R-value (thermal resistance)
The reciprocal of the U-factor (thermal transmittance). Units of R and h•ft2/Btu.
Higher R-values indicate a material's ability to resist more heat flow.
Rafter
The main beam supporting the roof system.
Raggle
A groove or slot, often cut in a masonry wall or other vertical surface adjoining a roof,
for inserting an inset flashing component such as a reglet.
Rail (Crane)
See "Crane Rail".
Rails (Door)
The horizontal stiffening members of framed and paneled doors.
Rake
The intersection of the plane of the roof and the plane of the endwall.
Rake Angle
Angle fastened to purlins at rake for attachment of endwall panels.
Rake Trim
A flashing designed to close the opening between the roof and endwall panels.
Rated Capacity (Crane)
The maximum load (usually in tons) that the crane is designed to support safely.
Reactions
The resisting forces at the column bases holding the structure in equilibrium under a
given loading condition.
Reinforcing Steel
The steel placed in concrete as required to carry the tension, compression and shear
stresses.
Reglet
A sheet metal receiver for the attachment of counterflashing, or the counterflashing
itself when mounted to a wall. (A reglet may be inset into a raggle, embedded behind
cladding, or be surface mounted.)
Remote-Operated Crane
A crane controlled by an operator not in a pulpit or in the cab attached to the crane, by
any method other than pendant or rope control.
Retrofit
The placing of new metal roof or wall systems over deteriorated roofs or walls.
Rib
The longitudinal raised profile of a panel that provides much of the panel’s bending
strength.
Ribbed Panel
A panel that has ribs with sloping sides and forms a trapezoidal shaped void at the side
lap.
Ridge
The horizontal line formed by opposing sloping sides of a roof running parallel with
the building length.
Ridge Cap
A transition of the roofing materials along the ridge of a roof; sometimes called ridge
roll or ridge flashing.
Rigid Board Insulation
Typically, a rigid polyisocyanurate or polystyrene foam insulation.
Rigid Connection
See "Moment Connection".
Rigid Frame
A structural frame consisting of members joined together with moment connections so
as to render the frame stable with respect to the design loads, without the need for
bracing in its plane.
Rolling Doors
Single or multiple leaf doors that open horizontally and are supported at the bottom on
wheels that run on a track.
Roll-up Door
A door that opens by traveling vertically.
Roof Assembly
All roof/ceiling components of the building envelope that are horizontal or sloped at
an angle less than 60 degrees from horizontal.
Roof Covering
The exposed exterior roof surface consisting of panels.
Roof Curb
See "Curb, Roof"
Roof Jack
(1) A synthetic rubber boot or collar that is used to seal around round roof projections.
(Also see "Flashing Collar".)
(2) A metal bracket used to support toe-boards on steep-slope roofs.
Roof Live Load
Loads that are produced (1) during maintenance by workers, equipment, and materials,
and (2) during the life of the structure by movable objects and do not include wind,
snow, seismic or dead loads.
Roof Overhang
A roof extension beyond the end wall or side wall of a building.
Roof Slope
The tangent of the angle that a roof surface makes with the horizontal, usually
expressed in units of vertical rise to 12 units of horizontal run.
Roof Snow Load
That load induced by the weight of snow on the roof of the structure. Usually obtained
by taking a fraction of the "Ground Snow Load".
Roof Seamer
A machine that crimps or folds adjacent edges of standing seam metal roof panels
together, to form a seam.
Ropeseal
See "Butyl Tape".
Runway Beam
See "Crane Runway Beam".
Runway Bracket
A bracket attached to the column of a building frame which supports the runway beam
for top-running cranes.
Runway Conductors
The main conductors mounted on or parallel to the runway that supplies electric current
to the crane.