CEILING SYSTEM
PARTS OF CEILING
Introduction
A 'coupled' roof is a conventional roof that is constructed on-site. It uses ceiling joists, hanging beams, strutting beams, struts, underpurlins, collar ties, rafters and ridgeboards.
Ceiling joists
-The ceiling joists have a double function:
--they provide the structure onto which the ceiling is fixed
--they are the member that connects or ties the lower ends of rafter couples (pairs). Therefore, they prevent the rafters spreading and causing the roof to sag or collapse.
-Ceiling joists are normally horizontal members, however, under special circumstances they can be fixed on a slope. They are spaced according to the material they support. Typically the material is plasterboard which can span 450 mm.
-For coupled roofs, ceiling joists have to be in single lengths or spliced. They must be at the same spacing and in the same direction as the main rafters so they can be fixed to, and act as ties between the feet of opposing rafter pairs. Where there is no internal wall to support the ceiling joist a hanging beam must be installed.
Hanging beams
-A 'hanging beam' is generally a deep timber beam located perpendicular (at right angles or 90º) to ceiling joists and directly above them. The function of a hanging beam is to reduce the span of the ceiling joists. This allows for a more economic joist size and consistent section. Hanging beams must only support ceiling joists and the attached ceiling materials.
-The hanging beam has to be adequately supported on its ends over load bearing walls. This is done using blocking pieces of the same timber as the ceiling joists. The ceiling joists are fixed to the hanging beam with: hoop iron straps timber battens or purpose made metal joist hanger brackets.
-Hanging beams are held in a vertical position at both ends. They can be nailed or bolted to an available rafter, gable end strut or held by means of angle strutting from internal walls.
Strutting beams
-'Strutting'
Introduction
A 'coupled' roof is a conventional roof that is constructed on-site. It uses ceiling joists, hanging beams, strutting beams, struts, underpurlins, collar ties, rafters and ridgeboards.
Ceiling joists
-The ceiling joists have a double function:
--they provide the structure onto which the ceiling is fixed
--they are the member that connects or ties the lower ends of rafter couples (pairs). Therefore, they prevent the rafters spreading and causing the roof to sag or collapse.
-Ceiling joists are normally horizontal members, however, under special circumstances they can be fixed on a slope. They are spaced according to the material they support. Typically the material is plasterboard which can span 450 mm.
-For coupled roofs, ceiling joists have to be in single lengths or spliced. They must be at the same spacing and in the same direction as the main rafters so they can be fixed to, and act as ties between the feet of opposing rafter pairs. Where there is no internal wall to support the ceiling joist a hanging beam must be installed.
Hanging beams
-A 'hanging beam' is generally a deep timber beam located perpendicular (at right angles or 90º) to ceiling joists and directly above them. The function of a hanging beam is to reduce the span of the ceiling joists. This allows for a more economic joist size and consistent section. Hanging beams must only support ceiling joists and the attached ceiling materials.
-The hanging beam has to be adequately supported on its ends over load bearing walls. This is done using blocking pieces of the same timber as the ceiling joists. The ceiling joists are fixed to the hanging beam with: hoop iron straps timber battens or purpose made metal joist hanger brackets.
-Hanging beams are held in a vertical position at both ends. They can be nailed or bolted to an available rafter, gable end strut or held by means of angle strutting from internal walls.
Strutting beams
-'Strutting'