You love the cool, elegant look of your stone or marble patio, but has white- or light- colored spotting and streaking begun to mar its beautiful surfaces?
What is that stuff? (And how can you get rid of it?)
Once you rule out bird droppings, it’s a good bet that you’re seeing calcium deposits erupting through hairline cracks on grout joints or other spaces.
These deposits may be small and patchy, or extend across large surface areas. They tend to build up just below the surface, and be dense and hard to wipe away. Unfortunately, the longer they’re there, often the harder they are to remove!
What causes calcium deposits?
They are the residue of dissolved calcium – a mineral that occurs naturally in stone or marble.
You see, stone or marble may look very solid, but it’s actually porous, with millions of tiny “pores” or “capillaries” where water can be absorbed, and minerals can escape. Typically the build-up occurs in and around joints and cracks.
That’s right: solid structures – even those of sealed stone and mortar – are permeable. They’re NOT water resistant!
As the water evaporates, the dissolved calcium carbonate is left behind, creating a calcium deposit.
In addition to deposits on the surface of your stone, many times the stains are more visible when the surface is mixed with cement and/or thin-set or adhesives.
Why is the residue worse on walls and tiled areas?
That’s because it also builds up when it dries on the surface of the joints.
All new structures settle after the installation of tiles or natural stone materials. When that happens solid tiles shift, creating almost invisible hairline cracks in the joints.
You’ll see this – and the resulting calcium deposit buildup – often in outdoor structures like terraces and high raised patios that are set in a solid cement base (They also happen indoors, in bathrooms and showers).
If the adhesive was not properly applied during installation – maybe the wrong thin-set product was selected, or it was applied unevenly – the cracks could be even more open or damaged.
Water infiltrates the cracks, causing the concrete and adhesive to always be wet. You will usually see the calcium deposit build up on the cracked grout joints and on the side wall where the trapped water finds a way to drain. Over time it builds up, as you can see in the sample photo.
To permanently correct this issue, the grout has to be removed, and the joints reinforced, in order for the new grout to stay in place and stop the water from seeping under the tiles. This is definitely a professional job!
Now, how to get the white stains off your patio!
You definitely want to avoid pressure washing! Assuming you don’t have a serious grout issue (if you have any doubt, call a professional marble or stone restoration team like TersoMR), you can eliminate the build up from calcium deposits and protect it from future damage by following a few key steps:
If possible, eliminate whatever’s creating the leaks and drips – clogged drains, plumbing leaks, etc.
Scrape any accumulated crystals away (being careful not to scratch or gouge the marble or grout surfaces):
Saturate the surface with an appropriate cleanser – we recommend: ½ c distilled water, ½ c hydrogen peroxide (3% solution), and 3 drops green Palmolive® dish soap. (Let it sit on the surface for several minutes to help with stubborn stains.)
Allow time for the mixture to soften the buildup (test periodically to confirm). Clean using a brush.
For tile or stone, rinse thoroughly to remove any cleaning residue. (For stone, especially if you used an acid-type cleanser, follow up with a pH-neutral cleaner prior to the final rinse, or the finish of the stone can be honed and changed. It’s recommended to call a restoration specialist.)
Seal the surface with the appropriate sealant for your type of stone and outdoor surface.
This step is tricky because there are so many stones and combinations, and the wrong match up can lead to discoloration or other problems. Consult with a professional (yes, TersoMR(R) can help if you’re in the NY-NJ-CT area), to get the right product, applied correctly, for the longest life possible.
While no solution is forever – these 3 simple steps will address the unsightly stains and help extend the life of your beautiful marble or stone surfaces. To permanently stop it from building up again, you have to have it properly repaired and reinforced to stop the water infiltration. If you’d like help getting the white stains off your patio and properly repair the structure, give us a call at 201-385-3484.