General Flooring Knowledge, Hardwood Flooring, Installation, Lifestyle

All About Hardwood Flooring

There are two basic types of hardwood flooring: solid hardwood and engineered hardwood. Let’s see if we can make some sense of what the differences are.

Solid Hardwood

The standard thickness for solid hardwood is 3/4″. For thin profile solid hardwood, 5/16″ is the standard. The planks are sawn in one of three ways, which affects the stability and the price of the hardwood.

Types of Hardwood Cuts

Flat or Plain Sawn: by far the most commonly used cut. It contains more variations than the others.

Quarter Sawn: cuts a log into quarters before it cuts the strips of wood to make hardwood flooring boards.

Rift Sawn: cuts a log at a different angle than quarter sawn before it cuts the wood into hardwood flooring boards. Though it is more expensive than the other methods, it is also more stable, providing higher quality flooring.

Solid hardwood floor planks are made with a tongue and groove edge locking method which makes it easy to join the planks together and make a strong joint. One side of the board has a tongue and the other has a groove. The tongue interlocks with the groove to fit the boards together.

One of the advantages of solid construction is that most 3/4″ thick solid wood floors have about 1/4″ or 6 mm of wood above the tongue and groove, meaning they can be sanded and refinished many times. If properly cared for, a solid hardwood floor can last for generations.

There are some potential disadvantages of solid hardwood. For instance, it cannot be installed below grade. Neither can it be installed over radiant heat. Most experts recommend not installing it over a concrete subfloor.

Engineered Hardwood

Engineered hardwood is made by gluing a real hardwood veneer to a core board made of either plywood or high-density fiberboard. Because of this construction method, engineered hardwood is more dimensionally stable than solid hardwood. In other words, it will not contract or expand as much due to changes in humidity or temperature.

Engineered hardwood has several advantages over solid hardwood:

  • It can usually be installed on all grades, including below grade
  • It can be installed over radiant heat (with some limitations)
  • It can be installed over a concrete subfloor
  • It can be floated

The number of plies used to create the plywood core may vary anywhere from 2 to 10, and while a 3 ply board is not going to be as stable as, say, a 5 ply board would be, this difference is not enough to be a deciding factor unless the flooring is going over a radiant floor heating system. Generally speaking, the more plies in the plywood, the higher the price. A high-density fiberboard core is more dimensionally stable than a plywood core.

Wood Veneer Sawing Methods

There are three different ways of cutting the veneer for the engineered flooring that, along with thickness, has an impact on price. The three methods of cutting the veneer include:

Dry solid-sawn: involves letting the wood dry out slowly with a low humidity level to keep moisture from inside the wood cells intact, reducing the risk of cupping. It is the most expensive type of engineered flooring, but looks and acts more like a solid.

Rotary-peel: involves boiling the log for a certain amount of time to prepare the wood. After the wood has been prepared, it is scraped from the log with a blade working from the outside in and then pressed flat. Rotary-peel typically has a plywood-like grain and can have issues with cupping and warping to try to revert to its original shape.

Sliced-peel: involves boiling the log for a certain amount of time to prepare the wood. After the wood has been prepared, it is sliced and then pressed to create a veneer.

The thickness of the veneer ranges from 0.6 mm to 6 mm. The thicker the veneer, the more expensive the flooring, generally speaking. For people who are planning to refinish the flooring at some point, it is important to consider the thickness because, unlike a solid hardwood floor, the engineered type can only be sanded and refinished so many times. Generally speaking, sanding removes +/- 1mm of the veneer. So, the thicker the veneer, the more times it can be sanded and refinished, within limits. Once installed, removing a vent to inspect the flooring from the side can provide an idea of the remaining thickness on the veneer.

Cannot be sanded & refinished:

  • Engineered wood floors with veneer thickness less than 2mm
  • Handscraped engineered floors, regardless of veneer thickness

Can be sanded & refinished:

  • Engineered wood floors with veneer thickness of 2mm or greater

Note: Sanding and refinishing an engineered wood floor with a veneer thickness of 2mm to 2.5mm is best left to a professional.

Engineered floor planks are made with either a traditional tongue and groove edge locking method or with a glueless click-lock method that requires no glue and allows the pieces to snap together to create a snug fit. This is the easiest do-it-yourself installation method.

Grades of Hardwood

This is an interesting area for shoppers, retailers, and manufacturers. While the National Wood Flooring Association, or NWFA, has established a grading system, it only applies to certain domestic species. There is no universal system for international grades of hardwood.

It is important to note that grading typically refers more to the look of the floor versus the quality of the floor. For example, an antique-grade floor is just as structurally sound as a floor graded as select and better. The antique floor will have more of a rustic look to it with more character marks.

Common Grading Names

When shopping for hardwood, there may be several different grade names present. The most common grades of hardwood are:

Clear Grade: This is the best of the grades of hardwood flooring because there are few color variations, board lengths are not widely varied, and there are little to no visible knots or pinholes.

Select and Better: This grade is slightly lower than the clear, still presenting uniform color and little to no knots and pinholes.

#1 Common: This grade presents with more color variation, with greater length variation, and an increased chance of visible knots and pinholes.

#2 Common: Boards show natural character, with darker and lighter boards, potentially shorter board length, with an increase in visible knots and pinholes.

Cabin Grade – Cabin grade is for those who are looking for a rough-hewn look in hardwood flooring; allowed checking, unfilled knot holes and worm holes, no splits, no loose knotholes.

Shorts: This has the most visible character with many knots, pinholes, and color variations present.

It is worth noting that some sellers combine grades of hardwood. For example, a floor may be sold as #1 common and better, meaning it is a combination of #1 common, select and better and clear grades.

Prefinished vs Site Finished

Prefinished boards are finished by the manufacturer, using several coats of finish with aluminum oxide (a surface coating which is the second hardest substance in the world, next to diamond). Special equipment dries the finish almost instantly, creating a durable surface. These are more expensive than unfinished floors, but can be installed in the home without having to worry about sanding and finishing.

Site finished flooring is unfinished hardwood installed on the site and then finished. There are several durable finishes and sealers to choose from.

Surface Texture Types

There are a few different surface textures available to help buyers get the look they want. Each one of the texture options below offers a different style to be considered for decor purposes.

  • Smooth: This refers to traditional milled boards.
  • Hand Scraped: This refers to boards that are distressed by hand.
  • Distressed: This refers to boards that are distressed by machine.
  • Antique: This refers to the boards with the appearance of extreme age.
  • Wire brushed: The wire brush texture consists of a wire brush run over wood flooring, creating a rough, hard surface. The wire brush gets rid of the soft wood on the surface, making the floor more durable, less slippery, and easier to maintain. This surface also hides scratches and makes the wood surface look old, which some people like.

Installation Types

Nail/Staple down: Nail down uses nails to attach the wood to the subflooring, and staple down uses staples to attach the wood. Staple down is simpler than nail down. Neither nail nor staple down is suggested for novice installers. Solid hardwood is often installed using this method.

Glue down: If the flooring is an engineered hardwood, it can be glued to the subflooring with a strong adhesive. This method is rarely used on solid hardwood floors, except for some thin profile solids.

Float: Available in the following two options

  • Glue-Seam: These floors use an adhesive to glue the pieces together.
  • Glueless-Click: These floors snap together and require no glue.

These floors are not attached to the subfloor and therefore can be installed over just about any surface. Usually, an underpad is placed between the subfloor and the engineered wood floor.

The Janka Hardness Scale

The Janka hardness test measures the resistance of a sample of wood to denting and wear. It measures the force required to embed a steel ball of diameter 11.28 millimetres (0.444 in) halfway into a sample of wood.

For hardwood flooring, the test requires a 2″ × 6″ sample with a thickness of at least 6–8mm. The Janka test is always carried out on wood from the trunk of the tree (known as the heartwood) and the standard sample is at 12% moisture content and clear of knots.

The results are stated in various ways, which can lead to confusion, especially when the actual units employed are often not attached. Overall, the resulting measure is always one of force. The measurement is given either in pounds-force (lbf), or in kilograms-force (kgf), or in newtons (N).

Janka Hardness Ratings for Selected North American Hardwoods


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