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you can apply tiles, wallpaper, and paint directly onto MgO sulfate boards, but because the board is mineral-based and alkaline, there are specific “best practices” you must follow to ensure the finish doesn’t peel or crack.

1. Painting MgO Sulfate Board

Painting is the most common finish. The key is managing the board’s alkalinity and dust.

• Primer is Mandatory: You must use a high-quality, alkali-resistant primer (often labeled for concrete, masonry, or “hot” plaster). Standard drywall primer may fail because the board’s high pH can break down the paint bond.
• Surface Prep: Wipe the board with a damp cloth to remove all fine white dust. If the surface is too smooth, a light sanding with fine-grit sandpaper helps the primer “bite.”
• Paint Type: Most water-based acrylic or latex paints work perfectly once the primer is cured.

2. Tiling on MgO Sulfate Board

MgO sulfate board is an excellent tile backer because it doesn’t swell or rot.

• Side Selection: Many MgO boards have a smooth side and a textured/rough side. For tiling, install the board with the rough side facing out to provide a better mechanical bond for the adhesive.
• Adhesive: Use a polymer-modified thin-set mortar. Do not use organic mastics in wet areas (like showers).
• Waterproofing: In “wet zones” (shower walls), you should still apply a liquid waterproofing membrane (like RedGard) over the MgO board before tiling, just as you would with cement board.

3. Applying Wallpaper

Wallpaper works well, but requires a “sealed” surface to allow for future removal.

• Sealing: You must seal the board with an acrylic-based wallcovering primer/sealer first. Without this, the alkaline nature of the board can dry out the wallpaper paste too quickly or cause it to lose its stickiness.
• Paste: Use a standard heavy-duty clear wallpaper adhesive.

Summary Checklist for Finishing

Important Note on Joints: Unlike drywall, MgO boards expand and contract slightly with temperature. Always leave a small 1/8″ (3mm) gap between boards and fill it with a flexible filler or reinforced joint compound to prevent the paint or wallpaper from cracking at the seams.