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Hardboard A panel manufactured primarily from interfolded wood fibres consolidated under heat and pressure in a hot press and used, for example, in the manufacture of siding products.
Hardwood (deciduous) Trees One of the botanical groups of trees that have broad leaves, in contrast to the conifers or softwoods. The term does not necessarily refer to the actual hardness of the wood.
Header A single member composed of two or more wood members, securely fastened together and used to increase load carrying capability at wall or floor or widow openings.
Heartwood The wood extending from the true centre to the sapwood, and whose cells no longer participate in the life processes of the tree. Hearfwood may contain gums, resins, and other materials that usually make it darker and more decay resistant than sapwood.
Heavy Timber Construction A type of combustible construction in which a degree of fire safety is attained by placing limitations on the sizes of wood structural members and on thickness and composition of wood floors and roofs and by the avoidance of concealed spaces under floors and roofs.
Heel Point on truss at which the top and bottom chords intersect.
Honeycomb A cellular separation in the interior of a wood piece, usually along the wood grain, a result of internal stress. It normally occurs during kiln drying, particularly in white or red oak, when too much heat is applied too rapidly.
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Importance Factor A factor applied to factored loads, other than dead load, to take into account the consequence of collapse as related to the use and occupancy of the structure, as in Limit States Design.
Intumescence The swelling of a fire- retardant coating when heated, resulting in the formation of low-density film which provides a degree of surface flame-spread resistance.
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Joint, Butt An end joint formed by abutting the squared ends of two pieces.
Joint, End A joint made by bonding two pieces of wood together end to end, usually by finger or scarf joint.
Joint, Scarf An end joint formed by joining with adhesive the ends of two pieces that have ben tapered or bevelled to form sloping plane surfaces.
Joist One of a series of parallel beams used to support floor and ceiling loads, supported in turn by larger beams, girders, or bearing walls.
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Knot That portion of a branch or limb that has been surrounded by subsequent growth of the stem. The shape of the knot as it appears on a lumber surface depends on the angle of the cut relative to the long axis of the knot.
Knot, Loose A knot which is not held firmly in place by growth or position and which cannot be relied upon to remain in place.
Knot, Pin A knot that is not more than 12.5mm (1/2") in diameter.
Knot, Sound A knot that is solid across its face, at least as hard as the surrounding wood, and shows no indication of decay.
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Laminate, Wood A product made by bonding layers of wood or other material to a wood substrate.
Laminated Veneer Lumber (LVL) A structural lumber product manufactured from veneers laminated so that the grain of all veneers run parallel to the axis of a member.
Latex A synthetic resin used in the manufacture of water soluble paint coatings. PVA and acrylic are two types of latex resins used to make latex coatings.
Level or Soffit Return Lumber filler placed horizontally from the end of an overhang to the outside wall to form a soffit.
Light Framing The use of dimension lumber, trusses, and other small cross- section members to provide support and enclosure for a building.
Lignin The second most abundant constituent of wood after cellulose. It is the thin cementing layer between the wood celIs.
Limit State A condition of a structure at which the structure ceases to fulfil the design function as applied in Limit States Design.
Live Load Any loading that is of a temporary nature such as snow, wind, earthquake, and construction loads.
Load Combination Factor A factor applied to the factored loads in Limit States Design, other than dead load, to take into account the reduced probability of a number of loads from different sources acting simultaneously as applied to Limit States Design.
Load Duration The period of continuous application of a specified load, or the aggregate of periods of intermittent applications of the same load.
Load Factor A factor applied to a specified load that, for the limit state under consideration, takes into account the variability of the loads and load patterns as applied to Limit States Design.
Lumber The product of the saw and planing mill not further manufactured than by sawing, resawing, passing lengthwise through a standard planing machine, cross- cutting to length, and grading.
Lumber, Boards Lumber that is less than 38mm (2" nom.) thick and 38mm (2" nom.) or more wide.
Lumber, Dressed Sized The dimensions of lumber after being surfaced with a planing machine.
Lumber, Machine Stress-Rated (MSR) Lumber which has been mechanically evaluated to determine its stiffness and bending strength.
Lumber, Matched Lumber that is edge dressed and shaped to make a close tongue and groove joint at the edges or ends, when laid edge to edge, or end to end.
Lumber, Nominal Size The size of lumber after sawing and prior to surface finishing by planing.
Lumber, Patterned Lumber that is shaped to a pattern or to a moulded form in addition to being surface planed.
Lumber, Rough Lumber that has not been dressed (surfaced) but which has been sawed, edged, and trimmed.
Lumber, Shiplapped Lumber that is edge dressed to make a lapped joint.
Lumber, Sizes of For metric measure, lumber size is based on actual size rounded to the nearest millimetre. For Imperial measure, lumber size is usually expressed in terms of nominal size which is the size before surfacing. The dressed size is usually 12 to 19mm (1/2 to 3/4") less than the nominal or rough size. For example, a 2" x 4" stud after dressing measures about 1-1/2" x 3-1/2".
Lumber, Structural Lumber which has strength in relation to the anticipated structural end use, as a controlling factor in grading or selecting.
Lumber, Visually Stress-Graded Lumber that has been graded for strength based on visual appearance, as opposed to MSR lumber which is evaluated mechanically and checked visually.
Lumber, Dimension Lumber 38 to 102mm (2" to 4" nom.) in smaller dimension
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