This Guide Includes Common Log Home Maintenance Terms and Information Regarding:
Maintenance Design Log Condition Log Preparation Stain/Finish/Coating/Preservatives Caulking/Chinking/Sealant Log Repair and Replacement And also… Common Log Home Insects
Maintenance Design Terms
Backsplash/Splash Back: Condition causing water to “splash back” onto the log surface such as: decks, ground, landscaping, or any objects too close to the log wall.
Roof Overhangs: The portion of roof that extends beyond the log wall. The International Log Builders Association (ILBA) Standards recommends one foot of overhang for every eight feet of log wall height. Longer overhangs help protect lower log courses from the elements.
Flashing: Protection added around doors, windows, chimney and wall terminations to protect against water, air and insect infiltration.
Ground Clearance: The distance between the ground and the 1st log course (sill). Higher ground clearance protects lower log courses from backsplash. ILBA Log Building Standards recommend a minimum of 3’ of ground clearance to the first log course to protect lower log courses from backsplash.
Exposed Log Ends: Term used when the log ends extend beyond roof overhang and are exposed to the elements.
Drainage System: System designed to protect logs by directing the flow of water away from the home such as gutters, sloping grade away from the home and footing drains.
Log Terms (Re: Moisture, Settling, Fungus, Checking, Log Parts and more)
Log Profiles: Profiles are the various milled shapes of the logs when looking at a cross-section. For example a flat/round log is flat on one side and round on the other.
Kiln Dried-logs: Method of drying logs using heated air flow.
Air Dried-logs: Method of allowing logs to dry naturally over an extended period of time.
Drip Edge: Log profile design in which water draining off a log surface will drip on lower log keeping moisture away from log joints.
Caulk Channel: Groove in a log profile which allows for the use of backer rod and caulk to properly seal between log courses.
Mill Glaze: The milling process can cause extractives to come to the surface and harden which may adversely affect stain adhesion.
Moisture Meter: Device used to measure moisture content.
Moisture Content: The amount of water contained within wood. Water contained within the wood may be ‘free water’ found in cell cavities or ‘bound water’ found in the cell walls. Drying of wood does not result in significant shrinkage until all free water has been removed. The point at which no free water remains and shrinkage begins is known as the fiber saturation point (FSP), which occurs at about 28 percent moisture content.
Equilibrium Moisture Content (EMC): The percent of moisture the log will seek to acclimate to the relative humidity in the area.
Equilibrium Moisture Level (EML): This refers to the geographic areas average experienced humidity level.
Fiber Saturation Point: Point in the drying process where cell cavities loose all their free water but bound water remains.
Bound Water: Moisture existing in the cell walls. The evaporation of bound water causes the logs to shrink.
Free water: Moisture inside the cell cavity. No shrinkage occurs while logs are losing free water.
Green Logs: Logs with moisture content greater than 19% are called “green” logs. Walls built of green logs can settle up to ¾ inch per foot.
Dry Logs: Typically logs with moisture content at 19% or below
Settling: The loss of log wall height over time. During the first two years when the majority of wall log settling takes place, a wall may lose ¾ inch per foot of wall height. This means that an 8 foot tall wall may lose up to 6 inches in height before it has finished settling.
Causes of Settling:
1. Shrinkage of log diameter as the logs dry to a stable condition. This condition is known as Equilibrium Moisture Content (EMC). EMC is reached when the log moisture content acclimates to the average relative humidity of the home site.
2. Wood compression: Over time, the weight of the structure will compress wood fibers, causing the wall logs to settle. Compression causes less settling than shrinkage.
Cellulose/Hemicellulose/Lignin: The three primary components in wood cells. Lignin acts as the glue that holds wood cells together.
Fungus: Wood destroying organisms. There are (3) types of fungi which can vary in color and texture most commonly seen on logs: black, blue-green and white.
Mold/Mildew: Discoloration on the wood surface but not structurally harmful and typically black.
Sapstain: Discoloration within the wood, typically blue-green.
Decay: This type of fungi can cause serious damage as they feed on the structural components of the wood cell.
Algae: Unlike fungi which feed on wood, algae produces its food from sunlight but is an indication of high moisture content in the log typically green in color.
Extractives: Wood chemicals found in heartwood that leach to the log surface.
Checking: Cracks that open in the log as moisture is released. Upward facing checks over ¼” should be sealed.
Microchecking: Many small checks that occur when moisture is released quickly due to excessive heat exposure from the sun.
UV Damage: Breaking down of cell walls which take on a black appearance. For sealants to give good long-term life they must be formulated for adequate UV resistance.
Weathering: Cell walls that are broken down causing the blackened appearance, common on the upper log curvature.
Log Preparation Terms
TSP: A product used for cleaning dirt, grease or wax.
Borate: A preservative applied to logs to protect them from decay and insect infestations.
Chlorine Bleach: Household bleach will kill mold and mildew but will not clean the logs. It may damage wood fibers and inhibit stain adhesion if not completely rinsed.
Sodium Percarbonate Bleach: Also known as “Oxygen Bleach”, kills mold and mildew but does not harm the wood fibers and is more environmentally friendly than household bleach.
Oxalic Acid: A naturally occurring acid which will remove iron and tanning stains but does not kill mildew.
Corn Cob Blasting: Similar to sandblasting but using corn cob grit to remove the existing finish. Corn cob is lighter than sand and will not be as abrasive to the wood.
Powerwashing: Water directed under pressure through a fan nozzle used to remove some weathered finishes. Must be done correctly and allow drying time before applying a finish.
Fuzzing: Fuzzy texture that may be left on a log surface after powerwashing. Can be removed by light sanding or the use of an Osborne Brush.
Osborne Brush: Commonly used on a variable speed angle grinder for removing fuzzing, texture, stains and any other debris from the log surface.
Chemical Stripping: The use of a chemical stripper on the log surface to loosen finish and remove with a power washer.
Exterior Finishes: Log homes must have a finish applied that will allow moisture vapor to pass through the finish while water in liquid form is kept out. Using a waterproof finish will trap moisture inside the logs and can cause logs to decay from the inside.
□ Water-Based: A type of finish which is usually non-penetrating.
□ Oil-Based: A type of finish which is usually penetrating.
□ Oil Borne: Requires solvent clean-up.
□ Water Borne: Requires water clean-up.
□ Oil Based/Water Borne: The latest technology includes oil based penetrating stains that clean up with water.
□ Semi-transparent: General classifications of finishes possessing certain amounts of solid materials that provide protection against damaging UV rays of and allow some wood grain to show through.
□ Translucent: Clear finishes which show the grain in the wood. These finishes may have limited UV protection.
Compatibility: The ability of a finish and sealant to work together.
Back brush: The act of vigorously brushing finish application into a log component
Coating: Another term for finish or stain.
Preservative: A chemical applied to logs or timbers to protect them from decay and the effects of weathering. Preservatives may contain a mixture of chemicals designed to protect against different threats such a mold, mildew or ultraviolet light.
Caulking: Sealant used to fill joints and spaces between logs. Caulk comes in tubes or pails and is applied with a caulk gun in a narrow strip or ‘bead’ that dries to a tough elastic coating.
Blended Caulking: Matches the log finish to hide caulking.
Contrasted Caulking: Usually a lighter color to enhance caulking.
Chinking: Filling used between rows of logs. Traditional chinking is mortar-based. Modern synthetic chinking, manufactured to look like traditional chinking, is similar to caulk but with greater elasticity.
Adhesion Failure: Term used when caulking pulls away from the log surface.
Cohesive Failure: Failure occurs when caulking adheres to log surface but the caulking itself tears apart.
Substrate Failure: Term used when caulking actually tears the log surface away from the logs.
Impel Rod: Borate rod which are inserted into an area of the log that is exposed to excessive moisture to prevent decay.
Backer Rod: Typically a foam-like material used to configure expansion/contraction joints and provide a surface that a sealant will adhere to.
Closed Cell Backer Rod: A closed cell round foam that repels moisture which is used on external log joints. Texture is firm and may need a blunt tool to push deeper into joint to allow for chinking.
Open Cell Backer Rod: Very flexible, soft and compresses to fit most size joints. This does not have a water resistant coating making it breathable therefore allows for a faster cure. Best used in the interior.
Two Point Adhesion: Sealants need to be applied so that they only adhere to the two opposing sides of a properly configured joint, usually created by using backer rod.
Three Point Adhesion: Term used when the sealant adheres to “3 points”. The top log, bottom log and the back of the caulking channel which greatly reduces its ability to stretch.
Gaskets: The presence of gaskets installed between log courses to help prevent moisture and air infiltration can sometimes be verified by examining exterior corners.
Acrylic Latex Sealants: Latest technology log sealants are latex based.
Log Repair Terms
Epoxy: Material used to solidify log components suffering some form of decay.
Liquid Epoxy: A liquid that reconstitutes existing rotted wood fibers.
Wood Filler Epoxy: Putty-like substance that once cured is harder than the log surface itself. Used to shape the log after the liquid epoxy has hardened.
Full Log Replacement: Logs that are replaced when more than 50% of the log is structurally unsound due to decay.
Half Log Replacement: A cost effective alternative to full log replacement to repair a log with surface decay (decay not exceeding 50%).
Log Crown: A log end that is replaced due to decay.
Prevention is the key… Apply a borate treatment and additive to your coating. There are numerous preservatives, finishes and coatings that are specifically made to protect log homes from insects and fungi. Also, routine inspections, trimming back landscaping, removing wood piles and tree stumps close to the home and caulking will help to prevent insect problems. If you currently have an uninvited guest, there are many different environmentally safe products to help in eliminating your problem. Below is a small description of the more common log home insects.
Common Log Home Insects
Carpenter Ants… do not eat wood; however they will build nesting galleries in moist and decayed wood where holes and eggs in various sizes may be found. Trim back any vegetation that is touching the logs (bushes, trees, and branches) and remove rotted stumps that can supply a root system leading to your home.
Carpenter Bees… Xylocopa bore ½” Round holes commonly found in fascia, trim, overhangs and deck rails creating tunnels. Females lay eggs in the galleries and have stingers while the males usually swarm the area for protection but do not have stingers. Once the area is treated, the holes should be sealed.
Termites… nest in the soil and build tunnels underground searching for wood. They thrive in a damp environment and feed on fungus. Log homes are not any more susceptible to termites than a traditionally framed home where they may be more difficult to detect behind sheetrock. With logs they most likely start on the outside and work their way in leaving obvious signs of dust or mud.
Powder Post Beetles… may be evidenced by tiny “pin like” round exit holes usually clustered in a group. Powdery talc like substance may also be found in certain species. Their life cycle is usually 1-2 years; however their larvae may feed for at least 6 years when the wood moisture is low. Because powder post beetles prefer unheated areas, their infestation seems to be more of a problem in seasonal homes.
Old House Borers… may be evidenced by larger oval or round exit holes, blistering wood, or boring dust. Also, homeowners may hear rhythmic ticking or rasping sound as the beetles gnaw through the logs. Larva can feed for 1-15 years and may cause structural damage. Contrary to the name, the Old House Borer primarily attack homes under 10 years old and usually feed on seasoned softwoods and prefer the sapwood of pine, spruce and fir.