Posted by Tim on October 23, 19100 at 20:29:16:
In Reply to: Response to writters comments about efflorescence posted by Evan Lauridsen on October 22, 19100 at 19:58:08:
:blah, blah, blah...inother words if your basement is wet its gonna stay that way, if not go with a engineered or laminate wood floor. K.I.S.S.
As a former technical consultant for one of the world's largest manuf. of mortars and grouts I would like to make some comments with regards to what is termed as negative moisture emissions from concrete slabs and its relationship with efflorescence or soluble salts.
: First off the writer is correct, efflorescence is basically a soluble salt. Efflorescence can occur from any portland cement product therefore it can come from cement based grout, setting materials, cement backer board or even the concrete slab below.
: While I use to recommend waterproof and crack isolation membranes on a regular basis (and still do today), most of the waterproof membranes on the market are designed for positive not negative emissions. In laymans terms, waterproof membranes for the most part are designed to protect against water intrusion from above (are are especially recommended in building that have tile on the second or higher floors).
: I have in my profession, seen job failures related to the installation of a waterproof membrane over wet concrete slabs (typically the failure related to not allowing the concrete sufficient cure before installing over such). While there are some membrane systems that tout there ability to withstand negative pressure from below, fact is every job is different (in relation to how much moisture and efflorescence is being emitted) and all products have there limitations.
: With regards to cementitious setting materials bonding ability being affected by negative moisture conditions, it is a rarity, being that portland cement is typically unaffected by such moisture unlike other bonding agents like latex based adhesives. Of course there is always an exception, such as you may have a hard time achieving a mechanical bond if there is puddles of water on the slab, but alot of this is just plain common sense, mixed with knowledge.
: As to tile itself being affected, ofcourse with anything some tiles will be affected by mositure easier than others. Take for instance marble. Some natural marbles are more affected by moisture than others, thus if water is introduced, discoloration can be the result. Ceramic tile on the other hand for the most part is unaffected by moisture, but some are more porous than others, so obviously choosing a tile with a lower absorption rate is best in such situations.
: With regards to tile not being a water barrier, I don't think any tile manufacturer of even impervious tiles such as porcelain is sold on the market as a water barrier, because even such tiles can have water absorption, even though it is very small in percentage compared with others.
: Any reference I made in my former posting to use of ceramic tile in a excessive moisture emission situation was not for the purposes of providing a moisture barrier, but rather an option for a consumer to choose to avoid expensive correction of the slab in question.
: With regard to installation of a waterproof membrane to protect against efflorscence, there is no guarantee that I am aware of on the market that such a membrane will be a 100% prevention of soluble salts coming up from the slab. First off soluble salts typically need a vehicle in order to drive such salts to the surface, that vehicle is moisture emitting from the slab. Even some of the most expensive vapor emission membranes on the market only reduce what is emitted through the membrane, they do not block all emissions 100%. Just like water will find its own level, moisture emitting from a slab will find a path and a way out. Just like a chain fence is only as good as its weakest link, moisture along with possible soluble salts or efflorescence, will seek to penetrate seams within the membrane as well as along walls, etc.
: The problem with creating too good of a barrier rather than a retarder, is that the moisture will continue to find an outlet. The outlet will typically be along the walls, which may sound like a good thing, but think again.
: Lets say you have a 10,000 square foot room, and you have tested the concrete for vapor emissions using test method ASTM F 1869-98 (which is the calcium chloride test method). So you follow instructions and you get an average emission rate of say 8 lbs. per 1,000 square feet in a 24 hour period, what does this all mean? In laymans terms you have approximately 10 gallons of water being emitted from the slab every day. Can you imagine installing a water barrier over a floor that has 10 gallons of water coming out of it every day? Well lets say you have installed the barrier, membrane or mat over the floor and lets say it has been down on the floor for 100 days. Now I realize that emissions can change from day to day depending upon conditions and that some area within a slab will emit more moisture than other parts, but lets just say for this exercise it is consistent throughout. My point would then be where does the 1,000 gallons of water wind up going? The answer is anywhere it wants too, so long as it finds that weakest link in the chain fence. If the weakest link is at the walls, then it will go to the walls. If the walls are constructed with drywall, well then being that gypsum is absorbant, the water can certainly go into the walls even if the applicator does a good job running the membrane up the walls 6 inches as some specs require (because the specs are designed typically to protect against positive not negative flows).
: Mold which tends to hit the news lately with a vengence (by the way there is currently about $600 million dollars worth of mold cases being litigated in the U.S.) grows best in dark areas where air is still and a food source provided. The paper backing used on the drywall makes a great food source for mold to grow on inside of the walls. While I buy into the idea that you can provide for water drainage along walls, fact is most tile setters do not have the training nor expertise to do such, because it is really not their jobs to control moisture within a slab. They are hired as tile setters not moisture emission reduction experts.
: As for the recommendation of white grout, it comes from years of talking to consumers who complain about efflorescence issues. While it is important to mix grout and setting materials within manufacturer specifications, fact is that you cannot control efflorescence despite an installers best efforts. Even sealing a grout with a water based or silconized sealer is no guarantee that it will cure the problem totally, but it can help greatly. Dark colored grouts tend to show up efflorescence with a passion as opposed to lighter versions, and while I agree that stains on white grout do show, there is nothing worse than a dark brown grout that has efflorescence here and there (my opinion). Sealing of grout will enhance stain protection, but the best stain resistance comes from epoxy grouts (of which I recommend going with dark colors as opposed to white, since some whites yellow over time in epoxy grouts). If you purchase a 100% epoxy formulation, you generally won't have an efflorescence problem, although there is never a guarantee that it can't happen. Also some of the fast curing grouts and thinsets on the market also reduce the chances of efflorescence from occuring from the mortar and grout as well.
: Reality is the best thing to do is to consult with a tile professional about all the issues before you proceed. Make sure you have a say in what membrane, setting materials, grout and sealers are used and obtain written warranties whenever possible, and have the floor tested for moisture and alkalinity before proceeding. If in doubt call the installation material manufacturers technical services line and ask them if what is being sold is best for your situation.
: Evan
:
: : Efflorescence is the migration of soluble salts from the grout or backing material to the surface. When it comes in contact with the air, it reacts with carbon dioxide forming a white salt.
: : While ceramic tile is highly water resistent and even waterproof in some types (depends on the tile) it should not be considered a water barrier. In other words, if water is migrating up through the slab a waterproofing membrane should be installed before the tile is installed otherwise the water may continue to migrate up through the tile itself. This can not only cause efflorescence but also tile/mortar failure.
: : While a waterproofing membrane will help to reduce the migration of water from slab to tile mortar bed it will not eliminate the possibility of efflorescence occuring. Most of the soluble salts come from the mortar and grout used to install and finish the tile. By the way these salts can migrate through and show up on the tile itself.
: : For what it's worth, the source of efflorescence is calcium hydroxide, a by product of the hydration of portland cement. By installing the waterproofing membrane and properly mixing the thinset and grout, you can greatly reduce the chances of efflorescence occuring. A deep penetrating grout sealer would also be recommended to seal the grout joints after proper curing times has elasped. Should efflorescence occur there are a wide variety of tile products formulated to remove these deposits.
: : I would recommend dark colored latex modified grout, perhaps grey considering the foot traffic. White grout can be difficult to maintain and any surface staining will show up like a sore thumb.