Surface preparation

Building boards, cement-based boards, asbestos and mineral fibre boards

Because all of these boards are porous, relatively permeable coatings such as emulsion paints should be specified as the first choice, as they will allow water vapour to pass through the film with less risk of blistering.

When storing any of these boards on site it should be taken into account that large quantities of water will be absorbed unless the boards are protected from the elements. This should also include storing the boards on spacers clear of the ground. If these boards do become saturated and are not allowed to thoroughly dry out before painting, early failure from blistering, flaking, alkali attack and efflorescence may result. Cement-based boards and asbestos are very alkaline but providing the surface is dry they can be successfully painted with emulsion paints.

Where a more robust/abrasion resistant coating is required, solvent-based paints or even acrylated rubber paints may be applied. However, it is essential that the boards are completely dry in depth and that the back and all edges are sealed and painted before installation. If this is not possible then a more permeable emulsion paint system should be used as a solvent based/acrylated rubber system will quickly fail.

Weathered unpainted boards

Where these boards are used externally, they can often be heavily contaminated with organic growth such as lichens mould and algae. These growths must be killed and the surface sterilised before painting. Dulux Trade Weathershield Multi-Surface Fungicidal Wash* may be used for this purpose. Where growths are particularly heavy a second treatment may be required. After treatment wash the surface with clean water to remove all residues.

Friable surfaces

When preparing asbestos surfaces the Asbestos Research Council or the Health and Safety Executive should be contacted for their advice before any work is specified. In the case of cement based boards and asbestos boards any loose/friable material should be carefully removed back to a firm edge. To help prevent the production of dust any manual preparation may have to be carried out wet. Where this is the case the surface must be allowed to fully dry out before painting. If the surface still remains friable after preparation, a suitable plaster primer/sealer should be applied.

Redecoration of building boards generally

Before repainting, the existing coating must be identified and its condition / performance assessed. If the surface is in good/reasonable condition then a similar paint system can be specified. General preparation should include scraping back to a firm edge, any areas of loose/poorly adhering coating, if necessary washing down to remove dirt dust and grease, rubbing down with an abrasive paper to provide a mechanical key and dusting off. Bare areas should be primed with an appropriate Dulux Primer. In the case of soft fragile surfaces such as fibre board, considerable care is needed to avoid damaging the substrates. Where the existing coating is in poor condition or is not suitable for the environment the surface should be completely stripped and a more suitable paint system applied.

When applying solvent-based paints to large surface areas inside or using in small confined spaces inside, the wearing of air supplied breathing equipment will normally be necessary in order to comply with a COSHH Assessment as required under the Control Of Substances Hazardous To Health Regulations 2002. Before specifying a solvent-based system a Dulux water-based equivalent should be considered.

Brickwork, blockwork and concrete

All surfaces must be sound clean and dry. Remove any efflorescence and mortar droppings. New or unpainted brickwork must be of a type that is suitable for painting (e.g. not fletton engineering or glazed bricks). In the case of redecoration carefully scrape back to a firm edge any/all areas of poorly adhering or defective coatings. Surfaces which are contaminated with mould or vegetable growth must be treated with Dulux Trade Weathershield Multi-Surface Fungicidal Wash*. In severe cases a second treatment may be required. Make good cracks and imperfections. Dulux Trade Weathershield Exterior Flexible Filler may be used for minor areas. Allow to dry. Rub down all making good and remaining paint coatings where practical. Prime bare areas and making good with an appropriate Dulux Trade Primer or a thinned first coat of the chosen Dulux finishing system. Where the surface remains powdery or friable after thorough preparation apply a coat of Dulux Trade Primer Sealer.

Plaster

New plaster should be prepared by carefully removing any plaster splashes and mortar droppings. Remove any efflorescence (white salts on the surface that appear as the fabric of the building dries out) and underbound slurry by rubbing with coarse sacking or stiff nylon brush. Apply a well thinned first coat of the specified Dulux emulsion. Make good any cracks holes or imperfections with a suitable plaster filler used in accordance with the manufacturers instructions. When dry rub down and dust off. Plaster may be highly alkaline when new and so solvent-based paints such as gloss or eggshell must not be used. If a solvent-based finishing system is required then the surface must be completely dry in depth and primed with Dulux Trade Alkali Resisting Primer.

When applying solvent-based paints to large surface areas inside or using in small confined spaces inside, the wearing of air supplied breathing equipment will normally be necessary in order to comply with a COSHH Assessment as required under the Control Of Substances Hazardous To Health Regulations 2002.
Before specifying a solvent-based system, a Dulux water-based equivalent should be considered.

In the case of redecoration carefully scrape back to a firm edge all poorly adhering or defective coatings. Rub down to feather broken paint edges and remaining coatings. Dust off. Make good all surface imperfections with a suitable filler used in accordance with the manufacturer's instructions. When dry rub down and dust off.

Prime bare areas and making good with the appropriate thinned first coat of the chosen Dulux Trade finishing system or suitable Dulux Trade primer.

Wallcoverings

ICI Paints do not manufacture wallcoverings and recommend that the wallcovering manufacturers' advice should be sought at all times.

Some wallcoverings are purposely made for painting, some are not but can still be painted; some simply cannot be painted without problems occurring. All paintable wallcoverings must be firmly adhering to the surface and be free from paste on the face side before painting.

Lining papers, Woodchips, Anaglypta etc. are purposely made for painting and can generally be painted with conventional emulsion type paints. Blown Vinyl's can sometimes be painted but will normally require a first coat of a Vinyl Matt emulsion.

Pulp papers generally can be painted provided the inks do not cause staining. Lincrustas need to be first coated with an oil based paint, normally Eggshell. Hessians can be painted with conventional emulsion type paints but this can look unsightly as it tends to raise the fibres.

Vinyls, Washables, Silks, Handprints, Flocks, Metallics etc. generally should not be painted.

Previously painted wallcoverings, are suitable for repainting with a similar type of paint provided the paper has been successfully painted before.

*Registered pesticide.