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Glossary of Roofing Terms - K
Kerf: The width of a cut made by the blade of a saw.
Kesternich Test: Common name for various tests which use sulfur dioxide, a significant component of acid rain, in order to measure the resistance to corrosion of industrial products.
Kick-out: A section of a downspout assembly which typically uses an elbow piece to divert out-flowing water away from a building.
King-post: A vertical support post which extends from the apex to the tie-beam within a triangular roof-truss. (Also see Queen-post).
King-post Truss: A type of triangular roof truss which incorporates a vertical support member, at the apex of the truss, connecting the tie-beam and the rafters.
Knee Brace: A brace placed across the angle formed by two connected members, such as a joist and a rafter, in order to strengthen the assembly. Also called a corner brace.
Knee Cap: During metal roofing installation, in order for a metal roof panel to be bent to conform to a plane change in the substrate, the panel's rib must be cut or notched at the location of the transition. A knee cap is the sheet metal cover piece that fits over the rib at the location of this cut.
Knee Rafter: A principal rafter which is bent at the lower end.
Knee Roof: see Curb Roof
Knee Wall: A wall which functions as a knee brace, extending from the rafters to the ceiling joists.
Knot: In membrane production, the presence of an imperfection that causes a surface irregularity.
Kraft Paper: see Building Paper.
K-Value: Also called k-factor, or lambda value, λ. A measure of a material's thermal conductivity regardless of the amount of the material. Thermal conductivity is defined by ASTM Standard C168 as "the time rate of steady state heat flow through a unit area of a homogeneous material induced by a unit temperature gradient in a direction perpendicular to that unit area". K-value is calculated using watts per meter-kelvin (W/(m⋅K)).
Kynar: Kynar 500® is the Arkema, Inc. trade name for a polyvinylidene fluoride (PVDF) resin-based metal coating considered to be a premier coating for metal roofing materials.