Trowel Help?

[K.Carr]

Hi,
I have found your website to be the most informative of any tile site I have seen. So thanks for the help, especially for all of the weekend warriors like myself. I removed the vinyl from my floor and scraped the concrete clean. The question is as follows. I plan on installing approx. 660 sq.ft of slate onto the concrete floor and was wondering what size trowel to use? 1\4 OR 1\2? The slate is Indian, 12 x 12 and gauged.
Thanks,
Kenny

[jay f]

Under normal conditions, I would use a 1/4 x 3/8" square notched trowel, although several of the guys here use a 1/4 x 1/4 trowel. But first, what is the condition of your concrete? Any cracks, major dips, or control joints in the area to be tiled? These would need to be addressed first. IMHO, I would seriously consider a isolation membrane over a concrete floor almost always.

[Bud Cline]

This is gauged slate???

[K.Carr]

Thanks for the response. The slate is gauged and there are no cracks or control joints to deal with. What do you mean by a isolation membrane?
Kenny

[John Bridge]

Hi Kenny, Welcome.

An isolation membrane (aka anti-fracture membrane) is glued to the floor first and then the tile is glued to it. It allows some movement between the slab and the tile. It "isolates" this movement to a degree.

Most membranes run about a dollar a square foot, and normally they aren't used over the entire floor because of the cost.

It it hard for me to imagine a concrete slab that large that has no cracks. Are you sure?

Furthermore, for an area of tile that large you will probably need a movement joint or two. Movement joints are created by substituting caulking for grout in strategic locations.

Tell us a little more about your project. More than one room, etc. Down the hallway, whatever.

[K.Carr]

I am sorry the area is approx. 560 sq. ft instead of 660. I have removed approx. 250 sq. ft. of the vinyl(hallway, bath, two closets and kitchen)and have found no cracks in the foundation. The rest of the area is still covered in carpet as I have to do the project in stages. The area to be tiled is downstairs and includes from the front door; the entry-way, hallway, three closets, a half bath, kitchen, den and utility room. The whole downstairs will not be tiled. There will be two areas in which the carpet will meet the slate when completed. My tiling experience has been a upstairs bathroom approx. 100-150 sq ft. that turned out great.I have never heard of a movement joint? I have seen areas larger than this tiled w/o the use of a movement joint, to my knowledge. Am I over my head with this project?
Help,
Kenny