Painting previously painted cementitious surfaces - in good condition

Note: Refer to the PDF flowchart for a visual of the steps below:

1. Treat moss and mould with Resene Moss & Mould Killer

2. Thoroughly wash using Resene Roof Wash and Paint Cleaner

3. Spot prime any bare flaked or cracked areas

4. Fill cracks and voids:

   1. Cracks under 1mm, use Resene Brushable Crack Filler
   2. Cracks over 1mm, use Selleys No More Gaps exterior formulation or similar
   3. Holes and voids, use either Resene Jointflex or an approved masonry filler

5. Refer to topcoat systems flowcharts

Things to consider

• What is the condition of the surface?
• Does it have any moss or mould present?
• Are there any cracks or voids that will need filling?
• What is the approximate size of the area to be painted - how smooth or rough is the surface?
• Are you going to do the work yourself?

Notes:

1. Typically repainting a sound paint system that has been applied over a cementitious surface is straightforward, because the substrate is inert and doesn’t usually cause any stress on the paint, unlike substrates like timber. As a result there are generally only three areas that need addressing:
   
   i) Mould and moss will need to be killed and removed – use Resene Moss & Mould Killer.
   
   ii) While the surface may be power-washed it is easier to clean using Paint Prep and Housewash. This is much more effective at removing surface chalking (old oxidised paint) from the old paint than waterblasting.
   
   iii) Any cracks or holes that need filling may need either an application of Resene Brushable Crack Filler or a suitable filler, such as Selleys Masonry Filler.

2. While sealants are unlikely to be needed on the concrete or cementitious substrate itself they may be required at the interface between the substrate and window flashings etc.

Key accessories essential to complete the job

• 50-75mm Resene Blue or Resene Professional brush for cutting in
• Resene Brushable Crack Filler
• Resene Moss & Mould Killer
• Selleys Masonry Filler or Resene Epox-O-Bond

Add-ons – to make the job easier or quicker

• 35-50mm broad knife (for filling)
• Dropsheet
• Rubber gloves and eye protection

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