Log Home Inspections
The internal structure of trees can have a strong effect on the way they behave after they're cut for logs. It's important that inspectors have at least a basic understanding of this internal structure and how it can affect a home even many years after the trees were cut and installed as logs. The wood cells differ with tree species in terms of function, size, concentration, proportion and chemical composition.
Checks, spiral grain, knots, insect holes and logs with sweep and taper are commonly found in log homes. These imperfections are not defects and are to be expected in most homes. It's only when they cause problems that they are considered defects.
The natural bowing found in most logs is identified as the Sweep. The variation from tip to base in a log is referred to as its taper. Knots indicate where branches grew in the live tree, and may be tight or loose. Knots affect the angle of grain as wood fibers bend to grow around the limb, so they may have an effect on log strength, but determining the extent to which this condition is a problem would require the services of a certified log grader.
Any plant species that grows taller than 20 feet when mature and has a dominant single stem (i.e., the tree trunk) can be referred to as a "tree." Plants that mature at less than 20 feet are called shrubs and aren't used for building. Wood is divided into two types, both of which (in North America) exhibit annual growth rings, but which perform different primary functions in the tree.
Sapwood helps to support the tree, but its main function is to transport water and mineral nutrients from the soil to the leaves. Its cells also store carbohydrates and provide protection. Sapwood is typically light in color.
The trunk and branches grow in diameter and circumference through new cells created in the cambium. Most new cells live only a short time. As the tree expands in diameter, sapwood cells slowly become closer to the center of the tree and their function changes from transporting fluids through the tree to storage of various toxic chemicals and compounds (extractives) created by the tree, often in response to injury. Cells that serve as storage are part of the heartwood, and it's the extractives they contain which give them their typically darker color. Some extractives are toxic to insects and decay fungi, which is why heartwood is more resistant to attack than sapwood.
Water and nutrients are absorbed by roots and transported from the soil to the leaves through the sapwood. Sapwood is composed of many millions of long, thin, needle-like cells connected end to end through which liquid is moved upward by capillary action and transpiration. Annual tree rings reflect different seasonal growth rates. Trees usually grow more quickly during spring and summer, and wood cells developed during those seasons, called early wood, are typically lighter in color than wood cells developed during fall and winter, called late wood.
The most effective method of identifying wood species is through the careful examination of wood cell arrangement. This requires a microscope or a hand lens. Wood texture, color, taste and odor also offer clues.
Virtually all trees start growing with left-hand grain. Some, prompted by genetic code after 10 to 40 years, will start to change grain direction and eventually develop a right-hand spiral. This process happens slowly. Because the butt of the log is older than the tip, severity of the slope of the grain will vary from one end to the other. Some trees never change direction and remain left-hand spiral trees.
Part of an inspector's job is to recognize and comment on signs of existing failure, allowing their client to negotiate for corrections and preventing future damage. Sometimes, no signs of failure may be visible at the time of the inspection, especially in newer homes. In these situations it's up to inspectors to recognize conditions which will eventually cause failure if not corrected.
You may be able to find certified or licensed home inspectors who specialize in log homes but you will probably have to do some searching. You may also want to contact a local log home restoration company and ask if they can inspect the home.
Checks, spiral grain, knots, insect holes and logs with sweep and taper are commonly found in log homes. These imperfections are not defects and are to be expected in most homes. It's only when they cause problems that they are considered defects.
The natural bowing found in most logs is identified as the Sweep. The variation from tip to base in a log is referred to as its taper. Knots indicate where branches grew in the live tree, and may be tight or loose. Knots affect the angle of grain as wood fibers bend to grow around the limb, so they may have an effect on log strength, but determining the extent to which this condition is a problem would require the services of a certified log grader.
Any plant species that grows taller than 20 feet when mature and has a dominant single stem (i.e., the tree trunk) can be referred to as a "tree." Plants that mature at less than 20 feet are called shrubs and aren't used for building. Wood is divided into two types, both of which (in North America) exhibit annual growth rings, but which perform different primary functions in the tree.
Sapwood helps to support the tree, but its main function is to transport water and mineral nutrients from the soil to the leaves. Its cells also store carbohydrates and provide protection. Sapwood is typically light in color.
The trunk and branches grow in diameter and circumference through new cells created in the cambium. Most new cells live only a short time. As the tree expands in diameter, sapwood cells slowly become closer to the center of the tree and their function changes from transporting fluids through the tree to storage of various toxic chemicals and compounds (extractives) created by the tree, often in response to injury. Cells that serve as storage are part of the heartwood, and it's the extractives they contain which give them their typically darker color. Some extractives are toxic to insects and decay fungi, which is why heartwood is more resistant to attack than sapwood.
Water and nutrients are absorbed by roots and transported from the soil to the leaves through the sapwood. Sapwood is composed of many millions of long, thin, needle-like cells connected end to end through which liquid is moved upward by capillary action and transpiration. Annual tree rings reflect different seasonal growth rates. Trees usually grow more quickly during spring and summer, and wood cells developed during those seasons, called early wood, are typically lighter in color than wood cells developed during fall and winter, called late wood.
The most effective method of identifying wood species is through the careful examination of wood cell arrangement. This requires a microscope or a hand lens. Wood texture, color, taste and odor also offer clues.
Virtually all trees start growing with left-hand grain. Some, prompted by genetic code after 10 to 40 years, will start to change grain direction and eventually develop a right-hand spiral. This process happens slowly. Because the butt of the log is older than the tip, severity of the slope of the grain will vary from one end to the other. Some trees never change direction and remain left-hand spiral trees.
Part of an inspector's job is to recognize and comment on signs of existing failure, allowing their client to negotiate for corrections and preventing future damage. Sometimes, no signs of failure may be visible at the time of the inspection, especially in newer homes. In these situations it's up to inspectors to recognize conditions which will eventually cause failure if not corrected.
You may be able to find certified or licensed home inspectors who specialize in log homes but you will probably have to do some searching. You may also want to contact a local log home restoration company and ask if they can inspect the home.
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