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Products> OSB FAQs> Applications


Use & Applications

Where can OSB be stored?

OSB is mainly used in the construction of new timber frame houses with standard or high energy saving requirements (low energy, passive or zero energy houses), but also for refurbishment of existing houses, for attics conversion and/or for adding storey.

There are many other possible side uses of the product, such as manufacturing of structural I-joist beams with OSB-webs, concrete shuttering, job-site hoarding, construction of stages, billboards, cabinets, shelves, packaging, garages, site barracks, exhibition stands, storage rooms, animal shelters, etc – in other words, whenever a rigid and affordable board is needed for indoor or limited outdoor use.

What are the main structural applications of OSB?

OSB is used as a stiffening or load-bearing component of the main structural elements of timber frame houses:

  • Walls (External / Internal) - wall sheathing on studs
  • Floors - structural floor decking on joists (subfloor), rigid underlay for floor covering in floating floors and/or structural floors


  • Roofs - roof sheathing on rafters (rigid underlay for roof covering) or below rafters Staircase - steps (rigid underlay for steps covering)

External Use

Can OSB be used on the outside of the building envelope (external to studs/rafters)?

OSB 3 or OSB 4 TOP can be installed as outside sheathing, but only covered by additional skins, such as cladding (ventilated or non-ventilated fa├žades) or roof covering (asphalt shingles, metal roofing, clay/concrete tiles, etc). Leaving OSB exposed (not protected) to weathering is not allowed!

Are there any boards that can be used externally?

Yes, wood-based panels certified as service class 3 (exterior grade) can be used.

Expansion Gaps

What are expansion gaps and where should they be provided?

Expansion (dilatation) gaps are narrow distances that must be provided at the panel joints when fixing straight-edge OSB boards on supports, in order to avoid dilatation stress on the board’s edges that could lead to buckling and disturbing squeaking noises.

Expansion gaps allow the boards to expand unrestricted before reaching the equilibrium moisture, which is likely to happen if the panels were not conditioned to the end-use climate before being installed.

The following rules must be noticed:

1. A dilatation gap of 2-3mm must be provided between all adjoining boards when fixing them on the supports; the gap must be continuous on all the 4 edges of each panel

2. A dilatation gap of 15mm between the floor-decking boards and the walls must always be left on the room perimeter if T&G panels are used; if using straight-edge panels, the expansion gap can be lower and should be calculated

3. A dilatation gap of 25mm must be left from the floor when fixing the boards on the studs, for the wall sheathing

4. A permanently elastic expansion gap of 10mm must be provided every 10m of continuous sheathing (floor, roof, wall)

For more details regarding correct installation of panels, the manufacturer’s guideline must be consulted.

Fixing & Gluing

Are standard carpentry nails with smooth shank recommended for fixing OSB on supports?

When fixing OSB, priority should be given to the use of galvanized wood screws (self drilling or self tapping), spiral / ring nails or staples.

Smooth shank nails are less suitable, because of their lower pull-out resistance.

Please follow the general installation instructions of the OSB manufacturer regarding the fasteners selection and the fixing distance.

Can OSB boards be glued to one-another, in the case of multi-layer sheathing?

Yes. When two boards are needed to be fixed to one another - for instance, in the case of a double layer floating floor - gluing is also a possibility. Permanently elastic adhesives based on polyurethane or silane are suitable.

Sanded boards are more suitable for gluing. If using unsanded panels, it is mandatory to slightly sand the surface before applying the binder, to increase the glue adhesion.

Exception is given to OSB 4 TOP, using the glue type Purbond HB 180/440/530.

The base boards must be plane, strong and dry, free of any loose or crumbly particles and free fromf oil, dust and dirt.

The adhesive can be applied either spread on the whole surface by means of a notched trowel, or „on-bead“ by using a gun in longitudinal continuous lines spaced 120-150mm.

Surface treatment & panel finishing

Can OSB boards be plastered, painted or wallpapered?

Yes, but in order to avoid the visible undesired "bleeding stains" of the support, we highly recommend to use sanded OSB panels and to apply 2-3 thin layers of primer before starting to plaster or paint.

Also, we recommend to perform the so called "paint test", to check the compatibility of the paint compounds with wood.

Can OSB be used as final finishing layer?

Absolutely. The wood strands in the surface layer of the boards “ennobles” and give walls or floors surface the warm and rustic look of the natural wood.

For an improved visual appearance and a dust-free surface, we recommend the use of T&G sanded panels, which can be simply coated with transparent or pigmented wood lacquers.

What kind of glue is suitable for fixing parquet on OSB underlayment?

In all cases, we recommend the use of permanent elastic water-free wood adhesives (polyurethane-based) for gluing parquets on OSB underlayment, to avoid excessive shrinkage of the parquet caused by moisture uptake from the binder.

The surface of underlayment (OSB) must be absolutely dry, stable and free of dust, dirt, grease and any other loose or crumbly particles.


If using an external bonded insulating system (ETICS) for insulating the side envelope of a house, what kind of bonding is suitable to be applied on OSB?

Fixing of ETICS on the external walls of the building is commonly done by first bonding the insulation boards (stonewool, EPS) on the walls with adhesive mortar (cement based), and second by additional mechanical fixing with dowels.

When the fixing support is masonry, concrete or aerated concrete (Ytong), the use of dowels is okay, but in case of OSB, they cannot be used because the fixing element is too thin for them to anchor.
In this case, mechanical fixing is not possible and the insulating boards should only be bonded.

To select the right adhesive, please contact the manufacturer of the ETICS system.

What is the most suitable insulating products for ETICS (mineral wool or polystyrene)?

In order to avoid damage resulting from the accumulation of water condensation inside the building elements, EGGER always recommends diffusion open systems for external walls and roofs.

A typical such system for the external walls of a timber frame house consists of OSB wall sheathing on the inside, and a paneling with a diffusive / vapour permeable product (such as DHF or wood-fibreboards) on the external side of the studs.

When a diffusion closed system is chosen (for instance, with OSB on the inside and outside), insulation of the walls is commonly provided by the use of external thermal insulating cladding systems (ETICS), whose insulating component is either mineral wool or EPS / expandable polystyrene (most common).

Since the façade mineral wool is hydrophobic (that is, allows vapours to go be released, but doesn’t allow moisture to get in), is more likely that condensation will not occur when using these products, so therefore we recommend the use of mineral wool.