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Unread 03-29-2002, 10:34 PM   #1
Rob Z
Posts: n/a
Mortar, Cement, and other Pookey

There are three main types of materials that can be used to install ceramic tile and stone. Each of these materials are used in what is referred to as the "thinbed" method of tile setting. The "thin" in thinbed refers to fact that the material bonding the tile or stone to the substrate is relatively very thin in cross section.

The thinbed method is contrasted by the older "thickbed" method. With the thickbed method, the substrate is produced and the tile/stone set and grouted in one step. The tile/stone is thus bonded with a relatively thick cross section of material.

For most of the jobs that we do, as well as virtually all projects undertaken by the DIY'ers that visit us here at the JB Forum, the thinbed method will be used.

The three main types of setting materials are:

1. Mastic

2. Portland cement mortar

3. Epoxy

Mastic is a latex or solvent based glue that cures by evaporation. Mastics are premixed and ready to use immediately. They have relatively low strength and water resistance as compared to cement mortar and epoxy. They are comparatively easy to use because there is no mixing or slaking involved, and because mastic grabs tile and prevents it from sagging. Home Depot, among other retailers, now sells something called "premixed thinset adhesive". This is not thinset in the traditional use, and is nothing more than mastic with sand in it.

On a case by case basis, your project may be suitable for the use of mastic. Please be sure to ask for advice on this before you start.

Portland cement mortar is what we typically refer to as "thinset". It is a mix of fine sand, portland cement, and other ingrediants to make it sticky, workable, and other desirable properties. It may be mixed with water only, a latex admixture, or come with powdered latex already in the mix.

All thinsets need to be mixed at the time of use, and all need to slake before use. Slaking is a period of time after mixing where all the dry and wet ingrediants continue mixing and reacting to yield a better, more workable mix.

Thinsets have tremendous strength, flexibility, water resistance, and virtually every other property that is desirable, when compared to mastics. Thinset will be the correct choice for your project in almost every case. Some types of natural stone, for example, require the use of epoxy. To be certain, be sure to ask us before you start for a recommendation for a particular type of thinset and possibly even a brand specific recommendation, based on what is available to you in your area.

One important note: thinsets are not a corrective material for substrate deficencies. Plan on using a trowel that gives good coverage on the back of the tile, with a thickness of thinset under the tile from 1/16" to 1/8". If this is not possible, you likely need to correct flaws in your substrate, and we will discuss those options separately.

Epoxy is very expensive, very strong, and generally not a user friendly type of product. You will need to use this to set tile/stone only in very rare situations. We will discuss the use of epoxy for projects that require its use.

[Edited by Rob Zschoche on 03-30-2002 at 11:29 AM]