Foot Traffic and Weather are Key Considerations
In another Ask the Painter article we discussed using epoxy to coat garage floors. But because it does not hold up to sunlight, epoxy is not well suited for exterior use, so what are some options for concrete patios and walkways?
Let’s be very clear that epoxy coatings are not suitable for exterior use. This is because the UV rays in sunlight will break down the chemical bonds in the epoxy causing premature discoloration, coating failure, and “chalking”. So leave the epoxies for garage or interior floors.
In terms of which coatings are suitable for use on driveways, patios, and walkways, there is a broad range of products to meet a variety of needs, looks, and budgets. This article briefly surveys 5 general categories of products:
- Concrete Stains
- Concrete Sealers
- Deck Coatings
- Stone Composite Coatings
Each of these will be discussed momentarily, but first let’s take care of a few points common to all possible solutions.
In addition to sun exposure, concrete surfaces that are meant to be walked on have some additional challenges: surface preparation requirements, durability to withstand foot traffic or patio furniture being moved across the surface, heat build-up, slip-resistance, and ability to withstand chlorinated water (from irrigation systems) puddling on the surface. So before getting to the product categories, let’s hit on two of these topics that are more or less independent of specific products that might be used: surface preparation and slip-resistance.
When working on concrete, most products require the surface to be clean, and many require an acid etch to “open up” the surface for better adhesion of the product to be used. Cleaning the surface may be as simple as powerwashing it, or it may involve mechanical abrasion and/or “degreasing” with a chemical such as TriSodium Phosphate (TSP) or a TSP-substitute. Acid etching is done with Muriatic Acid, and this basically “eats away” at the smooth surface and leaves a rougher surface for products to flow into for maximum bonding.
Slip-resistance of the finished surface is critical for surfaces that will be walked on. Water puddling on smooth concrete surfaces can be very treacherous, as slipping due to “hydroplaning” is possible. Slip-resistance comes from having a rough surface, either by virtue of the surface itself being rough (as when a broom finish technique was used when the concrete was wet), an additive in the coating, or the texture of the coating itself. Note that any rough surface will also be harder to keep clean is it will trap dirt and give pockets for mildew to take hold. OK, so on to product specifics.
In general, paint is not a great product choice for areas that will be walked on. While there are some products specifically meant for such areas, paint typically does not perform well enough for driveways, patios, and walkways. Getting the paint to stick to concrete may involve using a special masonry primer. Compared to other coatings, paint is relatively thin and soft, so scratching or wearing away of the color is likely.
Depending on the look to be achieved, concrete stains may be a good choice. The semi-transparent stains will, however, allow any underlying discoloration in the concrete to show through. Differences in concrete density or “porosity” will also play into how the concrete takes the stain leading to variations in color (whether this is desireable or notis a matter of personal preference). Additives for slip-resistance may also affect the color uniformity. Concrete stains are generally top-coated with a clear sealer.
Concrete Sealers are closely related to stains, but are generally either clear or solid colored. Solid colored sealers have more of a painted look, but the product is much more durable than concrete paint. Sealers may be either acrylic-based or “solvent-based”. Some of the solvent-based sealers are not suitable for application outdoors in Texas during summertime, as they require the surface temperature to be below 90 degrees for several days so that the solvents don’t try to “bake out” too fast, which can lead to bubbling. Slip-resistant additives are highly advisable with some sealers.
This category includes brand names such as “SUNDEK”, “Kool Deck”, “Spray Deck”, and others. It is typically what you see used around swimming pools because the sun does not heat it up as much as other materials so it stays cool under bare feet. Some of these products must be applied when concrete is new (applying a thin coat of new concrete over the old may be necessary), while others may be applied over an existing surface. The products are also typically given a “knock down” texture (similar to that on the drywall of many homes here in Texas), but this type of texture can trap dirt that is left behind as water evaporates away so it may require more frequent washing.
Stone Composite Coatings
Stone composite coatings contain actual stone, bound with a resin (typically acrylic) that binds the mix together and bonds to the surface being coated. The stone may range from pea-gravel sized pebbles to very fine particles of ground stone. The resulting looks from coatings of his type range from that of exposed aggregate to granite or other homogeneous rocks. By blending mixtures with different color bases and pebble or ground stone mixtures, a variety of finished results may be achieved.
Depending on the look you are trying to achieve, how much wear-and-tear it must endure, and your budget, there are a number of products that may meet your needs. Matching the right one to your project, and then getting it installed professionally, will give you results to enjoy for years to come.
Copyright 2010 Jeff Stec