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Chinking The Logs

When properly prepared and notched, logs were stacked such that they did not rest against each other except at the notch. A crack or chink of one inch or more was visible between the logs of a wall. Chinks allowed for warping and expanding when unseasoned wood was used. They also permitted builders to work with the irregular surfaces and natural tapers of logs. As with notching, chinking was influenced by different cultures.

Chinking was a two-part process whereby two fillers were used to close gaps (or chinks) between the logs. Daubing was the outer finish layer. If maintained, they effectively sealed the interior from exposure from the elements, intrusion from vermin, and pooled water on the tops of logs.

The materials used for the rigid filler varied, and were merely a product of local materials. Clay, stones, poles, wood chunks, and split wood shingles have all been used. The soft filler served to fill small cracks and crevices around the rigid fillers and provided a surface for the daubing to adhere. Oakum, moss, clay, straw, paper, cloth, and even dried animal dung were typical soft fillers.

Daubing was the final seal of the three-part process. Mortar was perhaps the most popular daubing. It was comprised of solely clay, mud, or dung; or consisted of a mix of lime and water. Binders included sand, hair, straw, ashes, flour, sawdust, and shredded newspaper. Bark remaining on the logs served as an excellent binding agent. Modern materials have included cement, and even chicken wire or metal lath are a daubing key, though all are unacceptable materials, being non-historic and incompatible.

NOTE: Although 'chinking' and 'daubing' clearly define the difference stages of the three-part process, the two words are often, albeit incorrectly, used interchangeably. Popularly, 'chinking' is used alone to describe all steps.

Cement and its various forms can do irreparable damage to log structures. It has most popularly been used as the sole ingredient in chinking, which in itself is historically inaccurate. Its density reduces uniform breathability throughout a structure, causing areas such as logs to become saturated with water - in effect taking in more water faster than it can release it.

Chinking should be flexible, and it should never be stronger than the material to which it adheres. By employing cement, a rigid, incompatible chinking is being introduced; the logs bear the full brunt of any seasonal movement and absorb the bulk of all water.


CAULKS AND SEALANTS

Caulks and sealants are soft moisture-impervious compounds; they have little or no ability to breathe. Caulks should be used in locations where movement is minimal. Sealants are designed to be flexible in areas with anticipated movement; their elasticity maintains the integrity of a joint.

However, these modern products are not suitable for historic log structures due to their non-porous nature as well as being historically inappropriate. Caulks and sealants, generally, have improved lately to achieve colour stability, and resist ultraviolet rays and mildew, but their impervious nature prohibits them from working with traditional building materials, particularly wood.

There are several suppliers of commercial materials to use for chinking. These include:

Here is some info that we located from Mother Earth News. Some of it is the same as above but we thought we would include it anyway:

"In the old days, hog bristles, horsehair, hemp and other tough plant fibers were incorporated into house plaster, stucco and log chinking. Their length held the amorphous fluid ceramic together during application and afterwards when dry. Exterior surfaces of "horsehair" plaster were (and still are) preserved and interior surfaces kept clean and solid with frequent applications of whitewash.

Earliest log cabins were chinked with what was available -- simple mud or mud mixed with straw, as done for eons in mud-wattle, adobe or cob wall construction. Many old cob walls (and chinking jobs) remain serviceable today after scores and hundreds of years; some all-cob domed granaries and houses in sub-Saharan Africa date back millennia.

Loamy soil is to be avoided for chinking, as its organic content will shrivel and continue to break down, leaving voids inside the chink that will initiate internal cracks and lead to eventual breakdown. Look for river mud with a high clay content, or dig down under dark topsoil to lighter, more dense subsoil, or mine a wedge of pure clay if you can find one. Mix with equal parts of sharp, clean sand and enough straw to hold it together. For hands-on information about how freestanding cob-walled homes are built today, read "From the Ground Up," available by clicking on "Building" under "Our Best Stories" on the home page. The same principles apply to mixing and applying mud chinking to logs. One thing: "point" -- or mold the outer surface of -- your chink in an inside curve that ends a couple of inches farther back on the bottom log than it starts on the top log . . . so that rainwater dripping down from the upper log will hit wood rather than the lower lip of chink.

Often the inside walls of the original log cabins were plastered flat to look elegant. In any event, it's the thin upper and lower edges of exterior chink that need attention and repair most frequently -- to keep water out.

Mixtures of quicklime with mud and straw or animal hair were tried but have not held up well for a century and a half. In 1824, a British mason invented Portland cement, which replicated Roman mortar and still holds up after 2,000 years. It is made by heating a mixture of clay and limestone (chalk) to burn off water content, then grinding the result. Mixed with water and a matrix of gravel or more sand, it rehydrates chemically and hardens back to waterproof rock. Mixed with a pure sand matrix, it becomes mortar that forms a permanent, waterproof bond between stones or ceramic, such as brick or block. Mixed with sand and gravel it becomes concrete.

Both mortar and concrete mixes have been tried for chinking -- either put in solid, mixed with straw, or in inner/outer layers with straw or other porous material in the middle. It is heavy and it cracks when water gets under thin edges. Cracks can't be patched effectively, as the continual motion of logs rebreaks it. It absorbs water (without modern concrete-waterproofer) and passes it through from outside to inner walls, where it stains and forces off paint, plaster, wallpaper and whitewash.

You are best advised NOT to use lime or Portland cement in any chinking mix. It is monolithic; as logs shrink and swell with the weather (and they all do) they will pull away from the chinking, leaving space for cold drafts to whistle in, bugs and varmints to enter and for rain to work between chink and log . . . to freeze and chip the former and pool and rot the latter. You will be forever patching. Today you see mortar-chinked log houses patched with new cement-mix, tar, caulks and mastics, chewing gum and pine tar. Most such have been painted long since and look awful.

If chinking of cement or mortar mix and sawdust or whatever sets up at all, the core of it will last forever; shaped as an "H" between two logs, it can't be removed except with a jackhammer. Some long-ago geniuses even inserted steel reinforcing rods (rebar) inside solid-concrete chinking so you need a cutting torch to remove it in sections.

In modern chinking systems, well-trained and well-equipped specialist contractors place backer rods of rigid or extruded expanded (poly) foam in the center of the space. Then, using special trowels and power-caulking guns and years of experience, they apply a thick plastic (vinyl) coating over the seam, inside and outside. It insulates well, adheres and remains semi-rigid for decades, expands and contracts with time and temperature, log movement and shrinkage, comes in any color you want, will last for decades with little or no upkeep, and is easily removable with little but a penknife if repairs or replacement are ever needed."


 

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