R Value    A measure of insulation. For example, typical new home's walls are usually insulated with 6" of bat insulation with an R value of R-19, and a ceiling insulation of R-28.
Rafter    One of a series of structural members of a roof designed to support roof loads. The rafters of a flat roof are sometimes called roof joists.
Rake edge    The overhang of an inclined roof plane beyond the vertical wall below it.
Random-tab shingles    Shingles on which tabs vary in size and exposure.
Rebar    When concrete cracks it will separate or become uneven, rebar is a rod of steel placed into the concrete, usually in square feet one or two.
Relative humidity    The amount of moisture in a volume of air as a percentage of the maximum amount of moisture that can be held in that air at a certain temperature - cold air can't hold as much moisture as warmer air.
Release tape    A plastic or paper strip that is applied to the back of self-sealing shingles. This strip prevents the shingles from sticking together in the bundles, and need not be removed for application.
Remodeling contractor     A general contractor who specializes in remodeling work.
Retaining wall     A wall, usually constructed of poured concrete or concrete block designed to serve retain earth and serving as a transition between two different grade levels. Structural requirements are set by ordinance if height is over a set minimum.
Return     - Continuation of a molding at a right angle to an adjacent surface
Ridge    The intersection of two roof planes, or the angle formed by them.
Ridge board     - A board placed on edge at the ridge of a roof into which the upper ends of rafters are fastened.
Ridge shingles    Shingles used to cover the horizontal external angle formed by the intersection of two sloping roof planes.
Rise, roof     - The vertical height of a roof truss or vertical frame.  The vertical distance from the eaves line to the ridge.
Rise, stairs     - This is either the vertical distance from the top of one tread to the top of the next.Rise may also refer to the total vertical distance of a stairway. Note: Stair dimensions are controlled by building codes. Accordingly, irregularities are negligence per se.
Roll roofing    Asphalt roofing products manufactured in roll form.
Roof deck    See deck.
Roof sheathing    : Boards or sheet material fastened to roof rafters on which the shingle of other roof covering is laid.
Roofing membrane or     The layer or layers of waterproofing products that cover the roof deck.
Roofing tape    An asphalt-saturated tape used with asphalt cements for flashing and patching asphalt roofing.
Run    The horizontal distance from the eaves to a point directly under the ridge. One half the span.