By:Monte Leeper
Q.
In the spring I added a new basement bathroom where my former laundry room wads in my aging home. Shortly thereafter the floor tiles began to crack (wall/floor tiles labeling). While we believe the floor (concrete on grade) was not properly prepared for the large-sized tiles, the contractor maintains it is a moisture problem and is not familiar with any leveling cement that would keep the tiles put and uncracking. I suggested a new mosaic tile attempt, but he claims they would much appreciate your opinion on this major problem.
A
. Unless the floor is subjected to high moisture from below or the slab has moved for one of several reasons, it sounds like a surface preparation problem. Under most conditions, tile is placed on slab using a mortar base that also levels the floor. This is often referred to as a "mud" base. The "mud" is placed using a board or level called a screed and smoothed out as it is leveled. Before the mud is put sown, a waterproofing membrane such as a thin sheet of plastic or a waterproofing product I like to recommend, by Schluter Systems, is laid down on the existing slab with a "Thinset" adhesive.
Thin-Set by Laticrete, Inc. is known far and wide throughout the industry and is available where you buy the products, The tile is then placed over the adhesive. Water cannot penetrate from below and movement is limited. I am guessing that the tiles went down without a waterproofing membrane, the slab was rough or angled and uneven, or the tiles were not set using the proper adhesive. the purpose of using tile is to stand up to moisture, such as in a shower or bathroom floor, exposed to running water and steam. I find the thought of a moisture "problem" is vague. If you decide to so the job again, remove the tiles and start with "Sitra" from Schluter Systems. 3 mil plastic can also be used. Some contractors also use tar paper, which may be more difficult to adhere to the slab.
Readers are encouraged to send
questions to: HERALD Homes, 379 Central Avenue, Lawrence, N.Y. 11559
Attn: Monte Leeper, Architect.
