Removing Hardened Grout from a Slate Walkway

WHMS Home talk question about removing hardened grout

Removing Hardened Grout from a Slate Walkway

This question was recently submitted by a blog subscriber:

Removing Hardened Grout questions

I forgot to wipe up a long line of grout when re-routing my slate walkway.  It is now extremely hard.  Is there any good way of removing hardened grout from the slate walkway?

Removing Hardened Grout answer

Removing hardened grout is likely going to be a rather labor intensive chore. The first step is to scrape or chip up the thicker areas of grout. If you have access to an oscillating tool, with a carbide scraper attachment, it could make this part a lot easier. Just be careful not to scuff up the slate too much. After scraping or chipping away as much of the grout as possible, using muriatic acid, available at many home improvement stores, to dissolve the remaining grout residue may be your best option. Read the label on the grout bag or container as well as the label on the muriatic acid to determine if it is appropriate for your particular application.

 I cannot stress enough, how important it is, that you should read and follow all warnings and instructions pertaining to the use, storage and disposal of muriatic acid, which can be extremely dangerous. Only after thoroughly reviewing the warnings and instructions and procuring the recommended equipment, clothing and protective gear should you proceed with this step.

Test a small area of the slate first to make sure the acid will not damage it. It may take several applications to completely remove the hardened grout. Be patient and let the acid work each time before rinsing and reapplying more acid. Using the corner at the end of a two or three foot piece of 2×4 lumber to scrub over the hardened grout as the acid is working may speed up the removal process.

Don’t forget to keep children, and pets completely clear of the entire area while using the muriatic acid.  Follow the instructions on how to neutralize all areas affected by the acid including any runoff areas.

I hope I have been of some help in this matter.

Best regards,


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About Tony Wood

Tony is a life time resident of North Carolina with over 40 years experience in multiple facets of the industrial, commercial and residential construction industry. For the past 33 years he has owned and operated Wood's Home Maintenance Service, providing services primarily in Johnston, Wake and Sampson Counties of North Carolina. ______________ ______________________________________________________ The information contained in this Blog is opinion derived, from hands on experience of over 40 years in the construction industry and by extensive research by the author. All postulations are referenced to the geographic location in which this experience was gained.
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