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Every woodworker has an opinion and experience with OSB. Many people hate it and a couple few love it. But even though many people do not like OSB it still has some uses and it is still valuable to know what it is, how it is made and when we would want to use it. So what exactly is OSB?
OSB stands for oriented strand board and is an engineered wood used mainly in construction. OSB is made of large wood chips that are oriented in different directions, mixed with adhesives, and pressed to a board in a heat press. The standard size of OSB boards is 4 x 8 ft (1220 x 2440 mm ).
OSB has a bad reputation, it is said to be of poor quality and to smolder up with the faintest touch of water. But the OSB technology is always improving and maturing, new boards of better quality and with more specialized uses reach the market every year.
But even though OSB has a bad reputation, it is still valuable to understand what OSB is so that you can make an informed decision if you want to use it for your next construction and woodworking project.
What is OSB?
You have probably seen OSB boards before when visiting your local home center or any construction site. Any home center will have OSB boards in different widths, thicknesses with some designed to be water-resistant and some just made to be dirt cheap.
OSB is an engineered man-made wood product with many of the same qualities as plywood and you can use oriented strand board in most of the same cases where you would use plywood. OSB is cut into large boards, which makes OSB a good choice if you have to cover larger areas with wood for a cheap price.
Many people choose to use OSB instead of plywood because OSB is cheaper.
OSB is usually cheap. Many times half the price of plywood. The reason OSB can be sold at such a low price is that the wood is sourced from quick-growing forests from trees such as Aspen, Poplar, and Pine. Since the trees are cut into strands the manufacturer does not have to be so picky on the width and size of the trees and can use trees that otherwise would go to waste. This helps to keep the cost of raw materials down.
Due to wood being pressed so densely together OSB becomes very heavy. A typical 4 x 8 feet board OSB that is 1/2 inch thick will weigh around 54lbs. The weight of the OSB board will of course change depending on the thickness, size, and type of wood used for the boards.
Pros With OSB
- Easy to find the right size boards
- Can make use of smaller trees
- Consistently stiff
- Sustainable materials used
- Less waste
- Can be made thick
Cons With OSB
- Swells up if water gets to it
- Bad at holding nails and screws
- Ugly Grain Structure
- Hard to paint (uneven texture)
How OSB Is Made | Step By Step
Logs Debarked: The first step of making OSB is acquiring the logs and debarking them. The bark is later used to create energy for the manufacturing process.
Cut to strands: The logs are cut into strands of similar sizes. The individual strands of OSB have a size of 1-inch x 6-inches.
Stands Dried: The Wood strands of OSB are dried in huge tumble dryers to a moisture content of 4% to 8%
Strands Mixed With Adhesives: Strands are mixed with adhesives that make the strands stick together when pressed. For the inner layer in OSB, Isocyanate or PMDI glue is used. For the outer layers, Melamine-Urea-Formaldehyde (MUF) or Phenol-Formaldehyde (PF) is used.
Mat Forming: The mix of adhesives and wood strands are formed into thick mats on conveyor belts. The mats are anywhere from 6 to 8 inches thick depending on the wanted thickness of the final board. The mat is separated at intervals and made ready for the press.
Pressing: Mats are pressed in a large hydraulic press or a continuous press. The illustration above shows a continuous press. The mats are pressed at up to 7500psi of pressure and at degrees of up to 400°F (205°C). And a mat will transform in thickness from 6 – 8 inches before pressing to 3/4-inches after being pressed.
Cooled: Now we have an OSB board. The board is cooled before further processing.
Cut to size: OSB boards are cut to the wanted sizes. The most common size for OSB is 4x8ft (1220 x 2440 mm). But can be acquired in many different sizes depending on need and can even be custom ordered and cut.
Sanding: Board is sanded before being sent for sale.
Packed and shipped: OSB boards are now ready to leave the manufacturing site, and the next stop is the countless home centers and stores that stock OSB.
5 Uses Of OSB
For many roofers, OSB is the best choice to use as roof decks. The main reason for using OSB as roof decks is the price. Other alternatives like solid wood or plywood usually come out to a minimum of two times the price of OSB.
And with an average roof size of residential homes of 1700 square feet, there is a lot of money to be saved.
OSB is becoming more and more popular to use for roofing and is slowly but surely taking over a larger part of the roofing market.
OSB does not handle moisture well and it will start flaking if exposed to moisture over time. So OSB is not recommended in moist climates or being exposed to the elements.
When roofing with OSB, it is important to use the proper thickness. Thick boards mean that screws and nails will be harder to pull out. At least 5/8 inch thick boards when roofing with OSB.
OSB can be used for furniture, but should it really?. Just kidding, it is totally fine to use for furniture, but making OSB look nice as furniture is an amazing achievement in itself.
I include furniture in this list because there has been a trend of creating OSB furniture in the last few years, just go and check Pinterest if you don’t believe me.
OSB is used to make tables, cabinets, shelves, sofas, beds, and everything else you can make out of wood.
But even though I don’t think OSB is particularly good to use for furniture, I still applaud the creativity of the people making them. It sure isn’t easy making OSB look presentable, and it must be even harder to work with.
Using OSB is a cheap way to get into furniture making.
I actually had an experience with OSB furniture at a restaurant the other day. The entire table was just a big OSB board with legs in it. I was kind of shocked, it wasn’t pretty but it seemed to work for them.
Construction is also one of the main uses of OSB and it is basically where the OSB boards are meant to be used.
OSB panel and sheeting are used anywhere you need to cover large areas with wood.
But as I said before, OSB should not be used anywhere where it is prone to being moist for long periods. So when used outside it is used underneath proper weatherproof paneling.
OSB can be used for any kind of DIY project that involves construction with wood.
If you just need some cheap construction material for your project, OSB can be a good choice.
OSB will usually not be used as the top layer of the floor cover, but OSB can be used as the sub layer of the floor. The sub-layer is the layer underneath the floor covering which is used for structural reasons.
OSB is becoming more and more popular to use as sub-layer flooring, and for the same reason as i have told you before, price. OSB is just cheaper than using plywood, OSB is stiff and has a consistent structure.
OSB can also be obtained in larger sizes, boards up to 8 x 24 (2.4 x 7.3 m) feet can be obtained from the manufacturer. This can also make the flooring job go faster, and save money.