Western Log Home Supply Archive Page
Sunday, December 28, 2008
Saturday, December 27, 2008
I hope that everyone had a great holiday season! Check out my new blog about military history and my Marine Model Johnson Rifle: Talking with Clyde
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.
by: Western Log Home Supply
Friday, December 12, 2008
The term sapstain and blue stain is used in many articles concerning rot and wood preservation. One should understand this term as a first step in understanding wood degradation and rot.
What is Sapstain?
A tree consists of many parts, but for this short treatise two terms, heart wood (physiologically dead wood located near the center of the tree) and sap wood, which are located on the outer periphery of the tree (physiologically active) will suffice. The sap wood carries water and nutrients up though the tree and thus is a perfect environment for sapstain growth.
When a board or timber is cut from a log, mold spores can come in contact with the nutrient rich wood with its inherent high moisture content and they begin to multiply and spread over the face of the lumber.
As they spread they create a stain which is normally blue, but can actually be different colors. Throughout the years I have seen not only blue, but also black, red and yellow.
If this mold/stain is not checked, it can penetrate into the wood with tendrils and take the infection deep into the lumber or timbers. They will eventually emit enzymes which will break down the wood and then you have the start of serious decay. We are talking about lumber which is wet (unseasoned) and in a nutrient rich environment. Many people talk of dry rot; but in reality there is no such thing. This is a misnomer. since wood needs to be between 30 and 60-percent moisture content for it to begin the decay cycle.
To prevent sapstain from discoloring the lumber and to prevent further degradation through decay, many mills will dip the product into a fungicide to deter mold from attacking the lumber. This is particularly important in the humid areas of the United States and its use is highly recommended for high quality, valuable lumber.
Lumber which has a high propensity of sapstain will not take a finish evenly. The area which has the sap- stain will absorb wood finishes more than unaffected areas. Thus, when finishing a piece of lumber so infected, one will have to use a number of wood finish coats to even out the look. For high quality products such as furniture or mouldings, the lumber infected with sapstain is discarded.
If one is installing wood which has mildew present, it should be washed thoroughly before applying any type of finish. We are talking about a surface coating of mildew, not a stain that has penetrated deep into the wood. Use a mixture of three quarts of water, one quart of household bleach, and 1/4 cup of liquid dishwasher detergent which does not contain ammonia. Never mix bleach and ammonia as it will give off hazardous fumes. This formulation can be sprayed on using a pump sprayer. After 15 to 30 minutes, it can be washed off using a power washer.
Remember that once the stain goes deep into the wood, it cannot be removed with bleach or any other product. It is there to stay. Always remember not to play chemist and experiment by mixing various chemicals as they could give off hazardous fumes...and more!
Please check out our section of wood cleaners and brighteners and log home preservatives. As always you can contact Clyde at 719 547-2135 if with any questions regarding wood or log homes or visit our website at www.westernloghomesupply.com
by: Western Log Home Supply
Monday, December 8, 2008
WHY DOES WOOD CRACK WHEN IT DRIES?
To get right to the point, wood cracks due to differential shrinkage! Differential shrinkage occurs because the outer fibers in the shell dry first and begin to shrink. However, the core has not yet begun to dry and shrink, and consequently the shell is restrained from shrinking by the core. Thus the shell goes into tension and the core into compression. With the stresses from the shell and core pulling in opposite directions the wood fibers break and a crack forms. The larger the wood member, the more stress is exerted to the wood member.
Lets take an example of a 1x8 board versus an 8x8 timber
This is just another reason why wood materials should be properly dried before using them in any mode other than for exterior use such as fence posts, landscape timbers or a rough fence. If they are being used where their final moisture content will be 15% or lower, they should be dried prior to milling and installed into their final end use. In this way the seasoning, stress cracks can be aligned in such a way that they are hidden or discarded.
Preventing Cracks – Proper drying techniques and PEG
What can be done to prevent this seasoning degradation in wood? With large quantities of lumber, boards to timbers one can only resort to proper drying following the many details that make up the complete process. This can be done with either a kiln or by air drying but many details have to be followed to have the results desired. It is not the purpose of this short subject to outline what must be done to properly dry wood. This will be covered in another article.
For small, fairly expensive items such as carvings, another method can be used to prevent degradation due to seasoning checks and cracks. This is done using a chemical called polyethylene glycol-1000 or PEG for short. This material looks like a block of paraffin in the solid state but will dissolve in water. The correct method for using this material is to soak the newly carved piece of wood in water for a month or more depending on its size. After it is completely saturated with water it is placed in a solution of PEG and water. It is kept in this solution for several months for best results. The solution should be warm and can be kept this way with a fish bowl heater. After the carving is thoroughly saturated with PEG, it must be dried slowly in a cool environment and out of the sunlight. The result is a wood carving that will not shrink when it dries and thus will not crack.
The physical explanation for the above process is this: PEG can only be transmitted through the wood if the wood is thoroughly saturated with water. When the PEG enters the cells, it fills the cell walls and the cell lumen located in the center of the cell. When the wood is dried, it cannot shrink because the cell walls are now filled with a solid (PEG) and cannot shrink. If the wood cannot shrink, it cannot crack or split!
As a final note, I used this method on a piece of sycamore that was buried in a clay pit for nearly 6,000 years. I had it made into a gun stock and after 30 years of use the gun stock looks like new without the slightest hair line crack in any surface of it.
P.S. To treat checks and cracks in wood we recommend that you use our chinking and sealant materials found here. If you have any questions regarding drying wood or wood in general just give me a call at 719-547-2135 or visit our website at www.westernloghomesupply.com
by: Western Log Home Supply
Copyright © 2008 Western Log Home Supply - All rights reserved