The Ultimate Guide To Oriented Strand Board (OSB)
10 Feb 2020
Often in construction projects there’s a need for some sort of material.
A material suitable for load-bearing construction applications, sheathing, walls, flooring or roof decking.
Luckily for builders and DIYers alike there is such a material.
This material is known as OSB Sheet Material.
In this ultimate guide we’ll learn what oriented strand boards actually are.
How OSB is made as well as their benefits.
We’ll answer questions such as if oriented strand boards are waterproof and how they compare to plywood.
We’ll then finish up with a nice summary to bring everything we’ve learnt together.
So without further ado, let’s start getting into the nitty gritty of oriented strand boards or OSB for short.
Chapter 1: What is Oriented strand Board (OSB)
So first of all you’re probably wondering:
“What on earth does OSB stand for?”
Simple answer: ‘Oriented Strand Board’.
But now you’re thinking; great but what is ‘oriented strand board’? And why does everyone keep telling me I should use it for my DIY project?
Invented in 1963 in California by Armin Elmendorf oriented strand board (OSB) is a type of engineered wood. In fact it’s quite similar to particle board.
OSB is created using adhesives and layers of wood strands (hence the name). We’ll cover this process in much more detail in the next chapter.
These wood strands give OSB its distinctive look:
OSB usually has a rough and variegated surface. You can see the individual strips of wood used during its construction.
The wooden strips are normally around 2.5cm by 15cm (1 inch by 5.9 inches).
They are laid unevenly across each other in different types and thicknesses. This gives the OSB its strength.
Chapter 2: How OSB Is Made
We briefly touched upon the OSB manufacturing process above.
But let’s examine this process in more detail.
Starting with sourcing the wood and finishing with cutting and delivery.
Obviously oriented strand boards are made from wood.
But what wood?
And where does it come from?
First off OSB typically uses wood that comes from small-diameter logs which are normally from a fast growing species which themselves are from sustainably managed forests.
This includes species such as:
- Southern Yellow Pine
- Black Poplar
Ideally logs will be sourced fairly locally, perhaps 50 to 150 miles from the processing plant.
This helps to reduce the environmental impact and cost of shipping logs.
Once the logs arrive at the processing plant they need to go through a few different processes before they’re ready to be used in OSB manufacture.
First off the logs are debarked (sometimes bark will be used as fuel for plant operations).
The logs once debarked are fed into stranders.
Stranders are a tool which have a ring or fan of blades that are used to slice and dice the entire log. Creating strands of wood which are typically three to six inches long, one inch wide and 0.03 inches thick.
Any undesirable strands are removed and used as fuel.
With the log cut into strands it’s now time to dry them.
The wet wooden strands are placed in a dryer. The pieces tumble along the dryer which has temperatures that range from 1,500 F at the inlet to 200 F at the outlet.
Once the wooden strands have been thoroughly dried it’s now time to blend them together using a concoction of resins and waxes.
The specific mix of resins, waxes, wood mix, time of year all vary by manufacturer.
Once the strands have been mixed with the resin and wax they are layered into three to eight inch deep mats on a conveyor belt which is roughly eight to twelve feet wide. Then length of said mats are cut to fit the plant’s presses.
With the wooden strands in mat form they’re ready to be pressed and baked. These wooden strand mats are baked under pressure at 400 F. The typical pressure applied is 1,300psi.
The final steps start by allowing the boards to cool after they’ve been baked.
Once cooled they will be cut into size, such as four feet by eight feet. Some additions then may be added to them.
Finally they will be sent out to be delivered to their destination.
Chapter 3: The Benefits Of OSB
By now you should have a pretty decent understanding of one) what OSB is and two) how its produced.
So now let’s look at some of the benefits of oriented strand boards.
With continued advancements in press technology OSB manufacturing is incredible consistent.
This results in a very reliable and consistent product that end users are happy with.
Ultimately allowing for quick implementation of the oriented strand board as there are no unwanted surprises in shape, size, quality or finish of the OSB.
Oriented strand boards are incredibly versatile and strong due the fifty layers of wooden strands that are laid laterally and longitudinally during manufacturing.
This means that OSBs have many different uses such as; sub floor construction, walls, flooring and decking. Oriented strand boards are also available in many sizes which can be easily shipped and transported.
This just adds even more versatility to an already versatile product.
OSB is a remarkably cost effective building product and solution. It is significantly less expensive than the sometimes used alternative plywood.
In fact if OSB is used for sub-flooring, wall and roof sheathing builders can benefit from significant cost savings when compared to plywood.
Oriented strand boards unlike some other building materials are very sustainable and good for the environment.
OSBs are considered sustainable as they are made from strands of wood which come from small trees that come from sustainably managed forests.
Using small logs saves using more mature trees which are saved as a consequence.
Furthermore during the manufacturing process there is zero waste.
All parts of the log will be used. Whether that’s as fuel for the plant or wooden strands for the boards; there is no waste.
Finally, new resins and waxes are much safer to use than those used in the past.
Greater shear strength (than plywood)
Compared to their plywood alternative OSB have far greater shear strength.
Due to the layered method of manufacturing, OSBs are incredibly strong making them great candidates for many different applications.
Chapter 4: Is OSB Waterproof?
We’ve established that oriented strand boards are a great construction material which are strong with many possible uses.
However, are oriented strand boards waterproof?
And what happens if they get wet?
As a general rule, most OSB are water resistant. Due to their construction process using wood strands, resins and wax they come fairly water resistant.
However, if you’re looking for a truly waterproof OSB you need to make sure it is stamped stating so.
This will mean that your OSB has been specially treated to be waterproof and as such is good to go.
However, each time an oriented strand board is cut it creates an area where moisture or water could be absorbed.
So you may want to think about adding a further waterproof sealant to any OSBs you buy. Especially ones which you plan on using for exterior jobs.
As if an OSB does become too wet it is likely to swell (usually at the sides). If it does swell this can cause issues with construction
So if you are going to use oriented strand boards where they might be in regular contact with moisture we advise that you add an additional waterproof sealant such as: (name of sealant).
Chapter 5: OSB vs Plywood vs Chipboard
As we’ve touched on the main alternative to oriented strand boards is plywood.
Both OSB and plywood have their own distinguishing characteristics which causes them both to have their own advantages and disadvantages.
- Manufactured into larger panels than plywood offering more cost savings for builders
- OSB panels do not have core voids whereas plywood panels do
- OSB panels are more sustainable and considered to be better for the environment than plywood panels
- OSB panels are stronger and have more shear strength than their plywood counterparts
- OSB panels are cheaper than plywood panels
- Though plywood panels will expand when exposed to water or moisture they will typically dry faster than OSB panels. However, proper handling and due care should be used for both to minimise their interaction with moisture.
- Whereas OSB panels are manufactured from layered wooden strands plywood panels are manufactured from continuous pieces of veneer. This gives them a much smoother appearance which is better for painting or laminating.
Chapter 6: Conclusion
Summarise everything discussed above, including some general points about the advantages of this type of OSB, and the types of business that should think about using them.
By now you should have a pretty in depth understanding of all things oriented strand boards.
We’ve covered what they are and how they’re manufactured.
Covering the type of wood that is used to make them as well as the layering process.
We now understand why OSB is so popular and what the benefits of it as a construction material are.
We’ve also covered how waterproof OSB panels are as well as how they can be made more suitable for outside use.
Finally we’ve compared oriented strand boards with their closest rival, the plywood panel.
We’ll be updating this guide regularly with more helpful tips, so please bookmark it and pop back at a later date.