PRO Deck Doctor - Park City Custom Decks, Deck Restoration, Deck Builder
Wood is truly an unique and wondrous thing. The beauty of wood is unsurpassed when compared to man made imitations. Natural wood requires a greater degree of maintenance than man made facsimiles. Unfortunately, many home owners have had their wood decks maligned in the past. This negative experience often results in homeowners opting not to do any maintenance allowing the wood to fall prey to deterioration. Or even surrendering their beauty of their wood deck for a composite under the guise of a 'maintenance free' deck. The idea of a horizontal structure being totally maintenance free is false. All decks require some maintenance. The degree of maintenance varies from deck to deck. A properly maintained deck need not be a burden to homeowners. However, to keep your deck looking and acting at it's peak performance one must understand some basics.
The information below touches on these basics. This information is universal for all wood and wood materials, even composite. ( A composite is a mixture of plastics and wood. There are several composite products and manufacturers out there. Trex is perhaps the largest and most recognizable.) Whether you have a Redwood, Cedar, Mahogany, or an exotic wood or a composite deck understanding these basics will help you maintain you decks in the future.
Wood is made up of cells. The structure of these cells is mostly tubular and compact. When a live tree is fell the cells are often filled with gums and resins At the mill, the wood is cut and dried and many of these resins are removed. The removal process alters the shape of the structure but not the structure themselves Many wood cells are elongated and pointed at the ends. These types of cells are called 'fibers.' These fibers weave and create the relative strengths of a give piece of wood. The lengths of fibers can vary considerably at different sections of a tree as well as between different tree species. Typically, hardwood fibers are shorter in length, and softwood fibers are longer in length.
Composite wood is made of a variety of refined wood types. Some contain wood pulp. . Some contain wood fibers. While others contain wood dust. These refined wood types act as food for lower plant forms. These forms are discussed under the decay section and he deterioration section.
Growth rings are structural shapes within the tree that designate the growth of the tree. Between the bark of a tree and the wood interior is a layer of thin -walled, nearly invisible living cells called the cambium layer. All growth of the tree takes place inside this layer. New cells are formed on the inside and new bark on the outside, No growth in either thickness or in length takes place in wood all ready formed. New growth is strictly the addition of new cells NOT the further development of old cells.
In climates where the temperatures vary there is usually enough difference in color and texture between early formed wood and later formed wood to designate a growth season. This designation appears in the well marked annual growth rings The age of a tree is determined by counting these rings. One ring represents one year of growth. The way the rings are formed depends on many factors not the least of which is the interruption of the growth cycle by seasonal changes. The seasons of a wood cycle are primarily twofold: Springwood and Summerwood. The size of these rings depend on the species and the seasonal changes the tree goes through.
Springwood is generally more swollen with thin walls. While Summerwood is less swollen but has thicker cell walls. Summerwood is often stronger and heavier than springwood.
Sapwood And Heartwood
The wood portion of the tree has two main parts. The outer part, which consists of a ring of wood around the tree just under the bark, is called sapwood. Within the sapwood ring is an inner core, generally darker in color is called heartwood.
The sapwood ring varies in thickness from one to three inches depending on the age and species of the tree. The Sapwood (including the cambium layer) contains the living cells and takes part in the active life processes of the tree. Heartwood consists of inactive (not dead) cells and serves mainly to give strength to the tree. Except for the slightly darker color of heartwood, there is little difference in the overall strength or physical characteristics of the heartwood and sapwood from a given tree.
As a tree grows older and larger, the inner layers of sapwood change into heartwood. Eventually the heartwood core forms the major part of the trunk and branches.
Heartwood - xylem that has filled with organic material, plugging it up and making it appear dark.
Each year a tree adds a layer of wood to its trunk and branches thus creating the annual rings we see when viewing a cross section. New wood grows from the cambium layer between the old wood and the bark. In the spring, when moisture is plentiful, the tree devotes its energy to producing new growth cells. These first new cells are large, but as the summer progresses their size decreases until, in the fall, growth stops and cells die, with no new growth appearing until the next spring. The contrast between these smaller old cells and next year's larger new cells is enough to establish a ring, thus making ring counting possible.
Chemical Composition of Wood
Wood is a complex aggregate of compounds which may be divided into two major groups: (1) those which make up the cells structure, and (2) all other substances, which are commonly called "extractives" or infiltrated materials.
The cell wall components consist primarily of cellulose and lignin. Cellulose is the most abundant constituent, comprising about 70 to 80 percent of the wood structure. Lignin, which comprises from 20 to 30 percent of the wood structure, is the cementing agent which binds the individual wood fibers together to form a substance of strength and rigidity.
In addition to cellulose and lignin, wood contains a small amount of mineral matter. These minerals are known as 'ash forming' minerals because they are left as ash when cellulose and lignin is burned, constitute less than one percent of the total wood substance.
The extractives are not part of the wood structure as such. But they contribute such properties as color, odor, taste, and resistance to decay. They include tannins, starches, oils, resins, acids, fats, and waxes. They are found within the hollow portions of the wood cells, and can be, removed from the wood by neutral solvents such as water, alcohol, benzyl, acetone, and ether. Redwood and cedar are very high in extractives. These extractives react with other chemicals Acidic and base solutions will have dramatic impacts on these extractives. Certain metals will adversely react with extractives as well resulting in discoloration.
Hardwoods and Softwoods
For commercial purposes all species of woods are divided into two classifications: Hardwoods, and Softwoods. magnoliids ('hardwoods'), and gymnosperms ('softwoods')
The hardwoods are broad leafed, deciduous trees which drop their leaves at the end of a growth season.
Softwoods are evergreen trees. Evergreen trees may have fern-like leaves, typical of redwoods Or needle shaped leaves such as those on pines and firs. Softwoods are often known as conifers ( cone bearing) because all softwood trees bears cones of one kind or another.
The terms 'hardwood' and 'softwood' are somewhat misleading in that they have no direct application to the actual relative hardness or softness of a particular kind of wood. Many hardwoods are softer than the average softwood Douglas fir, which is widely used as a construction material, is a softwood by definition; nevertheless, the better grades of Douglas Fir are dense and hard, and tough. Another example is the Pacific Yew, a softwood, is much harder than Balsa, which is classified as a hardwood.
The term 'grain' as it is applied to wood is often used to indicate the direction of the wood fibers relative to axis of the tree, or the longitudinal edges of a piece of cut lumber. I know this sounds technical but bear with me. Thus, if the fibers are generally parallel to the axis of the tree the lumber from the tree will be straight grained.. However, if the direction of the fibers makes an angle with the axis, the lumber will be cross grained.
The term cross grain is used to indicate a direction which is actually perpendicular to the grain. Edge grain refers to lumber in which the surface of a piece of wood is approximately perpendicular, or at right angles to the surface of the piece of wood. Flay grain refers to lumber in which the surface of a piece of lumber is approximately parallel to the direction of growth rings. Grain is very important both in appearance and performance. When selecting boards for various uses extra attention should be paid to the grain.
Living trees contain as much as 200 percent moisture by weight. After a tree is cut and converted into lumber, the wood begins to lose moisture. The process of removing moisture from 'green' lumber is known as seasoning, which is accomplished by exposure to the air or by kiln drying.
The point at which evaporation of free water is complete and cell walls begin to lose their moisture is called the 'fiber saturation point.' The fiber saturation point occurs at a moisture content of about 25 - 30 percent for most species.
Variations in moisture content above the fiber saturation point have no effect on volume or strength of wood. As wood dries below the fiber saturation point and begins to lose moisture from the cells walls, shrinkage begins and strength increases.
Wood in use over a period of time will give off or take on moisture from the surrounding atmosphere. When exposed to similar moisture condition different woods will have the same moisture content regardless of their density.
Moisture content has an important effect on susceptibility to decay. Most decay producing fungi require a moisture content above the fiber saturation point to survive. In addition, favorable temperatures, an adequate supply of air and a source of food are essential. Wood that is continuously water soaked, ( as when submerged) or is continuously dry (i.e. with a moisture content of 20 percent or less) will not decay.
Wood increases in strength as it dries. The strength increase begins at the fiber saturation point ( the point at which the cell walls begin to loose moisture) and increases rapidly as the drying continues.
These are some of the basic characteristics of wood. These terms will be used throughout the website. See the glossary for any terms that may still remain unclear.
I have omitted some material characteristics particularly the definitions of strength. These are very important, however the term strength was originally used for structural design terminology. Wood demonstrates many different types of strength depending on the forces places upon it. The term strength falls under several sections: Tensile strength, compressive strength, shearing strength, flexural strength, and stiffness and bending strength are all the terms of strength. As you can see these terms can become overbearing for the purposes here. As we discuss different types of wood I will use the term strength but only after I have explained it's exact meaning in relation to it's use. The Janka scale is a standard by which the timber industry measure the hardness of wood. Under this scale you can find the 'hardness' as it relates to the woods ability to resist impact distress.
The America Society for Testing Materials (ASTM) has defined the term defects as they pertain to wood as this: any irregularity occurring in or on wood that reduces its strength as compared to the strength of a clear grained specimen. Wood without defects is 'stronger' than wood with defects. Clear wood or that wood which has no defects is without question beautiful. However, these so called defects in wood can add tremendous character and enhancement of a wood's natural beauty. Many wood turners and artisans I know look for pieces of wood that contain some sort of defect because it allows for their piece to be unique.
These defects come in many forms, and some are definitely not desirable what selecting them for structural purposes. Defects can include: knots, checks and shakes, splits, cross grains diagonal grains, warping, waning and sometimes even direct decay. The lumber association has devised a series of grades by which lumber can be segregated or categorized. I will explain the grading values a little later.
A knot is a portion of a branch or limb which has been incorporated into the body of the tree. Knots are the most prevalent defect in structural timber. Knots, are very complex when looking at them from a structure point of view. But they can pose great difficulties, when finishing wood or trying to apply a topcoat.
Checks and Shakes
A 'check' is a separation of the wood fibers along the grain but across the rings of annual growth. A 'shake' is a separation of the wood fibers along the grain between and parallel to the rings of growth. Cedar shingles are often referred to as shakes. This is because they are formed by splitting the wood parallel to the growth rings.
Checks commonly occur as a result of unequal shrinkage during seasoning. Shakes are the result of the rupture of the wood cells in a weakened portion of the wood; they seldom develop unless they are present to some degree before the tree was felled.
Splits are lengthwise separations of the fibers extending from one surface completely through a piece to another surface. Splits are the result of internal stresses or rough handling.
As previously explained cross grained wood has cells or fibers running at an angle with the axis , or sides of the piece of wood. Cross grain can also be an application or technique, whereby one performs an act across the grain.
The consumer rarely gets cross grained wood knowingly. But often they will get a flat grain board. Flat grain, will result in naturally occurring splintering and or peeling. This condition is irreversible.
Diagonal grain is a lesser form of flat grain. Diagonal grain is produced in lumber by the method of sawing and has no reference to the natural alignment of the wood elements In cutting lumber, if the plane of the saw blade is not approximately parallel to the bark surface, the grain of the wood will not be parallel to the edges and thus is termed " diagonal."
Warping is defined as any deviation of a piece of lumber from a true or sawed surface. Warping most often occurs as a result of differences in the longitudinal shrinkage of the two faces of the board. It may also be caused by the internal stresses present in the log at the time of sawing.
Wane is a term used to indicate direction of lumber. Cut lumber is sometimes characterized by the presence of bark or by a lack of wood, on the otherwise square edges or corners of a piece of wood. This condition, termed wane, is commonly considered a defect although it has no direct effect on strength except as it reduces the cross sectional area of the piece. It was a common practice to chose wane side up in assembling a deck. This method is still accepted however it is not a proven method for deterring cupping. Cupping is a defect in the lumber where the face of the board warps up like the letter U.
And the final defect category is decay.
Wood is subject to attack by many low forms of plant life known a fungi. These ' wood inhabiting' fungi differ from ordinary green plants in form, lack of green coloring matter, and methods of nutrition. Unlike green plants they are unable to manufacture their own food, but must have organic material already prepared for their own use. This they find in the wood substance composing the cell walls. The action of the fungi results in the disintegration of the actual wood substance and gives rise to the condition known as decay.
The development of decay is dependant on the presence of an appreciable amount of moisture in the wood. Although the minimum requirements vary with different fungi, it is generally considered that wood must contain at least 20 percent moisture content before decay will occur. Consequently, thoroughly dried, air or kiln, lumber is immune from decay unless is it subjected to wetting over a long enough period of time that its moisture content is raised to approximately the fiber saturation level.
Note: Dry rot is term that is often heard. Dry Rot is a condition similar to decay. The fungi reduces the wood's fibers to the condition of a dry powdery dust, often accompanied by the presence of a peculiar fungus (Merulius lacrymans), which is sometimes considered the cause of the decay; but it is more probable that the real cause is the decomposition of the wood itself.
A small supply of oxygen is necessary for the fungi to grow and develop, so that wood which is completely saturated is immune to decay.
Since decay involves an actual breaking down of the cell walls, it is evident that it vitally affects the strength of the wood, particularly in the advanced stage.
Deterioration is a condition caused by many things outside of the realm of decay. Deterioration can be from natural causes or by negligence. Incorrect building practices will cause a deck to deteriorate. This most common form of deterioration caused by inappropriate building practices is placing wood in direct contact with concrete Deterioration, also can work in injunction with decay. When this occurs the decay will happen at an accelerated state.
Natural deterioration occurs in two ways. One way is that wood oxidizes. Oxidation is a chemical reaction whereby the wood turns gray. When this occurs ultraviolet light breaks down the remaining oils , resins, and waxes naturally found within the wood When the extractives, and resins are depleted the wood cells begin to separate Once the this condition starts there is no way to reverse it. Topcoats are designed to absorb the harmful effects of ultraviolet radiation.
The second natural process by which wood deterioration occurs is expansion and contraction This process occurs when the fluctuations in temperature vary from freezing to thawing. This cycle, separates the cells and allows for containments to enter the wood. Wood that has a large degree of moisture present,( any amount over the Fiber Saturation Point) contains enough water to negatively impact the performance of the wood cells. These freeze thaw cycles will deteriorate horizontal wood rapidly.
Negligence causing wood deterioration most commonly happens when chemicals or solutions are used inappropriately on wood surfaces. The common negligence is bleaching. While bleach, sodium hypo chlorite, is a chemical for eradicating lower plant form from deck surfaces. It also breaks down lignin from the cellulose. Bleach used on wood dissolves the lignin allowing for the wood fibers to separate. Once this separation occurs there is no 'glue' left behind to hold the wood together Seasoned wood has a homeostasis that must be maintained in order for it to remain intact and stable. Once this balance is offset the wood is susceptible to decay.
Wood grades are important when selecting wood for your decking material. There are a wide variety of wood grades. In some instances wood species have sub grades by which the manufacturer use as designation or classification. Below are some grades for redwood. Whenever you order wood make certain it is the grade you want. Many lumber yards will be happy to assist you with this but remember the better the quality the high the cost.
Clear Grade - The highest grade offering the most uniform look and is highly selected in order to obtain this uniformity. Defects: None allowed including knots, splits, checks, worm holes, excessive mineral streaks or contrasting sapwood. Color: Color selected to disallow any pieces that are too dark/light or wildly grained in order to create a harmonious color/grain selection.
Select Grade - The second highest grade, which differs only from Clear grade in that Select grade allows more of the full range of color/grain found in a species and includes the Clear grade that develops in the production run.
Defects: None allowed including knots, splits, checks, worm holes, excessive mineral streaks or contrasting sapwood.
Color: Minimally color selected but does disallow extreme dark/light or wildly grained pieces that contrast too strongly.
Low Select Grade - The third highest grade, which contains all the pieces that are Select Grade in terms of lack of defects, but that have been selected out from the Clear and Select grades as having too much color/grain variation. This grade is available only on an accumulation basis as it develops as a small percentage of the grading when producing Clear/Select grades of flooring.
Defects: None allowed including knots, splits, checks, worm holes, excessive mineral streaks or contrasting sapwood.
Color: Contains all the dark and light colored pieces as well as wilder grained pieces that have been selected out from the Clear and Select grades.
Natural Grade - This grade allows most of a given Species color and grain range along with most of the natural character that develops in a wood.
Defects: Allows small knots, splits, checks, worm holes, mineral streaks and contrasting sapwood.
Color: Contains the full range of Color and Grain to be found in a species.
Rustic Grade - This grade allows even more of the natural character that develops in a wood than found in the Natural grade.
Defects: Allows more numerous and larger knots, splits, checks, worm holes, mineral streaks and contrasting sapwood than found in the Natural grade.
Color: Contains the full range of Color and Grain to be found in a species.
Many lumber yards use a standard 8 category grading system for grading hardwoods FAS is the highest and No. 3B Common is the lowest. In short, the higher grades of lumber have more large clear area than the lower grades. The basic concept of grading is that the grade of all lumber is determined from the poorest face or side of the lumber, with a few cases considering the better face as well.
* FAS, which was years ago short-hand for the grade of "First and Seconds," which in turn originated from a combination of the very old grade of "Firsts" and the grade of "Seconds," is the highest grade of hardwood lumber.
FAS 1-Face (F1F abbreviation) is a Select piece of lumber that is 6 inches and wider
* Select is a No. 1 Common piece of lumber (the poorer side grades No. 1 Common) and the reverse side (the better side) grades FAS. The price of Selects and 1-Face is usually the same as FAS.
* No. 1 Common (often called Common or just No. 1) is the standard furniture grade lumber, and provides a good selection of long, medium length, and short cuttings at a reasonable price
* No. 2A Common (often just called No. 2 Common) has become the standard grade for cabinets, millwork, and other uses requiring medium to short cuttings
* No. 2B Common is the same as No. 2A Common, except that stain and other sound defects are admitted in the clear cuttings. It is an excellent paint grade
* No. 3A Common (which is often combined with No. 3B Common and the combination is sold as No. 3 Common) is widely used for flooring and pallets.
* No. 3B Common is graded on the basis of sound cuttings rather than clear cuttings. It is widely used for pallets and crating. Redwood however has many grades
Clear All Heart - Finest architectural heartwood grade, normally Certified Kiln Dried (also available unseasoned), well manufactured, free of defects one face (reverse face may have slight imperfections). Available surfaced or saw-textured. Uses Siding, paneling, trim, cabinetry, molding, fascia, soffits, millwork. Also fine decks, hot tubs, garden structures, industrial storage and processing tanks.
Heart B - Quality heartwood grade containing limited knots and other characteristics not permitted in Clear All Heart and Heart Clear. Available kiln dried or unseasoned. This grade can be surfaced or saw-textured. Uses Siding, paneling, trim, fascia, molding and other architectural uses. Quality decking, garden shelters and other above-ground outdoor applications.
Construction Heart/Deck Heart - A heartwood grade containing knots of varying sizes and other slight imperfections. Available seasoned or unseasoned This highly useful grade can be ordered surfaced or rough. Deck Heart has similar appearance and uses as Construction Heart but is also graded for strength. Deck Heart is available in 2x4 and 2x6 only. Uses Decks, posts, retaining walls, fences, garden structures, stairs or other outdoor uses especially on or near soil.
Merchantable Heart - This economical heartwood grade allows slightly larger knots than construction grades; holes limited to size of knots. Allows checks, some splits and some manufacturing flaws. Available unseasoned, surfaced or rough. Uses Fences, retaining walls, garden structures-especially on or near soil.
Clear - Same general quality as Clear All Heart except contains sapwood in varying amounts Some imperfections not permitted in Clear All Heart. Normally Certified Kiln Dried (also available unseasoned). Available surfaced or saw-textured Uses Siding, paneling, trim, cabinetry, molding, fascia, soffits. Also quality decking, garden shelters and other above-ground applications. B Grade
Pressure Treated - Much discussion has been made about pressure treated wood. And much of this discussion is warranted. There are 'treated woods' and then there are 'pressure treated woods.' This link may help in understanding the differences www.fpl.fs.fed.us/documnts/techline/III-1.pdf Treated woods are created with three different methods: creosote pressure-treated wood, pentachlorophenol pressure-treated wood, and inorganic arsenical pressure-treated wood. The pressure-treating process is done by commercial facilities and made available to users in the final wood product. Copper napthenate, zinc napthenate, and tributyltin oxide are other wood treatment options that can be site applied. All of these treatment processes involve dangerous chemicals .
Chromated copper arsenate (CCA) is the most popular wood treatment product available today The chemicals are inert within the material and offer protection from moisture and decay fungi. The chemicals do not penetrate into the heartwood effectively so a sealer is advisable on cut ends of CCA treated wood. Although CCA treated wood is sawn on jobsites, hardly anyone seals the cuts. All pressure treated products require adherence to safety precautions approved by the EPA.
The toxicity of the chemicals used in wood treatment has led to research into less toxic methods such as the use of borates derived from the natural element boron (borax). Borates (from boron) are used in wood in New Zealand and Australia and offer insect protection and fire retarding benefits to wood. Full-scale commercial introduction of borates in the U.S. awaits resolution of the leaching problem of borates. Since borates are water soluble, water dilutes them and leaves the wood unprotected from decay after a period of time. In a location unexposed to water, they are effective in preserving wood; site applied borate products are available.
CCA has been replaced with newer forms of treated lumber called ACQ (Ammoniacal copper quaternary ), ACA (ammoniacal copper arsenate); ACZA (ammoniacal copper zinc arsenate); ACC (acid copper chromate); CZC (chromated zinc chloride). These lesser known water borne preservatives are used in hard-to-penetrate woods.
These treatments are designed to resist decay from fungi and insects. However, these types of preserved wood products still need protection from ultraviolet light If these products are exposed to ultraviolet light they will breakdown and will begin to leach their protective compounds. These compounds are hazardous. Repeated direct contact with skin should be avoided.
There are many that should be taken with these types of products. There are newer products being tested currently that offer the same resistant factors but are less hazardous Borate is one such product. There are several different methods by which Borate is introduced into wood. Sometimes it is poured in a hollow core and the woods absorbs from the inside out. Other methods include a topical treatment in which the Borate is absorbed from the outside in. More to follow as developments become recognized.
Of Special concern right now in the industry is increased cost and increased corrosion. Copper is all ready present in other forms of pressure treated wood. ACQ has never 5 times the amount of copper in it according to the American Wood Preservers Association (AWPA). Most people already know that they should use corrosion-resistant nails, screws, and connectors when they're building with pressure-treated wood. But now the stakes are higher. Due to the high risk of galvanic reaction between the copper-impregnated wood and any dissimilar metals, fasteners and flashings should be stainless steel and copper whenever possible. At the very least, you need to use better grades of galvanized fasteners. Unfortunately, the fastener grades aren't always marked on the boxes of nails and screws.
Electrogalvanized stock is rated with a class scale that ranges from 5 to 110. Hot-dipped galvanization ratings are based on the actual weight of the coating. For example, a G-60 rating means that there's 0.60 oz. of zinc per sq. ft. of metal.
The G-60 and G-90 hot-dipped coatings are what we've been using until now. But engineers suggest stepping up to the heavier G-185 coatings for hot-dipped galvanized products, and they recommend class ratings of 40 or above when using electrogalvanized fasteners, such as expansion bolts.
Perhaps the most important point to keep in mind relating to copper-based wood treatments and galvanic corrosion is to avoid aluminum flashings altogether. Aluminum corrodes quickly in the presence of high copper concentrations.
The next wave of wood preservatives is right around the corner.
Wood Treatment Products, Inc. manufactures and markets EnviroSafe Plus™, a patented binding process, that keeps Disodium Octaborate Tetrahydrate (DOT) in wood. The active ingredient of DOT is boron, which has been used as a wood preservative since the 1930's for protection against rot, fungus, mold, termites, Formosan termites, carpenter ants, wood borers, roaches, fleas, silverfish and other pests.
DOT Borates and EnviroSafe Plus™ offer an effective alternative to commonly used wood preservatives that contain controversial chemicals such as arsenic, copper, chromium or various petroleum derivatives. Here's the website. www.eswoodtreatment.com . I will be watching them closely. Stay tuned.
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