Fix a sagging plasterboard ceiling

A sagging ceiling can generally be renewed with a minimum of trouble simply by fixing timber battens and plasterboard sheets below it.

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Tools: Chalk line; stringlines; hammer; electric drill and 5mm twist bit; screwdriver; tape measure; spirit level; straightedge; steps; panel lift (hired); plastering equipment; safety protection.

Materials: 68 x 18mm pine battens; plasterboard sheets; wedges and packers; 30, 75 and 100mm plasterboard screws; plasterboard adhesive, base coat and topping coat.

	STEP 1 Remove any cornices if they are fitted (see panel, page 230). Find the lowest spot on the ceiling using a level and a 2400mm straightedge. Transfer the location of this low spot to the closest wall by holding the straightedge level against the ceiling and marking the position of its top edge on the wall. You may need to ask somebody to help you hold the straightedge.
	STEP 2 Measure down 24mm from the mark to allow clearance below the lowest point for 18mm-thick battens plus a 6mm leeway. Use the long straightedge and a spirit level to extend this line around the room, making short tick marks on the end of the straightedge rather than a solid line. If the lines don’t match when you reach your starting point, level again as necessary until they do. Then snap chalk lines between the corners to create a solid level line around the room.
	STEP 3 Locate both ends of each ceiling joist. Joists usually run parallel to one another, and are about 45mm wide. They are typically 450 or 600mm apart. Probe with a hammer and nail, locate and mark the centre of each joist at opposite ends of the room. Snap chalk lines between these marks to indicate joist locations. The thin strips of timber seen through the hole here are laths, which were used to support a solid plaster ceiling like this one.

STEP 4
Lay out the ceiling for the 68 x 18mm battens. First make a mark 434mm from the wall, to fix the location of the far edge of the second strip. This allows the plasterboard to be fixed along or across the battens. Extend your tape from this point and mark every 400mm to locate the edges of the remaining strips. Repeat this process on the opposite wall and snap chalk lines between the marks.

STEP 5
Cut the strips to fit between the walls and temporarily fix them in the centre with a partially driven plasterboard screw.