A blog about the restoration, remodel and renovation of a 1929 Chicago-style brick bungalow

Cleaning the Limestone

Last winter we went to one of the Historic Chicago Bungalow Association lectures, which are held in various Chicago public libraries around the city. This particular one had a panel of experts in various home building fields — plumbing, HVAC, architecture, masonry, etc. — to answer questions from the audience. A couple people hogged a good part of the time, which was annoying, and one older woman asked the brick/masonry guy a question, who had a British accent and was very knowledgeable. He patiently answered her question and this woman kept saying, “What? Whaaaatttt?? I can’t understand him!! What is he saying???” OMG she was so rude; ugly American on her home turf. He was not hard to understand.

Anyway, I finally was called on and asked him what we could use to clean the limestone, which caps the brick walls next to the front steps and had become stained with what looks like dirt and grime, presumably from gutter overflow above it. He said to use a biocide, which is a cleaning solution for organic substances.


The limestone has always been a little stained as you can see from the early 2007 photo above, just before we owned the house. Over the years it has gotten much worse and looks like crap as you see below. I bought those urns a number of years ago at a flea market and I have wanted to take those down for a while now. I tried doing mums and other annuals a couple of times, but I’m just not diligent enough to water them. Plus, they were just too tall for those end caps.

Before cleaning

Before cleaning

Months ago I went to a concrete/masonry supplier, Henry Frerk Sons, on Belmont right off the Kennedy Expressway. I talked to a very helpful guy about our issue, and he gave me a couple of samples to try: one called MasonRE by Cathedral Stone Products and the other is Enviro Klean ReVive by Prosoco. He told me that it may take a couple weeks before we see the final results, as it keeps working after application.

On Sunday, Pete and I finally decided to try it out. We moved the urns to the gravel patio area, filled a little bucket with the Enviro Klean and diluted it with water. It could be used full strength for heavy soiling, 1:5 for medium or 1:10 for light soiling. We thought ours was medium?

Cleaning, after first application

Cleaning, after first application

As we scrubbed it on (with a soft bristled brush) it started to turn the stain green and it looked even worse. You’re supposed to let it sit for a few minutes and then rinse it off. It still looked pretty bad when we rinsed it, but now that it has dried it’s starting to look a bit better as you can see here.

I don’t know if the stain is supposed to magically disappear over the next couple of weeks or if we’ll have to scrub more. I’ll be very happy if we can get it clean enough to match the circle left behind by the urn.

If it works well, I’ll clean other spots which are only slightly soiled, like under the windows and at the base of the steps.

I’ll take more photos over the next couple weeks to compare. Fingers crossed!


  1. Jennifer on September 6, 2016 at 11:58 am

    A stone carver friend of mine, who used to work for Cathedral Stone, alway recommended dilute bleach for limestone. Maybe a bit harsh but could be worth trying in a less obvious spot if the biocide alone doesn’t work.

    • denise on September 6, 2016 at 3:35 pm

      Thanks for the tip Jennifer! Pete was wondering about bleach, but I’m hoping this will do the trick.

  2. Jan Hunyady on September 6, 2016 at 11:54 pm

    I don’t know if this works on limestone but I sprayed Round Up on my slate sidewalk and then forgot about it. A couple of weeks later I noticed that the black stuff was gone. The sidewalk needs spraying again because when it gets wet that black stuff is slimey.

  3. Jordana on September 20, 2016 at 7:13 pm

    Please let me know how it turns out. I would think that lots of scrubbing would help. It’s great that there are community events where people can share advice about cleaning limestone, ones where you can actually interact with people in person. (Internet DIY communities are great, but going to a lecture about DIY really sounds like fun.)

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