Oriented Strand Board

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Oriented Strand Board (OSB)

Oriented strand board (OSB) is a type of man-made engineered wood that is mostly associated with plywood boards. The two are different in some ways. Plywood boards have been around since 1860’s starting out in France. 

OSB is much newer but is starting to become the more popular choice for homeowners and construction companies. The board is very durable, strong, and mostly defect-free.

Differences Between OSB & Plywood Boards

OSB Board

  • Resists humidity better than plywood
  • Less expensive option
  • Made from wood chips that are deliberately stacked on top of each other in an orderly fashion
  • No soft spots throughout the board
  • Even distribution of wood chips to create a durable and lasting board

Plywood Board

  • Wets and dries much faster than OSB
  • Goes back to original shape once it dries if it gets wet
  • Made from thin sheets of wood
  • Stacked in no particular order, therefore creating soft spots throughout the panels at times
  • Well known and has been around for many years

Oriented strand boards and plywood boards are very similar but there are also some main differences between the two.

In humid environments, OSB should be a contractors choice. The makeup of the boards resist humidity much better than plywood boards. Although when exposed to water for a longer period of time it has a tendency to swell at the edges. Plywood has the advantage of going back to its original shape once dried. 


If your boards get caught in a rainstorm during the building process then plywood is going to get wet very quickly. Oriented strand board will take much longer to absorb the water, giving you time to cover and protect it.

Plywood boards are significantly more expensive than OSB. This alone is usually the biggest contributor when it comes to making a decision between the two. 

Because plywood is stacked without any regard for size there are often soft spots throughout the board. OSB doesn’t have this issue due to the meticulous nature of how it is assembled.

Similarities Between OSB & Plywood Boards

Both boards are used in similar construction settings. Oriented strand boards and plywood are very strong, long-lasting, and durable.

Similar in strength and functional purposes for building projects. 

Both are very well known and are terrific to use. Most home-builders and contractors are shifting from the long used plywood boards towards using OSB. There’s nothing wrong with plywood but now that there’s a new product on the market, contractors are leaning towards it. One of the biggest contributors in the decision is price.

Types Of Oriented Strand Board

There are five different types of OSB boards available. Each board comes recommended based on climate and humidity levels.


No added formaldehyde


General purpose in dry conditions


Load bearing in dry conditions


Load bearing in humid conditions


Heavy-duty load bearing in humid conditions

How Oriented Strand Board Is Made

Logs from small or large trees are taken and ground into small wood strands or chips. They are dried and treated with adhesive wax then stacked on top of one another strategically in alternating layers to create a strong and durable panel.

Typically one board will have nearly 50 layers of dried wood strips before being pressurized at a very high temperature. 

Because of the way they boards are layered in such a meticulous way, they become very sturdy throughout the entire sheet. If you’ve ever walked on a floor and felt some giving in specific areas, then odds are there is plywood underneath. OSB doesn’t create this issue.

Why we use OSB before installing Hardie Siding Board

We find it very important to provide exceptional service, quality workmanship, and lasting siding installations. With that being said, we find that it is in the home owners best interest to allow us to install OSB boards prior to installing hardie siding.

Hardie siding will last decades if applied correctly and taken care of. One of the best ways to ensure a lasting product is to start it initially with brand new OSB boards underneath. The siding will be installed on top of the boards for the ultimate lasting fit. 

Our installation team is incredible and we will adhere the James Hardie siding to the oriented strand board for the best long-lasting results. We can attach siding to your home without the boards, but there is no guarantee on how old, warped, or worn out the wood is that we will be working with underneath. This is why we highly recommend OSB installation before getting your hardie siding put on by our professional team.