Concrete Product – Doesn't Fit In

I installed self leveling concrete in the master bathroom (about 7 by 8 feet). It did not come out good with the primary issue being that it was not completely level. I had calculated how much of the SLC I needed to do the job but some of it seeped through holes in the concrete. I did my best to fill all of the holes but SLC will find it’s way through the smallest of holes. I had a situation where the SLC was draining through holes as it was drying, leaving some sloping in places.

For the master bedroom I decided to contract the install of self leveling concrete to third party. I choose to have Koch Mechanical install Gypcrete. Gypcrete is not the same as the concrete product I bought at Lowes for bathroom, some would argue it’s not a concrete product at all. There are a number of things I should have understood about Gypcrete before I had it installed, thankfully non of it’s issues would prevent me from using it.

Gypcrete is a brand name belonging to the Maxxon company. Although proprietary, the name of the product should indicated that it contains a large amount of gypsum. According to the Manufacturer it is superior at dissipating heat vs normal concrete. Thus, the company that installed it for me specializes is installing gypcrete over radiant floor heating.

Gypcrete is installed in a liquid form and can be walked on in few hours, and is completely dries in 30 days. It doesn’t cure like concrete, it just dries. The finished product is like having a floor made of solid chalk. It can be scraped and dented with sharp objects. I don’t know for sure, but it seems like it could be busted up and re-liquified.

Gypecrete absorbs water easily and might react with concrete products. It also isn’t a structural product and can crack easily. For these reason the manufacturer recommends some sort of anti-fracture membrane or barrier between the Gypcrete and thinset. Since I had it installed over a very solid concrete floor (as opposed to a more flexible wood floor) I wasn’t worried about cracks.

Although the thinset I used stated it was ok to use on top of Gypsum, I felt it was a good idea to put some kind of barrier. I put down RedGuard, which is an expensive waterproofing liquid plastic that is rolled on like paint.

I’m happy to report the tile has been installed and there have been no issues with the tile, thinset or gypcrete.

Another milestone is complete in the ongoing (3.5 year) master bathroom project as the self-leveling concrete was installed on top of the radiant floor heating. The process wasn’t exactly what I expected and the results weren’t perfect but the floor did come out level.

The manufacturer of the concrete product recommends not to install it when the heater is running and when the humidity is low otherwise cracking could occur. That meant I needed to wait until summer when the heater didn’t need to run and the evaporative cooler could be running. I didn’t need the cooler, it was installed on one of the rainiest days of May and the humidity in the house was over 75%.

Prior to pouring the concrete I made a riser out of aluminum flashing to extend the height of the air duct in the bathroom. I held the riser in with some cardboard and sealed it to the old duct with some concrete sealant. I did the same for the area around the toilet.

The entire house has an expansion joint around the perimeter and one wall of the bathroom has part of this expansion joint. The self-leveling concrete cannot go into the expansion joint or bridge it or it will crack. I sealed the joint with concrete caulking and put foam under the drywall so it sticks out over the joint.

I had scheduled 3 friends to come over to help (although only two showed up), one who had worked with self-leveling concrete before. It takes at least three people: 1 to mike the concrete with the drill, 1 to pour water and concrete into the 5 gallon bucket and 1 to pour the floor. My $88 corded Dewalt drill had a tough time with the concrete mixture. Luckily I had an old heavy duty single speed craftsmen drill that tore through the concrete without a single complaint.

The only problem we found during the pourig of the floor is there wasn’t enough water in the concrete and it wasn’t quite liquid enough. This made some rough spots where the different pours came together. it work in our advantage since one area where I had sealed the expansion joint gave in and started filling with self-leveling concrete and I completely missed a small crack in the concrete slab near another wall. The self-leveling concrete set too quickly for this to impact the level of the floor. Had it been more liquid the entire floor could have drained down these cracks.

It took four bags of self-leveling concrete and I ended up with a 3/4 inch floor, I will have to recheck my calculations as I expected a 1/2 floor. It cost about $50 in supplies and a few beers.

I was a bit hesitant about doing this pour myself and considered hiring someone. I’m glad I did this small area first and I’m confident I can do the master bathroom with enough people. I may have to have a pour-party and get about 10 people together to have a constant flow of self-leveling concrete then bar-b-que when we’re done. I had meant to take more pictures but I was too busy working on the project, the pictures I did take can be viewed on flickr.

The next step is to install the Schulter Kerdi waterproofing material and to finish up the shower stall before laying tile. This will be a non traditional installation of a shower floor. I’m not sure if I will start this during the summer as I plan to spend my time working on outdoor projects as much as I can.

Tag: Concrete Product

Information I Should Have Known About Gypcrete Before Having It Installed

Installing Self-Leveling Concrete In The Master Bathroom