Plaster OSB panels - instructions for inside and outside

OSB boards or coarse clamping plates are used both inside and outside. With the wood panels, however, there are some peculiarities when applying the plaster. The difficulties include a possible cracking and the absorption of moisture. To prevent this, you have to prepare the surface very well. Read how to do the best indoors and outdoors.

Surfacing OSB boards: an instruction for indoor and outdoor use - OSB boards are also known as coarse clamping plates and are mainly used for interior work. But also an outdoor use has many advantages. To protect the relatively inexpensive material, it is recommended to apply a plaster. However, this is not so easy in practice, since you must ensure sufficient adhesion, a reduction in moisture absorption and a failure to crack. With the right tips, however, both plastering outdoors and indoors is possible.

The difficulty in plastering OSB boards

OSB boards are often used indoors for interior decoration. However, since they are made of wood, it can absorb moisture. Apply the plaster directly to the panels, then draw this water and swell up. At the same time, the plaster becomes dry and crumbles over time. Changes in the indoor humidity also lead to cracking, as the plates "work". One way to eliminate these dangers is in the interior of attaching plasterboard. These protect the surface and create a separation to the plaster. In this case, use glass fabric tape for the joints. Put this between the joints of the plasterboard. Then apply a primer and a deep background. After this pretreatment, you can plaster the plates.

The procedure in the outdoor area

If you have attached the panels outside, then you can use HWL or polystyrene panels for cladding. Subsequently, the attachment of the reinforcing fabric and the plaster can be applied. Outside, the risk of moisture is particularly high because the panels are exposed to the elements. But even at sheltered places water quickly reaches the surface of the coarse chuck plates. Heavy rain, snowdrifts and fluctuating temperatures are a risk to the panels. These are optimally protected by the HWL or polystyrene plates.

The direct plastering of the panels outdoors

While it is better to protect the panels and not externally plaster them externally, it is possible under certain conditions and procedures. For this, treat the surface with a special acrylic primer. Make sure that the painting is complete and opaque. This is the only way to ensure that the panels are protected against moisture.

Let the primer dry and apply the reinforcement fabric. This should overlap at the joints to reduce the risk of cracking.

In the tile adhesive, the net should still be visible, so an optimal work is possible. Excess tile adhesive peel off. The tile adhesive fulfills two tasks. On the one hand it serves as adhesion, on the other hand it represents an additional layer, which keeps out the moisture outside. After this preparation you have to ensure a sufficient drying phase.

Tip: If you are working outdoors, make sure that the boards are left with enough time to dry. Therefore, pay attention to the weather forecast and decide during the execution for a dry day.

Prepare the OSB boards for plastering (inside and outside)

Plaster mortar can not adhere to smooth OSB boards. Since the material is exposed to the moisture without protection, it swells quickly and is thus damaged. To remedy this situation, mechanical adhesion promoters are necessary. Alternatively, an adhesive paint can be used. For example, a grid mat made of galvanized iron is suitable. It must have sufficient strength and be fastened well. If you use material that is too thin, the grid will deform quickly.

Prepare the ground

If you would like to apply a thin layer of plaster (light plaster up to 1 cm thick), then use an acrylic primer to prepare the substrate. This is effective against moisture. Then apply a reinforcing mat to the base, which you attach with tile adhesive.

Tip: Press the mat well so it will not slip. Allow the prepared substrate to dry well before continuing work.

Now follows the primer. For this purpose, a primer for concrete mortar is suitable. If you want to plaster with a clay building material, then special coating primers are offered in the trade, which are also suitable for OSB boards.

The plastering can begin (inside and outside)

As soon as the substrate is stable, you can start applying the plaster. There are several points to consider. If you have used a mechanical bonding agent, you must first of all throw down the mesh with a cement slurry. In the case of adhesives, apply two coats. The plaster thickness is divided into two operations. Make sure the first peel has dried before applying the second coat. Apply the mortar layer as thin as possible. A special focus is on the panel joints. These must be secured against cracking. If it is a clay plaster, then you can use this painting fleece.

Make the mortar
You have the choice of buying a ready mix or mixing the mortar yourself. This contains the following components:

• water
• sand
• cement
• slaked lime

The properties and the behavior of the mortar depend on the chosen mixture. By changing the ratios between the individual components, you can therefore determine the properties. High lime , for example, increases the strength and adhesion of the mortar. Be sure to mix water, cement and sand in equal parts to get a good result. For indoor work is a fine sand, as the plaster layer is thus smoother. Alternatively, you can also use a ready mix. Pay attention to the information on the packaging, here you will find information on the areas of application of the selected product.

Tip: Since the lime is kept rather low for many blends, you can add a little bit of lime if necessary. This is necessary if you want a firmer plaster.

As a rule, a plastic tray is sufficient for mixing the mortar. Ready mixes are now mixed with water so that the plaster forms. Add the mixture to the bucket and add the amount indicated on the package. To stir, you can use a drill with an attached blender. After mixing, you must leave the mortar for about 10 minutes.

You need these tools and materials for plastering:

• flat trowel
• Reibkelle
• spirit level
• Rod made of metal or wood
• plastic containers
• drilling machine
• Mixstab
• water
• Ready mix or cement, slaked lime and
• sand

A detailed guide to plastering

1. First use the trowel to spread the mortar evenly on the wall. Consistency of the material is important for the working speed and the further work processes. The mixture must not be too wet or too dry. The optimum mixing ratio gives you enough time to ensure a uniform layer of plaster.

2. In addition to the trowel need for the plaster work a rod. This must be sufficiently long and can be made of wood or metal, for example. It serves to distribute the plaster evenly. Guide the bar from one side to the other, smoothing the surface.

3. Afterwards you must pay attention to hollow places. Fill with mortar and smooth the surface again with the rod.

4. Repeat these operations until a smooth surface has been created and the plaster has sufficient thickness.

5. To check for uniformity, it is best to use a spirit level. If you notice any small bumps, you will need to rework until you have made up for any rough bumps.

6. Then insert the trowel to smooth the wall. Run the trowel over the plaster, smoothing the surface. Hold the trowel with one side bent. In this case, it usually comes to a pile of excess mortar on the trowel. You can return this to the tub.

7. Allow the mortar to dry before continuing.

8. Once the mortar has dried, insert the rubbing trowel to repaint the OSB panels. If you come across small bumps, then you can easily repair them at this stage.

9. After completion of the plastering, the plaster must dry for several days.

10. If you want to paint the plaster, you must first apply a gypsum mix. However, you do not need to use the friction trowel to keep the surface as smooth as possible. It is important to create as straight a structure as possible when plastering, so that painting is easy and good results are achieved.

Special features when plastering OSB boards

The edges and seams are an important issue when plastering OSB boards. There are special waterstops on the market that you can use for the edges. Self-adhesive versions are particularly easy to handle. To prevent cracks forming at the seams, you can also use a version with synthetic fibers as a plaster. The additives ensure a flexible shape and the material is easily stretchable. This reduces the pressure on the night stands and the risk of cracks decreases.

Tips for quick readers:

• Prepare the surface well
• Protect the chuck with a grid
• prevent the formation of cracks
• ensure a sufficient drying phase
• Mortar mixture with synthetic fibers is flexible
• Mortar must have the right consistency
• Let the mortar stand for 10 minutes after mixing
• Check the result with a spirit level