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Logs: Treatment and Preservation
This section addresses in greater detail the finish and care of log walls and woodwork.
Q. How does weather affect logs, and what is done to guard against deterioration?
A. Answer:
Weather and Logs
While logs have a unique charm and feel all their own, they also possess characteristics that can lead to problems later on. Because logs are not "typical wood," like flat siding, shingles or other woods used on the exterior of conventional homes, they must be treated differently. Several guidelines are used because your log home requires special treatment.
Home Design
To help protect logs from the ravages of sun and water, it's strongly advised to design and build homes with large eaves and overhangs whenever possible. It's also wise to use a gutter and downspout system to keep roof runoff from flowing down walls and splashing up onto the lower courses of logs.
Sunlight and Round Logs
The upper curve of round logs receives intense and powerful bombardment by the sun (see diagram). Normal vertical siding always receives sunlight at angles less than 90', reflecting much of the energy away. However, there is always some portion of the upper curve of a rounded log which receives sunlight at a 90' angle.
This intense light not only attacks the wood and coating with high-energy, ultraviolet radiation, it also drastically heats the surface of the logs, even on cold winter days. Measured the surface temperature of over 95 degrees farenheit occur even when the surrounding air temperature is as low as 50 degrees farenheit. When you consider that same morning the air was only 28 degrees farenheit, you can see that tremendous temperature swings may occur on the logs' surface. In fact, surface temperatures in the summer may exceed 135 degrees! These radical temperature fluctuations cause the logs to contract and expand significantly and continually.
Rain and Snow
In addition to round logs being subject to the effects of sunlight, Exterior wall round and square logs surfaces are also very susceptible to rain and snow (see diagram). Logs are unavoidably loaded with cracks and holes - all of which permit moisture to penetrate logs. The checks and cracks that occur on the "uphill" side of a log often collect large amounts of water which seeps into the adjacent wood. When the sun heats the log's surface, moisture trapped in the wood near checks and holes tries to escape through the coating. With enormous energy, the moisture then forces its way out, causing a heavily applied coating to peel off.
Most coating failures found on log homes are found in the immediate vicinity of these cracks and checks. The major problem is peeling, and peeling usually starts at the edge of a crack or check - where the water concentration is the highest.
Moisture entering the logs not only affects the surface coating, it can also contribute to destruction of the wood itself. Water trapped in a check can freeze and expand, opening the crack even further. Trapped water encourages the decay of wood by providing the moisture necessary for wood-destroying fungi to survive and flourish.
Q. What type of finish should I apply to the logs, and how should it be applied?
A. Answer:
If you're the homeowner, you probably have a "vision" of how your log home will look after it's stained. The paint or stain color you've chosen can give you that look if you prepare properly before application. Here are the Dos and Don'ts to achieving the color you really want:
DO Test the stain on a sample of log from your home. Test the clear also, as it may impart a slight golden cast.
DO Allow the stain to dry 24 hours for full color development.
DO Use the same application method for the sample as will be used on your home.
DO Give your contractor the final sample and ask him or her to match the look on your home.
DON'T Allow the contractor to apply paint or stain until she or he he thoroughly understands the look you want.
DON'T Use sample wood which has a different surface texture or color than the logs or woodwork in your home.
DON'T Stain your entire house before you verify you're achieving the proper look and color
Note: The wet color of paints and stains are usually different from the dried color. Don't be misled by the color in the newly opened can or by the initial color on the wood. To judge the final color, place the sample in the area of the wall to be coated. For example, if for exterior application, leave the sample outdoors by the wall to be stained (sunlight may vary the final color); for the interior, sample should remain indoors. For full color development, the sample should be allowed to dry 24-48 hours.
Q. What is meant by U.V. (ultaviolet) absorbers and log protection?
A. Answer:
Clear Coatings and U. V Attack
It is tempting to use only a clear coating to preserve the "justbuilt" look. But in sun-drenched areas where only a clear coating is used, the logs' natural color will begin to fade after only a matter of months. And eventually the logs will show signs of severe weathering.
This phenomenon is true of all clear coatings because it is impossible to load enough U.V. absorbers in any clear coating to protect your logs. But the pigments in quality stain will block U.V. rays from your logs, protecting them much longer and more completely than U.V. absorbers.
One heavily applied pigmented coat of stain gives excellent protection to your home. A second coat, lightly applied, will give a darker shade with some added protection. (Refer to your product's documentation for more information.)
Q. How does the Log Surface affect the coating?
A. Answer:
Mill Glaze
A typical log surface is coated with "mill glaze"-the hard, smooth film that forms on the surface of wood when leftover tree resins and sugars are acted upon by the mechanical and heat energy of the milling process. This layer of glaze can be almost impenetrable for a coating. It must be removed before good penetration and adhesion can occur. Mill glaze occurs on all types of logs and must be dealt with in order to maximize the chances for a trouble-free and durable coating job.
Hand-Peeled Logs
Hand-peeled logs are less prone to mill glaze since high temperatures are not common. However, hand-peeled logs exhibit a very smooth, slick surface with some residual tree resins and sugars present. Consequently, hand-peeled logs also need proper preparation before they are stained.
Skip-Peeled Logs
Sometimes a "skip-peel" treatment of logs is done. This style leaves patches of dark cambium, the layer underneath the bark, on the logs' surface. These sections will eventually peel off and will take whatever coating is applied with them.
Q. How should logs be prepared before finishing?
A. Answer:
BEFORE Staining
Preparation of the logs is as important as the staining itself, especially the first time a home is coated. Proper preparation can determine the stain's longevity and effectiveness.
Mill Glaze: The mill glaze present on virtually all logs must be removed. This is best done by aggressively power-washing with high-pressure water or with light sandblasting. This process will not only remove the surface glaze, it will also help roughen the surface for a better coating bond.
Moisture Content: It is important to know the logs' moisture content before applying any coating. The Forest Research Laboratories (operated by the US Government in Madison, Wisconsin since 1911) recommends that wood be allowed to dry to a moisture content of 19% or less before applying a coating. Applying coatings to wood "wetter" than 19% can lead to moisture-induced failures. If the logs are power-washed or sandblasted, let them dry completely before applying a finish.
Clean Surface: Make sure all surface dust, dirt, wax, pencil marks, fungi, mildew, grease, old paints or peeling stains, loose bark or cambium, and other contaminants are removed from the surface and the checks
Bark and Cambium: We recommend all bark and cambium be removed from the logs to allow the coating to adhere to a solid and permanent substrate.
Wood Preservatives: We recommend a wood preservative be applied to logs to help protect them from attack by wood destroying fungi and insects. However, some preservatives may contain additives that are not compatible with all stains. Check with the manufacturer before applying.
Checks and Cracks: Because of the logs' tendency to take on water from rain and snow through cracks and checks, it is important to thoroughly caulk as many openings as possible.
Caulking may be applied before or after the stain is applied, but it's usually better to caulk before staining to prevent moisture from entering the logs before you have a chance to stain. Use a high-quality caulk, such as Sashco Log Builder, in all cracks and checks 1/8" or wider, especially those on the uphill side of the log. Be sure to use backer rod in joints 1/4" or wider before caulking. For good adhesion, the inside surfaces of checks must be thoroughly cleaned to remove dirt and unsound wood.
When caulk is applied, use good pressure to inject it into the crevices, then tool it with a finger or spatula to ensure it comes in full contact with the sides of the opening, otherwise, poor adhesion may result. Avoid smearing the caulk on the log surface and tooling too much of the caulk out of the check or crack (the surface of the caulk should be flush with the logs).
Additional Fungicides: In areas with high moisture exposure, it is advisable to add an additional loading of fungicide to the stain just before application to ensure control of surface mildew. The additional fungicide may also protect against other forms of fungi which receive nutrients from dirt splashed on the surface of stained logs.
Q. How should finish be applied to Exterior Surfaces?
A. Answer:
Number of Coats
It's important to apply Paint or stain so it can easily "breathe" and permit some moisture vapor exchange through the surface film. We recommend that only one coat be heavily applied to exterior surfaces. If a darker shade is desired, a second, lighter coat may be applied. The first coat should be pigmented paint or stain for best protection. While you should never use clear alone on the exterior, it can be used to dilute the color if necessary-though you should be aware that diluting the color will result in reduced U.V. protection for your logs.
This system will provide a high level of pigmentation on the logs' surface to block the sun's destructive rays and will also provide a high level of resin to resist the penetrating effects of moisture. The resulting finish will be a very natural-looking flat to satin sheen.
The pigment concentration in your paint or stain is designed to provide as much defense for the wood as possible without overly hiding the grain. The pigment will cover some of the wood's grain, but this is an essential trade-off for a high level of protection.
Weather and Application
Make sure you apply paint or stain to exterior walls only when they are in the shade. Always work where the sun is not directly shining on the surface. Otherwise, the stain may dry too fast, not allowing good penetration.
With decks, work while the sun is shining at a low angle, either early in the morning or late in the afternoon. This will minimize the surface heat and will prevent the stain from drying too fast.
Avoid applying paint or stain in extreme cold or hot, dry, windy conditions, which can cause the stain to dry improperly.
If rain or dew is imminent in 4-8 hours, protect stained walls with plastic sheeting or wait until conditions are better.
Q. How should finish be applied to Interior Surfaces?
A. Answer:
Because the interior is not exposed to the same weather and moisture extremes as the exterior, log preparation need not be extensive, but large cracks and checks should still be caulked to prevent water and air infiltration from "spiraling" in from outside checks or cracks.
Usually, one pigmented coat, straight or diluted with clear, will be applied to the interior. For a more uniform color finish, apply a sanding sealer before applying finish.
Each coat may be lightly sprayed or brushed onto the logs and should become slightly tacky before applying the next coat.
Q. What constitutes proper care for my log home?
A. Answer:
For the first 1-2 years after the structure has been stained, the exterior logs' surface should be inspected regularly. During the early period in the life of the home, the checks in the logs continue to open up as they further dry out and settle onto the foundation. If severe problems are observed, they should be dealt with at the time of discovery; otherwise, see below.
The majority of the recaulking and recoating should occur when the logs are at their driest, when the checks and cracks are at their largest, so the openings can be filled with the most amount of caulk and stain. This is particularly true of the logs' uphill side.
The first recaulking and recoating effort, if needed, should be attempted during late Summer, 18-24 months after the new home is completed. These are the warmest and driest months so it is important to remember to work in the shade. Due to extreme weather exposure and foot traffic, decks and hand rails will usually need maintenance more often than vertical surfaces.
Q. Are there some general finishing pointers when it comes to staining and sealing my log homes?
A. Answer:
The first coat should be sprayed and back-brushed, thoroughly working the stain into the wood. Any subsequent coats may be applied with a sprayer alone, but be sure to apply lightly and evenly and brush out any runs.
All log cut ends should be coated several times until the pores are sealed. These areas are the most prone to water absorption and mildew damage, and they require special care.
An unevenness of sheen, referred to as flashing, may occur on soft woods, like pine. To stop or soften this effect on interior wood, apply a sanding sealer before applying finish. Follow the manufacturer's recommendations.
By controlling a paint or stain's penetration into the wood, a more uniform finish coat will be achieved. Deep penetration is not nearly as important for interior applications as for exterior, which must resist the extremes of weather.
Do not use sealers on the exterior because they prevent the finish from penetrating. The initial flashing that may occur on the exterior will often soften or be eliminated within 90 days by the action of the sun and weather.
Knotty woods are more prone to flashing than open-grained woods.
The lighter shades of stain may tend to give an uneven shading of the wood surface. Some areas of the log may absorb the pigment more deeply than other areas where the pigment remains mostly on the surface (such as knots). This unevenness can be compared to the antiquing effect sometimes seen in furniture and cabinetry and can be very attractive. However, if not desired, the effect can be minimized on the interior by using a sanding sealer.
