If your home, apartment or condo complex was built from the 1940s – 1970s, there is a good chance that your flooring and/or decking was built with Magnesite.


What is Magnesite?

Magnesite is a naturally occurring mineral MgCO3 or Magnesite Carbonate. Similar to dolomite, magnesite is mixed with inert fillers to create a sturdy, concrete-like surface for interior and exterior floors, stairs, and decks. Magnesite was highly popular because if its sleek, classic look, coupled with its strength and durability.

repair walkwaysWhile magnesite decks, walkways and stairways are durable and built to last many years, they have have some issues. Magnesite is not completely waterproof, and is prone to cracking. What many homeowners fail to realize is that even small cracks on a deck’s surface can allow moisture to penetrate to the supporting wood frame. If not repaired soon enough, wood rot and mold can spread to the building’s structural beams, that the decks and stairs tie into.



In the example pictured here, we can see the cracking on the surface of the walkways. Just by looking underneath the decks, we can see that wood rot, leaking and water staining. These decks have gone so far without fixing minor repairs, that we are now looking at a complete tear out, as the structural supports need to be replaced.

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Another issue with magnesite is that its high level of chloride can accelerate the corrosion of adjoining metal, as seen in these stair rails. The railings have been rusting for so long, that we can even see rust stains permeating through the surrounding magnesite. The metal corrosion issue can also be the result of faulty construction or lack of maintenance.



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By current industry standards, magnesite is considered an outdated product, since many new and better waterproofing systems have been developed. However, magnesite decks, walkways, stairs and floors can stay durable and beautiful with regular deck inspections and waterproofing maintenance.

Please Contact Us at WICR Waterproofing & Decking for a free deck inspection. We’re happy to help!