Bulletin #5

Revised September 1, 2005

Do's and Dont's Dry-Set Mortars/Latex-Portland Cement Mortars

1. Do use a factory prepared sanded Dry-Set mortar for all installations. Do not job mix uncertified concentrates with sand and cement or cement alone.

2. Don't apply Dry-Set mortar to concrete that has been treated with a sealer or curing compound until the surface has been properly prepared. Dry-Set mortars will stick to clean concrete but any foreign material must be removed first by sand blasting, power sanding or grinding, power wash etching, bead blasting, etc. - whichever will work best.

3. Do install all quarries; vitrified tile and pavers with a Latex Portland Cement mortar over concrete or similar Portland Cement back up surface, particularly where the surface is subject to shock action and weather.

4. Don't grout Dry-Set mortar installations while the setting mortar is still plastic or before it has cured sufficiently to prevent breaking the bond during the grouting procedure, usually two or more days.

5. Do use Latex-Portland Cement mortars for all exterior installations subject to exposure to weather: sun, water, frost, etc.

6. Don't use Dry-Set mortars over backup surfaces that are not compatible, such as plywood, Masonite, particleboard, metal, etc.

7. Do spray or dampen dry porous concrete before installing ceramic tile with Dry-Set mortar. Do not leave puddles or standing water - broom sweep surface dry.

8. Don't apply Dry-Set mortar over a Portland cement float coat, unless the float coat is still plastic or has cured a minimum of 24 hours at 70°F. When used as a neat cement bond coat over a plastic bed, a 1/6" layer is sufficient. When used in connection with "hard-walling" the float coat should be a lean mix, 3/4" maximum thickness, and sufficiently dry to prevent a failure due to excessive shrinkage – a minimum of 24 hours is recommended. Lightweight aggregate float coats need more time for curing to prevent damage from excessive shrinkage. Do not use directly over non-structural insulating cellular concrete (used for sound deadening and thermal protection).

9. Do check with the manufacturer of your Dry-Set mortar regarding the proper procedure and size of notched trowel to use on the job. ANSI A 108.5 and the TCA Handbook recommend a minimum setting bed, after beat-in, of 3/32"-1/8”.

10. Don't mix latex or Dry-Set mortars with high-speed power mixers. Mixing paddles turning over 150 rpm tend to beat in air and reduce the strength of the mortar.