3 steps (and extra tips) for patching fibre cement

Modern fibre cement panels are safe and easy to work with, but any jobs involving old-style asbestos cement should be left to the experts. Here are a few tips for working with fibre cement panels.

  • Until the early 1980s the building material known as 'fibro', 'fibrolite' or 'asbestos cement' contained asbestos fibres. When concerns were raised about asbestos-related illnesses, the use of asbestos was discontinued. Do not cut, saw, sand or otherwise disturb fibro if there is a chance it may contain asbestos. These days the product contains synthetic or cellulose fibres rather than asbestos and is known as 'fibre cement'. Fibre cement poses no health risks. Nonetheless, you should wear a dust mask and ensure that your work area is well-ventilate to avoid inhaling any dust.
  • If you suspect an old roof or outbuilding might contain asbestos, do your research before attempting to dismantle and dispose of it. There are laws governing its safe disposal. If you can remove whole panels, it may be safe to do the job if you wear protective clothing and a dust mask. But it is safer to arrange for a professional to remove asbestos.
  • Using the "score and snap" method is the simplest way to cut fibre cement. This metho involves repeatedly scoring the surface of the panel to a depth of about one-third its total thickness using a stout blade and a straightedge. Then press down on the straightedge and pull the outer edge of the panel upwards to snap it along the scored line. Fibre cement manufacturers make a special tungsten-tipped tool for this job.
  • Small holes in asbestos or fibre cement can be patched using an exterior-grade filler, fibreglass filler or car body filler. Just remember to not cut into the hole or attempt to make it bigger, either using your fingers or any type of tool—power or otherwise. Those commercial fillers are unlikely to shrink and, provided the original panels are sound and there are no crumbling edges to the hole, the patch should stick well. Don't bother filling the hole if it lies on a crack as the movement in the panel would most likely dislodge your patch. In that situation, the better solution would be to remove the panel entirely and replace it with a new one.

 

3 steps (and extra tips) for patching fibre cement

What you will need

  • Ruler and pencil
  • Jigsaw or narrow-bladed saw
  • Scrap fibre cement
  • Drill and drill bits
  • String
  • Adhesive
  • Filler and filling knife
  • Sandpaper
  • Paint

1. Tidy up the damage

  • To start, remove a neat piece of the fibre cement.
  • Mark cutting lines around the damaged area with your pencil and ruler, keeping the hole straight and square.
  • Use your jigsaw or narrow-bladed saw to cut out the square section you've just marked off.

2. Back up the hole

  • Cut a backing panel to measure slightly larger than the hole you're patching.
  • Drill two holes through this panel's centre and thread a loop of string through them.
  • Apply adhesive to the edges of your backing, ease it through the hole, then pull it up tight against the back of the wall.

3. Set the patch

  • Allow the adhesive holding your backing panel in place to set, then cut a patch to fit the hole exactly.
  • Apply adhesive to the back of your patch and press it gently into place.
  • Fill any gaps around the edges of your patch, sand them smooth and then repaint the patch to match the rest of the panel.

Keep these tips in mind and follow these three steps, for an easier time working with fibre cement panels.

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