Our monthly newsletter is packed with log home inspiration ideas plus new product updates and specials. All you need to do is sign up, sit back and enjoy.

    Welcome To Western Log Home Supply Blog
    Thursday, March 19, 2009

    Log Jam is the only chinking to hold a 1 hour UL fire rating when applied in accordance with the Fire Resistance Directory Design No. UL519. What does this mean and why is it important?

    What is UL?

    UL stands for "Underwriters Laboratory".

    UL develops standards and test procedures for products, materials, components, assemblies, tools and equipment, chiefly dealing with product safety.

    UL has developed more than 1,000 Standards for Safety, many of which are American National (ANSI) Standards, and evaluates nearly 20,000 types of products. A typica
    l standard for electronic products includes not only requirements for electrical safety, but also spread of fire and mechanical hazards. UL evaluates products for compliance with specific safety requirements. UL certification does not guarantee the product will perform acceptably or that it is safe under all conditions (such as product misuse).

    Why was a certification needed?

    The rebirth of the log industry in North America could be described in a number of terms. “Easy” would not be one of them.

    Log home companies and their product suppliers have constantly faced resistance from:

    • Architects
    • Building code inspectors
    • Loan officers
    • Governmental agencies steeped in the doctrines of conventional “stick” construction.

    The fledgling industry has often found itself in the frustrating position of being condemned not by facts but by biases.

    One such bias has been that water-based chinking materials used to seal the courses of log walls could never pass a one-hour fire test.

    The experts felt that since many of the compounds used to make water-based chinking decompose at temperature far below the 1700 degrees required by the test, a chinked log wall could not survive it.

    This belief persisted in spite of the fact that a one-hour fire test had never been attempted on any log wall system, chinked or otherwise.

    The end result of this widely shared view was that many log projects were held up or stopped completely since most major building codes required a one-hour fire rating in critical areas such as between the garage and house or in commercial structures.

    Often, log home customers were told that their log partitions would have to be covered by drywall in the critical areas.

    Certainly, this tended to dampen enthusiasms for solid timber walls.

    Now, a test conducted by Underwriters Laboratories has laid this belief to rest. Recently, it tested a complete chinked wall system which passed the one-hour fire test. The chinking compound under scrutiny was Sashco Sealants Log Jam Chinking compound.

    It cost Sashco, a Colorado-based company, about $10,000 and months of research and testing to perfect the formula for Log Jam Chinking. But the company believed an answer had to be found to the problem.

    Preliminary Research

    According to company officials Sashco began with a pragmatic “back yard” approach. A miniature log wall section was constructed out of 4” fence posts. In a crude simulation of the one-hour test, they exposed the section directly to flame from a propane torch for one hour.

    Researchers quickly discovered that they could not prevent decomposition of the chinking material. So, instead, they found a way to make the decomposition work in their favor. They reasoned that if they could not get the chinking to stay put and not melt away, the burned exterior might act as an insulator in much the same way as the charred surface of wood provides a thin barrier between the flames and the material behind it.

    They arrived at a formula which actually formed small “heat shields” as it charred. It gave an unexpected bonus in that it also expanded as temperatures increased. This further protected the integrity of the log joint.

    Funds were then made available for the Underwriters Laboratory test which essentially was to certify the results found by the Sashco researchers. Certification by UL meant that building inspection could be passed by log walls using Log Jam Chinking. Correspondingly, this would expand the availability of log structures for many commercial and residential applications where one-hour fire ratings were required.

    The Underwriters Testing Procedure

    The UL test involved the use of a giant furnace at the Underwriters Northbrook, Illinois laboratory.

    • A 10 foot high by 10 foot wide wall of 9 inch round lodge pole pine logs was constructed leaving one inch gaps between the logs.
    • Round backer rods were then fixed in the joints and Log Jam Chinking was tooled over the top to a minimum depth of ½ inch.
    • The wall was framed in brick and insulation to insure that no flames passed through the assembly which was not a result of wall failure.
    • Because it was felt that any residual water left might artificially aid the fire resistance of the chinking material, the assembly was left to stand for 30 days t allow all of the water to leave the Log Jam Chinking for a thorough cure.
    • The test wall was then rolled into the furnace where it was exposed to 68 gas jets throwing flames which raised the surface temperature to 1000 degrees F in 5 minutes, 1300 degrees F. in ten minutes and, ultimately 1700 degrees F. in one hour.
    • The unexposed side was left at room temperature.
    • After the test the wall was rolled out of a blast furnace and exposed immediately to a blast of water form a 2-1/2 inch fire hose, exposing it to “impact, erosion and cooling from a fire house stream” of 30 pounds per square inch of force. Of course, as UL officials explained, water could not be allowed to spray through the wall.

    Pass Requirements

    • The chinked joint obviously could not fail allowing fire to pass through the wall.
    • In order to pass the one-hour fire test, the unexposed side of the wall could only climb 250 degrees F. above its starting temperature.
    • Water could not be allowed to spray through the wall after the spray test.

    In other words, the Log Jam Chinking had to be a good insulator as well as being fire resistant.


    The investment Sashco made in time and money paid off. In July 1986 Sashco received the full UL test report. Not only did its Log Jam Chinking pass all aspects of the one-hour fire test, the unexposed side showed a rise in temperature of only 160 degrees F., qualifying it as an excellent insulator.

    Log Jam Chinking is now the only answer to a one-hour fire wall needed” said one Sashco official, “unless, of course, you’d like drywall over your logs”

    Information Courtesy of Sashco Inc.

    Labels: , , , , ,

    by: Western Log Home Supply
    Saturday, December 20, 2008
    With its thick walls of solid wood, a log home is one of the best-insulated buildings in which you could choose to live. But the nature of a log home's construction also presents a unique challenge: the opportunity for air to pass through the gaps between the logs.

    Fortunately, air infiltration is a challenge that's easily met, thanks to caulking, the general term for the seals that are introduced between logs. With the right caulking method, or "caulk joint" as it is generally termed, a log home can achieve thermal efficiencies to rival those of any building method.

    Two key elements are essential to effective caulking. First, the caulk used must form a "wet" seal, one that adheres to the wood surfaces rather than just filling the gaps between them. And second, it needs to be elastic (a quality sometimes referred to as "memory"), either stretching or compressing as the shapes of the logs themselves subtly move through natural expansion or contraction.

    With those elements met, four principles govern the most efficient caulk joint design: caulk depth, points of adhesion, a caulk "well," and the conditions under which the caulk is applied. Each principle is fairly simple to grasp, and understanding them all will help anyone buying, building, or restoring a log home make the right energy-efficient decisions.

    Principle 1: Apply the Right Caulk Depth

    In general, the depth of caulk in a joint is more important than the width of the caulk's application. Why? Put as simply as possible, the most critical factor is that the caulk have enough mass at any given point to absorb any movement in the logs.
    As a rule, whatever its width, the depth of a caulk joint does not need to be any more than 1/2 inch or any less than 1/4 inch. (See figure 1, which illustrates how a thinner cross-section results in less stress on the joint.). Also, a deeper joint is preferable to one that is too thin.

    Principle 2: Provide Two Caulk Adhesion Points

    Caulk works best when it adheres only to two elements, namely the two logs between which it is applied, so that the seal will hold if and when any movement occurs in the logs. (See figure 2, which illustrates how this principle applies whether the joint is being stretched or compressed.)

    Adhesion to three or more points, by contrast, would cause the caulk to be pulled in multiple directions, thus increasing the likelihood that the seal will break away from one or more of the points of adhesion. (See figure 3, which illustrates how such ruptures can occur under three-point adhesion.) Placing a backing rod inside the well

    With this principle in mind, any backing materials included in a caulk joint should provide a surface to which the caulk does not adhere. Doing so allows the caulk to remain at its most elastic.

    Principle 3: Create a Caulk Well

    Superior caulks have enough elasticity to absorb 25 to 50 percent of the total movement in the joint they fill. To allow for that movement, caulk joints require "wells," spaces that allow the joint to absorb that movement.

    For a reliable seal, the caulk well should be two to four times larger than the movement that is anticipated for that joint, thus reflecting the 25 to 50 percent absorption properties of the caulk being used. (See figure 4, which illustrates how an anticipated 1/4-inch movement calls or a 1-inch caulk well.)

    Obviously, the greater the movement expected in a particular joint, the larger its caulk well should be. Log homeowners can also take comfort from the fact that high-quality caulks currently being sold are capable of absorbing far greater movement than that for which they are rated.

    Principle 4: Apply Caulk Under Optimum Conditions

    Because logs expand or contract in response to temperature and humidity, the climate conditions at the time caulk joints are applied will affect the seal formed. On a very hot, humid day, for example, a joint will be at its smallest, since wood expands under such conditions; so caulk applied at such a time will later be subject to the maximum stretching. By contrast, a joint will be at its largest on the coldest, driest of days; so caulk applied then will later be subject to the maximum compression. (See figure 5, which illustrates the tension on caulk joints under both extreme and average temperature conditions.)

    With this principle in mind, it is wise to select a caulk with properties that best suit the range of local climate conditions, and to apply it at the most stable, least extreme point in the climate cycle. But smart log home builders will also apply caulk at optimum times; for example, sealing caulk joints on the cooler side of a home will work most effectively on a warmer day, while those on the side of a home that gets more direct and prolonged exposure to sunlight would best be sealed on a cooler day.

    By aiming to apply all four principles described above, you'll maximize the effectiveness of your caulk joint seal. That may require you and your builder or contractor to implement sealing techniques that go beyond the most obvious and simple solutions. (Figures 6 and 7, for example, illustrate how two logs conventionally sealed with caulk applied at their meeting point lead to a triangular, three-point adhesion that can easily rupture; but adding a caulk well with a backing rod to the same log cross-section results in much more secure two-point adhesion.)

    Keep these guidelines in mind, and you'll thus enjoy the maximum benefits of log homes' superior insulation and energy-saving capabilities.

    Labels: , , , , , , , , ,

    by: Western Log Home Supply