why is waterproofing done before grouting?why do we need to let the mortar/adhesive dry before grouting?
Water proofing is done before any tile is set into place.. Water proofing must be done on any horizontal surface in water prone areas such as showers. Not always done out side the shower area, but each case is different. You should allow the bonding material to dry before grouting so the bonding agent, mastic (walls in a non wet area )or a thin set won t bleed through and stain the grout. The only way to ensure of a good bond is to lift tiles during the setting process and make sure you have proper amount of mastic ( walls in a non wet area) or thin set under the tiles.. There are ways to check floor tiles to ensure a bond is to knock on the tiles to see if they sound solid. Hollow sound gives way to a no bond. And NEVER bond to just a green board in a shower or high moisture area. Failure will soon follow if you do. Any questions you can e mail me through my avatar and check my qualifications there. GL
You should use special green board for the shower. It is water resistant not water proof. This gives the best base for the tiles. You should leave the adhesive set up totally before grouting because the gases that are in the glue need a place to go. This includes thin set mortar because of the water vapor it out gases. Good luck
Should the grout come away it can damage underneath especially in shower areas. You should use green moisture resistant plasterboard but ideally cement board on top as it is waterproof and perfect for tiling. Grout will eventually become discoloured and fall away over time in wet areas. Using correct technique in applying adhesive ( notched trowel or plastic notched spreader ) evenly and working within you capability will give you a good result, many try to do too much in one go....which is Ok for the professional. This way the tile will not come away. When applying tile on adhesive try a slight twisting motion to firm the tile in place, by placing finger on the front of tile....Important allow tile adhesive to dry fully before applying grout it takes 12 hrs approx as manufacturers spec. If tile when tapping makes a different sound (kinda hollow sound) it is loose and will need to be removed. Scrap out old adhesive and redo. Tip: Buy sealer (spray for grout) in excessively wet areas as it will extend the grout life and very good for shower areas. You can but sealer applicators but slow....mask and vent out when using spray as not good to breathe in and smell at first....
