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74-472: Similar items not covered in this article include bathroom handrails —which help to prevent falls on slippery, wet floors—other grab bars , used, for instance, in ships' galleys , and barres , which serve as training aids for ballet dancers. Guard rails and balustrades line drop-offs and other dangerous areas, keeping people and vehicles out. British Standard and British Standard Code of Practice are harmonized to European Normal (EN) series. Handrail height

148-428: A construction material , for making tools and weapons , furniture and paper . More recently it emerged as a feedstock for the production of purified cellulose and its derivatives, such as cellophane and cellulose acetate . As of 2020, the growing stock of forests worldwide was about 557 billion cubic meters. As an abundant, carbon-neutral renewable resource, woody materials have been of intense interest as

222-700: A consistent height above walking surfaces, stair nosing, and ramp surfaces. When children are the principal users in a building or facility (e.g., elementary schools), a second set of handrails at an appropriate height can assist them and aid in preventing accidents. A maximum height of 28 inches measured to the top of the gripping surface from the ramp surface or stair nosing. Sufficient vertical clearance between upper and lower handrails, 9 inches minimum, should be provided to help prevent entrapment. Top of gripping surfaces of handrails shall be between 34 and 38 inches (864 and 965 mm) vertically above walking surfaces, stair nosings, and ramp surfaces. Handrails shall be at

296-775: A consistent height above walking surfaces, stair nosings, and ramp surfaces. When children are the principal users in a building or facility (e.g., elementary schools), a second set of handrails at an appropriate height can assist them and aid in preventing accidents. A maximum height of 28 inches (711 mm) measured to the top of the gripping surface from the ramp surface or stair nosing is recommended for handrails designed for children. Sufficient vertical clearance between upper and lower handrails, 9 inches (229 mm) minimum, should be provided to help prevent entrapment. Handrails are available in several different varieties including wooden/timber , stainless steel , brass , or aluminium . Some varieties are more hard-wearing than others, and

370-418: A doorway are usually added near a railing. In addition, grab bars can be placed on any wall where extra support is needed even if it is not the "usual place" they are used. Grab bars can be installed in different positions: There are many considerations when deciding which grab bar to use and how best to install it. Properly securing a grab bar is important so that it doesn't pull out of the wall when pressure

444-401: A heavy piece of pine is compared with a lightweight piece it will be seen at once that the heavier one contains a larger proportion of latewood than the other, and is therefore showing more clearly demarcated growth rings. In white pines there is not much contrast between the different parts of the ring, and as a result the wood is very uniform in texture and is easy to work. In hard pines , on

518-565: A horizontal bar. Scientific research has found that gripping strength is far greater using a horizontal bar than a vertical bar in a fall situation. This makes horizontal grab bars the safest choice. Grab bars were required on U.S. railroad cars by the Railroad Safety Appliance Act of 1893. Occupational Safety and Health Administration (OSHA) guidelines describe the requirements for grab bar clearance, diameter and spacing on fixed ladders. These regulations state that

592-405: A large log the sapwood, because of the time in the life of the tree when it was grown, may be inferior in hardness , strength , and toughness to equally sound heartwood from the same log. In a smaller tree, the reverse may be true. In species which show a distinct difference between heartwood and sapwood the natural color of heartwood is usually darker than that of the sapwood, and very frequently

666-406: A little more safety at night when using the bathroom. Many jurisdictions have regulations on grab bar placement and floorplans for public bathrooms (American ADA, British Doc M regs). Grab bars are often used in conjunction with other medical devices to increase safety. For example, a grab bar added to a shower is frequently used with a shower chair and hand held shower head. Grab bars installed by

740-400: A log is on the outside, it is more or less knotty near the middle. Consequently, the sapwood of an old tree, and particularly of a forest-grown tree, will be freer from knots than the inner heartwood. Since in most uses of wood, knots are defects that weaken the timber and interfere with its ease of working and other properties, it follows that a given piece of sapwood, because of its position in

814-425: A patient from one place to another. A worker may use a grab bar to hold on to as he or she climbs, or in case of a fall. Grab bars must bear high loads and sudden impacts, and most jurisdictions have building regulations specifying what loads they must bear. They are generally mounted to masonry walls or to the studs of stud walls (which may need to be specially strengthened). They can be mounted through drywall into

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888-481: A pretty definite relation between the rate of growth of timber and its properties. This may be briefly summed up in the general statement that the more rapid the growth or the wider the rings of growth, the heavier, harder, stronger, and stiffer the wood. This, it must be remembered, applies only to ring-porous woods such as oak, ash, hickory, and others of the same group, and is, of course, subject to some exceptions and limitations. In ring-porous woods of good growth, it

962-636: A source of renewable energy. In 2008, approximately 3.97 billion cubic meters of wood were harvested. Dominant uses were for furniture and building construction. Wood is scientifically studied and researched through the discipline of wood science , which was initiated since the beginning of the 20th century. A 2011 discovery in the Canadian province of New Brunswick yielded the earliest known plants to have grown wood, approximately 395 to 400 million years ago . Wood can be dated by carbon dating and in some species by dendrochronology to determine when

1036-465: A source of weakness. In diffuse-porous woods the pores are evenly sized so that the water conducting capability is scattered throughout the growth ring instead of being collected in a band or row. Examples of this kind of wood are alder , basswood , birch , buckeye, maple, willow , and the Populus species such as aspen, cottonwood and poplar. Some species, such as walnut and cherry , are on

1110-456: A strong wooden wall stud or other structural member, but not mounted only on the drywall, as it will not bear the users' weight. Grab bars are made of metal, plastic, fiberglass, and composites. For wet areas such as bathrooms, the material must be waterproof. Stainless steel , nylon -coated mild steel , epoxy-coated aluminum, ABS plastic , and even vinyl-coated metal and plastic. Grab bars increase accessibility and safety for people with

1184-564: A tree is first formed as sapwood. The more leaves a tree bears and the more vigorous its growth, the larger the volume of sapwood required. Hence trees making rapid growth in the open have thicker sapwood for their size than trees of the same species growing in dense forests. Sometimes trees (of species that do form heartwood) grown in the open may become of considerable size, 30 cm (12 in) or more in diameter, before any heartwood begins to form, for example, in second growth hickory , or open-grown pines . No definite relation exists between

1258-423: A type of imperfection known as a knot. The dead branch may not be attached to the trunk wood except at its base and can drop out after the tree has been sawn into boards. Knots affect the technical properties of the wood, usually reducing tension strength, but may be exploited for visual effect. In a longitudinally sawn plank, a knot will appear as a roughly circular "solid" (usually darker) piece of wood around which

1332-403: A variety of disabilities or mobility difficulties. Although they are most commonly seen in public handicapped toilet stalls, grab bars are also used in private homes, assisted living facilities , hospitals, and nursing homes . Grab bars are most commonly installed next to a toilet or in a shower or bath enclosure. Some grab bars also have a light feature and double as a night light offering up

1406-492: A wooden object was created. People have used wood for thousands of years for many purposes, including as a fuel or as a construction material for making houses , tools , weapons , furniture , packaging , artworks , and paper . Known constructions using wood date back ten thousand years. Buildings like the longhouses in Neolithic Europe were made primarily of wood. Recent use of wood has been enhanced by

1480-437: Is a season check in the knot, as is often the case, it will offer little resistance to this tensile stress. Small knots may be located along the neutral plane of a beam and increase the strength by preventing longitudinal shearing . Knots in a board or plank are least injurious when they extend through it at right angles to its broadest surface. Knots which occur near the ends of a beam do not weaken it. Sound knots which occur in

1554-456: Is also greatly increased in strength thereby. Since the latewood of a growth ring is usually darker in color than the earlywood, this fact may be used in visually judging the density, and therefore the hardness and strength of the material. This is particularly the case with coniferous woods. In ring-porous woods the vessels of the early wood often appear on a finished surface as darker than the denser latewood, though on cross sections of heartwood

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1628-428: Is an important consideration. The weakening effect is much more serious when timber is subjected to forces perpendicular to the grain and/or tension than when under load along the grain and/or compression . The extent to which knots affect the strength of a beam depends upon their position, size, number, and condition. A knot on the upper side is compressed, while one on the lower side is subjected to tension. If there

1702-509: Is applied to it. Each installation should be properly secured into wall blocking or studs to provide the best support. If no studs are available, specialized mollies can be used to spread out grab forces across a wider area of the wall. The Americans with Disabilities Act of 1990 Accessibility Guidelines for Buildings and Facilities (ADAAG) defines requirements for installing grab bars in public bathing and toileting facilities. The guidelines are supported by substantial research regarding

1776-422: Is dark colored and firm, and consists mostly of thick-walled fibers which form one-half or more of the wood. In inferior oak, this latewood is much reduced both in quantity and quality. Such variation is very largely the result of rate of growth. Wide-ringed wood is often called "second-growth", because the growth of the young timber in open stands after the old trees have been removed is more rapid than in trees in

1850-403: Is defined as either a circular cross section with an outside diameter of 1 + 1 ⁄ 4 inches (32 mm) minimum and 2 inches (51 mm) maximum or a non-circular cross section with a perimeter dimension of 4 inches (102 mm) minimum and 6 + 1 ⁄ 4 inches (159 mm) maximum and a cross section dimension of 2 + 1 ⁄ 4 inches (57 mm)) maximum. In addition,

1924-560: Is difficult to control completely, especially when using mass-produced kiln-dried timber stocks. Heartwood (or duramen ) is wood that as a result of a naturally occurring chemical transformation has become more resistant to decay. Heartwood formation is a genetically programmed process that occurs spontaneously. Some uncertainty exists as to whether the wood dies during heartwood formation, as it can still chemically react to decay organisms, but only once. The term heartwood derives solely from its position and not from any vital importance to

1998-399: Is in the walls, not the cavities. Hence the greater the proportion of latewood, the greater the density and strength. In choosing a piece of pine where strength or stiffness is the important consideration, the principal thing to observe is the comparative amounts of earlywood and latewood. The width of ring is not nearly so important as the proportion and nature of the latewood in the ring. If

2072-486: Is known as secondary growth ; it is the result of cell division in the vascular cambium , a lateral meristem, and subsequent expansion of the new cells. These cells then go on to form thickened secondary cell walls, composed mainly of cellulose , hemicellulose and lignin . Where the differences between the seasons are distinct, e.g. New Zealand , growth can occur in a discrete annual or seasonal pattern, leading to growth rings ; these can usually be most clearly seen on

2146-431: Is laid down on the outside of the wood previously formed, it follows that unless a tree materially increases its production of wood from year to year, the rings must necessarily become thinner as the trunk gets wider. As a tree reaches maturity its crown becomes more open and the annual wood production is lessened, thereby reducing still more the width of the growth rings. In the case of forest-grown trees so much depends upon

2220-470: Is more complex. The water conducting capability is mostly taken care of by vessels : in some cases (oak, chestnut, ash) these are quite large and distinct, in others ( buckeye , poplar , willow ) too small to be seen without a hand lens. In discussing such woods it is customary to divide them into two large classes, ring-porous and diffuse-porous . In ring-porous species, such as ash, black locust, catalpa , chestnut, elm , hickory, mulberry , and oak,

2294-437: Is not less than 1 + 3 ⁄ 4 inches (45 mm) below the tallest portion of the profile. The minimum width of the handrail above the recess shall be 1 + 1 ⁄ 4 inches (32 mm) to a maximum of 2 + 3 ⁄ 4 inches (70 mm). Edges shall have a minimum radius of 0.01 inches (0.25 mm). Handrails are located at a height between 34 and 38 inches (864 and 965 mm). In areas where children are

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2368-521: Is set between 0.9 and 1 metre ( 35 + 3 ⁄ 8 and 39 + 3 ⁄ 8  in). Various model codes—The International Code Council (ICC) and National Fire Protection Association (NFPA)—and accessibility standards—ANSI A117.1 and the Americans With Disabilities Act Standards for Accessible Design (ADASAD)—refer to handrail dimensions. Current versions of these codes and standards now agree that handrail

2442-431: Is the rule. Some others never form heartwood. Heartwood is often visually distinct from the living sapwood and can be distinguished in a cross-section where the boundary will tend to follow the growth rings. For example, it is sometimes much darker. Other processes such as decay or insect invasion can also discolor wood, even in woody plants that do not form heartwood, which may lead to confusion. Sapwood (or alburnum )

2516-413: Is the younger, outermost wood; in the growing tree it is living wood, and its principal functions are to conduct water from the roots to the leaves and to store up and give back according to the season the reserves prepared in the leaves. By the time they become competent to conduct water, all xylem tracheids and vessels have lost their cytoplasm and the cells are therefore functionally dead. All wood in

2590-400: Is then known as the latewood or summerwood. There are major differences, depending on the kind of wood. If a tree grows all its life in the open and the conditions of soil and site remain unchanged, it will make its most rapid growth in youth, and gradually decline. The annual rings of growth are for many years quite wide, but later they become narrower and narrower. Since each succeeding ring

2664-461: Is usually the latewood in which the thick-walled, strength-giving fibers are most abundant. As the breadth of ring diminishes, this latewood is reduced so that very slow growth produces comparatively light, porous wood composed of thin-walled vessels and wood parenchyma. In good oak, these large vessels of the earlywood occupy from six to ten percent of the volume of the log, while in inferior material they may make up 25% or more. The latewood of good oak

2738-494: The Occupational Safety and Health Administration (OSHA) require that the distance between the wall and handrail be a minimum of 2 + 1 ⁄ 4 inches (57 mm). The 1992 Americans With Disabilities Act Accessibility Guidelines (ADAAG) stated that there was to be an absolute dimension of 1 + 1 ⁄ 2 inches (38 mm) between a handrail and a wall. This was actually a "grab bar" dimension which

2812-401: The grain of the rest of the wood "flows" (parts and rejoins). Within a knot, the direction of the wood (grain direction) is up to 90 degrees different from the grain direction of the regular wood. In the tree a knot is either the base of a side branch or a dormant bud. A knot (when the base of a side branch) is conical in shape (hence the roughly circular cross-section) with the inner tip at

2886-429: The resin which increases the strength when dry. Such resin-saturated heartwood is called "fat lighter". Structures built of fat lighter are almost impervious to rot and termites , and very flammable. Tree stumps of old longleaf pines are often dug, split into small pieces and sold as kindling for fires. Stumps thus dug may actually remain a century or more since being cut. Spruce impregnated with crude resin and dried

2960-522: The International Residential Code (IRC) includes a definition of a "Type II" handrail that allows for handrail with a perimeter dimension greater than 6 + 1 ⁄ 4 inches (159 mm). The IRC and residential portion of the 2009 IBC define Type II handrail as follows: Type II. Handrails with a perimeter greater than 6 + 1 ⁄ 4 inches (159 mm) shall provide a graspable finger recess area on both sides of

3034-433: The addition of steel and bronze into construction. The year-to-year variation in tree-ring widths and isotopic abundances gives clues to the prevailing climate at the time a tree was cut. Wood, in the strict sense, is yielded by trees , which increase in diameter by the formation, between the existing wood and the inner bark , of new woody layers which envelop the entire stem, living branches, and roots. This process

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3108-418: The annual rings of growth and the amount of sapwood. Within the same species the cross-sectional area of the sapwood is very roughly proportional to the size of the crown of the tree. If the rings are narrow, more of them are required than where they are wide. As the tree gets larger, the sapwood must necessarily become thinner or increase materially in volume. Sapwood is relatively thicker in the upper portion of

3182-576: The best placement of grab bars. The following is a subset of ADA grab bar guidelines: While the ADA guidelines provide specifics on the placement of grab bars in public locations, they do not require a specific style. The British Doc M regulations specify a minimum contrast between bars and background. Many public facilities opt for the cheapest grab bars, which usually have an institutional look. However, grab bars are actually available in many styles, finishes and colors. Manufacturers have begun to understand

3256-449: The border between the two classes, forming an intermediate group. In temperate softwoods, there often is a marked difference between latewood and earlywood. The latewood will be denser than that formed early in the season. When examined under a microscope, the cells of dense latewood are seen to be very thick-walled and with very small cell cavities, while those formed first in the season have thin walls and large cell cavities. The strength

3330-458: The cell walls are composed of micro-fibrils of cellulose (40–50%) and hemicellulose (15–25%) impregnated with lignin (15–30%). In coniferous or softwood species the wood cells are mostly of one kind, tracheids , and as a result the material is much more uniform in structure than that of most hardwoods . There are no vessels ("pores") in coniferous wood such as one sees so prominently in oak and ash, for example. The structure of hardwoods

3404-435: The central portion one-fourth the height of the beam from either edge are not serious defects. Knots do not necessarily influence the stiffness of structural timber; this will depend on the size and location. Stiffness and elastic strength are more dependent upon the sound wood than upon localized defects. The breaking strength is very susceptible to defects. Sound knots do not weaken wood when subject to compression parallel to

3478-474: The clearance in the back of grab bars must be at least 4 inches, the diameter similar to the ladder rungs and, when horizontal, grab bars must be spaced by a continuation of the rung spacing. In 2008-2009 alone, the USDOL Bureau of Labor Statistics reported 241 casualties from ladder falls. Siderail extensions horizontal grab bars may be bolted or welded to fixed ladders. Grab bars may be mounted to

3552-445: The competition of the trees in their struggle for light and nourishment that periods of rapid and slow growth may alternate. Some trees, such as southern oaks , maintain the same width of ring for hundreds of years. On the whole, as a tree gets larger in diameter the width of the growth rings decreases. As a tree grows, lower branches often die, and their bases may become overgrown and enclosed by subsequent layers of trunk wood, forming

3626-433: The contrast is conspicuous (see section of yew log above). This is produced by deposits in the heartwood of chemical substances, so that a dramatic color variation does not imply a significant difference in the mechanical properties of heartwood and sapwood, although there may be a marked biochemical difference between the two. Some experiments on very resinous longleaf pine specimens indicate an increase in strength, due to

3700-426: The cost can vary depending on the style you choose. You can also choose various fixings to allow for a more modern/sleek look. Grab bar Grab bars are safety devices designed to enable a person to maintain balance, lessen fatigue while standing, hold some of their weight while maneuvering, or have something to grab onto in case of a slip or fall. A caregiver may use a grab bar to assist with transferring

3774-413: The curb for access to rooftops and rooftop hatches . Wood Wood is a structural tissue/material found as xylem in the stems and roots of trees and other woody plants . It is an organic material  – a natural composite of cellulosic fibers that are strong in tension and embedded in a matrix of lignin that resists compression. Wood is sometimes defined as only

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3848-415: The end of a log, but are also visible on the other surfaces. If the distinctiveness between seasons is annual (as is the case in equatorial regions, e.g. Singapore ), these growth rings are referred to as annual rings. Where there is little seasonal difference growth rings are likely to be indistinct or absent. If the bark of the tree has been removed in a particular area, the rings will likely be deformed as

3922-403: The exact mechanisms determining the formation of earlywood and latewood. Several factors may be involved. In conifers, at least, rate of growth alone does not determine the proportion of the two portions of the ring, for in some cases the wood of slow growth is very hard and heavy, while in others the opposite is true. The quality of the site where the tree grows undoubtedly affects the character of

3996-505: The grain. In some decorative applications, wood with knots may be desirable to add visual interest. In applications where wood is painted , such as skirting boards, fascia boards, door frames and furniture, resins present in the timber may continue to 'bleed' through to the surface of a knot for months or even years after manufacture and show as a yellow or brownish stain. A knot primer paint or solution (knotting), correctly applied during preparation, may do much to reduce this problem but it

4070-412: The greater the water content, the greater its softening effect. The moisture in wood can be measured by several different moisture meters . Drying produces a decided increase in the strength of wood, particularly in small specimens. An extreme example is the case of a completely dry spruce block 5 cm in section, which will sustain a permanent load four times as great as a green (undried) block of

4144-430: The horizontal bracket arm. There is an allowance however for variations in the handrail size—for every 1 ⁄ 2 inch (13 mm) of additional perimeter dimension over 4 inches (102 mm), 1 ⁄ 8 inch (3.2 mm) may be subtracted from the clearance requirement. Handrails are to support a continuous load of 50 pounds per foot (74 kg/m) or a concentrated load of 200 pounds (91 kg) applied at

4218-407: The larger vessels or pores (as cross sections of vessels are called) are localized in the part of the growth ring formed in spring, thus forming a region of more or less open and porous tissue. The rest of the ring, produced in summer, is made up of smaller vessels and a much greater proportion of wood fibers. These fibers are the elements which give strength and toughness to wood, while the vessels are

4292-480: The moisture content of the air) retains 8–16% of the water in the cell walls, and none, or practically none, in the other forms. Even oven-dried wood retains a small percentage of moisture, but for all except chemical purposes, may be considered absolutely dry. The general effect of the water content upon the wood substance is to render it softer and more pliable. A similar effect occurs in the softening action of water on rawhide, paper, or cloth. Within certain limits,

4366-777: The need to blend in with home decor, offering grab bars that have style and pizazz. For the home, grab bars do not need to be ADA compliant, but those guidelines should be considered. In addition to straight grab bars, there are fold-out bars, those that clamp onto the side of the bathtub, L-shaped, U-shaped and corner grab bars. Grab bars are also made with built in LED lighting and can come in many different colours. Grab bars in industry and construction are found on equipment or above fixed ladders where footholds exist but other handholds are lacking. They may be positioned horizontally, vertically, or at an angle. When using grab bars as safety devices in order to prevent falls, your best choice would be

4440-542: The other hand, the latewood is very dense and is deep-colored, presenting a very decided contrast to the soft, straw-colored earlywood. It is not only the proportion of latewood, but also its quality, that counts. In specimens that show a very large proportion of latewood it may be noticeably more porous and weigh considerably less than the latewood in pieces that contain less latewood. One can judge comparative density, and therefore to some extent strength, by visual inspection. No satisfactory explanation can as yet be given for

4514-404: The plant overgrows the scar. If there are differences within a growth ring, then the part of a growth ring nearest the center of the tree, and formed early in the growing season when growth is rapid, is usually composed of wider elements. It is usually lighter in color than that near the outer portion of the ring, and is known as earlywood or springwood. The outer portion formed later in the season

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4588-605: The point in stem diameter at which the plant's vascular cambium was located when the branch formed as a bud. In grading lumber and structural timber , knots are classified according to their form, size, soundness, and the firmness with which they are held in place. This firmness is affected by, among other factors, the length of time for which the branch was dead while the attaching stem continued to grow. Knots materially affect cracking and warping, ease in working, and cleavability of timber. They are defects which weaken timber and lower its value for structural purposes where strength

4662-503: The principal users of a building or facility, the 2010 ADASAD recommends that a second set of handrails at a maximum height of 28 inches (711 mm) measured to the top of the gripping surface from the ramp surface or stair nosing can assist in preventing accidents. The distance between the wall and handrail gripping surface is also governed by local code with the most common requirement being 1 + 1 ⁄ 2 inches (38 mm) minimum. The National Fire Protection Agency (NFPA) and

4736-407: The profile. The finger recess shall begin within a distance of 3 ⁄ 4 inch (19 mm) measured vertically from the tallest portion of the profile and achieve a depth of at least 5 ⁄ 16 inch (8 mm) within 7 ⁄ 8 inch (22 mm) below the widest portion of the profile. This required depth shall continue for at least 3 ⁄ 8 inch (10 mm) to a level that

4810-411: The properties of the wood. Certain rot-producing fungi impart to wood characteristic colors which thus become symptomatic of weakness. Ordinary sap-staining is due to fungal growth, but does not necessarily produce a weakening effect. Water occurs in living wood in three locations, namely: In heartwood it occurs only in the first and last forms. Wood that is thoroughly air-dried (in equilibrium with

4884-468: The reverse is commonly true. Otherwise the color of wood is no indication of strength. Abnormal discoloration of wood often denotes a diseased condition, indicating unsoundness. The black check in western hemlock is the result of insect attacks. The reddish-brown streaks so common in hickory and certain other woods are mostly the result of injury by birds. The discoloration is merely an indication of an injury, and in all probability does not of itself affect

4958-453: The same size will. The greatest strength increase due to drying is in the ultimate crushing strength, and strength at elastic limit in endwise compression; these are followed by the modulus of rupture, and stress at elastic limit in cross-bending, while the modulus of elasticity is least affected. Wood is a heterogeneous , hygroscopic , cellular and anisotropic (or more specifically, orthotropic ) material. It consists of cells, and

5032-567: The secondary xylem in the stems of trees, or more broadly to include the same type of tissue elsewhere, such as in the roots of trees or shrubs. In a living tree, it performs a mechanical-support function, enabling woody plants to grow large or to stand up by themselves. It also conveys water and nutrients among the leaves , other growing tissues, and the roots. Wood may also refer to other plant materials with comparable properties, and to material engineered from wood, woodchips , or fibers . Wood has been used for thousands of years for fuel , as

5106-708: The top of the handrail. As handrails come in different materials, the strengths can vary. From timber to stainless steel, it is best to pick a handrail that will be right for the area. Stainless steel will be stronger and more durable outside, whereas timber can be just as strong but less durable outside. ADA Handrail height requirements are issued to create a safe enjoyable space to enjoy for everyone. The ADA height of handrail requirements that will primarily be used by children have their own unique requirements. The top of gripping surfaces of handrails shall be 34 inches minimum and 38 inches maximum vertically above walking surfaces, stair nosing, and ramp surfaces. Handrails shall be at

5180-430: The tree, may well be stronger than a piece of heartwood from the same tree. Different pieces of wood cut from a large tree may differ decidedly, particularly if the tree is big and mature. In some trees, the wood laid on late in the life of a tree is softer, lighter, weaker, and more even textured than that produced earlier, but in other trees, the reverse applies. This may or may not correspond to heartwood and sapwood. In

5254-445: The tree. This is evidenced by the fact that a tree can thrive with its heart completely decayed. Some species begin to form heartwood very early in life, so having only a thin layer of live sapwood, while in others the change comes slowly. Thin sapwood is characteristic of such species as chestnut , black locust , mulberry , osage-orange , and sassafras , while in maple , ash , hickory , hackberry , beech , and pine, thick sapwood

5328-416: The trunk of a tree than near the base, because the age and the diameter of the upper sections are less. When a tree is very young it is covered with limbs almost, if not entirely, to the ground, but as it grows older some or all of them will eventually die and are either broken off or fall off. Subsequent growth of wood may completely conceal the stubs which will remain as knots. No matter how smooth and clear

5402-418: The wood formed, though it is not possible to formulate a rule governing it. In general, where strength or ease of working is essential, woods of moderate to slow growth should be chosen. In ring-porous woods, each season's growth is always well defined, because the large pores formed early in the season abut on the denser tissue of the year before. In the case of the ring-porous hardwoods, there seems to exist

5476-438: Was part of the 1986 ANSI A117.1. ANSI changed the notation to 1 + 1 ⁄ 2 inches (38 mm) minimum in 1990. This was not corrected in 2010 with the approval of the new ADASAD which now calls for a 1 + 1 ⁄ 2 inches (38 mm) minimum clearance. Codes also generally require that there be a 1 + 1 ⁄ 2 inches (38 mm) clearance between the underside of the handrail and any obstruction—including

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