ANSI A108.5 (2005)
Ceramic tile installation practices are published by the American National Standards Institute (ANSI). This standards also includes quarry pavers (natural stone tiles).
ANSI A108.5 - 3.3.2 says that on exterior floors, the average uniform contact area with the thinset mortar shall not be less than 95%. 3 tiles will be inspected to determine the average coverage and compliance.
Both the Tile Council of North America (TCNA) and the National Tile Contractors Association (NTCA) have adopted these standards as the minimum acceptable level of performance and workmanship.
Let's face it, humans beings are like electricity and water - they will take the path of least resistance and effort - lazy !
Trowel marks are actually called "gauge marks." They are used to create a measured thickness of thinset mortar. Leaving the trowel marks in place will mean only 50% contact at 100% thickness of the gauge marks.
|Improperly installed floor tiles show only 50% coverage. Buttering the edges will hide these marks and give the "appearance" of 100% coverage. Click on the image to enlarge.|
A 1/2 inch comb trowel will leave 3/8 inch thick layer of thinset, once the grooves are flattened and leveled. This means that to achieve a total of 1/2 inch of thinset, both the substrate and tile will require 1/2 inch trowel marks that are knocked down and smoothed.
Why do they do this?
It saves them 50% on their thinset costs.
They are lazy.
They don't care.
No one ever taught them how to do it correctly. They have never been involved in a construction defect case.
Tile setters must be reminded that tiles installed in exterior floor and shower applications, must achieve 95% contact with the setting material.
This will ensure decades of performance and a lasting tile floor.
Paolo Benedetti - Aquatic Artist "Creating water as art."™
Aquatic Technology Pool and Spa ©www.aquatictechnology.com
You may contact Paolo Benedetti at: firstname.lastname@example.org or at 408-776-8220