What is OSB in construction

OSB panels: Popular in interior design

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Transport boxes, concrete formwork, prefabricated screed or cladding: OSB panels can be used in a variety of ways. Just like chipboard or MDF, this makes it popular in interior design. Do-it-yourselfers shouldn't forget that these panels are made of wood - and should be pretreated accordingly and protected from moisture.

Laying board, chipboard, OSB - three names for one and the same product. In technical terms, it is always wood-based panels, colloquially they are usually only called chipboard. They differ from these, however, visually: In contrast to the fine sawdust of a chipboard, the wood chips (strands) of an OSB panel are more like long, coarse wood chips. These are mechanically piled up in several layers and aligned in a special way (oriented). The oriented strand board, or OSB for short, is ready.

Both OSB and chipboard are available sanded and unsanded as well as a plug-in system with tongue and groove or with blunt edge, each in different thicknesses and sizes.

OSB: manufacture and standard

Formerly a waste product of the wood industry, the long chips for OSB panels are now cut from debarked trunks and then dried. After glue has been applied finely to the dry chips, they are arranged crosswise in three layers and pressed under high pressure and high temperature.

According to DIN EN 300, OSB panels are subdivided according to their intended use. The following applies: the higher the number, the more valuable and resilient the product is.

  • OSB / 1: Panels for general purposes for use in dry areas and for furniture construction
  • OSB / 2: Boards for load-bearing purposes for use in dry areas and for the production of packaging material
  • OSB / 3: Boards for load-bearing purposes in damp areas
  • OSB / 4: Heavy-duty boards for load-bearing purposes for use in damp areas

This is how the production of OSB panels works

Much discussed: Health hazard from formaldehyde & Co.

During production, the chips of the OSB panels are bound with different binders. The synthetic resins used often contain formaldehyde, but wood-based panels also contain other volatile substances (VOC), such as hexanal or terpenes. These binders can outgas and affect the air in the room. According to the Federal Environment Agency, there are no meaningful studies on the effects of these substances, but undesirable effects cannot be completely ruled out.

In order for building materials to be classified with regard to their health effects, the Committee for the Health Assessment of Building Products (AgBB) Test criteria and an evaluation scheme were developed.

In order to counteract damage to health, rooms in which wood-based panels have been newly installed should initially be well ventilated. One should bear in mind that the emission increases with heat and that formaldehyde takes longer to volatilize. Anyone who reacts to formaldehyde or other volatile ingredients should either avoid wood-based panels entirely or use coated and sealed products.

Areas of application for OSB panels: From shell construction to interior work to furniture construction

OSB is already used in the shell construction, as a building board or, for example, as formwork for concrete. However, the areas of application in interior design are far more diverse.

As pre-fab screed, OSB panels as well as chipboard are laid floating in one or two layers. If the floor is laid on relatively fresh screed, a vapor barrier should be installed; if the area is not built with a basement, it is better to use a vapor barrier. In addition to the vapor barrier as moisture protection, it should also be considered to avoid cross joints and to leave at least ten millimeters distance to walls or other adjacent components. Since tiles with tongue and groove are usually installed on the floor as an installation plate, the profiles should be glued.
The tongue is cut off for the first row of panels. This side then points to the wall at a distance of ten to 15 millimeters. Apply joint glue to the tongue of the next row of panels and push the profiles tightly into one another. Immediately remove any drops of glue with a spatula. At best, it is laid in a bond, so the joints are offset by about 40 centimeters from each other. The glued floor can be used again after around 24 hours. Finally, the floor can be protected against moisture penetration with a lacquer seal.

As part of the substructure of the floor covering, the panels can also be laid on beams or battens. The distance between the individual bars should not exceed 50 centimeters. With this construction too, moisture protection and sufficient air to the wall must be ensured. A creak guard is also recommended.

OSB panels are also used more and more directly as flooring, after all, the distinctive material has its very own effect. If you decide to do this, you should treat the wood with a colorless primer and then paint it with a matt or glossy finish. The joints remain visible, because the installation panels are simply plugged into one another at the tongue and groove and glued there.
If the OSB panels are laid over underfloor heating, Heimerker should opt for panels that are especially suitable for this use. If the wood-based panels dry out on one side, they can warp.

In interior work, OSB panels are used as cladding for walls in drywall construction or as roof cladding in roof construction. The versatile wood-based panels often form the end of the under-rafter insulation, especially if the roof insulation was added later to create more living space. For roof insulation and loft extensions, OSB panels are usually screwed directly onto the roof beams. In addition, tongue and groove can be glued together. The distance between the bars should be less than 60 centimeters.

In principle, OSB boards can also be used in damp rooms, but then they should be sealed and sealed with particular care. This is the only way to avoid moisture damage.

Of course, you can also build furniture with the chipboard. If you leave the surface and only seal it, you can even highlight the special look of the plate particularly well.

OSB as a vapor barrier

Due to their high vapor diffusion resistance (µ-value of around 200), OSB boards are principally suitable as a vapor barrier. However, there is heated debate as to whether they should be used in this function. The opinions range from “clear, no problem at all” to “in no case at all”. It is difficult to make a general statement, the local conditions have a decisive influence on a decision.

If OSB boards are to be installed as a vapor barrier, the board joints may have to be taped on the inside with special adhesive tape. Otherwise, if the panel shrinks, a joint can occur and moisture can penetrate.
If the joints lie directly on the stand construction or the rafters, masking is not necessary, and neat nailing is sufficient in most cases.

It should be borne in mind that in most cases the panels must have a certain thickness - which puts a not inconsiderable weight on the rafters. In many cases, do-it-yourselfers should better use a film as a vapor barrier or vapor barrier.

Before installation and further processing

Before OSB boards are processed further, they should first acclimate for about 48 hours. Once they have been installed, the surface should be treated or the top covering applied within the next 36 hours. If the panel is only painted afterwards, it can happen that the panel edges bend upwards.

When installing panels with tongue and groove profiles, follow the manufacturer's installation instructions.

Painting: paints, glazes, waxes and oils for further processing

If the OSB board is firmly mounted on the wall, it can be processed further. The surface should be dry and free of dust and grease. If sanded panels were installed, an even coating is guaranteed. If you want to process unsanded panels, you should take the time to smooth the surface.

Care should be taken when applying water-based paints. The OSB material can withstand light, briefly acting moisture, but not moisture - the panels can bend. This risk is lower if solvent-based paints or wood oils are used or if the panel is treated with a barrier primer before applying varnish or glaze.

Sanding and impregnating protect light colors in particular. The wood chips on the board contain pigments and tannins that can migrate into the paint over time and turn it yellow.

Further processing: wallpapering

Most manufacturers advise against wallpapering OSB, as wood-based panels can expand due to moisture. The wallpaper would tear at the board joints. If you still want to wallpaper, you should either clad the OSB panels with gypsum fiber or gypsum plasterboard or glue on a crack-bridging reinforcement fabric and fill it.

Alternatives: chipboard, plasterboard and gypsum fiber in comparison

In addition to OSB, chipboard or medium-density fibreboard (MDF) are also wood-based panels:

With chipboard, finer wood chips are dried, usually glued with formaldehyde resins and pressed into panels under heat. In contrast to the coarse-chip OSB board, the chipboard is equally strong in both bending directions. Chipboard is often coated with a film, decorative paper or veneer and is then primarily used in furniture construction. This sealing cover layer can also reduce the amount of evaporation.

For medium-density fibreboard (MDF), wood chips are ground very finely. The material is therefore even more homogeneous and stronger than conventional chipboard.

Especially when used in damp rooms, it is recommended that do-it-yourselfers fall back on the easier-to-process and already pre-impregnated, green plasterboard or gypsum fiber boards:

While gypsum plasterboards only have a gypsum core with a cardboard lamination, gypsum fiber boards contain additional reinforcing fibers. This makes them a little more complex to work with, but also more stable.

Cement-bonded building boards are also available for do-it-yourselfers. These consist either of coniferous wood chips, Portland cement and aggregates or are purely mineral.

materialadvantagesdisadvantage
OSBstable and resistant to bending
high water vapor diffusion resistance of μ 200/300, appropriately installed OSB can act as a vapor barrier
high heat storage capacity (good for summer heat protection)
less formaldehyde vapors than chipboard
resistant to bending in one direction only
possibly a vapor barrier effect is undesirable
Exhalations
must be sawed
Joints in the visible area difficult to fill
Chipboardstable and resistant to bending
high heat storage capacity (good for summer heat protection)
inexpensive
possibly high formaldehyde vapors
must be sawed
Joints in the visible area difficult to fill
Plasterboardinexpensive
easy processing (scoring, breaking)
moisture buffering
fire retardant
Wallpaper is difficult to remove
Plasterboardstable
no vapors
must be sawed

 

Isabella Haag


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