How is plywood different? Plywood classification

The difference between FSF and FK plywood lies in the composition of the glue that connects the veneer layers. For FC, this is urea-formaldehyde glue, and for PSF, it is phenol-formaldehyde. The first one tolerates moisture worse, so FK plywood, although it does not let moisture through, swells after a while. Therefore, FC plywood is not suitable for outdoor work, installation of street trends and panels, as well as for rooms with high humidity. The main area of ​​application of FC plywood is interior wall decoration and furniture manufacturing. Main advantages:

• Environmental friendliness;
• Low price.

The glue found in FSF plywood provides better moisture resistance, but is toxic. Therefore, such plywood is used mainly in production conditions, as well as in outdoor work. But the differences between FK and FSF plywood do not end there. Since FSF plywood is better suited for production conditions and transport, a refractory grade of plywood was made. But FSF plywood contains phenol, which does not allow the use of this plywood in the manufacture of furniture and in the decoration of domestic premises.

Based on the scope of these types of plywood, they are made from different types of wood. There are several criteria for distinguishing FK plywood from FSF. Plywood FC does not contain phenol, so it is lighter. In order to determine the type of plywood, you need to look at the cut. For FSF plywood, the cut will be darker, with a reddish tint. It is important to distinguish these types of plywood from each other, as they, despite the similar appearance, have different uses.

The choice of any variety (modification) of products from one group of goods always raises many questions. The main reason is that it is sometimes difficult even for a specialist to find differences between samples, since in many parameters (size, appearance, color scheme, etc.) they are often almost identical.

It is even more difficult for a potential buyer, since it is not always possible to place products side by side and make a comparative analysis of the structure, shades, or something else. This fully applies to plywood. FK and FSF have a difference in individual characteristics (physico-chemical, technical), which determine the specifics of the use of sheets. So what is she?

Focusing only on the abbreviation indicated on the plywood price tag is not entirely correct. Moreover, the difference between FK plywood and FSF is not only in some operational parameters, but also in cost (although not so significant). It is hardly appropriate to hope for professionalism, and even the decency of the seller, if the building material is not purchased at a specialized outlet. Therefore, when buying, be sure to make an external inspection of the sheets. Such meticulousness will help not only to identify defective samples, but also to make sure that this is exactly the type of plywood that is needed.

Unfortunately, it is not uncommon for unscrupulous merchants to go for an obvious forgery, hoping for the incompetence of the buyer. Otherwise, it is not a fact that after the repair, after a short time, you will not have to deal with restoration, alteration, or even complete dismantling of the entire structure.

Plywood FK and FSF have a lot in common. This is what often confuses potential buyers. For example, both plywood belongs to the category of "moisture resistant", "multilayer". Yes, and the varieties of veneer are the same - coniferous wood (pine), hardwood (birch, sometimes alder in FK) or a combined version. The fundamental difference is in the adhesive composition, as evidenced by the product labeling.

• F - the letter in the first position in the designation of all modifications of the sheets. It stands for simply - plywood.
• K - urea-formaldehyde composition.
• SF is already a slightly different adhesive, resin formaldehyde.

It is the means used for fastening the veneer in these modifications of the wood-laminated board that determines the properties of one or another type of plywood.

The difference between FC and FSF

It is easier to understand if you compare the sheets on the most important performance characteristics of plywood.

Damp resistance

The adhesive used in the manufacture of FC is destroyed upon contact with moisture (this process begins in about an hour). As a result, sheets of this type of plywood deform when wet; even veneer peeling is possible. But the restoration of the PC geometry during drying does not occur. Therefore, after the cause has been eliminated (excessive moisture, leakage from the water supply system), the sheet will have to be unambiguously replaced.

With the FSF, it's a little different. The sheet in such conditions will only swell, but then it will take its former shape. That is why this modification of plywood is recommended for use outside buildings - a continuous crate under the roof, sheathing of the "skeleton" of the structure when erecting gazebos or other buildings in the country house, adjacent territory, and so on.

When purchasing FK plywood for interior work, you need to focus on the specifics of the room. If it has constantly high humidity (kitchen, unheated basement, cellar, garage), then it will not last long under such conditions. So, you have to deal with the surface protection of the sheets. What it will result in (processing complexity) and how much it will cost - that's what should be taken into account. Perhaps, instead of FC plywood, it is better to buy a different sheet (board) material (OSV, chipboard, etc.).

Strength

According to this indicator, FSF plywood is the leader. For loaded structural elements - just right. But FC is most often used only for sheathing, as a future basis, for example, for pasting walls (internal partitions) with wallpaper. An intermediate option is multilayer assemblies. The lower level is FSF (for reliability), the upper level is FK, since it is easier to varnish.

"Ecological cleanliness"

An important indicator. Especially when you consider that various "chemistry" in everyday life surrounds us literally from all sides. In this regard, FC plywood wins. In the composition, which fastens its veneer, there is no formaldehyde in its pure form. Therefore, there are no harmful fumes. This is one of the factors why FC is recommended for interior work. PSF is more "poisonous" (due to the toxicity of the adhesive), so if it is used indoors, then only non-residential. Moreover, provided that the temperature in them does not rise to high values.

This is not a mandatory requirement, since not a single regulatory document indicates a direct ban on the use of FSF inside buildings. But it's better not to experiment. If there is no other choice, then it is worth considering this feature of this type of plywood.

Plywood FK, taking into account the specifics of the adhesive composition, is more suitable for use inside buildings (structures) as the safest from an environmental point of view, but less resistant to moisture. FSF sheets are recommended for outdoor use, moreover, they practically do not absorb moisture. Consequently, they will serve in such conditions much longer than FC.

The author deliberately does not give approximate prices for sheets, since they vary significantly depending on the manufacturer, the region of sale (and, therefore, plus transport surcharges), as well as the geometry of the samples and their thickness. Generally speaking, FC is somewhat cheaper than PSF, which is easy to guess, knowing the differences between these plywood modifications.

A reader who has read this article will involuntarily have a question - there is enough information, everything is written clearly and understandably, but is it possible to visually distinguish FC from FSF without having special training so as not to trust the seller too much? Yes, and it's easy to do.

When choosing plywood, you need to carefully examine the end of the sheet. In FC, the adhesive layer is lighter than in PSF. This is immediately noticeable. Moreover, it is not necessary to put samples side by side and compare. If you look closely, the glue in the FSF plywood structure is not just dark, but with a certain reddish tint. In FC, it is more reminiscent of fresh linden (or May) honey. The difference is obvious - this glue is light (as a rule, it matches the veneer).

If fire resistance is an important aspect of using plywood in a particular case, then you should focus on FSF sheets, the marking of which contains the letters TG. These are samples with extremely low flammability, that is, the category of “hard-to-combust materials”.

Everything else - the quality of grinding, deviations from the declared linear parameters, the number of knots per unit area (grade of goods) and the like - is a topic for a separate discussion.

Well, what kind of plywood to purchase, only you, the reader, will have to decide. Knowing why it is needed and the fundamental differences between the sheets of FK and FSF, it is easy to make the right choice.

When carrying out certain construction and repair work, it is fundamentally important to know what is the difference between FK and FSF plywood. Outwardly, at a glance, it is quite difficult to distinguish one species from another; only an appropriate specialist can handle this. The visual difference can be found in the color of the interlayers: in FK they are lighter, have a shade of veneer from which the sheet itself is made. PSF is layered with darker glue, which has a slightly reddish tint.

However, the average user will be able to notice such subtleties only if you put the samples next to each other. Meanwhile, when buying plywood for repair and construction purposes, you need to know exactly what to take, since both the physico-chemical characteristics and the purpose of these types are quite different. You should not make a mistake even if you value health (for yourself and your family) and want to get reliable and beautiful repair results that do not require an urgent rework soon.

What is the difference between FK and FSF plywood and what is each of them intended for? The tasks and some technical characteristics of the compared materials differ. What and how - we will try to tell in detail in this article. We hope that our advice and recommendations will help you to approach responsibly the choice of interior and exterior finishes.

What is hidden behind the letters "FK" and "FSF"?

Any plywood sheet is a minimum of 3 (more often - even more) layers of wood veneer, each of which is perpendicular to the previous one. Due to this arrangement, significant strength and ability to maintain a given shape is achieved. Pine and birch are most often used for veneer, although plywood can also be made from other types of wood, mainly hardwood. The most common types of plywood are:

• birch - all layers of veneer are made from the corresponding tree;
• coniferous: only pine went to the veneer;
• combined - the middle layer is made of pine veneer, the outer ones are made of birch.

The very name of plywood already contains an indication of the type of glue that went to connect the individual layers. So, "FC" is deciphered as follows:

• "F" - plywood;
• "K" - urea-formaldehyde glue.

Plywood FK is produced more often from birch or alder - deciduous trees, conifers usually do not participate in it.

In the abbreviation "FSF", the first letter means the same plywood, and resin formaldehyde glue is hidden behind the SF.

Differences between FC and FSF

The whole difference is determined by the glue that is part of the sheets.

Environmental friendliness

In this regard, plywood of the FK brand is cleaner: during its operation, phenols simply cannot physically be released - they have nowhere to come from. PSF contains phenols in an amount of 8 mg / 100 g - an indicator not too high, but considered unsafe in residential areas. In order to maintain fairness, it must be said that the FSF emission class is assigned to E1, that is, there is no direct ban on its use in dwellings. But where there is an opportunity to avoid it, it is still worth using it and not using this material.

Water resistance. In this regard, formaldehyde glue provides higher performance. Strong wetting of the PSF causes the plywood to swell, but after drying, if it did not stay in the wet state for long, the PSF returns to its original dimensions, and this practically does not affect its appearance and properties. FC, on the other hand, from moisture will certainly either begin to exfoliate or curl. The reverse mission of restoration is impossible, the loss of appearance and characteristics occurs irrevocably.

Application area

It is determined by the above features of building materials. Experts recommend using FC only in interior work due to low moisture resistance, including children's rooms - and also due to the safety of this plywood. PSF, due to the harmfulness of the components and good water resistance, is more often recommended for outdoor use, in particular for the manufacture of frame structures.

Strength

It is larger for the FSF, so such sheets are used for the manufacture of supporting structures. For example, this plywood can be used for subfloor equipment, provided that a continuous finishing coating is laid on top. If plywood will act as the top layer, for example, varnishing of sheets is planned, then the FK brand is taken.

The decorativeness of both types of plywood is approximately the same and depends on the class - the higher it is, the less knots and defects on the sheet. But due to the shade imparted by the PSF glue and insufficient environmental friendliness, FC is used in finishing work.
The combustibility of both types of plywood is the same, with the exception of the FSF-TV brand: it is known as "hard to combust" and is used in car building.

Worthy alternative

If for some purpose you need plywood that combines the advantages of both described types and is devoid of their inherent disadvantages, pay attention to sheets marked FB. The third letter in the abbreviation indicates the solvent base for the adhesive resin: B - water-soluble, C - alcohol-soluble. The high characteristics of FB plywood are due to the peculiarities of its production: before pressing with glue, the veneer is impregnated with bakelite varnish (it is this that is meant by the letter B). This technology provides high physical and technical characteristics:

• FB plywood has the highest water resistance: it can be used even in sea water, due to which it is widely used in shipbuilding;
• the material is refractory, does not ignite, and when exposed to temperatures of the order of 350 Celsius, it chars, but does not burn;
• FB is non-toxic, can be used even in children's institutions;
• plywood does not deform at temperature drops in the range from minus to plus 50;
• it is not affected by many aggressive media that are harmful to wood: gasoline, weak acids, kerosene, oils, alkalis;
• FB weighs more than wood, but it doubles in strength;
• without the slightest changes, FB plywood serves in difficult conditions for up to 10 years.

An interesting fact: it was from it that kamikaze planes were constructed, from which the idiomatic expression "plywood over Paris" appeared. So the material can be considered unique and devoid of flaws. Except for one thing: FB costs 2-3 times more than FK and, moreover, FSF, and therefore it is usually used in industry and large-scale construction. And ordinary people, having found out what is the difference between FK and FSF plywood, make a choice between these two brands: for repair purposes, their qualities are usually more than enough.

Task number 1 that an ordinary buyer sets: how to buy the required brand and grade of plywood for your tasks without overpaying? The range of plywood is huge, let's look at the differences.

Plywood grade - what's the difference?

In fact, it's just an appearance. And that's it. You will notice visual differences in the quality of the outer layers of the veneer. The grade does not affect strength and other characteristics. The exception is grade E (elite), but we do not consider it, those who need it know the difference very well.

Sanding plywood - why is it important?

In general, it is convenient, such a sheet pleases with its appearance and touch. Sanded plywood is taken for furniture, for painting, quite often for flooring (the so-called subfloor). In most cases, one-sided grinding (marking Ш1) will be enough for you - it will come out cheaper.

Plywood brand

It's more interesting here. difference in properties. Water resistance depends on the brand most of all. It is affected by the type of adhesive composition: the most popular are FK - compositions with carbamide resins and PSF are used - adhesives based on formaldehyde resins. It is customary to consider the FK brand to be moisture resistant (normal water resistance), and the FSF brand to be water resistant (increased water resistance, in terms of GOST).

In 99% of cases, for interior work, the FK brand will be enough for you (an exception may be the floor in a private house that is constantly in moisture). By the way, the FK brand is more environmentally friendly than the FSF, so it is more suitable for interior work.

FSF - take more for outdoor work. It is possible to use FSF in arranging formwork, but if this is not a one-time job, then laminated plywood is more suitable.

By the way, as regards laminated plywood, it so happened that we have formwork structures - this is its main application. In this regard, the most popular thicknesses of laminated plywood are 18 and 21 mm.

There are also special brands - bakelized, aviation, etc. We do not consider them, who needs them, he knows why.

Geometry and more

Thickness. The biggest dilemma here is what to take on the floor. In general, there is such a rule that at least 3/4 of the thickness of the subsequent floor covering. From experience - they don’t take less than 10mm on the floor. For residential premises with a small load, this is usually a thickness of 12-15mm. Here, it is not the thickness, the quality with which the sheets will be laid, that is more important. 18mm plywood can also creak and sag beautifully.

There is nothing to advise on the format - it is chosen based on their design needs. The most popular format of the FK brand is square sheets 1525x1525mm.

There is also such a factor as the manufacturer: the price may differ by 20% or more. For example, laminated plywood is successfully produced by both China and the Russian Federation. Guess what is cheaper :) There are really many manufacturers of plywood with the same marking - it is better to be interested in the differences at the supplier's place. Touching the product is also a significant factor in the choice.

Plywood is an artificial sheet building material. It is made by tightly gluing and pressing an odd number of thin layers of wood (veneer) in such a way that the fibers of adjacent layers of veneer are mutually perpendicular. In this case, the plywood sheet must be symmetrical with respect to the middle (central) layer of veneer. Thanks to this technology, the plywood sheet has excellent characteristics in terms of strength, durability, load resistance, impact resistance and moisture resistance.

Plywood is classified: by brand, by type of wood, by surface grade, by degree of mechanical surface treatment, by content of free formaldehyde.

By grades, plywood is mainly divided into four types: FK, FSF, FB, FOF.

"FK" and "FSF", "FB" or "FOF", denote resistance to moisture, which is determined by the type of adhesive and coating of the top veneer of the plywood sheet. Plywood is glued with synthetic thermosetting adhesives: phenol-formaldehyde and carbamide.

• Plywood FC- medium water resistance or moisture resistant. Glued together with adhesives based on carbamide resins. Recommended for use, as a rule, indoors.
• Plywood FSF- increased water resistance. Bonded with adhesives based on phenol-formaldehyde resins. Recommended for use both indoors and (mainly) for outdoor use.
• Plywood FB- bakelized plywood. Each layer of veneer of such plywood is impregnated with bakelite varnish, after which it is glued together with glue based on phenol-formaldehyde resins. Recommended for use in aggressive environments, tropical climates, aquatic environments. Scope - aircraft - shipbuilding.
• Plywood FOF(laminated plywood) – birch plywood of the FSF brand lined with a film coating (high-density paper impregnated with synthetic resin) on one or both sides. Recommended for outdoor use. Scope (mainly) - monolithic construction, formwork structures.

By the type of wood from which plywood is made.

Depending on the type of wood used for the manufacture of plywood, such main types of plywood as birch (made from hardwood veneer), coniferous (made from softwood veneer) and combined plywood are divided. As a rule, plywood is considered to be made from the type of wood from which its outer layers are made.

birch plywood- for the production of furniture and interior decoration, medium moisture-resistant plywood of the FK brand is used, and for outdoor work, birch plywood of increased moisture resistance of the FSF brand is used. Birch plywood is also used in the manufacture of containers and packaging.

Coniferous plywood- highly resistant to decay and fungal infection. Coniferous plywood has such qualities because the needles are impregnated with resins and have gluing based on phenol-formaldehyde glue. Coniferous plywood is used for roofing. Coniferous plywood will serve all term of service of a "soft" roof.

According to the surface grade, depending on the appearance of the outer layers, the following main grades are distinguished: grade I (or 1), grade II (or 2), grade III (or 3), grade IV (or 4), grade V (or 5). The variety designation consists of two numbers - two sides of the sheet and is written through a slash (fraction) as follows: 2/3, 4/4, etc. or II/III, IV/IV, etc.

In some cases (European designations), plywood grades can be designated by the letters: E (elite), A, B+, B, S, Bs, BBx, BBxs, BB, CP, CPs, C, WG.

Determinant of grade - the number of knots per 1 square. m surface of the outer sheet.

Plywood of the first grade- plywood that has practically no external defects. Only a few healthy intergrown knots with a diameter of up to 8 mm and slight brown veins are allowed.

Second grade plywood- plywood that allows minor restoration of the sheet surface with the help of veneer inserts and patching of knots and open defects.

Plywood of the third grade differs from the first and second in that such plywood is used for the manufacture of structures hidden from the visual view. It is used for various special containers and packaging. By and large, the third grade is what is rejected from the second.

Plywood of the fourth grade- plywood allowing all production defects. This concerns, first of all, knots, which can be an unlimited number. The main thing is that the manufacturer guarantees good gluing of sheets. Plywood of the fourth grade is used in the manufacture of containers and packaging.

According to the degree of mechanical surface treatment, plywood of the following types is distinguished:

• NSh - unpolished;
• Ш (Ш 1) - polished on one side;
• Ш (Ш 2) - polished on both sides.

A letter indicating the degree of machining is added to the designation of the grade and grade of plywood.

For all types of sanded plywood, it is mandatory to indicate the free formaldehyde emission class E1 and E2. The quality of sanded plywood is assessed by many indicators, for example: chipping strength, static bending, sample tensile strength, as well as the following indicators - moisture content, the presence of defects. The thickness of sheets (plates) of sanded plywood is produced from 4 to 40 mm. Plywood is sanded to create a smooth plywood surface and equalize the thickness, remove dirt and scratches.

• plywood E1- the content of formaldehyde per 100 g of absolutely dry weight of plywood is not more than 10 mg inclusive.
• plywood E2- formaldehyde content per 100 g of absolutely dry weight of plywood from 10 mg to 30 mg inclusive.

The main factors in the overall assessment of the quality of a plywood sheet are the tensile strength in shearing, in static bending, and tensile strength of the samples. Important properties - moisture content, structure, color of knots, the presence of defects.