New mortar doesn't bond to old concrete - read this!

New mortar doesn't bond to old concrete - read this!

Concrete slab was the foundation, original tile installation had mortar applied directly to concrete slab. Removal of tile with a pry-bar easily separated the tile/mortar from the concrete slab. Why was is it so easy?

Concrete, mortar or similar materials are not designed to stick or bond to old surfaces. You will not get any satisfactory results if you simply add new mortar to old. It just doesn't work. Using a modified thinset mortar would be the preferred method for this type of installation.

Same thing for grout. New grout will not stick to old grout. You need to use a bonding agent such as Grout Bond for repairs and re-grouting projects. Even then, you really need to make sure the area is completely free of dirt, grease and grime. 

Make sure you take the needed time to prepare for any repairs grout/mortar related. As with most projects, the more time spent in preparation, the more professional your results will be!

Previous post Next Post


  • Terence Robinson - September 04, 2019

    I am repairing a landing at the top of stairs with concrete do I have to lay a waterproof under lay under the concrete

  • Fred Parker - August 06, 2019

    I have an old chimney and hearth in a house built in 1941. I have a tile comming through the bottom or floor of hearth. The hearth or floor had several large cracks. I chipped out the old cracks by removing about an inch of the hearth [floor]. What do I need to use to fill and level the hearth[floor]?

  • Alison Hamilton - January 22, 2017

    Hello my name is Alison Hamilton and I just wanted to send you a quick message here instead of calling you. I discovered your New mortar doesn’t bond to old concrete – read this! | TheGroutStore website and noticed you could have a lot more visitors. I have found that the key to running a popular website is making sure the visitors you are getting are interested in your subject matter. There is a company that you can get keyword targeted visitors from and they let you try the service for free for 7 days. I managed to get over 300 targeted visitors to day to my site.
    Alison Hamilton

Leave a comment