How to Repair Cracks In Ceilings And Walls

The method of repairing holes and cracks in ceilings and interior walls depends on the extent of the damage and the situation. Smaller cracks can usually be repaired with cellulose filler whereas large cracks in ceilings will need different treatment.

Wide cracks: Wide ceiling cracks or those which re-open after filling indicate excessive ceiling movement. This is a common problem. If you fill these cracks with cellulose filler you will probably be back to square one in on time.

However, it may be possible to achieve a permanent, invisible repair by using a scrim mesh and, if necessary, lining paper.

Crack How to Repair Cracks In Ceilings And Walls

Whether in ceilings or walls, fill all nail holes and smaller crack with cellulose filler such as Polyfilla. Before filling a crack you must first undercut it with a filling knife. Undercutting means deepening the cavity behind the crack to form a V-shape. The V should be widest at its deepest part. Dust all loose material from the crack and fill the cavity with the filler. Allow to set before rubbing flush with the surface using glass paper wrapped around a wood block. A flush finish can also be achieved by drawing the filling knife at right angles across the surface. A 3in. filling knife with a flexible blade is ideal.

For large areas it is more economical to use a plaster such as Sirapite. Dampen the crack beforehand and apply the plaster with a trowel. Sirapite sets quickly so work in a continuous session.

To get flush finish, draw a timber straight-eight across the wet plaster to level it off. Rub a steel float across the area when the plaster is touch dry. This will leave a smooth surface.

If you prefer, fill the bulk of the cavity with plaster. Allow to dry and then ‘top up’ with cellulose filler, as before, using a filling knife.

  • Alternatively fill crack with cellulose filler. Cut out some scrim mesh) available from decorating shops; it is sold in rolls) and stick it over the crack with cellulose paste. The scrim should be slightly longer than the crack.
  • When dry, cover the mesh with filler. Allow this to set and then rub it smooth with the surface.
  • To add more strength to the repair, tear off a piece of lining paper about 1ft wide. Paste the central 6in. with cellulose paste and brush it over the repaired area leaving its ‘day’ border hanging down.
  • When dry, tear off the border to leave a feathered edge on the ceiling. To completely disguise the feathered edge, apply a thin coat of cellulose filler, having first primed the surface with emulsion paint.

Fix a timber straight-edge to an external corner as guide when repairing with thistle plaster.

Loose plaster: Chimney breasts and other areas near fireplace are likely points at which to find whole chunks of loose plaster. These should be lifted out with a board knife, if necessary going right back to the brickwork. Repairs can then be made with Sirpite. When repairing an external corner of a window or doorway, use thistle plaster. This dries rock hard and will stand knocks. And plaster of this type which is left too long before use will start to harden in the container. Do not add fresh water to the mix to activate it or it will set hard immediately. So always use fresh material.

Plastering electric cable channels

Before working in the vicinity of electrical wires, always turn off the current at the mains. The wiring from a wall switch should be covered with protective plastic conduit before plastering with Sirapite. These conduits should always be used when cable is to be fed into walls and covered with plaster. It will be necessary to unscrew the switch cover in order to plaster around the switch box sunk in the wall.

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