what to do under your encaustic tiles:
it’s a fact. what’s under your tile is just as important as the tile itself. and for encaustic cement tiles, that means a perfectly level, clean, dry, and slightly roughed surface. this is the time to make sure that your professionals have a handle on the strength and make-up of your substrate (the support floor beneath your tiles).
If you’re installing floors:
1) your installer will need to allow for 3/4" below your finished floor height (5/8" for the tiles and 1/8" for mortar). If your substrate is plywood, be sure the plywood complies with the architect’s specifications for your site and use an installation mat to insure the perfect installation. (schluter and noble are two of the best for installation mats)
2) now that you know your concrete surface is the right height and completely level- you’ll need to make sure it is also completely dry before installing your cement tiles. if it isn’t, the moisture in the concrete will want to escape through your tiles. if that happens you can expect powdery white limestone deposits (efflorescence) to surface. not a good look! also, do not lay your cement tiles directly onto fresh (uncured) concrete.
IMPORTANT: just because your concrete surface has cured does not mean it is moisture-free. this can be a problem if not checked. a quick way to find out is to tape a piece of clear plastic onto your slab (about the size of a piece of paper). be sure all edges are thoroughly taped down. If you see condensation of moisture, you will need to apply a waterproof membrane before proceeding with your installation.
3) but level and dry isn’t all you’ll need on your way to a quality substrate! you will also need to add expansion joints to any larger floor or wall application in order to prevent cracking or fracturing from the possible movement of the substrate. you’ve heard that construction always settles? with expansion joints placed according to the proper guidelines (check that TCNA site again!) expansion, construction, isolation, contraction, generic and perimeter joints will ensure what’s under your tiles has plenty of the right kind of “give”.
*to be extra sure when reviewing your substrate needs – always consult your architect or engineer. clé tips are only to help lead in the right direction for all installations, but everyone’s installation is unique and therefore requires your professional who is in-the-field to give the exact specification for your installation.
assuming that your floor joists are sufficient and not flexing, you can install tile on a wood floor if you first put down a cement backer board like you would do in a shower behind the tile. Your installer can use any quality-brand dimensionally stable fiber/cement wall boards and especially the latest magnesium oxide boards.
if you are installing walls:
1) walls require just as much care under your tiles as the floor prep we’ve just outlined. however, unlike the concrete substrate required for floors, your encaustic cement tiles can be installed over drywall, plaster, cement block, and cement backer board (for moist areas). you’ll want a flat, smooth and dry surface, completely free of any loose coatings (paint). any cracked surfaces must be scraped smooth and patched. if using backer board be sure to follow the installation guidelines of the backer board manufacturer.
2) again, be sure that a concrete substrate for your walls has gone through the same drying steps. any excessive moisture will want to escape through your cement tiles.
3 for areas like showers, pool surrounds, and other areas subject to moisture, the underlayment should be sealed with a waterproof membrane or other moisture-resistant product. cement-fiber backer board is an ideal underlayment for tile in wet locations. Again please review the manufacturer’s recommendations if using for a wet application.
and as with your floors, check with your architect or engineer for expansion joint requirements.