Thinset, Mastic & Grout Compared: Modified vs Unmodified, Sanded vs Unsanded for LA Tile Jobs

Use polymer-modified thinset for most tile, unmodified only over a properly prepared concrete floor, and choose grout by joint width: sanded for joints 1/8 in. and wider, unsanded for narrow joints and polished or soft stone. This guide compares the thinset and grout options in our tile-setting collection so a Los Angeles bathroom, kitchen or patio tile job gets the right bond and the right joint on the first order.

Which thinset should I use?

Thinset is the mortar that bonds tile to the substrate. Pick it by the substrate, the tile and how fast the room must be back in service. The table compares the options we stock; details follow.

Modified vs unmodified thinset

The economical non-modified thinset is a cement-based dry-set powder for ceramic, porcelain, stone and cement tile over properly prepared concrete floors, left about 24 hours before grouting. The fast-setting professional thinset is polymer-modified, meets ANSI A118.4 and A118.11 without additives, sets quickly even in cold weather, and is approved for wet areas including showers. Polymer modification is why it bonds over cement backerboard, drywall, exterior-grade plywood and existing tile as well as concrete.

Crack prevention, rapid-set and premixed

The FlexBond crack prevention thinset can be applied directly over cracks up to 1/16 in. and flexes up to 1/16 in. in service, which helps on older LA slabs. The rapid-setting fortified thinset allows grouting in 2 hours and foot traffic in 6 hours, useful for repairs and occupied homes. The white premixed thinset comes ready to spread from a 3.5 gal. pail for smaller tile on interior floors, walls, countertops and backsplashes. For large format tile see the large format rapid-setting mortar, and for translucent tile the white thinset for glass tile.

What about mastic?

Mastic is a premixed organic adhesive for small wall tile in dry areas. We do not stock a separate mastic, and in wet areas such as showers a polymer-modified thinset is the safer choice. The premixed thinset above is the ready-to-spread alternative we carry.

Sanded vs unsanded grout

Grout choice follows the joint. Sanded grout has the sand load to fill joints from 1/8 in. to 1/2 in. without slumping. Unsanded grout fills narrow joints and will not scratch highly glazed or polished tile, marble or natural stone. Pre-mixed grout skips the mixing and fills 1/16 in. to 1/2 in. joints.

Examples: Arctic White sanded grout, 25 lb., Arctic White unsanded grout, 10 lb. and Arctic White pre-mixed grout, 1 qt. Each color has matching caulk and a grout renew colorant in the tile settings collection.

Prep, caulk and the rest of the tile job

Thinset is only as good as the substrate. In a shower, set cement board first; see the cement backerboard guide and the cement boards collection. Use caulk, not grout, at changes of plane and corners; the sealant comparison and the tile setting materials overview cover that step.

Tile setting checklist

• Choose the substrate first: cement board in wet areas, concrete for floors
• Use polymer-modified thinset for showers, walls and mixed substrates
• Match coverage to trowel notch and tile size
• Wait about 24 hours before grouting unless using a rapid-setting mortar
• Pick sanded grout for 1/8 in. joints and wider, unsanded for narrow joints and polished stone
• Caulk corners and changes of plane instead of grouting them

Conclusions

Modified thinset is the default for LA tile work, and the grout follows the joint width. Order the thinset, grout, caulk and backer together so the job does not stall between steps. Confirm coverage and cure times on the bag label before ordering for a large floor.