I wrote this article for Floor Covering Installer in 2004 and after pulling it out of the archives for a refresh nearly 20 years later, we are still seeing many of the same moisture-related issues.
Water is essential for life on earth, yet hurricanes and torrential rain cause flooding and destruction on a global scale.
Seventy-five percent of the Earth’s crust is covered with water. In the U.S., flooding is the most destructive natural event because nearly 50% of the nation’s cities and towns are built along waterways. The Grand Canyon in Arizona is proof that water can carve through rock.
Knowing that the Earth is comprised of so much water, is it any surprise that installers are faced with moisture-related challenges on a daily basis? The floor covering industry deals with moisture vapor emissions. This means that water is in vapor form; you cannot see it because the particles are so small. So, if water in a solid state can carve through rock, imagine what water in vapor form can penetrate.
The Romans invented cement-based concrete more than 2,000 years ago. You would think that after all this time modern man would be able to control any moisture-related issues concerning floor coverings, but unfortunately that is not the case. We have technology (photo 1) that gives us an idea of moisture in a slab just by placing a meter on the surface. The calcium chloride dome test can measure the amount of moisture at the surface of the slab. In situ relative humidity testing measures the internal portion of the slab, so now we have the ability to see what’s happening on the surface and the interior of the slab.
There are ways to determine the level of alkali on a concrete slab by placing just a small test strip in some distilled water (photo 2), yet even with all of this technology, we still encounter moisture-related failures. Yes, there is an abundance of moisture retarding products that manufacturers produce to minimize moisture intrusion from concrete slabs, but it is still not a complete, 100-percent fix-all.
To get a little better understanding of what’s going on with the cement finishing side of the industry, let’s look at two different techniques used by cement finishers. The first placement is in a sub-division in Tucson, Arizona. The slab forms and reinforcing steel are all in place, ready for the pour (photo 3).
Here is the completed pour being hard-troweled with a power trowel and water being added to keep the surface workable for the finisher (photo 4).
The next pour is at the WFCA facility in Anaheim, California. There was an area of the existing slab that had movement and several stress fractures that had to be replaced prior to staining the concrete. The subsoil being compacted, this procedure minimizes settling of the subsoil, which can create hollow voids beneath the slab if not done. (photo 5).
A vapor retarder is set in place followed by the reinforcing steel and a doweled construction joint to tie into the existing slab. The existing slab is drilled and then epoxy is placed into the hole, followed by the reinforcing steel (photo 6). Next comes placement, consolidating and screeding (photo 7). A bull float is used for the first float and a power trowel for the final float. (photo 8). The finished slab (photo 9).
By looking at the surface of each slab, there is no way for the flooring installer to see what transpired prior to installation of floor coverings. Let’s review what took place. The first slab, which was poured outdoors, does not have a vapor retarder placed beneath the slab, which is a plus and a minus, depending on who you are. If you are the cement finisher, it’s a plus as the excess bleed water will pass into the subsoil. If a vapor retarder is in place, it takes a great deal longer for the bleed water to evaporate. The results of more water that stays in the slab: more shrinkage will occur, settling and cracking will occur with steel reinforcement, longer stiffening times, which can result in surface cracking.
The second slab has a vapor retarder and it did take the finishers a bit more time to finish, but the end result is a much better-suited slab for floor coverings. If you are a floor covering installer, a vapor retarder is a plus. The chances of moisture intrusion are greatly reduced, the necessity of a vapor retarding system on the slab are greatly reduced, compatibility of vapor retarding systems and adhesives will not be an issue since no vapor retarding system would be required.
So, what is the solution? The cement industry and the flooring industry need to maintain a dialogue so that each understands the needs of the other. Both industries have become more proactive over the past few years, but this dialogue needs to continue. What installers need to do in the meantime is document the jobsite conditions both inside and out. This goes for both concrete substrates as well as wood substrates. Exterior conditions need to be documented (photo 10) for foundations and surrounding areas (photo 11).
There are times that the installer does not see the structure as it is being framed. Here is a photo of a house being framed that was not enclosed prior to rain (photo 12). Can this make a difference? You bet! Following are two photos of lumber—these to 2x4x12’s were in the same shipment. Notice the weight difference of the two. The lumber in photo 13 (photo 13) weighs in at 23 pounds, while the lumber in photo 14 (photo 14) weighs in at 30 pounds. Keep an eye on the building that is occurring around your local area to help protect you from getting caught up in all of the moisture-related headaches.