Frequently Asked Questions

What is Cem-Rock®?

Cem-Rock® is a family of magnesium oxide cement boards designed to replace plywood, OSB, fiber cement board and interior and exterior gypsum based sheet building products. 

What is Cem-Rock® made of?

Cem-Rock® is made of Magnesium Oxide (MgO). 

What is Magnesium Oxide?

Magnesium Oxide (MgO) is a naturally occurring inorganic mineral that is mined from the earth much like Portland cement. 

Can Cem-Rock® be used externally?

Yes, Cem-Rock® can be used internally or externally. 

Where is Cem-Rock® most commonly used?

Cem-Rock® is most commonly used as exterior sheathing, interior wallboard, subflooring, ceilings, roof decking, fire-resistant wall and subfloor assemblies and tile backerboard. 

What sizes is Cem-Rock® available in?

Cem-Rock® is available in 1200, 2400, 2700 and 3050mm lengths and 1200mm wide sheets. Other sizes are available by special order. 

What thickness is Cem-Rock® available in?

Cem-Rock® and Cem-Rock® eXtreme are available in 6, 10, 12 and 15mm. Cem-Rock® FLOOR is available in 18 and 20mm. Other thicknesses are available by special order. 

How do you install Cem-Rock®?

Cem-Rock® is installed in a similar fashion to gypsum board, plywood, or OSB. 

Can you nail Cem-Rock®?

Cem-Rock® can be nailed or screwed. 

Does Cem-Rock® feed mould?

Cem-Rock® is completely inorganic, does not rot, mold or feed mildew and has a 0/0/0 mold rating. 

Is Cem-Rock® flammable?

No, Cem-Rock® is non-combustible and is Class A1 fire rated, with a 0 flame spread and 0 smoke
developed rating. No other plywood, OSB or gypsum based product can claim this.

Is Cem-Rock® heavy?

No. A sheet of Cem-Rock® weights approx. 30kg and Cem-Rock® eXtreme weights approx. 37kg

Is Cem-Rock® people safe?

Yes. Cem-Rock® is completely non-toxic. It is manufactured from 100% natural inputs and does not off-gas. It is exceptionally good for Asthma or chemically sensitive people.

How do you cut Cem-Rock®?

Cem-Rock® can be scored and snapped like gypsum board, or you can use a circular saw. 

Is Cem-Rock® contractor friendly?

Yes, Cem-Rock® can be cut with a utility knife using score and snap method and also, dust generated when cut with a circular saw is non-carcinogenic. Cem-Rock® does not contain known toxins such as formaldehyde, crystalline silica or fly ash. 

Is Cem-Rock® an approved building material?

Yes, Cem-Rock® carries all required certification. 

What happens when Cem-Rock® gets wet?

Nothing. It dries out and is unaffected by exposure to water. 

Is Cem-Rock® waterproof?

Cem-Rock® is impervious to water, both fresh and salt. Being cementitious, it does however absorb some water. 

Is Cem-Rock® termite proof?

Yes, Cem-Rock® is completely resistant to all wood boring insects. 

Is Cem-Rock® dimensionally stable when wet?

Yes. Cem-Rock® is one of the most dimensionally stable sheet building materials on the market. 

When should Cem-Rock® be used?

Cem-Rock® should be used wherever there is a need for a fireproof, mold proof, insect proof, waterproof and high impact alternative to gypsum board, plywood, OSB or fiber cement board. 

What kind of screws do I need to fasten Cem-Rock®?

Stainless steel, yellow zinc coated or rust proof coated screws for fastening into steel framing or wood framing are recommended. Traditional (black) gypsum screws are not recommended. 

Is pre-drilling necessary?

No, pre-drilling is not necessary. 

Do I need blocking to hang objects when using Cem-Rock®?

When using Cem-Rock® eXtreme, you can hang practically anything with no additional blocking needed.
(See Product Data Sheet for maximum fastener capacities). When using Cem-Rock®, blocking or plasterboard dowels might be required, depending on what is being fixed.