PB1767 Wood Protection For Log Home Owners

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7.00PB1767WoodProtectionfor LogHomeOwners

ContentsBasics of Wood 3Wood Anatomy 3Sapwood and HeartwoodWood Species Differences 4AppearanceStrengthWood and Water 5Moisture Content of Wood and theFiber Saturation PointGreen Wood and SeasoningHardwoods vs SoftwoodsWood ShrinkageKiln DryingWood Deterioration 7Physical and Mechanical Damage 7Sunlight and WeatheringSettlingCheckingStanding Dead Timber for Log HomesFireBiological Damage 9Insect Attack of WoodFungal Attack of WoodMold on WoodNon-microbial StainsDry Rot Isn’t DryWood Protection for Log Homes 15Importance of Keeping Wood Dry 15Wood Preservatives 16Sapstain ChemicalsRestricted-use PreservativesBoron-based PreservativesNatural DurabilityFinishes 18The Weathered Look — A Traditional Finishfor Log HomesApplication of Finishes & RefinishingThe Durability Pyramid 19Dry DesignCareful ConstructionDurable MaterialsInspection and MaintenanceReferences 22

WoodProtectionfor LogHomeOwnersAdam M. TaylorAssistant ProfessorTennessee Forest Products CenterUniversity of TennesseeStephen L. QuarlesWood Durability AdvisorUniversity of California Cooperative ExtensionKaren M. VailAssociate ProfessorEntomology and Plant PathologyUniversity of TennesseeLog homes can be beautiful and long-lasting. Themost important factor in making your log home adurable structure is a design that keeps the wood dry.the logs in a home always contain some amount ofwater. The relationship of water and wood is themost important factor in determining the behaviorof wood and how long it will last. In addition, lumber and other wood-based products come from awide range of tree species that have different properties. Trees also change as they grow older, so woodis highly variable. Finally, wood — an organic material — is biodegradable and can be broken downin many ways into the carbon dioxide and energy(trapped sunlight) from which it was made.Wood is a beautiful material that has been usedfor centuries for building log homes. Wood is alsoa high performance composite with good strength,insulation, fire resistance and durability characteristics. This means that uniquely beautiful log homescan be as efficient and long-lasting as structuresmade from wooden lumber, steel or concrete.An understanding of wood properties will helplog home owners protect and enjoy their homes.This publication is designed to provide basic information about wood, wood protection and the use oflarge timbers to build log homes.Wood is made of thousands of small cells,which are long, slender tubes. Most of the cells areoriented parallel to the length of the tree trunk,and this gives wood a grain in that direction. If youcut across the tree stem, you expose the open endsof thousands of cells. This end grain absorbs (orreleases) water much more quickly than the otherwood surfaces, which can have important implications for trying to keep wood dry and protectedfrom decay and insects.Basics of WoodSapwood and heartwoodThe role of wood in trees is to provide structuralsupport and to conduct water up from the ground tothe leaves. Thus, wood needs to be strong but alsoporous. Wood in living trees contains a lot of waterand, although wood dries and shrinks after harvest,Wood AnatomySapwood is the outer band of wood that containssome living cells and also conducts water in theliving tree. The inner core of heartwood containsonly dead cells. The heartwood of some naturallydurable tree species contains chemicals (extractives)

that repel fungal decay (rot) and insects. Examplesof naturally durable woods that are used in loghomes include cedars, cypress and white oak.Extractives can also result in special colors or odorsin the wood. For example, incense cedar heartwoodgives pencils their characteristic odor and theheartwood of ebony (used for the black keys on apiano) is black. The sapwood of all species is light incolor and is susceptible to decay and insect attack.Wood Species DifferencesMany different trees are used for making loghomes, including various pines, oak, cypress, cedarand others. Logs from these trees vary in appearance, strength, weight, how easily they dry, andtheir natural resistance to decay and insects. Loghome builders can take advantage of the naturalfeatures of some species, but given proper design,any species can be used to make an attractive anddurable structure.AppearanceWood varies in color, grain, knot pattern, tendency to split or stain, and other features that canaffect the look of a log. The most attractive woodspecies is a matter of personal choice. The outerwood closest to the bark (sapwood) of all tree stemshas a light color, so if round logs are used, the colorof the fresh log will be light. The inner wood (heartwood) can be exposed when logs are cut, for example, in squared timbers. In species such as cedar andredwood, the heartwood has a dark color. The color(and odor, in some cases) of these species is prizedby some people. Of course, the color of logs canalso be changed by using finishes; a wide variety ofstains is available for this purpose.StrengthWood is remarkably strong. Depending on howstrength is measured, wood can be stronger perunit weight than steel. Different wood species havedifferent strength ratings; and, in general, heavierwoods (hard hardwoods such as oak) are strongerthan less dense woods such as pine or cedar. However, wood is sufficiently strong that the strengthof the wood species is not an important consideration for log walls. In general, all species will bestrong enough given proper design.Tangential direction —shrinks twice asmuch as theradial directionHeartwood —may be naturally durableOne growth ring of woodis formed each year.Sapwood — lightcolored woodAnatomyof a logBarkLongitudinal direction —almost no shrinkage

Wood and WaterMoisture content of wood and the fibersaturation pointFor wood products, the amount of water in woodis called the moisture content (MC) and is measuredas the weight of water relative to the weight of bonedry wood. According to this method of measuring, unseasoned (green) wood can have a moisturecontent over 100 percent! Fully seasoned wood willhave a moisture content ranging from 5 percent to15 percent, depending on the temperature and relative humidity of its environment.Water exists in two forms in wood. Liquid, orfree, water fills the hollow centers of wood cells andother void regions. Bound water is chemically linkedto the cell wall. As green wood begins to dry, freewater is removed. After all of the free water hasgone but all of the bound water remains, the woodis at the so-called fiber saturation point (FSP). Thisoccurs at about 25 percent moisture content. Furtherdrying below the fiber saturation point is more difficult (requires more energy) because the bound water has a strong attraction to the wood. It should benoted that during drying, moisture is not evenly distributed throughout the wood. Thus the surface of adrying log might be below the FSP at the same timethat the inner portions of the log are still very wet.The fiber saturation point has important implications for wood properties. Below the fiber saturationpoint, fungal growth (mold or decay) cannot occur andwood is less attractive to many insects. If wood canbe dried rapidly and maintained at a moisture contentbelow the FSP, it will be very durable. Fortunately, ifwood is kept out of contact with liquid water, it willeventually dry to a moisture content below the FSP.Green wood and seasoningWhen a living tree is cut, the wood is green — itcontains a lot of water. In some species, there canbe more water by (measured by weight) in the woodthan there is dry wood. The moisture content of thewood exceeds 100 percent in these situations. Afterthe wood is cut, most of this water (but not all) willevaporate from the wood. Eventually the amount ofwater in the wood will come to a balance with theamount of water in the air. At that point the woodis dry or seasoned. The amount of time that it takesHardwoods vs. SoftwoodsPeople often refer to some speciesof trees as soft hardwoods or hard hardwoods. To make matters more confusing,pines can be grouped as hard pines or softpines, even though all pines are softwoods.So how can wood be hard and soft at thesame time?The classification of tree species ashardwoods or softwoods is based on a botanical distinction. Softwoods (or gymnosperms) are the conifers, or cone-bearingtrees, that are often evergreen and haveneedle-like leaves. Softwoods include thepines, eastern redcedar and cypress. Hardwoods (or angiosperms) are broad-leaved,mostly deciduous trees, that is, they droptheir leaves. Oaks and poplar are examplesof hardwoods.The wood of both hardwoods and softwoods varies in hardness, and this is thesource of confusion: hard and soft wood occurs in different species of both hardwoodand softwood trees. Hardness is a functionof the heaviness, or density, of the wood: theamount of wood material compared to airspaces. Hard woods are denser, soft woodscontain more air. On average, the wood ofsoftwoods is softer than hardwoods. However, there are many exceptions to this trend.The Southern pines are softwoods, but theyare denser than yellow poplar, which is ahardwood. Because of the wide range ofwood density in the hardwood tree species,people will often distinguish between hardhardwoods (e.g. hickory, oak, ash) and softhardwoods (e.g. yellow poplar, gum, willow).Likewise the pines, which are softwoods,can be organized into hard (e.g. Southern,red) and soft (white, sugar) groupings.Both hardwoods and softwoods are usedto make log homes. Factors such as size,cost, natural durability and appearance aregenerally more important considerationsthan whether the wood is relatively harderor softer, or a hardwood or a softwood.

As mentioned above, fully seasonedwood has a moisture content rangingfrom 5 – 15 percent, depending on its“GREEN”environment, while green wood has aWOODmoisture content well above 25 percent 8%(60-150%)(above the FSP). Thus shrinkage isNO FUNGAL GROWTHSinevitable when wood is used forBELOWFSPHRhouses. Even more importantly,IShrinkage starts when woodwood shrinkage is not uniform.NKdries below 25% M.C.Wood shrinks very little in length butAGsubstantially across the grain (5 – 10Epercent from the green size). This0%means that the walls of a stick builtONLY “ BOUND” WATER“FREE” WATER PRESENThouse will change very little in height 25%MOISTURE CONTENTas the wooden studs in the wall cavities0%dry out. In contrast, a wall made fromlogs can shrink several inches in heightWater has a large impact on wood properties. Trees are wet,(the width-wise direction in the log) asbut the logs in a house are relatively dry. Drying results inthe wood dries.shrinkage, but it also helps protect the wood from attack byinsects and fungi.It is also important to know thatwood shrinks about twice as much parallel tothe growth rings (tangential direction) as it doesfor wood to go from green to seasoned dependsperpendicular to the growth rings (radial direction).on many factors, including the temperature andThis imbalance is the reason why some splittingrelative humidity of the air, and the size and speciesof the surface of logs is inevitable (see checking,below).of the piece of wood. In the case of logs, this processcan take a few years. If logs are kiln-dried prior toKiln dryingassembly, the time to reach moisture equilibriumKiln drying refers to putting wood into a heatedwill be reduced.enclosure (a kiln) to accelerate the drying process.If the logs in a log home are wetted due to rainKiln drying can reduce the drying times for someor other water sources, the moisture content of atlumber species from months to days and can also releast the surface region can eventually become veryduce drying time for logs and other large members.high. Once the water source is removed, the woodwill again dry to an MC that is in balance withthe temperature and relative humidity of the airsurrounding it. This eventual balance of moisturein wood with conditions in its environment is calledthe equilibrium moisture content (EMC).NORMALIN-SERVICERANGE(5-15%)WOOD & WATERWood shrinkageShrinkage occurs when wood is dried below thefiber saturation point. Above the FSP, the removalof free water simply empties the wood cells anddoes not change their dimensions. When boundwater is removed from the walls of cells, they beginto shrink. As a rule of thumb, for every 3 percentreduction in moisture content below the FSP, thewood will shrink in volume by about 1 percent. Resin is bleeding from this pine log. Kiln drying ofthe logs can prevent this.

An extreme example is the high-temperature drying of pine lumber, which can reduce the moisturecontent from green ( 100 percent) to 19 percent ina couple of days. In addition to the rapid removalof water, the heat in a dry kiln can kill insects andother organisms that might be living in the wood,particularly those that may be in the standing trees,and will also help to set the pitch. In resinous species such as pines sticky, defensive liquids (pitch),produced by the tree as a defense against insects,can leak out of the wood after it is cut. Exposing thewood to high temperatures will harden the pitch sothat it will no longer be an aesthetic problem.Removing water from wood to lower the moisture content below 25 percent will prevent attackby mold and decay fungi (rot). Kiln drying canshorten the time required for a log to get to thissafer condition. Hardwood lumber is kiln dried toachieve a moisture content (5 – 15 percent) thatwill prevent most future shrinkage (assuming thelumber stays in an interior environment and isn’trewetted). Because logs are not kiln dried to suchlow levels, shrinkage of logs will continue after alog house is assembled.Wood Deteriorationrelease of carbon dioxide, water and energy. Withappropriate design and maintenance, deteriorationcan be delayed almost indefinitely; thus, a log homecan last virtually forever.Physical and Mechanical DamageSunlight and weatheringJust as ultraviolet rays (UV) in sunlight cancause chemical changes in our body by tanningour skin or bleaching our hair, they can also causechemical changes in wood. UV breaks apart compounds on the surface of exposed wood resultingin degraded wood fibers and changes in color.When UV exposure is combined with wind andwater exposure, this can result in the slow erosionof wood fibers from the surface of the wood. Thisprocess is called weathering. Weathering is usually uneven and depends on how much sunlightand water the wood is exposed to and how soft thewood is. Soft woods such as cedar will weatherfaster than harder woods such as oak. Also, thedifferent parts of the annual growth rings in apiece of wood will weather unevenly because theearlywood (wood formed in the spring) is softerthan the latewood (formed in the summer). ThisWood can be degradedby both physical factorsand living organisms.Wood is an organized,solid combination ofcarbon dioxide, water andenergy from sunlight. Thevarious agents that breakwood down are part of thenatural recycling of woodthat ultimately ends in theThis building hasweathered siding. Thedarker areas are exposedto more sunlight. Inprotected areas under theeaves, the wood is closerto its original light color.Finishes can be used toprevent weathering andimprove the appearanceof exterior wood.

results in rough surfaces on weathered wood —especially on the end grain.The effects of weathering are limited to the surface of wood, and the process is quite slow overall.Research suggests that wood removal due to weathering is only about ½ inch per century, even withsoft woods. Thus weathering is not a structural concern for log homes with walls that are many inchesthick. The bigger concern with weathering is thechanged and irregular (non-uniform) color of unprotected wood, which is an aesthetic issue.Weathering can be prevented by protecting thewood from exposure to sunlight and water and byapplying finishes that block ultraviolet radiation andshed liquid water. Clear finishes can contain chemicals that are UV blockers. Pigmented (colored) finishes also protect wood against UV exposure.SettlingAs explained above, wood shrinks when itdries. Log homes always continue to dry after theyare assembled, so some shrinkage of log walls isinevitable. Because shrinkage is greatest acrossthe grain, log wall shrinkage — or settling — canresult in a considerable change in wall height. Forexample, a 10 foot log wall may settle 2 inches ormore, depending on the wood species and the moisture content of the logs when they were assembled.Because lumber is oriented in the longitudinal (lowshrinkage) orientation, other components in a loghome — interior stud walls, windows and doors,and cabinets — do not settle appreciably. Allowances for settling must be made wherever log wallsconnect to these items.CheckingChecking is the development of cracks in thesurface of wood. Wood shrinks more parallel to thegrowth rings than it does across the growth rings.This imbalance results in large stresses as logs dry.In logs, these stresses eventually overcome thestrength of the wood, which fails, resulting in thedevelopment of a check. These checks appear on thesurface as wide cracks that extend inward towardthe center of the log. These checks are due to natural wood characteristics combined with inevitabledrying. Because shrinkage parallel to the growthrings (the tangential direction) is approximately A check in a house log. This kind of split is theinevitable result of the normal drying process andthe uneven nature of shrinkage in wood.Standing Dead Timberfor Log HomesIn some areas of the country,thousands of trees have been killed byinsect or disease outbreaks. This standingdead timber can be used for log homes.Such logs may have a lower moisturecontent than normal green wood, whichresults in lighter logs and potentially ashorter seasoning time. However, evenstanding dead timber will continue toshrink and check after it is assembledinto a log home. Furthermore, standingtimber can be attacked by decay fungior insects before it is harvested. Logsshould always be inspected before use,but inspection is particularly importantwhen the use of fallen, or standing deadtrees is being considered.

twice that in the direction perpendicular to the growth rings (the radialdirection), checks are impossible to prevent and should be considered a normalpart of the log home look. Logs usuallydevelop one large check instead of several smaller ones. If you can see wherethe check is starting, it is sometimespossible to rotate the log during installation to hide the check or position it ina less vulnerable location.Checking can also occur in woodbecause of rapid drying. When thesurface of wood dries, it starts toshrink before the inside of the piecedoes, causing stresses to develop inthe surface layers. If these developing stresses exceed the strength of thewood, a check develops. These checksdo not necessarily extend across thegrowth rings and can be prevented bycareful drying.Dry wood has good insulating and fire-resistance properties.However, the gaps between logs are important in determiningthe overall performance of the wall. If the chinking that fillsthe gaps is missing, is in poor repair or has low fire-resistanceproperties, the wall may leak or perform poorly in a fire.FireWood is a combustible material. This is a goodthing when the fire is confined to a fireplace orwood stove, but it also means that log houses canburn. However, the dangers of fire are not usuallygreater in log homes than in structures framed withother materials. Fires can occur in almost any building when kitchen accidents or electrical problemsignite interior furnishings. The potential combustibility of log walls is not really an additional dangerbecause such large pieces of wood actually burnquite slowly due to the char layer that develops.Therefore, logs retain most of their strength duringthe initial stages of a fire. Because of the protectiveeffect of the char layer, building codes usually assign better fire ratings to larger members.In wildland/urban interface areas where wildfires are a concern, log walls can be a positivecomponent of a more fire-safe home. The mostvulnerable part of the log wall in a log home is thebetween log joint. The joint should be filled to provide protection comparable to the log itself.In a wildfire, many homes are lost as a result offlame or ember entry into attic or cathedral ceilingspaces. To avoid these exposures, highly combustiblevegetation should be removed from near the logwalls. Similarly, other items that could result in ignition of the log wall (e.g., gasoline containers), withsubsequent flame spread to the eave area, shouldalso be avoided.Biological DamageInsect attack of woodMany kinds of insects can attack wood. Woodprovides some insects with suitable habitat (a placeto live), for at least part of their life cycle. Examplesof these insects include carpenter ants, carpenterbees and some wood-boring beetles. Other insectsattack wood because it provides a food source.Examples of insects that eat wood (or parts ofwood) include termites and wood-boring beetles.TermitesTermites are the most serious insect pest oflog homes. Termites eat wood and thus can causemajor structural damage. Termites either live inthe wood they are eating (drywood or dampwoodtermites) or in the soil in the vicinity of the housethey are infesting (subterranean termites). Becausesubterranean termite colonies are larger than

Drywood termite damage in a fence. Drywoodtermites inhabit the wood they are eating.drywood termite colonies, they are capable of doingmore damage to a wood structure. Formosan termitesare one very destructive species of subterraneantermite found in the southeastern Unites States.Formosan termites can be found in the soil, butalso in above ground locations in carton nests thatmaintain a moist environment. Carton nests aren’tin wood members but can be in wall cavities andhollowed out trees. Because dampwood termitesrequire wet wood, they aren’t usually found inside.Fortunately, a number of effective termitepesticides and treatments are available from pestcontrol management professionals. Knowing wherethe termites live can help you understand the besttreatment for a given infestation. Soil treatments(baits and liquid soil applications) can be effectiveagainst subterranean termites, including theFormosan, but won’t be effective against drywoodtermites. Similarly, whole house fumigation or localchemical treatments injected into wood memberswill only be effective against termites residing in thetreated member. These treatments are not effectiveagainst subterranean termites, where only a smallfraction of the colony is in the home at any giventime. The best treatment for dampwood termites is todry out the affected wood members.A preconstruction termite treatment isrecommended for new homes. Homeowners canalso take steps to discourage termite infestations intheir homes. Keeping potential termite food, suchas mulch and firewood, away from log walls canhelp to prevent termite infestation. Termites are also10The surface of this log has numerous powderpost beetleentry holes. Powderpost beetles can attack and re-infestlogs after they are assembled into a home.attracted to moisture or partially-rotten wood, sokeeping a log home and nearby areas dry will helpto reduce the risk of termite attack in addition toreducing the risk of fungal decay or mold.The following are a few practical ways to preventa termite infestation: Repair structural and plumbing leaks. Clear piles of wood and trash. Keep firewood piles away from the structure. Keep gutters clean. Ensure that when downspoutsterminate at the ground, water is directed awayfrom the foundation. Grade around the foundation to draw water awayfrom the building. Use preservative-treated lumber when wood isin ground contact and for the structural supportmembers for exposed porches and decks.Wood-Boring BeetlesCertain beetles will attack wood. They can begrouped into those that stay near the bark layer (barkbeetles) and those that bore into the internal structure of the wood (wood-boring beetles). These insectsbore into wood to lay their eggs and feed on carbohydrates (sugars and starch). Signs of a beetle infestation include small holes in the surface of the woodand nearby piles of sawdust mixed with waste (frass). Some species can re-infest seasoned wood (logsin this case) while others that infest a living tree willnot return once they have left the seasoned wood ina log home. These insects also vary in the amount ofdamage they cause. For these reasons, it is important

to identify the insect so that the proper control measures can be taken. In some cases, “control” willinvolve only waiting for the insects to finish emerging from the logs because they will not return.Reinfesting beetles. Powderpost beetles includelyctid, anobiid and bostrichid beetles. They can bedistinguished by the type of wood they attack, thesize and shape of the bore and emergence holes andthe frass. Powderpost beetles can reinfest dry woodand can eventually cause significant damage; however, this is a slow process. Some powderpost beetlesprefer unfinished wood with relatively high moisturecontent, so keeping the wood dry and applying afinish layer may be enough to keep the insect fromreturning to the wood. Borate-based wood preservatives or insecticides require unseasoned (wet) woodto penetrate and kill the beetles. Spray- or brushapplied treatments (to logs already in a home) willnot penetrate very deeply. Therefore, in order to betruly effective against existing powderpost beetleinfestations, borate-based preservatives must beapplied, prior to assembly, using a pressure impregnation process. Other dip, brush or spray chemicaltreatments do not penetrate the wood, but theywill provide localized protection and may preventreinfestation. Certain longhorned beetles (Cerambycidae), such as the old house borer, can also re-infestlogs in a home. These insects prefer the sapwood ofsoftwoods such as pine. Large old house borer larvaecan be heard as they feed. A stethoscope or otherlistening device can be used to locate these larvae.Wood near the gallery can be drilled and injectedwith insecticide. Despite their name, old house borersare usually found in homes less than 10 years old.Non-reinfesting beetles. Ambrosia beetles, barkbeetles, and most flat-headed and round-headed borers are insects that will not re-infest logs in a home.Except for the bark beetles, these are boring beetlesthat penetrate into the wood. Although the appearance of these insects may be unsightly and alarming,they are not a significant threat. Once they come out If beetle attack is observed, the type of beetle should bedetermined. Contact an Extension entomologist for help withidentification. More information on managing wood-infestinginsects can be found in UT Extension’s PB1703 Wood Destroying Organisms at level/WDO/WDOindex.htm. Extension personnel inmany states have prepared Web-based information on woodinfesting organisms.This log shows attack by bark beetles that occurredwhen the tree was standing. This log is still structurallysound and the beetles will not cause further damage.A carpenter bee hole in a rafter. Carpenter beesare a common pest of log homes.of the log, they are gone for good. However, someof these insects can take many years to develop andemerge, so it is important to have the correct identification before considering control measures.Carpenter BeesCarpenter bees are large flying insects that resemblebumble bees. They do not eat wood; rather, theybore large (1/2” diameter) holes into logs and otherexterior wood surfaces to excavate galleries in whichto lay their eggs. Carpenter bees are not aggressiveand rarely sting. Although carpenter bees createbig holes in wood as brood chambers for theiryoung, they are unlikely to cause structural damage11

Both termites(top) and ants(bottom) have flyingreproductive forms(alates). Termiteshave straightantennae, equallength wings andabdomens thatare as wide as therest of their bodies.Ants have bentantennae, wings ofunequal length andconstricted waists.initially; however, repeated use of the same galleriesover many years may cause significant damage. It isbelieved that carpenter bees are less likely to boreinto wood that has been painted, but the finishesgenerally used on log homes do not prevent attack.More research is needed to evaluate preventivecarpenter bee control strategies. Carpenter bees’galleries (holes) can be treated with dust, spray orfoam insecticides and, after a 24-hour waiting period,physically blocked with a wood dowel to discouragefurther activity. Carpenter bees are also very slowmoving and will often hover around their holes. Forthis reason, many people recommend a fly swatter ortennis racket as the most effective means of control.Carpenter AntsCarpenter ants are large, often black, ants thatcan nest in wood. They often prefer wet or partiallyrotten wood. Unlike termites, carpenter ants do noteat the wood and are less likely to cause significantstructural damage. Signs of a carpenter ant infestation include flying ants (alates) in or around thehome and piles of sawdust containing insect partsbelow ant entry points. Carpenter ants can be a nuisance and can be controlled by locating and treatingthe nest with spray, dust or foam insecticides; baitingforaging ants; or treating trails and potential entrypoints with a nonrepellent, professionally-appliedinsecticide. Cleaning up kitchen waste and other potential food and eliminating water sources will helpdiscourage ant infestations. Trimming vegetation sothat it does not touch the structure and sealing wireand pipe wall penetrations can also reduce ant entryinto the home12Fungal attack of woodThe fungi, which include t

An understanding of wood properties will help log home owners protect and enjoy their homes. This publication is designed to provide basic infor-mation about wood, wood protection and the use of large timbers to build log homes. Basics of Wood The role of wood in trees is to provide structural support and to conduct water up from the ground to

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For a given antenna log 1. and log are constant. Consequently the log of n. increases in equal steps with . n. That is, log n. increases periodically, hence the name log periodic. It is also implied that whatever the electrical properties the antenna may have at a frequency . f. 0, will be repeated at frequency given by * f. 0 (3) 2. Antenna Design

Figure 1: Example document Table 5: Calculating log likelihood values log2 L(dlct ) 1 x log s .04 3 log s .30 -9.85 log s L(d]cs) 1 log s .29 3 x log s .65 -3.65 HCM can handle the data sparseness p

the accounting profession - have come to be known as 'creative accounting'. (1988: 7-8) Terry Smith reports on his experience as an investment analyst: We felt that much of the apparent growth in profits which had occurred in the 1980s was the result of accounting sleight of band rather than genuine economic growth, and we set