What is better plywood or OSB - comparison of materials

Plywood and OSB (OSB, OSB) are two materials that have similar characteristics and are used in similar situations. However, there are differences between them, which for some cases may be important. In order to choose the most suitable material and not make an unfortunate mistake, it is worthwhile to understand their parameters and features that determine the answer to the question of which is better, plywood or OSB for a specific application.

OSB and plywood are twin brothers?

The main difference between these materials is that the plywood is made from several layers of veneer, and for the production of OSB, wood chips are used - actually wood processing waste. Accordingly, their appearance is different. The plywood has a flat surface with a natural wood structure, and the OSB is similar to a compressed scattering of chips and large chips.

The name OSB is an abbreviation of the words Oriented Strand Boards, which means "Oriented Chipboard". OSB is an abbreviation of translation into Russian, and OSB is a transliteration of the English name.

Otherwise, these plates are very similar. Wood chips in OSB are arranged in three layers, in each of which it is oriented perpendicular to adjacent layers.

The veneer structure in adjacent layers of plywood is also located at right angles to each other.

The bending strength of both materials depends on the direction of the bend - along or across the structure of the outer layers. For bonding plywood and for forming OSB, the same binders are used - urea and phenolic resins.

Differences in the raw materials and the technology of forming the slabs give a discrepancy not only in appearance but also in technical characteristics, and these differences can determine the answer to the question of which is better, OSB or plywood for each specific case.

Given that there are several brands of OSB and plywood that differ in their parameters, for a correct comparison we will use OSB-3 and plywood of the FC and FSF brands, since these versions of materials are most often used for a variety of purposes. For the correct use of regulatory data, slabs up to 30 mm thick are involved in the comparison.

What is stronger than plywood or OSB

Speaking about the strength of sheet and plate materials, they usually mean bending strength. Tensile strength is the maximum bending stress that does not lead to destruction of the material.

Another important aspect of strength is the resistance to delamination, which is defined differently for different materials, but has the same practical meaning.

Durability under normal conditions

According to GOST R 56309-2014, the standard bending strength along the main axis for OSB-3 ranges from 16 to 22 MPa, depending on the thickness of the sheet. In the transverse direction, the strength is two times lower.

Technical parameters of plywood are determined by GOST 3916.1-96. In accordance with it, the bending strength of plywood along the fibers of the outer layers is 25-60 MPa, depending on the type of wood used and the brand of plywood.

That is, a strength comparison is clearly in favor of plywood. This is not surprising. The natural structure of wood, preserved in veneer, holds tensile loads much better than agglomerate from wood chips and a binder.

Plywood has 2–4 times higher bending strength than OSB.

Moisture resistance

To determine the moisture resistance of materials, there are many different methods, and they use different control parameters. In order for our comparison to be correct, we choose the data obtained with the same test method, recorded in GOSTs No. P 56309-2014 and 3916.1-96.This is a test boiling test method.

After exposure to boiling, the OSB-3 flexural strength decreases to 6–9 MPa, that is, approximately twice as compared to the initial one. The bending strength of plywood under such an impact varies little and is not standardized due to the fact that even intensive moistening with subsequent drying practically does not affect the strength of wood fibers, and this is what determines the strength of a laminated veneer plate.

The greatest influence of humidity has on the resistance of the boards to delamination. It is the weakening of bonds between the woody parts of the material that is the main reason for the decrease in bending strength for OSB.

The tensile strength in the direction perpendicular to the plane of the board for OSB and plywood is measured differently, but the same dimensionality of the results makes it possible to compare them.

The strength of plywood to shear along the adhesive layer after boiling is 0.6–1.5 MPa, and the tensile strength of OSP-3 in the direction across the bed is 0.06–0.15 MPa. Here, as we see, the strength differs by an order of magnitude.

Plywood has a higher moisture resistance than OSB due to the fact that in each layer a single wood structure is preserved, not fragmented, as in the case of chipboard.

Weight Comparison

The weight of the plates is determined by their size and density. It makes sense to compare exactly the density of the material. This indicator may vary from manufacturer to manufacturer. It changes with humidity fluctuations, including when the season changes. Most OSB boards have a density of about 650 kg / m³. Moreover, the thinnest sheets have the highest density. According to GOST, they have the highest relative bending strength. For plates with a thickness of 18–20 mm, the density decreases to 635 kg / m³.

Plywood has a density of 670 - 680 kg / m³. Some varieties, usually from birch veneer, reach 750 kg / m³. They are also distinguished by the highest strength.

Plywood is slightly heavier than OSB, but for most applications this difference is not significant. And taking into account the higher strength of plywood, the weight of structures made of it can be even less due to the use of thinner sheets.

However, the answer to the question of which is better, OSB or plywood, can be given only taking into account other qualities, including the cost of materials.

What is cheaper plywood or OSB

Confronted with plywood or OSB, which is better for the floor, for the base of the roof or for sheathing the frame, it is important to consider the price of materials.

In terms of cost, OSB wins significantly compared to plywood. It is quite simple to find out if you compare the price of sheets of the same thickness and bring it to one square meter. To avoid confusion, it is better to immediately divide the plywood by type (FC or FSF) and by grade.

• FC 3-4 grades are more expensive than OSB 1.1-1.3 times.
• FSF 3-4 grades are more expensive 1.6–2 times.
• Higher grades of plywood are 2–3 times more expensive than OSB-3.

Manufacturability

The technology for using plywood and OSB is almost the same. Sheets are cut on special machines or by hand tools. The processing of the ends of the parts is also very similar. But OSB gives more flakes when cutting with a jigsaw or non-specialized circular saw. Therefore, to obtain a smooth edge requires a deeper grinding of the ends.

The complexity of processing the formation depends on the type of plate and surface requirements. First-class sanded plywood requires no processing.

OSB does not give such an opportunity. Therefore, plywood should be considered a more technological material. The ability to hold fasteners is equally good for these materials.

Flammability

Both plywood and OSB belong to the G4 combustibility group. It means:

• materials are flammable;
• spread the flame and burn out completely even when the external heat source disappears;
• form a large amount of flue gas with high temperature.

There are no differences in fire hazard class between them.

Plywood or OSB - which is more environmentally friendly

Environmental issues of these materials arise in connection with the use of urea-formaldehyde resins for their production. These resins serve as binders, but they are a constant source of volatile formaldehydes harmful to humans.

According to the degree of danger, these plates are divided into classes (emission classes). Materials of class E2 and higher are used only for technical purposes, outside residential premises. Class E1 is allowed for residential premises, children's and medical institutions. Most wood composites used today belong to the class E1.

In the current GOSTs, there is one difference between OSB and plywood. For chipboard, class E0.5 is provided, and for plywood - only E1. Although this does not mean that in the world there is no plywood with a class of E0.5 or even E0.

Modern environmental standards have equalized plywood and OSB, and made them equally safe.

Assortment of OSB and plywood

Both plywood and OSB can have different sizes and thicknesses. OSB can have a thickness of 6 to 40 mm in increments of 1, and plywood from 3 to 30 mm in increments of 1–1.5 for thin sheets, and in increments of 3, starting with a thickness of 9 mm.

The standard OSB sizes are 1220x2400 or 1250x2500 mm. GOST defines a minimum size of 1200 mm. The maximum depends on the capabilities of the production equipment. Plywood is produced in 1220x2440 and 1525x1525 mm formats.

The actual range available on sale differs from production standards. So, OSB is most often sold with a thickness of 6.9,12,15 and 18 mm. Often, trade organizations cover standard sheets on two or four parts of the convenience of retail customers.

Aesthetics

When comparing the appearance of materials, deciding which is better, OSB or plywood on the floor, on wall linings or for furniture, several factors should be considered.

At first glance, plywood seems more aesthetic than OSB. But in fact, it is very diverse. Its appearance is determined by the type of veneer of the outer layers and its quality. Low-grade technical plywood can hardly be used for interior decoration or for facade furniture parts. She has many knots and other defects.

For furniture and finishing works, grades 1–2 plywood are used, on the surface of which there are very few or no defects. In terms of aesthetic qualities, such material is not inferior to solid wood. Plywood of lower grades in its pure form is unsuitable for decoration, except for its use in non-standard design solutions.

In custom finishes, you can use OSB. With the help of special processing, its surface structure can be turned into a good decoration. But still, particle boards are more appropriate as a structural or underlying material that does not catch the eye.

Final Comparison of OSB and Plywood

 

OSB and plywood are very close in physical and technical qualities and have deeply intersecting applications. Knowing the characteristics of these materials will help optimize the selection and achieve the best combination of strength, reliability, safety and cost-effectiveness of structures.