Methods and materials for external coating of OSB boards.

What can be used to paint?

OSB boards (Orient Stand Board) are a multilayer “pie” of chips pressed under high pressure and glued with resins. Thanks to the chips laid in different directions, the boards gain high strength and an impressive texture, while the surface becomes rough and complicates painting.

Untreated OSB boards are attractive not only for their reliability and relative availability, but also for their relief. Sunlight falling on the facades covered with them creates a special texture.

The panels consist of at least 80% wood, so various compounds intended for painting wood are suitable for processing. Their choice depends on whether you want to leave the texture of the material or prefer to completely cover it.

To preserve the unique pattern of wood chips, you can apply a transparent semi-matte paint with an ultraviolet filter, produced on the basis of alkyd resins, to the board. It will protect the base from adverse environmental influences. Apply in 2 layers.

Special glazes are suitable not only to preserve the texture, but also to emphasize it. They give the surface a shine and, depending on the selected shade, paint the wood in the color that best suits your style – facades can be either lightened or darkened.

To create a glossy effect, give preference to water-based or oil-based wood varnish. Yacht varnish is also suitable, which will give the OSB board a beautiful shade. It is best to choose weather-resistant antiseptic compounds with wax and plasticizers: after drying, they form a strong film.

There are special antiseptic varnishes for wood, made on an acrylic basis. It has an antibacterial effect, perfectly protects the boards from water ingress, as well as the formation of fungus.

Also, to emphasize the pattern, use a stain, choosing any suitable color. Using water or solvent, you can dilute the composition and thereby control the saturation of the shade. Tinting is done in three stages:

1. application with a brush or spray gun;
2. drying;
3. coating with polyurethane primer.

But transparent varnishes and stains have a significant disadvantage: they do not mask the joints of the OSB sheets.

If you want to hide the relief of the OSB board, pay attention to dense covering paints. The most budget option is alkyd enamels. After drying, they form a thin film on the surface that protects the OSB sheets from aggressive outdoor conditions: moisture does not leak into them, ultraviolet radiation and temperature changes do not destroy the coating.

Alkyd-based paints have a noticeable odor, but are completely safe. Require careful preparation of the base.

Acrylic facade paints are another suitable type of coating. They are produced on the basis of water and acrylates, providing a high level of resistance to moisture. After application, the paint and varnish material forms a polymer layer on the base, due to which the material is not afraid of either cold or sunlight. Despite the fact that water evaporates when drying, acrylic paint helps the boards to acquire resistance to combustion. It lends itself well to tinting.

Latex compositions for outdoor work are also suitable for painting the boards: they are expensive materials, but fully justify their cost. The latex coating does not crack, as it is elastic, is not afraid of mechanical impacts and perfectly isolates OSB sheets from water. When used, latex paints do not emit harmful substances, since the binding component is rubber. Eco-friendly, the service life is up to 10 years.

It is not recommended to use oil paints, where the main component is drying oil, when painting OSB boards on the facade: they are highly toxic, expensive and take a long time to dry. Oil paints and varnishes do not tolerate the adverse effects of sunlight and moisture, quickly crack, and also have an unpleasant odor.

Pay attention to another important point. If you want to make your home safe, give preference to paints and varnishes with a fire-bioprotective function. Wood and resins, which are the main components of the boards, emit hydrocyanic acid and formaldehyde when burning, which are harmful to humans and the environment. In its appearance, fire-bioprotective material is a liquid paint, after application of which the surface gains the ability to extinguish flames.

Thanks to the paint with fire-bioprotection, facades become moisture-resistant, they are not afraid of mold and fungi. The required density of the composition does not allow it to flow during application. Manufacturers claim that with such treatment the base will last at least 15 years.

How to prepare the surface?

Unlike solid wood, OSB boards are not sanded before painting. If the chips have peeled off in places, you can sand these places locally. The surface is thoroughly cleaned of dust and dirt using brushes, a wide brush and rags.

If the material outside the house was painted earlier, it is necessary to remove the peeling paint with a scraper. After that, the base should be sanded and a special primer should be applied, which will increase adhesion (adhesion of the compositions). If oil paint was used earlier, the boards should be treated with a wire brush.

The joints of the sheets and cracks should be sanded, cleaned of dust and filled with putty. Acrylic putties for OSB, which are made specifically for leveling wood-chip bases, as well as nitro putties and joint sealants are suitable. They have good adhesion and strength, and have almost no shrinkage when drying. For reinforcement, use repair interlining.

Advice: to preserve the texture of the material, use putty, pre-mixing it with sawdust.

Step-by-step instructions

Experts have different opinions on the technology of painting facades made of OSB boards. If you do not like the texture of the chips, sand the boards using a grinder with a P320 abrasive wheel. In other cases, the material does not need to be leveled.

1. Primer is the first stage of the painting process. If you do not use a composition designed specifically for OSB sheets, it will be difficult to achieve high-quality adhesion. Since OSB-3 without special moisture protection is usually used for outdoor work, they require additional processing.

To prevent OSB boards for facade finishing from deforming and swelling during operation, the ends should be primed before installation. The ends are the most vulnerable part of the material. The primer will provide maximum protection for the material and increase its service life.

2. If you want to achieve a perfectly flat surface, the base should be completely covered with fiberglass mesh and leveled with water-resistant and cold-resistant putty. When using opaque latex paint, the leveling stage can be skipped: experts say that the painted surface is smooth even without puttying.

3. After the materials have dried, the slab is painted with facade paint in two or three layers. The first of them should be as thin as possible. Facades are painted in dry weather, in the sun and at a temperature of +5°C.

The paint is conveniently applied with a brush or roller: either foam rubber or faux fur will do. But a spray gun will provide the lowest consumption of the composition and high painting speed.

4. The first layer of paint is left to dry for several hours: the exact time depends on the type of composition. Be sure to read the instructions before you start applying the paint. It is desirable that there is no strong wind or sudden temperature changes outside when drying. To achieve a uniform coating, the composition should be applied in an even layer without gaps or drips.

Tip: to make the facade look stylish and neat, cover the seams with decorative 25×100 mm boards. Their location is dictated by the size of the boards, so before cladding, you should calculate not only the amount of material, but also the placement of the sheets. Dark boards against a background of light paint, covering the joints, imitate half-timbered timber.

Video for beginners

You can see how to paint the surface of OSB boards in more detail and clearly in the following video. The author competently and in detail talks about most of the nuances that arise when working on finishing the facades of a house made of OSB boards. A sealant, alkyd primer, paint and spray gun are used.

The construction materials market is wide and diverse, but today OSB boards are especially popular, having become fashionable and having a number of advantages. In order to choose what mixtures to paint OSB boards outdoors, decide on the budget and the desired result. This choice determines how long the finish will last unchanged and how aesthetically pleasing the surface will look.