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Product Description: 

Superior replacement for all gypsum and fiber cement wallboards, can also be used structurally to replace osb or plywood sheathing. Particularly useful for assemblies rated against damage by fire, water, sound, impact and mould. MgO boards also make a superior exterior cladding, MgO Cladding System features no visible fasteners, dry fit with 4 sided shiplap joints and integral 15mm pressure equalized cavity. Easy to cut on site with carbide saws. No toxins or carcinogens, full cycle of life uses via recycling or repurposing.

What are the building code requirements for MgO boards?

A: Currently there are no proscribed code compliance requirements and so these are considered “alternative solution” materials which means the supplier is required to provide certified test results acceptable for designers and code officials. The only formal MgO Fiber Reinforced Cement Board standards are currently in China where these materials have been developed. MOCA, the Magnesium Oxide Cement Association is in the process of developing the MOCA Standard for use in US and Canada. The MOCA Standard committee includes senior code officials and certification agencies from USA, Canada and China. MOCA is a member of ASTM C17 Committee on Fiber Reinforced Cement Boards.

In USA ICC has issued AC386 which references ASTM standards for gypsum and calcium (portland) cement boards.

How do I fill joints between boards?

A: You can apply the board similar to gypsum but we suggest using methods more suitable to MgO’s characteristics maybe a better choice. We are continuously developing our best practices and invite your contributions.

We can bevel or rabbet the edges if you like for a tape and mud joint. Gypsum mud will bond to MgO however we do not recommend the light weight pre-mixed types. Board edge profiling costs $10 per sheet. It is also easier to apply tape and mud joints to a square edge joint as the smooth hard surface is easier to tool and sand.

There are experiences of micro cracking on many installations and, to reduce or eliminate this tendency MgO continues to experiment with new materials and methods including:

You can apply MgO using a caulked joint achieving level 4 and perhaps a level 5 finish. This requires creating a 3 to 6mm wide gap between the panels where the depth of the gap is controlled by the use of polyethylene backer rods such that the width is greater than the joint depth. Non shrinking paintable caulk is gunned in, tooled off and prime coated when cured. After priming a thin coat of Spackle or appropriate mud can remove any joint telegraphing. Outside corners should be glued, sanded or routed smooth and flush and filled with caulk, plaster or grout.

Inside corners should also be glued or butt jointed with a bead of painters caulk.

We are also experimenting with a 2 layer system using an 8 mm or so base layer with little to no joint filling and a 3 mm or thicker pre-finished decorative board glued on with tightly butted or tile like joints.

Outside corners can be butted and sanded smooth or routed for bull nose or mitered, there is no need for corner bead but it will work if you prefer. Adhesive should be applied to the corner board joint MgO bonds well to itself, metal, EPS, wood etc using Chemcraft M1 or moisture cure urethane adhesive. Other tested products can be found in the caulking chart. Joints can also be captured in aluminum or pvc extrusions such as products by or MgO is able to bundle caulking, trim, paints, fasteners with your board order.

What thickness should I use?

A: For ceilings screw applied to light gauge steel or wood you can use 8mm and thicker if you want to countersink the screw head. If you have T-Bar drop in ceiling panels we have decorative boards down to 2mm thick. For walls 10mm and thicker, 12 is common here and some jobs use 15mm for greater fire and impact resistance. If the walls have continuous backing, cement or rigid insulation thinner boards can be considered particularly where weight is a concern. Some trailer homes have used 3mm as fully supported wall covering boards. We are developing a new way to install the boards using 2 layers, 8mm roughly applied over the studs using screws but not filling the joints and gluing a decorative layer of 3 or 6mm over top with either tightly

butted joints or applied like ceramic tiles with defined joints and contrasting or matching grout or caulk joints.

For sound abatement thicker is better, we tested a party wall with one layer each side of a party wall and tested at STC 54 on wood and STC 55 on light gauge steel.

20mm for squash court walls more extreme strength or sound abatement qualities or as a backer for counter tops or furniture.

How do we stop the joints from micro-cracking

A. Micro cracking can occur when the building moves either from force from wind etc or from thermo graphic or hydrometric expansion of the structure, wood shrinks when it dries and metal expands when it gets hot. Also the boards themselves shrink during curing and drying to ambient humidity and they have some movement due to thermal or moisture changes. Most interiors maintain relatively even temperatures and most paints prevent moisture absorption so this issue becomes easier to solve.

It is important that the boards are allowed to acclimatize at the job site before installation. Also following the “tile application” method by leaving a space between boards and applying non-shrinking caulking followed by a primer coat of paint and then a application of spackle or plaster to hide any telegraphing or imperfections. Joints should also be isolated from the structure using a splicing technique with strips of MgO or metal clips keeping the joints between studs.

Q: What about fasteners, Mud, Tape etc. do you use the same as normal drywall?

A: If you really prefer to use tape and mud choose the self adhesive fibreglass tape and a mud or plaster suitable for moist environments. MgO boards can have moisture that will eventually equalize with the building and lightweight pre-mixed mud does not like moisture.

Finely ground hydraulic cement fillers such as RapidSet One Pass will provide industrial strength joints as will many caulking types. Urethanes in particular bond well to MgO. We have a chart of caulks, adhesives and paints we have tested.

For fasteners use corrosion resistant types ideally with a barrier coat of epoxy, ceramic or such. 318 and other suitable grades of SS and phosphoric coatings found on drywall screws has been found by Grabber to work quite well with MgO products.

For ease of installation it is best to select screws with self counter boring heads .

Gun nails can also be used in both wood and LGS framing with the appropriate pins or nails.

MgO bonds well to itself, metal, EPS, wood, laminates etc using Chemcraft M1 or moisture cure urethane adhesive.

We have aluminum and PVC sections available for edge trim details from Stockton and Plastic Components

Q. What is the weight or density of MgO boards

It’s density is around 1 gram per cc or just over 2.2 lbs per sq ft for 12mm (1/2 inch) board, somewhere between gypsum and ordinary Portland cement


Q. What is the best way to cut MgO boards

The best way is to use a thin carbide circular saw, we particularly like the Exakt Cut Saw or other mini worm drive saws. Edges can be routed using carbide tooling although for extensive work diamond tooling would last much longer.

It is possible to score and snap from the smooth side using a disposable razor knife but this will not provide such a clean edge meaning more finishing work. Corners should be glued to prevent micro cracking.

Q. Are there any dangerous ingredients in MgO, VOCs etc

MgO boards are made from natural minerals, Magnesium oxide, Chloride and Sulphate otherwise known as Epsom salts along with wood dust (cellulose) perlite or vermiculite and a glass fiber mesh. There are no VOCs or toxic ingredients.

Q. How does MgO compare in cost with other wall boards.

The cost per sheet for the same thickness MgO is greater than regular gypsum but the same or less than specialty types and generally less than most Portland cement products, neither of which are as versatile. MgO can provide additional cost savings though because the time to finish the boards can be much less, it does not require 3 coats of mud over tape or corner beads. Also MgO is strong enough to support light shelving, pictures etc meaning no need to pre-install backing supports

or use more expensive anchors. MgO can also be disposed of in any waste-stream, no expensive gypsum recycling requirements in those areas like Vancouver which prohibit gypsum going into landfills. Strips of left over MgO can be used to edge your garden or make a shelf or somewhere to put hot pots and plates on.

Q. What sort of finish can I use on MgO

MgO boards are alkaline in nature so the primer needs to be suitable for this. SW Loxon has worked very well for us as does the non-organic paints which react molecularly with the cement forming a UV impervious coating that will last for years. Acrylic stucco topcoats or polymer modified cement base coats can be used as a system or individually directly to the board. We have also had good success with powder-coating but this is quite specialized and requires shipping the boards to Edmonton. More recently has tested and approved their faux stone coatings on MgO. Many other paints could work, we recommend conducting a cross-hatch tape test for best results. Simply brush or spray a small area, let dry and cure, make an X with a sharp razor knife, apply masking tape over the cut pressing firmly and rip it off like a band-aid. If the paint stays on the board you have a good bond. Many paint bonds will increase over the first week or so.

Q: We’re interested in using this board material for interior walls and ceilings. What’s the cost compared to regular gwb please?

Are you referring to material cost, installed cost or lifetime cost? I would suggest that MgO will most likely provide a cheaper lifetime cost and a similar installed cost to gypsum when all the expenses are considered.

1. Quicker installation, using a “tile” approach to joint finishing boards can be painted the same or next day. No corner beads required saving up to 40% on gypsum installation costs.

2. No backing required for shelving, cabinets, grab bars etc

3. Cheaper disposal, no dedicated waste removal needed.

4. Thinner boards can be used, 10mm for walls and 8mm for ceilings reducing MgO costs.

5. Built in seismic resistance, adds stiffness to walls perhaps reducing bracing or interior plywood shear panels

In addition to the other inherent benefits of water, fire, mould and impact resistance.

Q: Some people have told me the Mgo is great for exterior wall board, but not as good for interior drywall because cracks can form in the seems if not properly prepared. I live in an area with a great deal of earthquakes (small in richter scale, but frequent). I did notice your preparation in the videos of putting spacers and calking between the joints, but I’m wondering how well this will hold up long term with frequent small shaking of the structure. Will cracks develop anyway (above what would develop with gypsum)?

Also, I would like to use Mgo as subfloor, I’m wondering if you have an opinion on that.

Vibration will over time cause more issues in rigid structures and assemblies than flexible ones. For this reason we suggest using a good grade of adhesive caulking and securing the panel joints panel to panel and away from the structure. We will be relying on the panels to increase the stiffness of the structure and in extreme cases this assembly would need to be engineered.

Q: Which side of board is fire rated?

A: Boards are assembled smooth side face out for fire testing.

Q: What kind of pallets to bundle the boards?

A: The pallet must be 4 sided with openings of 90mm to allow for extended forks. The pallets must use certified solid wood, hardwood or engineered materials.

For non-local LTL orders all pallets will have solid OSB side and end protective panels.

Q: I was doing some research in a project for a cafeteria. One question that I also had was if it is recommended to use MgO as a subfloor? Or does it only go on walls?

A: MgO can be used as a sub floor and the correct thickness and strength boards can be used as structural sheathing. This will depend on the design of the floor, joist span, spacing and size etc. Dead load and live loading factors.

MgO boards are very suitable for food and health related structures due to their antimicrobial characteristics. Sorel cement has long been used for floors due to its antimicrobial properties and although we have not completed its biological analysis it has been tested to show that it does not allow mould growth as per ASTM D3273. It is most likely that the alkaline salt content provides these benefits. Q: What metrics are commonly used to define MgO boards?

Boards are sold in standard 4×8 4×9 and 4×10 sizes in multiple thickness from 3mm to 20mm. (fractions are too complicated and NA construction is based on the 4×8 module)

Colors are off white to light grey when fly ash is part of the formula. Solid pastel colors of red, green and blue are available by adding ferrous oxides and dark grey to black when adding carbon black. Various formulations can provide greater stiffness or flexibility.

The MOCA Standard separates boards into 5 grades:

“G Grade” – General interior use, and interior wet use. Applications include interior wallboard and tile backer board. All board materials of higher grade shall also meet the G requirements. G grade boards will meet the requirement for non combustible construction in USA but not in Canada (see NC grade)

“E Grade” – Exterior use. Applications include siding and outdoor applications that allow for direct weather exposure with appropriate coatings.

“NC Grade” – Non-combustible for Canada; meets the requirements of CAN/ULC S 114 Or ULC S135

“S Grade” – Structural grade. Applications include SIP panels and wall and floor sheathing; meets impact and racking shear and other structural requirements, and shall be (7/16” (11 mm) minimum thickness to be confirmed).

“FR Grade” – Fire Resistant grade. Eligible for used in MOCA fire resistant wall and floor/ceiling assemblies.

Cladding System


Q: Is there a reason to believe a 15mm board will outlast a 7 or 8mm board in a residential siding application?

A: We use the 15mm board to be able to machine the edge to accept the clip system which removes the need for fastening through the face of the material. It also provides a pressure equalized cavity that is mandatory in some areas and is a superior exterior wall assembly providing increased protection from water, sound and fire. We have no data comparing actual or expected life of MgO and 8mm cladding panels but intuitively a thicker more robust product will outlast a thinner one made of similar materials.

Additional Comments

MgO cements are a more sustainable alternative with full cycle of life uses. They are completely safe being made from minerals required for the health of people and plants, they also have low embedded energy and absorb CO2 from the air. MgO boards are very easy to cut and install, they can be used to make furniture.

(Cre: MOCA)