical wood flooring products are in multi-ply or HDF-backed formats. In below-grade installations, you should only use engineered wood because of moisture. The subfloor material and condition is always very important, and engineered is generally used over concrete and radiant heat.
Lastly, there are a number of environmental issues that may be a consideration for you and your clients, including but not limited to the items on this list. Once again, we have an excellent program that addresses these issues in some detail, Wood Flooring for Green Building, which we would be happy to bring to you another time.
Thank you very much for your time and attention. Are there any questions?
Essentials of Specifying Wood Flooring.AIA.CES
www.woodfloorrg.comWood Floor Resource Group is a Registered Provider with TheAmerican Institute of Architects Continuing Education Systems.Credit earned on completion of this program will be reported toCES Records for AIA members. Certificates of Completion for non-AIA members are available on request.This program is registered with AIA/CES for continuingprofessional education. As such, it does not include content thatmay be deemed or construed to be an approval or endorsement bythe AIA of any material of construction or any method or manner ofhandling, using, distributing, or dealing in any material or product.Questions related to specific materials, methods, and services will beaddressed at the conclusion of this presentation.
Copyright Materials This presentation is protected by US and International copyright laws. Reproduction, distribution, display anduse of the presentation without written permission of the speaker is prohibited. Wood Floor Resource Group 2007 www.woodfloorrg.com
Learning Objectives Understand the fundamental characteristics of wood as a material: sources, types, hardness, stability, etc. Understand the essentials of wood flooring: species,formats, performance issues, common pitfalls, etc. Understand the pros and cons of solid vs. engineered wood flooring
Where Wood Comes From – Recycled/Salvaged/Reclaimed < Recycled (Pre-Consumer/Post- Industrial) Wood pieces or fiber that are manufacturing by- products Example: Sawdust < Reclaimed Previously manufactured wood products Example: Building deconstruction < Salvaged Logs Examples: Urban Forest, Agriculture, Waterways, Deadwood
Where Wood Comes From – Forests & PlantationsSome well-managed, some not Teak plantation Natural forest Want to know more? “Wood Flooring for Green Building”
Hardwoods vs. Softwoods Hardwoods come from broad-leaf trees deciduous Softwoods come from needle-bearing trees coniferous Most hardwoods are harder than most softwoods, but there are soft hardwoods and hard softwoods. the Janka hardness of red oak (a hardwood) is 1290 the Janka hardness of balsa (a hardwood) is 75 the Janka hardness of Australian Cypress (a softwood) is 1375 !
Growth Rings Early Wood Late Wood Fast Growth Slower Growth
Heartwood vs. SapwoodSapwood HeartwoodS pc n u t n a o d c io Ha d n da d ree n s if e e d a t fn d edSpecies where sapwood c l s– n l n e el o o gris desirable: c n u t gs p o d c in aM peB c a l , ir h Species where heartwood is desirable: Ch r y M h g n , er, a o a y Ta ek
Lumber & Veneer – Plain Sawing/Slicing Plain sawing = the most efficient way to convert a round log into rectangular pieces of lumber Plain slicing
Quarter- vs Rift-Sawn - Appearance Quarter-sawn Rift-sawn Only species with pronounced medullary rays (oaks, maples, sycamores, lacewood) present this difference.
Plain vs. Quarter-Sawn/Sliced -- Appearance Quarter sawn Plain sawnQuarter sawn synonyms:• Vertical grain/VG• Straight grain• Comb grainPlain sawn synonyms:• Flat sawn• Flat grain Only species with pronounced growth rings will present this appearance
Rotary Peeling – Process & AppearanceThe log is peeled by a blade and is worked A sample of veneer produced byaround the log toward the center, creating a rotary peeling.wood veneer.
Wood HardnessAll wood will dent if sufficient force is appliedHigh heels will dent even the hardest woods 115 lb woman exerts about 2500 lbs of force via a high heel
Hardness TestingWood hardness is measured by theJanka hardness test
Comparative Hardness Graph Industry Standard
The Structure of WoodThe cellular structure of wood: a big bundle of “straws” Notice how it looks very much like a sponge
Why Wood Moves• All wood gains and loses moisture• When it does, all wood expands and contracts• The MC of wood will always equalize w/ ambient humidity Dry Sponge Wet Sponge
Differential ShrinkageTwo main dimensions on which wood moves:2. Radially3. Tangentially (twice as much)R = RadialT = TangentialL = Longitudinal
Shrinkage: Different Amounts & Directions Large shrinkage in the tangential direction Small shrinkage in the radial direction A lumber B A = bark face, or sap face B = heart face
Plain-Sawn Lumber More Prone to Cupping Quarter sawn cross-section Plain sawn cross-section
Quarter-Sawn Lumber is More Stable Quarter-sawn lumber Plain-sawn lumber Arrow thickness denotes movement amount
Some Species are More Stable than Others Tangential Shrinkage Species Tangential Radial Shrinkage Shrinkage Hard Maple 9.9% 4.8% This 6” wide piece Red Oak 8.6% 4.0% of Maple will shrink 10% (3/4”) in width. Brazilian Cherry 8.5% 4.5% Teak 5.8% 2.5% Values are percentage of shrinkage from green to oven dry
What does all this mean for wood flooring?Water & wood do not mix well • Wet concrete slabs or other subfloors • Wet mopping • Flooding
What does all this mean for wood flooring?Big changes in relative humidity also a problem Wood flooring performs best in RH ranges of 35% - 65% (typical of house interiors)
What does all this mean for wood flooring?Solid Wood Flooring:Wood properties = performance
What does all this mean for wood flooring?In conditions of fluctuating moisture, care must be taken whenusing wood flooring in the following: • Solid formats • Plain sawn • Wide widths • Less stable species
What does all this mean for wood flooring?• In conditions of fluctuating moisture, generally best to specify wood flooring in… Engineered format – more stable in width than solid (about 50%) Veneer face very stable because of fractures When sawn face, cross plies help control movement But engineered format is generally less stable than solid lengthwise Solid wood doesn’t move longitudinally Cross plies move sideways and can affect lengths
Engineered FlooringEngineered flooring is more complicated than solidMany formats that perform differently in different situationsTwo main components wear layer substrate
Engineered Flooring: Wear LayersSawn • 2 to 3.5 mm (6 - 8 mm possible) • Less efficient (sawdust) • Properties same as solid wood • Entire face movesVeneer (sliced or peeled) • Sliced 0.6 to 1 mm • Peeled 1.5 to 2.5 mm • Efficient (almost no waste) • Knife checking/fracturing
Engineered Flooring: Appearance Sawn wear layers Same as solid Sliced veneer Same but slightly more repeating pattern Peeled veneer Rotary – whacky plywood look
Engineered Flooring Formats: 3-Layer3 layer (must utilize thicker wear layer or “telegraphing” may occur) 1. Wear layer 2. Cross-slat core 3. Veneer backPros – least susceptible to cuppingCons – telegraphs in super-dry and wet conditions
Engineered Flooring Formats: 2-Layer2 layer 1. 2 mm or thicker sawn face 2. Plywood substratePros – Not susceptible to telegraphingCons – More susceptible to cupping, end peaking
Engineered Flooring Formats: Multi-LayerMulti-layer 1. Wear layer < 2 mm 2. Plywood substratePros – Not susceptible to telegraphingCons – More susceptible to cupping, end peaking
Engineered Flooring Formats: HDF CoreHDF core 1. 2 mm or less sawn face on HDF substratePros – InexpensiveCons – Quality of HDF = how it holds up to moisture absorption
Engineered Flooring – Edge/End TreatmentsEdge and end treatments• Beveled• Micro-beveled• Micro-eased• Square edge• True square Square edge
Engineered Flooring – Flooring TreatmentsSurface treatments and finishesTreatments• Smooth• HandscrapedFinishes• Glossy• Matte• Cashmere/Low-Gloss Hand scraped wood flooring
Engineered Flooring – T&G Systems Click T&G Regular T&G
Installation MethodsNail/StaplePros - Cheap, fast (where substrate exists), more integrity than floatCons - No substrate, need to install one, no particle board substrateGluePros - quiet, solid, any sound, dry, flat substrate, more integrity than floatCons - relatively costly & labor-intensive, messy, curing timeFloatPros - very fast, inexpensiveCons - “Springy” feel, clicking or tapping sound
Installation Really MattersThe performance of wood flooring is only asgood as the installationYou need to choose the correct installationmethod for your conditions and otherrequirementsConsult with Bob Goldstein, WFRG Director of Technical ServicesPhone: 856-705-1118Email: email@example.com
Job site conditions really matterBiggest pitfalls • Wet slab • No heating/ventilation
Common Pitfalls – Color ChangeSome species dramatically change color (esp. exotics) • With exposure to air and/or • With exposure to light Brazilian Cherry expected color change Fresh> Aged>
Common Pitfalls - Moisture• Too wet: • Swelling (and subsequent compression set) • Lifting off the floor • Telegraphing • Tips up• Too dry: • Shrinking • Cupping Cupped floor usually caused by a wet subfloor • Cracking • Telegraphing
Engineered vs. Solid Wood FlooringComparing the sandable wear surface Engineered wear layer; 1.5 mm – 2.5 mm once, 3 mm+ twice Solid wear surface; 3 - 4 re-sandings total
Engineered vs. Solid Wood FlooringHigh-quality wood efficiency usage
Engineered vs. Solid Wood Flooring Solid wood flooring has to acclimate Engineered wood flooring does not. Result… T&G can be milled to tight fit, plywood “built in” Glue-down or floating installation Eliminate plywood subfloor Save $$$ and resources!
Unfinished vs. Prefinished Solid flooring – usually unfinished, must be site-finished Engineered flooring – factory finish
Quality of Finish Site-applied finish • 2 or 3 coats max. • solvent- or water-based (may off-gas VOCs) Factory finish • 9 coats urethane, aluminum-oxide sub-coats • UV-cured (no off-gassing) Site-applied finishes less durable but scratches can be more apparent in factory finishes
Benefits of Screening/Top-Coating• Relatively quick/inexpensive - $.75 - $1.75/sq. ft.• Repairs most signs of wear• Creates uniform look• Seals surface of floor• Chemical system doesn’t require mechanical sanding Bona Prep Recoating Adhesion System Basic Coatings “TyKote” Sandless Recoating System• Can be repeated indefinitely Bob Goldstein: “Remember, you walk on the finish, not the wood!” Phone: 856-705-1118 Email: firstname.lastname@example.org
Wood Flooring in Commercial ApplicationsFactors affecting how well wood flooring performsin demanding commercial applications: Pick the right product for the application and site conditions in terms of: Format Species Finish Hardness Pick the right installer and installation method Care and maintenance over the life of the floor
Wood Hardness High traffic = harder woodsIndustry Standard
Care & Maintenance• Humidity/moisture issues Operate a humidity control system Clean up spills quickly—DON’T wet mop • Use recommended cleaners Bona Swedish Formula Hardwood Floor Cleaner Basic Coatings Cleaner • To remove scratches BonaKemi fill stick and marker touch-up kit
Other ConsiderationsBudget • Least expensive installed product is generally multi-ply or HDF- backed engineered flooringOn- or above-grade or below-grade • Engineered only below-gradeSubfloor material and condition • Engineered often used over concrete, almost always over radiant heat $
Environmental Issues• LEED compliance• Forest certification• Plantations vs. Natural Forests• Recycled/Reclaimed/Salvaged• Rapidly Renewable• Regional Sourcing• Offgassing/IAQ Wood Flooring for Green Building