By: Elizabeth Wanga
The proper planning of a coating removal project can save time and money over the long term. While the approach may change as the project progresses, an initial understanding of the coatings, substrate materials and the available compatible cleaning products is imperative. Coatings are often installed to make the surface appear uniform after damage, soiling or deterioration has occurred. Therefore, theA owner and practitioner should be prepared to restore or replace damaged surfaces. Although coatings are usually installed to mask surface inconsistencies, there are instances where the paint or coating is part of the original design or part of a major period renovation of the building. In these cases, the layers of coating should be examined prior to removal so the finish color can be determined and the appropriate coating can be specified during design.
During design, the preservation consultant should identify the material and test several compatible cleaners in discrete locations. Itas important to prepare mockups and review samples of cleaning products. The level of cleaning and the desired results should be agreed upon by the engineer or architect, the conservator, the contractor and the building owner. In certain municipalities, landmark officials may also need to be consulted on cleaning products and methods.
Many buildings have several layers of paints or coatings. Each layer may be composed of an alternate base or chemical that reacts differently to removal compounds or solvents. Therefore, a few different solvent products may be required to remove the coating down to the substrate material. Many existing coatings or paints were not designed for breathability or compatibility with the masonry. These coatings can trap water, leading to further deterioration of the masonry. It is important to fully remove all coatings in their entirety so that all areas that require repair, additional cleaning or patching can be assessed.
In addition to aesthetic considerations, health and environmental impacts should be considered before beginning a coating removal project. The contractor should ensure that materials can be properly collected and that workers and the public are adequately protected during removal. These precautions may include installing filters on building intakes, collecting water and residue, and limiting the use of abrasive materials. The contractor should also ensure that all openings in the wall are permanently or temporarily filled or protected so that water and cleaning agents do not damage adjacent surfaces or penetrate the walls.
If access for material testing is not available during design, it must be undertaken once scaffolding and protections are in place. The preservation consultant should research the building and make educated assumptions regarding substrate materials and their conditions. However, since more unknowns regarding the substrate and its condition exist whenever testing is not performed during design, the owner should be prepared for potential additional costs associated with cleaning highly stained or severely damaged materials. In these cases, additional cleaning, repairs to the masonry or re-coating of the facade may be warranted.
Our series on facade cleaning will continue with a review of building materials, cleaning methods, installation of new coatings and removal and prevention of graffiti.