Log Home Chinking
When logs are first cut, they are very wet. When they dry out, the logs shrink in diameter. Most of the movement takes place in the first 12 to 18 months, from then on seasonal moisture variations cause smaller but continuing cycles of shrinking and expanding.
The problem, of course, was that any chinking material used to seal in between the logs did not adhere to the logs, and did not have any ability to stretch and follow the movement of the logs as they continually expanded and contracted. Mortar chinking lasted longer than mud, or cow dung, but very quickly cracked, or separated from the logs.
This was as good as it got until 1981 when Perma-Chink Systems invented the first polymer based synthetic chinking. The advantage of this chinking material is that it adheres very tightly to the logs (even wet logs), is an elastomeric (when the logs move, it stretches and contracts to follow the movement without breaking or separating), and is colored and textured to look just like conventional mortar chinking.
Perma-Chink does not contain cement – it is a pure acrylic polymer. It’s flexible and it stretches. The chinking product is easily applied, can be trowelled to just about any thickness or width, comes in different colors. The chinking will last for the life of the structure and will provide that all-important barrier to keep the wind, water and insects from penetrating the wall system. Perma-Chink in essence revolutionized the chink style log home market. Up until its introduction, all chinking had to be constantly maintained, always leaked air and water, and at some time, had to be replaced. Currently synthetic chinking is used in virtually all-new chink style log homes.
Thick chinking vs. thin chinking. Do different logs lend themselves to different types of chinking.
Yup, different log building styles do lend themselves to different chinking appearance. Square logs with dovetail corners, by their geometry, typically have a dovetail that interlocks the logs at the corners, as a result of this geometry, the chinking gap between logs can be 3 to 4 inches wide. Some square logs have chinking gaps that approach 6 to 8 inches and more.
Round logs with saddle notch corners typically have a log sit right on top of the bottom log, yielding a gap of 1.5 to 2 inches. Milled log houses are designed with a tongue and groove system, or a cope system that utilize interior gasket material to seal the space between logs and sometimes need a thin 1/2 to 3/4 inch added chinking to seal any gaps. All gaps require a backing of some type to apply Perma-Chink over.
For reclaimed logs, or logs with an irregular chink joint, scribed foam bead board is used for backing, then the required layer of Perma-Chink is applied over the backing. In other applications beaded foam insulation, or specifically designed backer rods are placed in the gap, then a 3/8 “ layer of Perma-Chink is applied over the backing. Then the chinking material is trowelled smooth and pressed tightly to the upper and lower logs. The white backing material is applied first, then the Perma-Chink is applied over the backing at a depth of 1/4 inch to 3/8”. The applied chinking is then trowelled to achieve a smooth surface, paying particular attention to pushing it tight against the upper and lower logs. The goal is to have a consistent layer of chinking that, when cured, is a minimum of 1/4 inch thick.