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Chinking Application Guide

Log home chinking should be a one-time job. Below are some important points to consider about the application process.

Moisture Content

When preparing for chinking, a moisture content reading of the logs should be taken in several different locations. Use a lignometer and check the depth 1” below the surface. This is particularly important on new construction. A moisture content of 18% or less is recommended for homes that are to be sealed with chinking.

Preparing The Logs

Logs must be free of any oil-based finishes, factory-applied oil-based mildewcides/preservatives, residual cleaners or wood restorers, or any non-penetrating surface finishes, including polyurethanes and polycrylics, etc.

Logs must also be free of any fungus or mildew. To remove fungus or mildew stains, we recommend that the logs be thoroughly cleaned with any commercial, non-acid cleaner being sure to follow all manufacturer’s instructions for application and safety. Rinse the surface thoroughly with water to remove all traces of cleaning solution. Test the wood surfaces with Litmus paper to verify pH neutral surface. The range should be slightly acidic to neutral, and in the natural pH range of the wood species (for example, pine is 6-8). Wear protective clothing and eye protection when using caustic solutions. 

Remove any loose bark, sawdust or construction marks from the logs. A cleaner such as Spic & Span will take care of most soiling, although some areas may need to be lightly sanded. (Try a gum eraser on pencil marks and light scuff marks.) Use a damp, clean lint-free rag to wipe down the log surfaces.

Be sure to allow adequate drying time after washing and recheck moisture content before proceeding with chinking or caulking application. Drying may take several days depending upon weather and location.

We recommend applying UV Guard® Exterior Wood Finish, UV Guard® II Exterior Finish, SuSTAIN® or Log Guard® Interior Top Coat prior to application of Triple Stretch® chinking or UV Guard® Caulk. If other products are to be used as the finish, be certain to check with Weatherall Technical Support regarding compatibility and recommendations.

Stain Selection

We recommend and guarantee that all Weatherall stains and finishes are compatible with Triple Stretch® chinking or UV Guard® Caulk. As previously mentioned, it is important to use a finish that does not contain any parafins, waxes or non-drying oils in order to get good adhesion. Incompatible stains can cause chinking materials to lift from the surface.

Temperature and Humidity

Best results are achieved with chinking application during temperatures of between 45° and 75° F. Avoid chinking in direct, hot sunlight or on wood surfaces that have been exposed to the hot sunlight for several hours. Do not chink when rain is imminent, or when temperatures are expected to fall below freezing without complete cure time. Do not apply when dew or frost is present and do not apply to frozen surfaces. Special application procedures must be followed for sub-freezing chinking application; contact Weatherall Technical Support for further information.

Scheduling

Planning ahead prevents the loss of valuable work time due to lack of materials or preparation. (Refer to Appendix B for chinking coverage guidelines.) Draw up a well-planned schedule that will allow for shipping of materials, custom color matches, seasonal weather conditions, holidays, etc. Items such as the type of equipment used and log preparation may greatly affect scheduling.

On new chink-style construction, the chinking is generally applied after the roof is on, the door and window openings are cut and bucked and the wiring is in between the logs, but usually before the doors, windows, and trim are installed. On scribe-fit or milled log homes, the chinking may be applied anytime after the building is enclosed, but it is best to leave the window and door trim off so that these vulnerable areas can be well sealed with the chinking or caulking material.

Equipment

A caulking gun is frequently used by homeowners who wish to apply chinking themselves. Both bulk-loading manual and bulk-loading air-powered models are available. Be advised that the use of a caulking gun will require additional time. A caulking gun is ideal for very small jobs, small areas that require special tips, or touch-up. (HINT: Spraying the inside of the gun barrel with the troweling release agent will allow the chinking material to slide and load smoothly without air pockets.)

Renting a commercial pump is initially more expensive, but the amount of time saved is significant. These pumps operate at an efficient rate of speed, have pistol-grip handles and large capacity hoppers. Follow the pump manufacturer’s instructions for pump operation. Various tip sizes for the commercial pump can be achieved by cutting different sizes of PVC and chamfering the tip ends.

Assemble all of your equipment, tools and materials together at the job site. Know where the electrical and water supplies at the site are located and be prepared with proper hoses, cords, etc. A secure, temperate area should be used for storage of the chinking. DO NOT FREEZE and do not allow materials to become overheated.

If you are using a hand or air-powered caulking gun, check it for proper working condition. If you are using a battery-powered gun, have an extra battery pack available. If you are using a commercial pump, check it for proper working condition. Extra pump parts, such as stator, rotor, nozzles, and hoses and other maintenance parts will help avoid costly delays. Be sure to carry several heavy duty extension cords and follow the manufacturer’s recommendations for operation of the pump.

Recommended Tools & Supplies List

  • Chinking pump and/or bulk-loading caulking gun(s)
  • Tool Pouch
  • Clean, lint-free rags for wiping down log surfaces, for spills, runs and cleanup
  • Sharp knives suitable for trimming backer-rod
  • Cardboard box or table for holding backer-rod while adhesive is applied
  • Spray adhesive (such as 3M™ 77) for installing backer-rod
  • Spray bottle for ‘release agent’
  • Isopropyl alcohol – combine with 50% water for ‘release agent’ mixture (label for precaution)
  • Masonry margin trowels of appropriate sizes (1/2” to 2” most commonly used)
  • Spatula for scraping pails
  • Sheets of heavy plastic or canvas to protect job site from spills and inclement weather
  • Backer-Rod in appropriate sizes, or other backing materials
  • Adequate quantity of chinking/caulking

Backer Rod

Select a high-quality flat-sided, closed-cell backer-rod such as Better Backer or GripStrip. Backing is installed in the log joint to provide a flat non-adhesive, insulating surface for the chinking to be applied over. We do not recommend use of either round backer rod or split round rod for chink joints ¾” and wider. Round rod will not give the proper joint design. Split round rod will cause the chinking to stick to the cut open-cell surface reducing the area of elasticity. Split round rod also tends to roll in the joint creating weak spots and unattractive bulges. For joints under ¾”, we recommend that Better Backer or GripStrip be cut to a smaller size and placed in the joint with the cut face facing inward. Alternatively, closed cell round rod may be used in joints of less than 3/4”, but care must be taken that the chinking is applied at a uniform thickness on the surface.The joint will have a generally convex shape. Slick-surface bond-breaker tapes may be applied to joint configurations where foam backer-rods cannot be used; for example, the flat joints found in square log construction.

NEVER APPLY CHINKING WITHOUT A BOND BREAKER! A bond breaker is a smooth surface or finish on the chink joint to allow the chinking to pull away, only bonding to the wood, once joint movement begins. Elasticity of the joint will be greatly compromised if chinking is applied directly to an adhesive substrate such as rough surface (open cell) backing, logs, blocking, drywall, etc. The chinking should adhere only to the wood at the edges of the joint. A ‘slip-joint’ is necessary for proper joint design and performance.

Applying Backer Rod

First determine the correct size of Better Backer or GripStrip by laying various sizes into the joint. Choose the size that fits well into the joint and keeps the flat surfaces snugly against the logs. Next, place the chosen pieces onto a flat box, table or rack and spray the two upward exposed surfaces lightly with a high tack spray adhesive, such as 3M Super 77.

Let adhesive dry until tacky, then carefully insert the backer-rod into the log joint and press firmly until it fits snugly between the logs. Continue in this manner until the backer-rod is installed in all the log joints. NEVER SPRAY ADHESIVE DIRECTLY ONTO THE LOGS! This will result in an unsightly film on the wood surfaces and will weaken the chinking bond to the wood causing adhesive failure in the joint. For aesthetics, take your time to avoid “steps” in the face of the installed Better Backer; do not change sizes abruptly. You may trim the adjoining pieces on the top or bottom edges to ease the size transitions. Make certain that the exposed outer face is installed parallel to the wall plane and does not tilt in or out.

When installing Better Backer around knots, corners, curves, over protruding wiring, etc., the back side of the backer-rod may be cut out as long as the (front) flat surface is left intact. Where blocking is used between the logs, apply backer-rod over the blocks as well. To do this, place backer-rod over the block and mark the back of the rod at the edges of the block. Cut along the mark, being careful not to cut through the front face. Cut horizontally to remove excess. Leave enough surface depth to maintain the smooth, flat face of the finished joint. It is best to request samples of the various sizes of the backing and test fit them into the joints before ordering.

Most handcrafted homes will require several different sizes. A smooth surface backing that will not adhere to the chinking or caulking material should be used in ALL applications. If the joint configuration has a flat surface, as with log siding, square hewn logs, etc., bond breaker tape may replace the HBR and/or Better Backer.

Weather Conditions

Apply chinking only to dry wood surfaces. Heavy dew or frost will wet the logs and will adversely affect the adhesion of the chinking. Additionally, chinking should not be applied to surfaces that are too cold. If ambient temperatures or sunlight are not warming the surfaces to above 40°, then mechanical heat sources should be available and utilized.

Be sure to keep the chinking in a warm area until immediately before use. Chinking should not be applied when rain is likely and should not be subjected to freezing weather until it has cured. If rain or heavy moisture occurs after chinking, protect the chinking by placing a heavy sheet of plastic or canvas over the chinked area. Pull the covering out and allow air to circulate. Do not allow covering to contact chinked surfaces.

If it is absolutely necessary to chink during freezing temperatures, please contact Weatherall Technical Support for details. It is possible to chink in subfreezing temperatures, but special equipment and procedures are required.

Application Tips

Choose an appropriate size nozzle for the width of the chink line. Round nozzles as small as 1/4” diameter and up to about 1” in diameter are commonly used. For narrower chink lines (less than 1½”), hold the nozzle tip close to the joint surface (within 1/8” to 1/4”) of the backing material and allow the material to flow smoothly as you move the nozzle along the joint. (HINT: If you have not done this before, it would be a good idea to practice in a location where the chinking will not show, such as the interior of a closet or behind cabinets. Move in a smooth steady motion down the line of the log and do not let the material build up in thickness. In areas where the joint is larger (1½” or more), apply the chinking in a side to side motion, from the top to the bottom of the joint. Blend the overlap lines with a dry trowel, using no release agent, then retrowel as described below. Start slowly and use caution not to apply too much or too little material. Be sure not to cover too much area at one time, thereby allowing the material to ‘skin’ over before troweling can be completed. Whenever feasible, it is preferable to apply one continuous line of chinking down each log joint from end to end. Stopping in the middle requires more effort to trowel and blend the start-stop lines. With any application motion, the goal is to apply just the right amount of chinking so that the finished troweled thickness will be between 3/16” and 1/4”.

Troweling

When troweling it is important to see that the material is worked carefully into the joints and that edges are firmly tooled to achieve maximum adhesion to the wood and form a weather-tight seal. To begin troweling the applied material, lightly mist the bottom of the trowel with the release agent, then proceed to trowel the material neatly and firmly into the joint and along the edges. Use a trowel stroke of 6”- 12”. The release agent, when used properly, will allow the trowel to glide smoothly over the chinking without sticking and pulling. Using too much release agent will cause excessive wetting and/or runs, and may prevent the chinking from properly sealing the wood. Although normally you should not spray the release agent directly onto the logs, under some circumstances it may be necessary to lightly spray the applied chinking as you trowel it. Spray only as much release agent as is necessary to give a smooth texture without pulling. Care should be taken to force out any air bubbles/pockets that may have developed. Air bubbles/pockets can be created during the loading of the material into the equipment or by an overlapping application pattern. Check your troweled thickness by inserting the tip of a clean trowel into the freshly tooled chinking material. After examining the depth of the material adhering to the trowel, correct the depth if needed and retool the area to reseal. Finished troweled thickness of the chinking on chink lines 3/4” and wider should be between 3/16” and 1/4”… no more, no less! Properly prepared and applied applications will result in chinking material that is tightly bonded with the wood at the edges of the joint. After fully curing, substantial force will be required to remove the chinking, tearing out wood that has become embedded within the chinking edges. Very specific conditions may cause poor bonding of the chinking to the wood; surface contaminants, failure to use a compatible wood finish, failure to firmly trowel the chinking at the edges, failure to apply the chinking at a minimum thickness, application to wet or frozen wood, or use of too much release agent.

Cure Time

Chinking will be ‘skinned’ over on the surface in approximately 30 minutes, under average temperatures and humidity conditions. It will be surface dry in 8-10 hours. However, it will be several days before firmly cured. If weather conditions are humid or cold, curing will take longer.

Clean Up

Wipe up all spills, runs, etc. immediately. When chinking is completed for the day, promptly clean up tools and hand guns with warm water. Lubricate all metal parts with a light oil to prevent rust; lubricate gun seals to prevent drying. Follow the commercial pump manufacturer’s instructions for maintenance and clean up. NEVER allow material to dry in pump, in hoses, or any place it is not wanted. Once cured, it is very difficult to remove.

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