The manufacture and curing process of concrete tilt panels can present challenges for painters.
Paint manufacturers have developed guidelines to assist painters in effectively preparing these surfaces for painting. Some points to consider include:
Concrete panels should be allowed to cure for at least four weeks to reduce alkalinity. The concrete must be allowed to dry thoroughly to a maximum of 15 per cent moisture content after all alkalinity has been neutralised.
Bond breaker materials or release agents are often used in the construction of tilt up panels between slab castings. These materials can break down and disappear through weathering and may interfere with surface painting. All surfaces should be checked for water repellence before painting. If water repellence is evident, all traces of bond breaker should be removed.
- Patching surface imperfections
After surfaces have been cleaned of all contaminants, any imperfections should be filled to bring the surface to the standard required by the particular coating system.
While there is a range of coating systems available on the market, it is up to you to decide which is best for the intended application. Refer to the manufacturers' recommendations before deciding whether a product is appropriate to apply to a tilt-up panel.
When painting paper-faced plasterboard, care must be taken to avoid or rectify any tannin staining resulting from exposure to sunlight.
Australian Standard (AS) 2311 Section 2.4.5 Paper-faced Gypsum Plasterboard identifies that the paper facing on the boards has a tendency to yellow upon exposure to light, especially sunlight, and should be painted as soon as practicable.
As stated in AS2311 Section 5, Table 5.1 Paint Systems for Interior Service – New Unpainted Surfaces, one coat of a B16 type latex sealer should be used for sealing gypsum plasterboard.
In most cases it is difficult to ascertain if plasterboard has been exposed to sunlight prior to its installation. Often it is not until a water-based sealer has been applied to the plasterboard that any sign of tannin staining becomes evident.
After the application of a water-based sealer, it is best practice to use a solvent-based sealer to counteract the potential tannin staining process and prevent it from penetrating from the substrate to any additional coats of paint.
Under no circumstances should the problem of tannin staining be rectified using flat enamel type paint, as the solvents contained in these paints may penetrate the previous water-based coating and result in the entire coating system leaving the substrate. Similarly, applying a solvent based sealer directly to the plasterboard will cause furring (where fibres of the plasterboard are lifted up) requiring extensive sanding back.
The popularity of dark finish colours has accentuated the visibility of white rust on galvanised iron fascia, gutters and down-pipes. The problem is not related to the materials used in dark coloured paints but rather to the contrast between the dark colour and the white rust, a contrast that is minimal when using light coloured paints.
Paint manufacturers' specifications identify the appropriate coating system being one priming or etch coat and one coat of oil based undercoat, followed by at least one finish coat.
The Building Commission suggests that a more durable coating system should be used in areas affected by salt laden air and strong prevailing winds.
The combination of moist weather and enclosed spaces are notorious for creating conditions that can result in ventilation and condensation issues that can affect paintwork. These typically occur on ceilings when the building is 'locked up' prior to and after the completion of the work.
Even for short periods of time the build up of dampness or fumes from latex-based wall and ceiling paints inside an unventilated building can be significant enough to cause problems such as:
- plaster welting of set plaster walls;
- sulphide type discoloration to painted ceilings;
- mould growth to confined areas; and
- yellowing to enamel finishes.
Australian Standard (AS) 2311 Section 7.6 Discolouration of Paint Films identifies that treatment of the sulphide stains caused by lead or mercury compounds in old-style paints can be difficult, but once treated, better ventilation to reduce humidity may prevent recurrence.
The AS2311 also advises that yellowing may occur when enamel paints are applied to interior trim areas while fumes from latex-based wall and ceiling paints are still present in the room. This discolouration is permanent but can be avoided by providing ample ventilation prior to applying the enamel paint.
You should ensure that internal environments and all surfaces to be painted are suitably prepared to receive the coating system specified by the paint manufacturer and/or the Australian Standard prior to painting areas that may not have been properly ventilated.
After the painting work has been completed, painters should advise the builder or client to provide continued ventilation until the surfaces have dried properly in order to reduce the risk of problems occurring.
Many painters are incorrectly tinting the base coat of galvanised iron primers in an effort to obtain better coverage and paint finish on galvanised products.
This has become a common practice when using a two-coat system with medium to dark colours. However, breakdown of the paint may be accelerated due to excessive amounts of tint which affects the adhesion of the primer to the substrate. Paint manufacturers recommend that instead of using a tinted primer, an additional coat should be applied after the untinted primer coat to obtain the appropriate base and colour prior to the application of a final top-coat.
When carrying out roof restorations, the Board recommends that you work according to manufacturers' recommendations and follow best practice procedures. Information about roof preparation and painting is specified in AS2311 Section 5.3.1 Specialised Applications: Roofs.
- Carry out a high pressure clean.
- Replace broken tiles.
- Repoint ridge capping with a flexible cement.
- Apply an appropriate sealer.
- Apply two coats of 100% acrylic.
- Place stocking material over downpipe outlets to catch any fibres
- Clean the roof using a low pressure hose and soft broom
- Apply a chlorine solution over the entire roof surface to remove any mould or fungus
- Apply an oil-based sealer or a solution acrylic with a lacquer-based primer
- Apply two coats of 100% acrylic
Note that: There may be restrictions that apply when working with asbestos. For more information, visit the WorkSafe website.
The use of gloss and semi-gloss paints highlights imperfections in the surface being painted. Residual marks from brushes or rollers can further emphasise these imperfections, particularly if used in hot weather.
Painters should make sure that they prepare the surface appropriately to reduce the visibility of imperfections and discuss with their clients the difficulties caused by using gloss finishes.
Door manufacturers recommend that exposed edges of all doors be sealed in such a manner so as to avoid potential moisture damage.
Exterior finishes (preferably enamel paint) must be used on external doors and full gloss paints produce the best results. Exterior doors should be finished in light reflective colours to reduce the risk of heat absorption which may cause warping.
It is recommended that you apply one coat of primer to all faces, sand lightly in the direction of the grain, apply another coat of undercoat and finish with two coats of enamel colour, ensuring that all exposed edges are properly sealed.
Painters often experience difficulty obtaining fair and reasonable coverage of light coloured acrylic paint to metal. This can be overcome by applying the appropriate etching primer to the metal before painting.
- acrylic paints do not hold back rust so any rust should be adequately treated prior to carrying out metal repaints; and
- to avoid ropiness, do not apply acrylic paints to metal fascias and gutters in extremely hot and windy weather.
External clear finishes
You should ensure that they are using appropriate clear finishes on external surfaces, particularly is the surface is exposed to salt, wind and other adverse weather conditions.
It is important to discuss with your clients the short life of clear finish products.
When carrying out painting work using light coloured acrylics on new timber, you should discuss with their client the possibility of timber stain bleeding through the paint and any additional costs involved with the application of an appropriate sealer coat.
Peeling of paint from ceilings when ceiling finishes have broken down is a common problem seen by the painting inspectors.
In such cases, it is often found that no sealer had been applied and excessive jointing material existed beneath the peeling paint, indicating that little or no preparation had been carried out. The cost and time spent rectifying a peeling ceiling is often greater than the original value of the contract.
You are responsible for the preparation of the ceiling, including cleaning and dusting, prior to the application of paint. Always check the nature of the ceiling material and the type of paint previously applied and ensure that any previous paint has adhered to the substrate.
Before repainting plasterglass ceilings, identify whether a sealer had previously been used and, if not, it is recommended all existing paint is removed and an application of appropriate sealer prior to painting.
Should the specification on which you are quoting not identify the appropriate sealer, bring it to the attention of the client or builder. If a specification is not provided and you are requested to provide one, make sure it complies with AS2311 or the recommendations of the paint manufacturer.
Painters are often required to seal or paint materials containing the hazardous substance asbestos. If asbestos fibres become airborne, it is a health risk to those in and around the area. It is therefore important to plan ahead to avoid disturbing asbestos material and to follow the correct safety procedures.
The National Code of Practice for the Management and Control of Asbestos in Workplaces is available to help eliminate or otherwise minimise the risks of exposure to airborne asbestos fibres. The following guidelines have been adapted from the Code.
Check the asbestos
When sealing or painting materials containing asbestos, first check that the asbestos is in good condition. If it is weathered, damaged or broken, it should not be painted but rather be removed and replaced with a non-asbestos material.
Under no circumstances should asbestos materials be water blasted or dry sanded. Power tools should never be used when preparing surfaces for painting or sealing.
- Personal protective equipment – P1 or P2 respirator, disposable coveralls, safety goggles and disposable gloves.
- Brushes, rollers, duct tape, plastic drop sheets and plastic bags for rubbish removal.
- A sealant designed specifically for use on asbestos.
- A bucket of water and spray bottle for misting.
Prepare the work area
- Advise neighbours and restrict entry to the asbestos work area.
- Cover the floor of the work area with plastic sheeting and secure with duct tape.
- Wear your personal protective equipment.
- Check the fit of your respirator as per the manufacturer's instructions.
- Ensure all asbestos waste, including dust and contaminated protective equipment, is kept separate from other waste.
Surface preparation and painting
- Wipe dusty surfaces with a damp cloth.
- Wash with sugar soap or another cleaning chemical.
- If needed, sand the surface lightly by hand with water (no power tools).
- Avoid abrasion or damage to asbestos material.
- Use high-pressure water or compressed air cleaning equipment.
Note that: Regulation 5.43 of the Occupational Safety and Health Regulations 1996 requires that the employer, main contractor, self-employed person or person in control of a workplace identifies the presence and location of asbestos at the workplace and assesses the health risks. This identification and assessment is to be in accordance with the Code of Practice for Management and Control of Asbestos in Workplaces.
This information will be recorded on the asbestos register. If the conditions or location of any asbestos presents a health risk, then the employer has a duty of care under Section 19 of the Occupational Safety and Health Act 1984 to implement controls.
For more information about working with asbestos, see the WorkSafe website.