FEATURE
Proper preparation is key to painting success
By SA Paint Manufacturing Association
Preparation is the most important element for any successful painting project . This applies to both raw concrete surfaces as well as previously-painted exterior walls or interiors .
Once the surface is adequately prepared , primed ( if needed ), and stable , finish with a minimum of two coats of the correct topcoat to ensure a solid , closed , uniform and long-lasting finish .
SA Paint Manufacturing Association ( SAPMA ) CEO , Tara
Benn , provides some guidelines for tackling exterior painting jobs – and says that from the outset you need to pick the right weather for any exterior painting job : do not even think of painting in rainy weather .
NEW PLASTERED WALLS :
The new plaster rendering must be completely dry before any paint application can commence .
The drying time of the plaster can take weeks and will be dependent on factors such as thickness of plaster rendering , and weather conditions during curing and dry-out phase of the plaster . The typical curing time for new plaster is between three to five weeks ( can be longer in cold / wet weather ). With high substrate moisture , high alkali levels will also be present , so it is therefore even more important to allow adequate curing / drying . Applying a paint system to damp plaster will negatively affect the long-term performance of the paint system and can cause premature failures such as blistering , peeling and alkali burn .
A good way to test the dryness of the plaster is by taping a 30cmx30cm piece of plastic , ensuring the edges are closed , to the rendering and leaving it overnight . When the plastic is removed and no water is visible on the inside ( the side which was facing the plaster ), your plaster is dry enough to accept paint . If wet , further curing / drying will be needed .
SAPMA
Another method is by using a moisture meter ( refer to paint manufacturer for acceptable damp levels ).
Once you are sure the surface is dry , it must be thoroughly inspected to ensure that no loose materials are present , as this can influence the adhesion of the paint system . A good brooming of the surface is normally sufficient to brush off any loose particles . If plaster spills and other imperfections are visible , it may be required to sand and scrape this off , before brooming . Fill any imperfections with the appropriate filing compound and allow the compound to dry within the manufacture ’ s specification .
Once the surface is stable ( free of any loose / friable material ) apply a good quality plaster primer . The plaster primer will aid with adhesion , uneven porosity ( sealing the surface ) and produce an alkali resistant barrier for the topcoat .
Normally the drying time of a traditional ( solvent base ) plaster primer coat is around 18-24 hours . However , waterbased options are available with recoating times of about four hours ( again consult with the paint manufacturer ). Never allow the primer to stand for long periods uncoated - primers must normally be overcoated within 14 days .
Once your primer is dry , apply a minimum of two coats of the appropriate finishing product to ensure a solid , closed , and uniform application . By following these steps , your paint system will give the best possible protection and long-lasting performance .
PREVIOUSLY PAINTED WALLS :
A previously-painted surface can either be easy to repaint or might require some extra attention to ensure a long-lasting paint finish .
Not all previously-painted surfaces will pose the same problems . Some surfaces or substrates might have a few cracks , while others might have larger or more serious ones . The same applies to dampness : one structure might have a slight damp problem that can be fixed with a damptreating paint application , while others might require more professional attention such as by a damp-proofing specialist who will use other construction materials to repair damp issues .
All existing loose and flaking material must be removed by suitable hand preparation ( sanding and scraping ) or a more effective method such as high-pressure water jet . If any fungus
14 MARCH - APRIL 2021 SAAffordHousing saaffordablehousingmag SA Affordable Housing www . saaffordablehousing . co . za