The Challenge of Buying MgO Products

Magnesium oxide boards have flooded the market over the past decade, with products arriving from a wide range of manufacturers — particularly from China, which dominates global MgO board production. While many products perform well, quality can vary significantly between manufacturers and even between production batches. Knowing what to look for before you buy can save considerable time, cost, and frustration on a project.

Step 1: Define Your Performance Requirements

Before contacting any supplier, clearly establish what the board needs to do:

  • Fire rating required: Is a specific Class A1 or Class A2 non-combustibility classification needed for your building code?
  • Moisture exposure: Will boards be in wet rooms, exterior applications, or below grade?
  • Structural role: Are boards purely lining, or do they contribute to racking strength?
  • Thickness needed: Typical ranges are 6mm, 9mm, 12mm, 15mm, and 18mm.
  • Surface finish: Smooth face for direct decoration, or textured/sanded for tile or render bases?

Having these requirements defined upfront lets you quickly filter out products that don't meet your specification, rather than discovering problems after purchase.

Step 2: Understand What's in the Board

MgO boards are not pure magnesium oxide — they are a composite. A typical MgO board contains:

  • Magnesium oxide (binder)
  • Magnesium chloride or magnesium sulphate (hardener)
  • Perlite, sawdust, or fly ash (filler/weight reducer)
  • Fibreglass mesh layers (tensile reinforcement)
  • Various additives for workability and surface quality

The magnesium chloride issue: Boards made with magnesium chloride (sorel cement boards) can absorb moisture from humid air and release chlorides — a phenomenon known as "sweating" or "chloride weeping." This can corrode metal fixings and cause surface staining. Boards using magnesium sulphate as the hardener or those using alternative binder chemistry avoid this problem. Always ask your supplier which hardener system is used.

Step 3: Request Key Documentation

A reputable MgO board supplier should be able to provide:

  1. Third-party fire test reports — ideally from accredited laboratories such as UKAS-accredited labs in the UK, or equivalent bodies in your country
  2. Technical Data Sheet (TDS) — covering density, flexural strength, moisture content, and surface characteristics
  3. Certificate of Analysis (CoA) — confirming MgO content and key material properties
  4. Compliance declarations — CE marking, UKCA marking, or relevant regional certification
  5. Warranty documentation — what the manufacturer covers and for how long

Step 4: Evaluate the Supplier

The supplier relationship matters as much as the product specification. Consider:

  • Track record: How long have they been supplying MgO boards? Do they have documented project references?
  • Stock and lead times: Can they supply consistently in the volumes and timeframes your project requires?
  • Technical support: Do they offer installation guidance and can they answer technical questions?
  • Returns and dispute process: What happens if boards arrive damaged or don't meet spec?

Step 5: Conduct Your Own Basic Quality Checks

When boards arrive on site, carry out simple checks before installation begins:

  • Visual inspection: Boards should be flat, consistent in colour, and free from surface cracks, delamination, or moisture damage
  • Weight check: Weigh a sample board against the specified density — significant underweight can indicate hollow fillers or reduced MgO content
  • Edge quality: Edges should be clean and consistent — ragged edges suggest poor manufacturing control
  • Snap test: A piece broken across the fibreglass mesh should show clear fibreglass layers — if boards crumble without any fibre pull, tensile reinforcement may be inadequate

Red Flags to Watch For

  • No third-party fire test data available
  • Price significantly below market — usually signals reduced MgO content or poor-quality fillers
  • Supplier unable to confirm the hardener chemistry used
  • Boards with a damp or musty smell on arrival (moisture absorption in transit)
  • Inconsistent board dimensions within a single batch

Summary: Buying MgO Boards the Right Way

Taking time to specify correctly, request proper documentation, and vet your supplier before ordering will help you avoid the quality issues that have given some MgO boards a poor reputation. The right product, properly sourced and installed, offers outstanding long-term performance.