Does GIB board or old plasterboard contain asbestos?

What is GIB board made of?

Gypsum plaster sandwiched between sheets of paper. Winstone Wallboards' safety data sheet for its plasterboard range lists gypsum at more than 70% and paper (cellulose fibre) at under 15%, with additives making up the rest. Asbestos is not an ingredient. GIB is a brand name, but in New Zealand most people use it for any plasterboard, the way "Pinex" gets used for any soft board.

The product has a long local history. Winstone Wallboards' own history says New Zealand-made plaster wallboard started in 1927. Until 1931 it was a sawdust-and-plaster core sold as Winstone Board; that year pumice replaced the sawdust and the name changed to Gibraltar Board. Plants followed in Lower Hutt in 1946, Christchurch in 1961 and Penrose in 1971.

So where is the asbestos near plasterboard walls and ceilings?

Usually in the material next to the plasterboard, or on top of it. WorkSafe's list of where asbestos is commonly found in New Zealand homes includes several things that sit right alongside plasterboard linings:

• Textured ceilings — the sprayed or troweled finishes over a ceiling board. See asbestos in ceilings.
• Ceiling tiles, often mistaken for softboard (see Pinex board) or plasterboard.
• Wet-area lining substrate — the sheet behind bathroom and laundry tiles, which in older houses was often fibre cement rather than plasterboard.
• Hot water cupboard linings, bath panels and partition walls.
• Interior window panels and fireplace surrounds.

Jointing and stopping compound is the other question people ask. We could not find a New Zealand source that says older local stopping compounds contained asbestos, and we won't claim either way. Overseas, some older joint compounds did. If you are about to sand back old stopped joints in a pre-2000 house, testing the compound costs less than guessing.

How do you tell plasterboard from fibre cement?

Look at an edge you can see without breaking anything: behind a removed switch plate, around the ceiling manhole, or where an old fitting came out. Plasterboard has paper on both faces and a soft, white-to-grey core that crumbles and can be scratched with a fingernail. Fibre cement has no paper, is grey and dense all the way through, and feels much harder; knocked with a knuckle it sounds hard rather than hollow.

If it turns out to be fibre cement, that's when the age question matters. See fibre cement or asbestos? for the dates.

What to test before you renovate

1. Bathroom or laundry: the wall sheet behind the tiles, and any vinyl on the floor.
2. Ceilings with a texture or a patterned tile, before you scrape, sand or remove them.
3. Old stopped joints, before you sand them back for a new finish.
4. Hot water cupboard linings, before the cylinder is replaced.

One $249 test covers a surveyor visit and one sample, with extra samples at $85 at the same visit. If you are gutting whole rooms, a refurbishment survey covers everything the work will touch. Plain plasterboard that tests clear is ordinary building waste; anything mixed with asbestos becomes asbestos waste, which has its own disposal rules.