Plastering requires the application of a primer, which is a crucial step that shouldn’t be skipped. In order to guarantee that the plaster adheres correctly and produces a more even and long-lasting finish, primer acts as the foundation.
By applying a primer, you can improve the plaster’s ability to adhere to the wall and avoid problems like peeling or cracking in the future. Additionally, it aids in wall sealing, which lessens moisture absorption and improves the efficiency and smoothness of the plastering process.
This post will discuss the importance of primer before plastering, how to select the best primer, and application best practices to guarantee a smooth plastering project.
Why do you need a primer
Increasing the base’s adhesion with finishing materials is the primary goal of impregnation.
Other uses for primer beneath plaster include:
- provides protection against mold and mildew;
- increases the fire resistance of the structure;
- gives the surface additional strength and rigidity;
- improves the waterproofing properties of the coating;
- allows to reduce the consumption of plaster solutions;
- by bonding loose areas, it prevents delamination of structures;
Primers applied to surfaces aid in enhancing plaster’s overall quality.
Prior to plastering walls, primer must be applied in order to establish a solid bond between the plaster and the surface and guarantee an even, long-lasting finish. Primer is an essential step in any plastering project because it helps to seal the wall, lessen absorbency, and avoid problems like peeling or cracking.
Types of primers
A large selection of primers for plastering walls are available in the construction market.
They are separated into three primary categories based on their objectives:
- Universal. Multifunctional impregnations that improve adhesion, strengthen the bases and form a film on the surface that reduces the consumption of plaster.
Based on acrylic, silicone, or silicate.
Both indoor and outdoor use is acceptable.
Applied to any non-porous, non-smooth base for putty, regular plaster, and ornamental plaster; also used for interlayer priming.
High technical and operational properties define this:
- no smell;
- fast drying speed;
- affordable cost;
- excellent antiseptic effect.
- Deep penetration. Designed for application on loose porous substrates. Suitable for strengthening the old layer of plaster, processing clay plaster on shingles and porous walls made of gas and foam concrete. Penetrates to a depth of 10 centimeters.
They aid in lowering the amount of plaster mixtures used by sealing pores and creating a film on the exterior.
It is an odorless, water-based composition that dries fast.
- Adhesive. Very effective impregnations that impart roughness to the surface due to the presence of abrasive components. Manufactured from organic solvents containing alkyd resins.
Used to treat wood walls, smooth concrete surfaces, bases coated in oil paint, or ceramic tile interiors for plastering.
When adhesive impregnations are applied, the surface feels, well, like sandpaper.
Primers are separated into three categories based on their composition: mineral, acrylic, and alkyd.
Mineral primers are made with a base of cement, lime, or gypsum. Appropriate for initial application beneath plaster on brick, concrete, aerated concrete blocks, or expanded clay concrete.
Acrylic primers are all-purpose, water-dilutable compounds that can be used to treat concrete, cement, wood, plasterboard, putty, and subfloor surfaces. Used at a maximum temperature of +35 degrees. Wetness takes two to four hours.
Treating wooden bases is the only application for alkyd compounds. These impregnations take ten to fifteen hours to dry.
Choosing a primer for a specific base
Certain primer types must be applied to different bases.
The best primers to use on wooden bases composed of boards, OSB, fiberboard, or chipboard are those that have antiseptic additives to prevent the growth of microorganisms and fire retardant additives to boost the structure’s fire resistance.
Based on gypsum, mineral compositions are used to make primer for gypsum plaster. It is applied to the base both after it dries and before gypsum plaster is applied.
Glass, laminate, and ceramic tiles that have hydrophobic surfaces are coated with polymer resin-based compositions.
Due to their absorption qualities, foam and aerated concrete block walls need to be treated with materials that create thick, water-permeable layers at their base.
Water-soluble deep penetration mixtures based on silicone or acrylic are appropriate for priming brick walls under plaster. Cement or gypsum-based mineral primers also offer high adhesion.
On dense bases, deep penetration compounds shouldn’t be utilized. The thick layer that forms on the surface hinders the plaster’s ability to stick to the base and may even cause it to peel.
Preparing walls before priming for plaster
Any base that will be plastered needs to be cleared of any old finishes, dirt, dust, or oil contaminants before priming the walls. Solvents can be used to get rid of grease stains.
Should any signs of mold or mildew be found, clean the walls and apply antiseptic treatments.
Brick
In order to guarantee a strong bond between the plaster mortar and the masonry, brick walls must be adequately prepared before applying the primer.
Remove old plaster from surfaces.
Dust should be removed after swelling the brick joints up to one centimeter deep.
Use cement mortar to seal any cracks, crevices, or irregularities.
After washing, let the brick walls dry.
Concrete
Concrete drips must be removed from the surface prior to priming concrete structures to improve adherence to cement plasters.
Cavities and fractures that already exist need to be widened and mortared over.
Eliminate roughness and irregularities.
Using a spatula, remove any dust or dirt from the base.
Wood
Dust off any wooden wall surfaces.
We place thin slats at a 45-degree angle to the floor and stuff them with shingles to improve the adherence of the base to the plaster. The second row of slats is positioned at an angle to the first row, facing the opposite direction. You can use pre-made shields in the shape of slat lattices.
Fire retardant or fungicidal additives are required in primers for treating wooden surfaces in order to boost fire resistance and provide mold and mildew protection.
Fiberboard, chipboard, OSB and plasterboard
Prior to applying primer, polymer reinforcing meshes must be fixed to flat surfaces composed of plasterboard, wood fiber, or chipboard sheets for plaster leveling.
When applying plaster to chipboard or OSB, metal mesh works better than polymer reinforcement because it allows for a thicker layer to be applied.
| Type of Primer | Purpose |
| Deep Penetrating Primer | Strengthens loose surfaces and ensures better plaster adhesion. |
| Universal Primer | Suitable for most surfaces, providing a solid base for plastering. |
| Alkyd Primer | Used on metal surfaces to prevent rust before plastering. |
| Adhesive Primer | Enhances the bond between smooth surfaces and plaster. |
| Stain-blocking Primer | Prevents stains and discoloration from bleeding through the plaster. |
Primer application is an important step that should be done before plastering walls because it can greatly affect the outcome. Ignoring this step can result in uneven plaster, poor adhesion, and a short-lived finish.
By using the proper primer, you can make sure that the plaster adheres to the surface well, giving the finish a smoother, more resilient finish. A more polished and durable outcome is achieved with a minimal time and effort investment.
A quick and easy way to guarantee the success of your plastering project is to take the time to properly prime your walls. It helps avert typical issues and improves the overall efficiency and dependability of the process.
