Association of Home Appliance Manufacturers
How to a Repair a Sagging Plaster Ceiling
In many older homes you'll find ceilings with large areas of loose and sagging plaster, which has broken free from the supporting lath. Sometimes it makes sense to remove the old plaster and lath right down to the bare studs and then upgrade the insulation and install new wallboard. On the other hand, removing plaster and lath from a ceiling involves a terrible mess with a showering of accumulated dust and dirt, not to mention 6 or 8 inches of loose fill insulation.

Here's a repair that's an alternative. You can stabilize an old plaster ceiling and then laminate a new wallboard surface over it. If there is a ceiling, molding it can be removed and then reinstalled after the resurfacing. The easiest test to determine the condition of old plaster, to see if it's a candidate for laminating, is to push on it. If it moves, the plaster has lost its grip on the lath and should be removed or refastened to the lath.

Remove small areas of loose plaster and don't worry about the void because it will be covered by the new wallboard. Areas larger than 8 to 10 in. in diameter should be filled with a scrap of wallboard. Most plaster is about 3/4-in. thick, including the lath, but the plaster itself is only about 1/2-in. thick, so a piece of 1/2-in. wallboard makes a good patch to level the area. The joints between the plaster and wallboard patch don't require filling, since the new wallboard surface will cover it.

To stabilize large areas of loose plaster, use thin metal disks called plaster washers and drywall screws. These spring steel disks are about an inch in diameter and prevent the head of a standard dry wall screw from pulling through the plaster. This increases the holding power of the screw and allows it to pull the old plaster tight against the lath and hold it there.

Once the plaster is pulled tight against the lath, a new wallboard surface can be laminated right over the old plaster. Interior Sheetrock(R) Gypsum Ceiling Board by USG Company is ideal for this job because it is formulated to resist sagging. While it will not hold up an old plaster ceiling by itself, it is designed to resist sagging in applications that have wide joist spacing (24 in. on center) and heavy insulation loads resting directly on the wallboard.

When using plaster washers, the drywall screws must be long enough to pass through the plaster and lath and penetrate the joist at least one inch. This usually calls for a screw at least 1 3/4-in. to 2 1/2-in. long. Screws should be placed on 8 -in. centers along the ceiling joists for maximum holding power. Additional screws can be placed anywhere the plaster is loose since they pass through the plaster and penetrate the wood lath, which gives them considerable holding power. To assure that the plaster is as tight against the lath as possible, push hard in the area next to the screw as the screw and washer are being drawn up tight against the plaster.

To stabilize a small area, place screws and washers around the perimeter of the loose area. Then place several in the area's center with at least a few of the screws driven into a ceiling joist.

After the loose plaster is stabilized, cover the ceiling with 1/2-in. thick wallboard. First, carefully remove any ceiling molding so it can be reused. Then mark the ceiling joist locations on the walls. The wallboard is installed the same as if it were applied directly to the ceiling joists. The sheets should be applied so their long dimensions run parallel to the longest side of the room. Most home centers stock 12-ft. long sheets of ceiling board, which makes for fewer joints to finish.

The board should be installed with standard dry wall screws placed on 8-in. to 10-in. centers. You don't have to use plaster washers, since the screws only have to support the weight of the wallboard. There are a lot of fasteners to install so a screw gun is very helpful. A self- loading screw gun converter, like The Rocker (TM) , makes driving these screws easy. The screws are fed into the head of the gun from a belt.

If you don't have a screw gun, consider the Simpler(R), an adapter that turns a standard drill into a screw gun. The adapter contains a pare-adjusted clutch mechanism that countersinks a drywall screw into the wallboard to the proper depth.

After the wallboard is installed, it must be finished. The joints are first coated with dry wall compound and then a reinforcing tape is embedded in the compound. When dry, two additional coats of compound are applied, each overlapping the other by several inches. The gaps between the new wallboard and walls can be concealed with molding or taped. If they are taped, fill any large gaps between the new ceiling board and the walls with a hard setting compound like Durabond(R) before finishing with tape and standard compound.

Sanding the joints smooth raises a huge amount of very fine dust, but with the Aqua Sand System, fine dust that can pass through a shop vac's filter is trapped in a simple water filter. The system comes with a pole-mounted sanding head that connects to the water filter with a flexible hose. The filter is hooked up to a standard shop vac. The system sucks in most of the dust as you sand and traps it in water filters so it can settle to the bottom of the container. The sanding head uses an abrasive cloth, which cuts very fast because it is kept clean by the suction.

Written by the editors of HouseNet
Copyright HouseNet, Inc.

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