You can build a new ceiling at any practical height. However, the height of window openings may limit your choice. About 2.4m (8ft) is a useful height for a lowered ceiling; it is a common room height for modern houses and relates to standard wallboard sheet sizes. Most manufacturers of built-in furniture adopt it as a standard height for ceilings.
Planning the layout
Making a lowered ceiling requires a considerable amount of timber for the framework and boarding to cover it. Work out your material requirements by drawing a plan to establish the most economical way to construct the ceiling. If you intend to use plasterboard, choose a vapour-check type. Arrange the panels with the paper-covered edges set at right angles to the timber supports. Stagger the end joints between each row of boards and arrange them so that they fall on a joist.
If you plan to use tongue-and-groove boarding buy it in lengths that can be cut economically to suit your joist arrangement, as short offcuts are wasteful. From time to time you will have to join boards end to end, using butt joints. Stagger short boards so that two adjacent joints do not coincide.
Materials for the framework
Make a cutting list of the materials you will need to make up the structure. Use 75 x 50mm (3 x 2in) sawn softwood for the ceiling joists. Calculate the number of joists you will need; they should span the room in the shortest direction and should be spaced at 400mm (1ft 4in) or 600mm (2ft) centres according to the thickness of the plasterboard. These dimensions are also suitable for other types of boarding.
You will need extra joist timber for the noggings fitted between the joists, plus 50 x 25mm (2 x lin) sawn softwood for wall battens to run round the perimeter of the room.
Support spans of over 2.4m (8ft) with hangers and ties, made from timber not less than 50 x 50mm (2 x 2in) and fixed to the original ceiling above. Support the joists at about the middle of their span.
It is possible to use more hangers and reduce the section of the joists from 75 x 50mm (3 x 2in) to 50 x 50mm (2 x 2in). In this case place the hangers about 900mm (3ft) apart.
Constructing a Lowered Ceiling
Mark the height of the new ceiling, including the thickness of the boarding, on one wall. Draw a horizontal line across the wall at this level, using a straightedge and spirit level for accuracy. Continue the line around the room at this height. Cut the 50 x 25 mm (2 x lin) wall battens to length. Nail or screw them to the walls at 400mm (1ft 4in) intervals, with the bottom edge level with the line.
Cut the 75 x 50mm (3 x 2in) ceiling joists to length. Notch the ends to sit over the wall battens to bring the bottom edges flush. Skew-nail the joists to the wall battens. Cut and fit hangers and ties to prevent Jong joists sagging (see opposite). These supports also stiffen the structure.
Cut and nail noggings between the joists to support the edges of the plasterboard. Nail tapered-edge plasterboard to the joists, noggings and wall battening. Fill and tape the joints between boards and walls.
You can lower part of a ceiling to overcome problems with tall window openings or to create a split-level effect. Follow the method for constructing a ceiling as described above, but enclose the end drop with plasterboard nailed to hangers suspended from a cross-tie member fixed above the last joist.
Planed softwood planks 150 x 25mm (6 x 1 in) in size, set on edge and spaced apart, can create a simple yet effective slatted ceiling. Smaller sections can be used where the span is short, as with a narrow hallway.
Cut four lengths of planking for the perimeter of the slatted ceiling. Before nailing or screwing them at the required height, mark and cut housings in two opposite planks. Space the housings 225mm (gin) apart. For boards less than 150mm (6in) wide, space the housings about 100 to 150mm (4 to 6in) apart. Cut notches in the ends of the ‘slat’ boards to sit in the housings so that the bottom edges finish flush.
Before fitting the slats, paint the walls and ceiling above the perimeter boards with a dark emulsion paint. Paint ducting or plumbing to disguise it. Finish the slats with varnish, stain or paint.
A suspended ceiling is a framed panel that gives the impression that it is floating away from the walls. Fluorescent lights can he placed around the edge of the panel to enhance the floating effect and provide wall- washing illumination. Cover the panel with plasterboard, decorative veneered ply or mineral-fibre ceiling tiles.
Locate the position of the ceiling joists by noting the direction of the floorboards of the room above; the joists run at right angles to them. Pinpoint the joists from below by drilling pilot holes through the ceiling, then mark the centre of each joist.
Setting out the grid
Measure the lengths of the walls and draw a scaled plan of the room on graph paper. Set out the shape of the ceiling panel on the drawing with its edges approximately 200mm (8in) from each wall. Then set out the position of the 50 x 50mm (2 x 2in) softwood ceiling ties. The ties should run at right angles to the joists of the ceiling above. The ends of the ties and sides of the two outer ones should be about 300mm (1ft) from the walls. The number of ties you need depends on the size of the ceiling, but three should be a minimum. They should be spaced not more than 900mm (3ft) apart for adequate support.
Constructing the ceiling
Counterbore and securely screw the ties in position to each of the joists they cross. Cut 50 x 50mm (2 x 2in) softwood hangers to the required length and fix them to the ties with coach bolts not more than 900mm (3ft) apart.
Cut additional ties to the same length as the planned ceiling panel. Bolt them across the ends of the hangers with an equal space at each end.
Cut the required number of 50 x 50mm (2 x 2in) planed softwood furring battens to suit the spacings necessary to support the boards or tiles used as a covering. Their length should be the span of the ceiling panel less two 50 x 25mm (2 x lin) capping battens. Space the furring battens equally and screw them to the tie members. Counter-sink the screw heads.
Mark off the positions of the furring battens along the sides of each capping batten. Drive 50mm (2in) nails into, but not quite through, the cappings at these points. Apply woodworking adhesive and nail the cappings to the ends of the furring battens.
Finishing the assembly
Run electrical wiring for the fluorescent lights. Cover the underside of the frame with plasterboard, decorative veneered boarding or ceiling tiles. Fill and finish the surface and edges of a plasterboard ceiling panel. Finish the exposed edges of the frame to match the other materials as required.
Wire up slim fluorescent light fittings and fix them to loose boards that rest on top of the projecting frame. The light fittings can then be removed easily for servicing at any time. Provide enough spare electrical flex to allow the lights to he lifted clear.