PRO Deck Doctor – Park City Custom Decks, Deck Restoration, Deck Builder

Deck with a topcoatTopcoats

Topcoat is a term we use to designate any material used to seal, color, or other wise protect deck surfaces. Topcoats come in all shapes and sizes. They all make claims to do one thing or another but in the end they rarely do what we expect them to do. And all to often manufactures make blankets statements regarding the performance of products that don’t hold up when put to the test. Most consumers look at two issues by purchasing topcoats: color and price point. While these are very important factors there are a whole set of other things that you, the consumer, should look at when you go to purchase the topcoat for your deck.


Color is a tricky thing. The samples of color really depend on what the color is going on. Color samples that are on a piece of paper rarely match the final color once it’s on the deck. With paints you usually start with a flat white surface. The color chips you get at a paint store are usually a dead on match. Why? Because the paint has actually been applied to a white surface. So to, when you go to paint a room you usually start by painting the room white. Wood comes in a broad spectrum of colors or tints or hues. The grades of the wood will contain different tones of color. These variations carry through to a the final appearance once the stain is applied.

Many manufacturers offer color chips just like paint chips. These chips often are on Cedar, rarely Redwood, and never on exotics This is an import feature to note because if your deck Redwood and you are looking at a Cedar chip then you will be very surprised when you ally it to your deck. If you read the manufacturer’s recommendations often they will say to place a small sample of the topcoat product on an inconspicuous area to assure the color is what you want. This is really the optimal way to do it however as mentioned, differences will be evident on each an every boards. ( NOTE: Clear grades offer the least amount of differences due to the fact that the wood is all from the similar part of the tree.)


The price of topcoat is really driven by the market So, rarely is the price an indicator of the quality. It is always interesting to see a dozen products all at the same price. More expensive does not necessarily mean better quality. There are certain instances when this is true. The manufacturer Sikkens makes a topcoat called DEK. It is more expensive in relation to other topcoats however, the quality of this product far surpasses anything on the market There is a caveat to this. DEK can only and should only be used in certain applications

Sikkens makes a variety of products and they do have price points to match. We at PRO Deck Doctor recommend all the Sikkens products. Conversely, there are products out there that charge a hefty premium but only perform under certain conditions. How do you know what conditions apply to you? You probably don’t but perhaps our reviews from the research and development are may help. In the end don’t spend the top dollar unless you know the product is for your particular situation.

Other areas that should be of concern when deciding on a topcoat are waterborne, waterborne with oil base, alkyd borne, transparent, semitransparent, solid based.

Water proofed deck during rain storm

Waterborne Deck Topcoats

Water-borne latex stains are more porous, allow more rapid moisture movement into the wood than solvent-borne oil or alkyd stains, and thus do not provide good protection from water soluble extractive staining. Since these stains use water as a carrier for the various components of the stain, they may actually create an extractive discoloration problem at the time of application. This can be particularly noticeable with light-colored latex stains. Although many latex stain labels do not exclude their use over staining species such as redwood or cedar, they may recommend the use of a stain blocking primer, especially for lighter colors.

True water borne products are harder to find these days. One manufacturer that still makes a true water borne is

Topcoats are perhaps the most confusing issue. There are a great number of different choices out there. Topcoats are a broad term used to designate a material that is added to surface of the deck in order to give it color, water repellency, ultraviolet protection along with others. Topcoats come in the form of paints, stains, and clear coats. Paints should never but used for exterior horizontal surfaces. Stains are the most common form of topcoat used for protecting decks. Stains typically come in two styles : penetrating and film forming. Clear coats are used to seal the wood for moisture. They offer little in the line of protection from anything but water. Most clear coats are just a wax based formula. I would like to say that there is one product applicable for every application. Unfortunately, there is not. Some water topcoats are quite good for a specific purpose namely, repelling water. However oil based formulas have a greater resistance to overall deck detriments. Oils or alkyd based have a broad spectrum unto themselves. Lets look at some differences that exist amongst oil based. I will come back to the water borne products.

Stains are the most common product used to protect a deck surface. Stain come in many guises. There are Transparent stains, Solid based, Semitransparent, and Translucent stains. How you know what product is right for you? The make up of most oil topcoats is fairly straight forward. There is a base or binder The binder is an oil or resin, a urethane or acrylic,. Or a combination of these. It can be man made or synthetic, or it can be natural. Then there usually is an agent incorporated called the carrier. The carrier serves many purposes. The biggest purpose is to create a substance that can be used. Without the carrier the product would be very thick and unable top be worked with efficiently. The other major reason for the carrier is as a drying agent. Oils by nature do not dry They do not contain substances that evaporate, like water.

Manufacturers put solvents into the formulas to assist in the drying process.. Without the solvents the oils would remain tacky for an indefinite amount of time. ( Have you ever done you deck and even 2 weeks later your shoes stick to the surface. That is a result of the oils not drying The stickiness diminishes for two reasons: one the product may actually , finally dry, or 2 the pollutants from the air coat the surface and create a new coating, with dirt.) Solvents, come in many forms.

Manufactures use a variety of oils as their base formula There is however a systematic approach to selecting which topcoat will work best for your purposes.

The first thing you need to consider is the wood type. Hardwoods require a finer or low viscous oil in order to penetrate into the wood.

There have many recent introductions of wood coatings specifically for hardwoods. Companies often will refine the binders prior to incorporating into their specific formula.

After the binder and carrier, are the colorants. These colorants come in the form of pigments, and dyes.


Pigment is a finely ground, inert, colored powder. They can be natural or man-made, organic or inorganic. By organic we generally mean containing carbon along with hydrogen and oxygen, as well as nitrogen and sulfur. Pigments are classified industrially according the chemistry of the main colorant. While any pigment can be used to stain wood – the ones that find the most use are: Iron Oxides – iron oxide is the yellowish to reddish-brown inorganic constituent that makes rust brown and clay red. The natural iron oxides are dug up out of the earth, washed and ground into pigment and some of these are called the earth colors -the sienna’s, umber’s and ochre’s. The burnt form (burnt sienna, burnt umber) is the raw pigment that has been calcined – or heated to the point just below melting which confers a redder shade to the pigment. A pigment called Van Dyke brown is also in this group but somewhat incorrectly because it is composed of mostly organic matter with only a small amount of iron. The natural iron oxides are well-suited as wood stains because they contain a high silica content which makes them transparent (what technicians call a low refractive index) and they are muted in color which mimics wood-tones well. Synthetic iron oxides are available in red or yellow shades. They are more opaque (high refractive index) – which makes them ideally suited for use in paints, but they can be used in stains in micronized form (ground very fine), usually in combination with the earth pigments.


A dye is a complex organic chemical derived from petroleum products like benzene, toluene and naphthalene. Through chemical processes such as nitration and sulfonation, these chemicals are processed into dye intermediates such as aniline which are processed further by special operations like diazotization to give the final product – a dry chemical powder. These powders can be dissolved in various to yield colored solutions which can be applied to wood. The conventional classification used for many years in woodworking has been to classify dye powders as water-soluble, alcohol soluble and oil soluble dyes. While this classification serves as an adequate framework – it has also given rise to erroneous generalizations about dye performance (like alcohol dyes are not lightfast). The classification used by the dye industry provides a more accurate classification. While there are thousands of dyes used in everything from textiles to plastics – there are only several types used in woodworking applications.

Dye stains are composed of only two components – a dye and a carrier. While at the surface this may seem to be a simpler arrangement than a pigment stain- dyes are little more complex to understand

There are three main physical differences between dyes and pigments and these affect the working qualities and performance of the stain. The differences are size, how they attach to the wood and lightfastness.


The difference between pigments and dyes can be best visualized by their size. Pigment particles in most wood stains are about 1-2 microns. (1 micron =1/1000 meter) That means that you can see them under a magnifying glass. When a pigment stain is applied to the surface of a piece of wood and wiped off, the discrete pigment particles get lodged in pores, crevices and scratches, any cavity that’s larger than the size of a pigment. On ring porous woods like oak – the stain accentuates the pore structure because more pigment is deposited in the pores than in the flat grain between. On diffuse-porous wood like birch – the pigment stains more evenly. On very dense, close grained woods like hard maple, the pigment stains very light because the surface cannot hold much pigment. Because 1-2 microns is well above the wavelength of visible light ( .4 – .7 microns or 400-700 nanometers), pigments absorb light (to produce color) and block it’s transmission by reflecting it. If built up too thickly to achieve dark effects, pigment stains can obliterate wood grain but if used correctly can add contrast and depth.

By comparison, dye molecules are much smaller- it would be like comparing a soccer ball (pigment) to the head of a pin (dye). Dye molecule size results in several other differences. Dye colors evenly – regardless of the density or pore structure of the wood and light is not blocked by the dye molecule, it’s absorbed and transmitted. This gives dyes their unique ability to accentuate grain and subtle figure even though the dye color is bold and dark.

Method of Attachment

Pigment requires a binder to glue it to the surface of wood because it’s an inert substance that’s merely suspended in a carrier/binder A dye is in solution and to understand how a dye “sticks” to wood it’s important to be able to visualize dyes at the molecular level – something easy for chemists but not so for the average person. Both the dye and the substrate being dyed (wood) are chemicals – possessing certain characteristics which chemists call functional groups. At the molecular level these groups can be visualized as open pockets of electrostatic charges (+ or -) or acid-base characteristics. In dyes, the functional group can serve as a method of attaching the dye to the wood. Acid and direct dyes can attach themselves through molecular electromagnetic forces like zillions of tiny little magnets, basic dyes can have an acid-base attraction (wood is acidic) while solvent dyes are just absorbed into the wood (which is why oil and alcohol dyes have more of a tendency to bleed) . This is why dyes do not require a binder like pigment does. Water dyes penetrate the deepest because wood is hydrophilic (water-loving), but water causes the wood fibers to swell – which raises the grain Non-grain raising solvents are used in industrial finishing because of the extra time necessary to re-sand the surface.


The performance difference between dyes and pigments is in lightfast ness. Since light is comprised of electromagnetic radiation – it can have a destructive effect on both pigments and dyes, but dyes are most vulnerable. Light destroys colored objects by breaking electronic bonding within the molecule. An inorganic molecule such as iron oxide has very stable, strong molecular forces which hold the atoms in the molecule together. The energy in sunlight is not sufficient to break these bonds Conversely – the bonds that hold an organic dye molecule together are much weaker – and sunlight is ultimately able to disrupt or break the bonding arrangement which causes the color to fade. This is why there are no dyes rated for exterior use. Some dyes are more lightfast than others – and the best performance can be expected from the metallized dyes. A common misconception is that alcohol dyes are not lightfast, but the solubility of a dye does not determine its lightfast ness, it’s chemistry does. Alcohol soluble basic dyes have been used in woodworking for so long that they’ve given a bad rap to all alcohol dyes in general. The metallized alcohol/ketone soluble dyes such as those made by Ciba-Geigy and BASF are very light-stable – even if compared to all other dyes. Benzotriazole additives available that can be added to finishes to mitigate dye fading and wood patination. These additives are called UV absorbers and they work on a process called tautomerism, in which harmful UV is absorbed and dissipated as harmless heat. The iron oxide pigments, titanium white and carbon black are all lightfast – even under harsh conditions Some organic pigments are not as lightfast and while fine for interior use, aren’t rated for exterior conditions.

The first step in selecting a topcoat is recognizing what adversities your deck faces. This starts with your specific geographic region. Study the atmospheric conditions that exist. Selecting an inappropriate topcoat can result in an unsightly, unhealthy deck, and a deck that is difficult to maintain. The two main factors that most decks have to be protected against are moisture and UV light. If moisture is your deck nemesis then you will want a topcoat that protects against water penetration and with inhibit fungal growth. If UV light in what your deck contents with you will want a topcoat that either reflects or absorbs and disperses this damaging radiation. Analyze what your deck most contents with and go from there.

If you moisture is the issue select a topcoat that contains these two thing : synthetic resin and fungicides. Topcoat products that contain Linseed oil, vegetable oils, animal fats or even Tung oils or other ‘natural resins’ can actually promote organism growth. These types of oils are high in fatty acids which are food for mildew and fungus. Many manufactures are incorporating mildew ides and fungicides in their topcoat formulas. These additives are good are retarding growth. But remember, these products are only as good as their application. Remember the humidity level underneath some decks can be very high. Under the deck is dark and humid. These conditions are perfect to promote fungal and bacterial growth I recommend treating all six sides of the deck boards prior to installation, if possible. If this is not done and you content with high humidity issues, then your deck will always face mold and mildew issues. These organisms take a foothold on the underside of the deck boards and slow permeate through, eventually showing themselves on the topsides. Once this process starts it may be very difficultly to eradicate them all together.

If UV radiation is intense on your deck you will want a topcoat that reflects this radiation These formulas additives react and protect against in two ways: UV absorbers or UV stabilizers. The principles that exist here are some what complicated. ( Beer Lambert law) But simplify put these absorbers and stabilizers repel or disperse electron radiation. This radiation breaks down the lignin or ‘glues’ in the wood. When this break down occurs the wood fibers become susceptible to check and cracking Once these fissions occur in the wood, natural weathering takes a foothold and the process continues until the boards eventually break apart.

To know whether you content with UV light, check you local UV index. Generally speaking, if you live in higher elevations you have a higher UV index. There is a world of difference between 3000 ft elevation and 7000 feet elevation. Just because you receive a large amount of sunlight on your deck does not necessarily mean you have a high UV index. Likewise living at a high elevation does not necessarily mean you need to focus your deck’s topcoat qualities toward UV protection (IE a North facing ground level, covered deck with poor gapping and poor ventilation)

If you have any questions regarding what topcoat is right for you feel free to contact PRO Deck Doctor. No one topcoat is universally good. But there are some that we would be happy to recommend. We continue to test a variety of topcoats in a variety of conditions. and would be happy to share our experiences.