12-31-2011 02:20 PM
12-31-2011 03:31 PM - edited 12-31-2011 11:58 PM
Good afternoon avghomeowner!
Sorry to hear about your troubles with getting the mastic off your floor
Mastics and thin-set mortars tend to dry very hard, and due to their chemical make-up, you are literally chipping away at a form of cement. With that said, the razor blades can help, but using Krud Kutter in this instance is not recommended. Krud Kutter is an amazing cleaner, but that's exactly what it is, not something that can effectively take up thick, dried amounts of mastic. So, what I would recommend is to still use a large razor blade to scrape and you can use a scrubbing pad (steel wool would be better in this instance) and then obtain a product that can save you time and more importantly energy. That item would be an acidic treatment, be it sulfamic acid or the product shown below, which are both safe-to-use indoors and work great to get your floor mastic-free.
The sulfamic acid is a concentrated form of mortar removal, that you can use if you really need to get rid of stubborn spots. However, if you the mastic is level and only a skim-layer, you can use the grout haze remover to safely take off most if not all areas of the mastic that is still there. If you are going to retile the floor, the new mortar/mastic you choose will cover the subfloor as long as the surface is level and clean, even if there are trace amounts of mastic still down on the floor.
If you have been using a small razor blade knife, consider using a larger floor stripper to get the mastic up better. While I'm aware you aren't going to have a lot of elbow room in a half bath, you can use a 8 inch razor floor scraper, shown in the image below...
From what you are stating, you want the entire floor free of mastic and (i'm assuming) want the subfloor to be used without any flooring on top of it. If your existing subfloor is concrete, you can use a grinder with an attachment suitable for concrete/cement to really get a lot of mastic off, but again not all of it needs to be up as long as its level IF you choose to place a new flooring on top of it. Do not use a grinder if tiles are still down, however, as they can damage and ruin the tiles that are down. At this step in the project, you are at a crossroads to choose the next choice that works for you, highlighted below...
Floor is tile and you just want to renew it
I would recommend to get as much off as possible, in between all grout joints and surfaces, and let set after cleaning the area or dust and debris. Afterwards, you can use a sealer rated for tile to protect the floor from water penetration issues in the future. Sealing a tile floor should be done every year. To test the floor to see if it does need sealer, you can place a few drops of water on the tile, if it beads up the sealant is still good. If the beads soak in, the sealer can be reapplied.
Concrete subfloor and you aren't putting flooring on top of it
When all of the mastic is off, the subfloor is concrete, and you decide to seal the floor with a clear coat, you can use a low-lustre or wet-look sealer for concrete to protect and make cleaning easier for your floors. If the subfloor looks still unsightly and you would like to paint it, refer to the step below.
Wood subfloor and you aren't putting flooring on top of it
Get as much mastic off as possible, and next prime the wood subfloors with a moisture barrier such as an oil-based primer. Next, you can use a paint rated for porch and floors to give the subfloor a nice new look again.
If you do decide to put down new flooring
Just remember to get the subfloor as clean and level as you can. If you do decide to retile with ceramic or stone tiles, consider waterproofing the subfloor to make sure no issues come up in the tiles eventually. With any new floors, be sure to prepare the surface that it is going on as best as possible.
With that said, I hope this post has been informative and useful for you.
Please update us with your progress and please let us know if you have any further questions,
I am a 12 year Home Depot Store Associate, trained and authorized to help people on the Internet.