Cleaning Outdoor travertine

Hi Maurizio, I have 2 questions: 1) I recently instaled an outdoor patio with a travertine (I believe honed but not filled & not polished). Anyhow, as per your suggestions I did not put a sealer on it. It seems to be building up some greenish areas in several spots that could be mold - not sure. I don't know what I can do to clean it but my minimal efforts of trying to brush it or scrape it off did not work. My landscaper seems to think it needs to be sealed (he's giving me one of those "see, I told you so"). The area is about 3,000 square feet and the job was wet-lay with grout. 2) There are still many areas where the tiles are covered with a film of grout from the install - what can I use to remove the film? Someone told me a little acid and water mixed - should I do that?

 

Dear Michael:

Wet install with grout is not the right type of install for outdoors. It should have been installed on dry-pack and no grout (just sand or sand mixed with cement 8 : 2).

When installed outdoors the grout will begin to give and crack and water will find its ways under the tiles, and, hence, the development of mold. Of course, if you had sealed your stone the mold would have appeared earlier and would be much more difficult to remove, because is coming from within – not from without; whereas the cleaning can only be made from without. (Makes sense, don't it?... J )

At any rate, no biggie about the cleaning: you can power-wash it with a solution of water (1 : 1) and alkaline cleaner designed to remove mildew stains rated for natural stone, like MB-9. Keep the pressure at no more than 600 PSI and the nozzle at no less than 2' from the surface. Do not expect to see immediate results as you clean. You have to let the chemical do its magic.

Once you cleaned the mold off, you will take on the grout film issue. Forget about the acid cleaner thing! Acid and stone should never appear in the same sentence, especially when dealing with a calcareous rock like travertine.

You must scrape the worst off with a 3” or 4” razor blade and then finish the job with a professional floor machine setup with a scrubbing brush and an alkaline heavy-duty cleaner with chelates in its formula, rated for natural stone like MB-3.

Keep in mind that, because of the faulty installation the mildew problem will never stop.

May I ask you now to please read and e-sign our Statement of Purpose at: http://www.marblecleaning.org/purpose.htm?

Ciao and good luck,

Mauri zio Bertoli

 

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