Coatings and Paints for Commercial Building Exteriors
The Surface and what Primers to Use
- Some masonry coatings are self priming check the labels for manufacturer recommendations before deciding whether to use a primer or not.
- Galvanized metal. Alkyd coatings are not recommended for galvanized metal, use a good acrylic primer instead. Wash the metal with hot water and detergent, rinse and do not paint until completely dry.
- Rusted metal should be treated before applying a DTM (Direct To Metal) coat. First remove any loose rust, sand and wirebrush until shiny. Prime the surface soon after with a good rust inhibitive primer. We had good results using a marine grade rust converter called Blue Steel. This was a big exterior painting project for a property manager and years later the railing still looks good.
- Wood decks and walkways are the most difficult to maintain and require yearly maintenance. The best options are penetrating stains. Stains do not require a primer.
Sealants and Caulking for Building Exteriors
Acrylic caulking is the easiest to apply and tools can be cleaned with water. Their ease of application makes them the most popular with painters and carpenters. Their flexibility is limited and do not allow for much expansion and contraction. The better ones contain silicone to help with flexibility and still remain paintable.
Polyurethane sealants are good for big gaps in building exteriors and have superior adhesion to different materials. Because it adheres well to different materials, this is the caulk of choice between materials with different contraction and expansion rates. It is difficult to apply and for cleaning you need mineral spirits. Polyurethane caulk dries to a solid rubber compound that expands more than 400% and still is paintable. It resists chemicals and has a lifespan of 5 to 10 years.
When maximum flexibility and durability is what you are after, Silicone caulk is the ideal product. Silicone sealants offer the most flexibility, even during serious temperature fluctuations. Cracks will stay watertight for a long time, in fact, manufacturers will offer a 20 year warranty. Since most polyurethane sealants are guaranteed for 5 years, the longer lifespan of silicone is more economical in the long run. What are the disadvantages? Silicone is more difficult to tool, produces very strong fumes and is not paintable.
The Finish Coatings
- The organic resins in alkyd paint are food for mould. As a result there is mould in shady and humid areas of the house.
- It has higher VOC (Volatile Organic Compounds) content, which makes it a bad environmental choice, especially when painting building interiors and hallways.
- The long drying time makes painting front doors very inconvenient.
- Chalking is what happens when alkyd paint ages. The binders break down and leave pigment (chalk like) to the surface. This happens more on surfaces exposed to the sun. It is very evident when running your hand over the chalky surface. As a result, alkyd paints have poor colour retention rates.
Acrylic Coatings can be as Tough as Alkyd
- Quick drying times allow for multiple coats in the same day
- Tools and hands can be washed with soap and water
- Superior flexibility makes cracking almost impossible
- Resists chalking and has better colour retention
- Most acrylic paints today have very low VOC content which makes them a better choice for the environment and a preferred choice for Ecopainting.
Stains, Varnishes and Waterproofers
Varnishes are protectants for wood surfaces but unlike their interior counterparts they contain UV Ray inhibitors. Clear waterproofers are water based, mostly invisible and also contain UV Ray inhibitors. Their protective coating breaks down in less than a year and surfaces should be recoated anually.
Masonry and Concrete paints
Epoxy Finishes for Floors and Concrete Walkways
There are different grades and blends of epoxy and they can be used on existing concrete. Taking into account the cost and inconvenience of replacing existing concrete, installing an epoxy finish is a favourable alternative. Epoxy comes in different colours and can enhance the look of concrete walkways by blending in with existing landscape.
DTM Metal Paints – Rust Inhibitive Coatings
Paints for Pools
The most durable pool paint is solvent based two part epoxy. It has a lifespan of 7 to 8 years. It can be applied up to 8 mils thickness per coat, which helps smoothen imperfections. Despite the longevity and the other benefits of epoxy, these are some reasons property managers use acrylics:
- It can only be used on bare concrete and previous epoxy coatings
- The preparation work is very extensive when applying over existing epoxy
- It needs a perfectly dry surface. In fact, a condensation test is necessary and no epoxy can be applied if any moisture is present.
- It comes in two parts, has to be mixed well and needs to be applied fast.
- It has the longest drying and curing time, about 7-10 days depending on weather conditions. This is difficult to manage when painting it for a townhouse complex or a condominium corporation.
Maintenance of Surfaces and What Your Painter Can Do
Double check all joints and make sure they remain watertight. Moisture is the biggest enemy of exterior finishes.
Ask your painting contractor if they have an exterior paint maintenance program. If they do not, call them back every year or two to address any maintenance issues. Ecopainting offers a limited warranty and we can also arrange an annual maintenance visit.