Listener Submitted Question:
Listener: Kameron

Ok I have a 90 year old house which I've completely gutted top to bottom and now... we are hitting the bottom (ie foundation) A t his point I'm just submitting this small portion for the ground floor as it will relate to the foundation wall in the end. Long story short, I need to pour conrete on top of concrete and I'm looking for the best way to make it level, strong and solid. I don't want it to crumble off like the old mortar job so I'm looking for the best chemical or concrete/mortar to do the job. HELP!


Bryan’s Answer:

Whenever you’re pouring concrete on top of concrete, it’s not easy to guarantee that you won’t run into problems with cracking or flaking in the future. Wet concrete will bind together, but pouring new concrete on top of the old will result in what’s called a ‘cold joint’, and it won’t bind together as well as if it were all one solid slab.
 
You’ll want to first clean the existing floor by scrubbing all of the dirt and debris off, and if it’s fairly smooth you will want to consider etching it with muriatic acid before attempting to pour on top of it. If you’re looking to level a portion of the existing floor, you can go with a self leveling cement as trying to trowel a floor smooth is an art that can take some time to perfect. Keep in mind that you don’t want your entire basement to be perfectly level – you want a bit of a slope running towards the floor drains.
 
You’ll need to pick up some cleaning and scrubbing supplies as well as a concrete acid wash or primer, expansion tape to tape the perimeter of the room along the bottom plates to create a dam for the new concrete, a few bags of self leveling cement, buckets and a mixing paddle and drill. It’s also a good idea to get some concrete sealer to apply to the floor after it’s cured to give yourself a nice smooth surface that will be easy to clean in the future.
 
Good Luck!