Coatings and Paints for Commercial Building Exteriors
Buildings need paint and other coatings to protect them from the weather elements. In Toronto we are faced with harsh elements both during the winter and in the summer. During the winter, coatings are affected by snow, ice and low temperatures. In the summer, rain and ultraviolet radiation are the enemy of exterior surfaces. By painting commercial building exteriors regularly, you can protect them from the elements, improve their look and increase their value.
The Surface and what Primers to Use
Before deciding what paint to use, you need to determine what is currently on the surface. If the surface is bare, it needs to be solid and sound, clean and dry. There are undercoats made for all surfaces such as masonry primers, wood and metal primers.
- 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.
Epoxy primers are for industrial environments like power plants, exterior tanks, structural steel, marine applications, etc. They are resistant to abrasion, moisture and chemical exposure. By curing chemically these primers provide an unbeatable base coat that adheres to all tough surfaces. In combination with industrial grade paints, these undercoatings help to create corrosion resistant paint film integrity. Two part epoxy primers are more expensive, not widely available and require knowledgeable professionals to apply them.
Sealants and Caulking for Building Exteriors
The job of the exterior caulk and sealant is to protect buildings and their exterior surfaces from moisture. By containing flexible materials such as silicone, sealants accommodate expansion and contraction. There are three basic types of caulks and sealants.
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
There are manufacturers making exterior paint and they all have different grades. When dealing with exterior painting, top line paint is recommended. Manufacturers invest all their R&D money in their top lines and they test it for harsh environments. There are also some good regional and specialty paint producers available.
Because of environmental concerns and government regulations, paint manufacturing companies spend most of their effort in researching and producing water based acrylic paint. As a result, acrylic based coatings are now superior. Still available, alkyd used to be the paint of choice for exterior. Similar to the interior oil based paints they produced a tough and durable finish. The best of them had additives such as linseed only to help with flexibility. Because of the longer drying times, alkyd paints penetrate the surfaces better and their resins allow for superior adhesion. Alkyd has some problems:
- 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
The majority of paints used today are water based and acrylic based. A top line acrylic paint offers many benefits:
- 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
Stains and varnishes are used often for decks, walkways and some wood siding and trim. Stains are available in both water based and alkyd based coatings. Alkyd stains penetrate the surfaces better and last longer. Acrylic stains contain extenders for longer open time and resins to help with better adhesion.
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
Masonry surfaces such as cinder and concrete blocks, brick, retaining walls, stucco, and foundation walls, are porous, with millions of little pinholes. A masonry grade paint seals the porosity to protect the structure from moisture. Some masonry coatings are self priming, eliminating the need for an undercoat and sealer. Concrete floors are primed with a thinned version of the finish paint. Some of these coatings contain waterproofing agents and can be used with good results on foundation walls and even water fountains and aquariums.
Epoxy Finishes for Floors and Concrete Walkways
Exterior Floors receive a lot of wear and tear especially on walkways and public spaces. In tough weather climates floor finishes do not last very long. If possible, leaving the surface bare is not a bad alternative. There are porch and floor enamels and different types of penetrating stains but none offer the coating film strength and durability of epoxy.
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
Metal is one of the last few substrates that was used as a reason to justify the continued existence of alkyd paint. There are still alkyd primers out there but waterbourne enamels are quickly increasing their market share for industrial metal enamels. Direct To Metal coatings are getting better, they are easier to use and have lower odour and VOC levels. As far as performance is concerned, they are as good or better than their alkyd counterparts for almost nny applications. After prepping the substrate according to industry standards, DTMs offer superior chemical and corrosion resistance. Pitt-Tech® from PPG is one of the main manufacturers with a complete line of DTM paints in all finishes. We had good experiences with Benjamin Moore and Dulux DTM lines. As with any commercial coating, follow the recommendations the manufacturer recommends for prep and application.
Paints for Pools
There are acrylic paints for pools that will do a good job if applied properly. They are a good replacement for chlorinated synthetic finishes because of their compliance with VOC regulations. Acrylic paint can be used over the synthetic rubber pool paints as well as over uncoated concrete surfaces. The curing time is about one week depending on weather conditions.
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
Maintaining the paint will go a long way in protecting the exterior surfaces and save money in the long run. If possible wash contaminants off the surfaces gently with water. If using a pressure washer use very low pressure as not to damage the existing paint and caulking. Horizontal surfaces such as ledges and walkways need the most attention and they should be maintained more frequently. Painting floors every year or two is not uncommon, especially in areas that receive a lot of ice and snow.
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.