Home Improvement--General/slates grout overdue



I forgot to wipe out a very long line of grout when re grouting in the backyard.  It got really hard...

Is there any good way of removing this hard grout from the slates?

Thank you very much,   Gabe

Hi Gabriel,

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 on the end of a two or three foot piece of 2x4 lumber to scrub over the 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,

Home Improvement--General

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Tony Wood


I can answer a wide range of home improvement and maintenance questions. My expertise is in carpentry, painting, framing, siding/boxing, doors, windows, decks and screen and glass enclosures. Wood's Home Maintenance Service


I am a life time resident of North Carolina with over 30 years experience in multiple facets of the industrial, commercial and residential construction industry. For the past 23 years I have owned and operated Wood's Home Maintenance Service , providing services primarily in Johnston, Wake and Sampson Counties of North Carolina.


Several Home improvement articles published on Angie's List and other online forums.

High School graduate ~ proficient in CAD (computer aided design), Open Office program suite.

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