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Careful assessment is required before carrying out external decoration outside of the traditional painting season. In addition to the normal considerations, such as current surface integrity, nature of previously applied coatings, application methods, and the demands placed upon the finish, it will, at the very least, be necessary to consider basic aspects such as the state of the surface to be decorated and to consult the weather forecast on the day of planned application.

The demands placed on exterior decorated surfaces become increasingly evident in more extreme weather conditions. For example, the orientation of the surface can contribute to particular stresses placed on the finish; how rain and wind can cause flaking or promote mould growth on north facing walls. Equally, prolonged periods of sun can cause bleaching to those facing south. The need for thorough surface preparation becomes all the more essential.

Paints applied to south facing wooden surfaces can suffer from flaking or blistering if the right product is not selected or applied correctly. This can be exacerbated by the use of dark colours which absorb more heat than lighter shades. Heat absorption gives rise to a greater chance of the finish splitting when under stress, which can allow moisture to penetrate the wood - a problem most commonly seen in the joints of wooden window frames. It may also cause a high degree of movement in the substrate due to natural expansion and subsequent contraction when it cools. It may also activate resin in the timber and force out any moisture.

At all times of the year, the location of the building to be painted also needs to be taken into account before an exterior coating is specified. Is it in a coastal area and likely to be affected by salt? Is it in a busy city centre, likely to be subject to a build-up of smoke staining and grime? In this case it is important to provide a surface that is easy to clean. Exterior walls can also be affected by mould and fungus, so a coating with protection against mould and fungal regrowth is essential for long-term protection of these surfaces.

Preparing the surface correctly can add years to maintenance intervals and make it easier to apply subsequent coats. Surfaces need to be clean and dry, with all traces of grease or dirt removed to ensure the coatings adhere successfully, maximising aesthetic appearance and longevity of the project.

Correct priming and undercoating promotes better topcoat adhesion, helps prevent cracking and can contribute to a better finished colour. It is essential to prime any new or bare surface, or any surface that has been exposed during repairs.

An undercoat can contribute to opacity when painting a light colour over deep or bright colours.  This is the best way to optimise topcoat performance and cut down on the number of subsequent coats required.

The application of the finish also needs consideration. One problem that can be created is the wrinkling of paint during drying. This can be caused by a coating being applied too thickly or by the premature overcoating of an undercoat or gloss. Oil based coatings, especially those with a gloss finish, tend to become thicker and more difficult to apply at low temperatures. This can result in the application of excessively thick coatings, which can cure slowly and develop surface defects.

Low temperatures and high humidity can restrict the application of many exterior finishes not specifically created for winter application, limiting painting to warm, dry months only. Applying coatings that are not specifically suitable for application in cold, damp conditions during those times of the year may mean that such coatings take too long to dry and become affected by inclement weather during drying. Recoating may be delayed and, in the worst case scenario, removal and reapplication may become necessary.

So, the final and essential piece of the external painting puzzle is choosing the correct products to perform in challenging weather conditions and still produce a long-lasting result.

Systems based on Acrylated Alkyds, such as those in the Sandtex Trade product range, enable the successful completion of projects in cold, damp environments.

External refurbishment programmes conducted ‘out of season’ can pose challenges to the manufacturer, specifier and the contractor, but none that cannot be overcome with careful preparation and application, teamed with the specification of the right products. A carefully considered redecoration programme can not only prolong maintenance intervals, but also dramatically increase aesthetic value and reduce costs.