Expert: Perry Vellenga - 7/25/2006

Question
Since I have a somewhat uneven bathroom floor, I bought a bag of self leveling compound. I followed the directions as to how much water to add. I remember the directions indicated that I would want a "pea soup" consistency.

AFter the application dried, I noticed a white dust on the surface. I also noticed that after 24 hours the new surface was not as hard as I expected. I could makes marks in it with my fingernail, same effort as when scratching a piece of chalk.  I called the company listed on the bag of compound. The advisor stated that I had added too much water to the mix and that the white dust on the surface was the result of the bonding chemicals rising to the top rather than staying mixed.

As a suggestion, the advisor said I could scrape it all off (!?!) Then he suggested that instead I should apply another coat of the self-leveling primer that I used as an earlier prep. and then use flex bond with setting the tiles.

I hope this is good advice. I am thinking adding too much water may be a common problem. I just hope my tiles will not come lose in the future.  I really appreciate your advice. Thank you

Answer
Thank you for your question Maureen,

  As with most things Maureen, having a proper understanding of how things work before beginning the process is helpful in reaching a successful conclusion. "Self-Leveling" Compounds are a bit of a misnoamer as what often times really happens in this process is a "self-flattener" result. So areas...in particular old homes with wooden floor trusses beneath a wooded sub-floor...where it wouldn't be practicle to truely "level" a floor because over the years one side of the room has settled maybe 2" from one side to another or a hallway that has tipped that you can actually feel as you walk down it. So if you were to actually level this condition you could "raise" a floor "finish" that would also create a 2" trip hazard right at your door opening...follow me? So this material is an aid to deal with deficient sub-floor conditions in a effort to making a tough install go easier but not perfect. I like the visual "food" descriptions often given to describe how the mix should "look" in order to use it. If I were to use their vernacular your mix should have looked more like a thin milk shake and not soup. These compounds Maureen are hydraulic in nature which means that the body of the material is heavier than normal once mixed properly and will spread out on its own raising a low area or filling in where it needs to be filled in. It sometimes may need a little coaxing to run out to the desired space but not much. You don't mention whether this was poured over a slab or a wooden sub-floor. You could do another pour over the top of the old one but you have to be aware that you are "adding" more height to the existing condition...follow me? This will affect doorways and apliances like a dishwasher under a counter that sort of thing. So if you haven't installed the tile yet try another batch of the material mixed stiffer to the consistancy I suggested earlier. And that will help harden the original layer and isolate the tile from it as well, ok? I hope this helps you Maureen move forward, feel free to return anytime....

Perry V.