Radon
A naturally occurring radioactive gas found in some parts of the country with granite bed rock.
Rafter
A pitched roof timber, usually running from ridge down to eaves level. See also Jack Rafter.
R.C.D Residual Circuit Device
A form of 'Circuit Breaker'.
Render
Cement-based mortar used to cover walls, often where prone to wetness and can be finished in a variety of textures.
Retaining Wall
A wall that supports adjoining ground on one side. Adequate drainage should be provided to relieve a build up of water pressure.
Ridge Board
A horizontal timber forming the apex of a roof, to which the heads of pitched rafters are attached.
Ridge Tile
Tiles provided over the 'Ridge Board' at the apex of a roof, usually angular or half-round in section.
Riser
A vertical timber beneath the 'tread' or 'nosing' of a step.
Rising Damp
The upward movement of moisture within a structure as a result of 'Capillary Action'.
Roof Spread
Describes the outward thrust movement of an inadequately tied roof structure.
R.S.J 'Rolled Steel Joist'
Used as a beam or lintel, most commonly 'I'–shaped in section.