Colorcoat® Column: Overpainting
With the onset of summer many building owners may decide that there is a need to refurbish their building and one method they may wish to undertake is to over-paint. Here are a few queries we often get with regards to over-painting.
What is the preparation required prior to over-painting ?
This will depend on the condition of the existing cladding, which there are three main types:
1. Colour change e.g. change of ownership of building and a requirement for new colour scheme.
This in many cases will mean only thoroughly washing down with a suitable detergent/water solution to remove all dirt, grease and deleterious matter and fresh water rinse. New Plastisol surfaces may need to be wiped with white spirits before washing
2. Paint weathered but still sound to substrate.
Areas of algae growth should be treated with a proprietary fungicidal solution (use as per manufacturers instructions) to sterilise surfaces. This must be done prior to washing which must be thorough to remove all dirt, chalk deposits, oil, grease, residues from sterilisation and any other deleterious matter. Fresh water rinse and allow to dry. If there are any areas that have corroded remove corrosion with abrasive tools back to bright metal and feathering to sound paint
3. The original coating is very old and delaminating.
All existing coating removed back to the metallic substrate by a suitable means. These can include Chemical Stripper – use as per manufacturers instructions Abrasive Blast Cleaning – wet or dry blast clean in accordance with equipment manufacturer’s recommendations High Pressure Water Equipment With all methods you must ensure all surfaces are thoroughly clean before application of any paint. I would point out that before commencing with removing of coating and over-painting you may which to price a re-cladding of building, which often proves to be a cheaper alternative.
How is paint applied and when?
There are paint systems available that can be spray, roller or brush applied. Application technique should ensure that an even wet film is applied to surface at a thickness as recommended by paint manufacturer. If brush applied an appropriate brush size for cladding profile should be chosen. When spraying, ensure all site restrictions are considered and areas not to be treated should be protected or adequately masked up. Application should be carried out in weather conducive to painting, obviously not in heavy rain or strong winds if spraying. Otherwise problems such as rain spotting, pinholing, blisters or blooming etc. can occur.
What paint system should I use?
There are many manufacturers systems that are compatible with our coating systems and choosing the right coating for over-painting is important. Using a high performance, water-based paint can reduce the amount of Volatile Organic Compounds (VOCs) liberated during the over-painting operation compared with conventional solvent based paint. However, water-based systems can sometimes be restricted by weather conditions i.e. rain