Underlayments and membranes encompass a broad range of categories, from self-levelers, moisture mitigation products, patches/fillers and crack isolation, to systems that deaden sound or often extra cushioning underfoot. Whether available in bags, rolls or buckets, these products are all designed to keep the installation as stable and trouble-free as possible. We asked several leading manufacturers and contractors to weigh in on the segment.

Ardex. Ardex LevelMaster Elite installer Bob Seman of Seman Flooring said his mainstay product in Ardex MC Rapid, a moisture mitigation system. “What I like about it is you don’t get any outgassing with the product,” he said. “Some products tend to have bubbling when you pour. They also have MC Plus, a two-coat moisture control system. If I’m doing a deep pour, I use that.”
For underlayment, he prefers Ardex V 1200, a self-leveler. “What I like about V 1200 is it’s a value-oriented product. I did a mall in Cleveland with V 1200. It was an outdoor mall that had to be changed into an indoor mall, so the slopes had to be adjusted. V 1200 was my product of choice because of the cost.”
Seman also likes ArdiSeal Rapid Plus for joint filling. “It’s a self-leveling material that you put into an expansion joint. That’s one of the products I use every day.”
Bone Dry Products. Roy Reichow, president and owner of National Wood Flooring Consultants and Reichow Parquet Flooring, prefers penetrating sealer products like Bone Dry when working with hardwood flooring.
The amount of bow allowed for certain engineered planks and solid hardwood with its hollow-backs can make it difficult to ensure even coverage of the product, Reichow noted. “When you start pushing a thicker engineered plank with allowable bow into position, more pressure is applied to the tails of the planks,” Reichow explained. “In solid hardwood, more of the product is going to push up into the ridges of the hollow-back than be in contact with the concrete itself.”
He said the different systems, from penetrating to two-component, all have their place provided they’re used correctly. “Two-component products are great for engineered planks without much flex, because at least you have some consistency when you apply it with a roller. But I personally prefer a penetrating product.”
Bonsal/ProSpec. “We use ProSpec Level Set 300 on our jobs,” said Peter Natale, owner of Concrete by Design. “We find that to be the most versatile product for our needs. We did a project recently in New York where a very large company came in and supposedly leveled the floor. We went back over it to get it nice and flat for VCT.”
Natale added that his firm likes to concentrate on medium and smaller projects. “We don’t do really large projects. We like to do our own mixing with buckets. We don’t use a pump. We like a very controlled environment.”
Custom Building Products. Steve Taylor, Custom Building Products director of technical marketing, said both liquid- and sheet-applied membranes have their advantages. “Often, the best solution depends on the specific job requirements. Some products, such as Custom’s RedGard liquid applied membrane or SpiderWeb II uncoupling mat, offer both crack isolation and a moisture barrier.”
He stressed the importance of measuring the thickness of any liquid-applied product with the appropriate gauge. “Guessing the thickness will not produce the desired results.”
Dependable LLC. Joe Hostler, Dependable general manager, gives one piece of advice when working with underlayments and membranes: “The best prep is always the best practice. If you want a successful installation, then make sure your substrate is well prepared. I can’t stress that enough.”
Halex Corp. According to Mike Glennon, national sales director for Halex’s VersaShield underlayment, contractors are increasingly moving toward sheet membranes to save time. “VersaShield MBX Rolled Moisture Barrier is extremely user-friendly,” he said. “Simply roll it out, tape the seams, cut it in and then install the finished flooring.”
H.B. Fuller/Tec. Tom Plaskota, H.B. Fuller Construction Products technical support manager, said prep-work is vital to the installation. “Always make sure the substrate is clean and sound. When primers are required, be sure to use the recommended products. Different substrates may require different types of primers or different dilutions of multipurpose primers.”
Kevin Fox of Fox Ceramic Tile counts several products among his regular rotation, including Tec HydraFlex waterproofing crack isolation membrane, Tec Fast-Set Deep Patch and MAPEI Planipatch. “For projects which call for waterproofing, we almost always use a liquid membrane, but we will switch to fabric for certain applications, typically showers,” Fox said. “The challenges will liquid membranes is attaining the proper mil thickness the manufacturer requires. I find it very difficult to get a consistent mil thickness without using a small v-notched trowel to place (gauge) the material.”
He noted that while self-levelers are popular, he doesn’t use them very often. “The biggest problems I see with floor prep products are their misuse. These products have limitations on how thick they can be built up, whether or not they can be used in water-exposed areas, and also if they can be used in exterior freeze thaw environments. ... It is the tile contractor’s job responsibility to educate its workforce” so the products are used correctly, he said.
HPS Schonox. Craig Fisher, owner of Royal Floor Covering, said he prefers Schonox products. “In typical renovations where the subfloor has flex or is crumbling, we would have to tear out the subfloor. Schönox APF eliminates the need for demolition,” he said.
Russell Wright, HPS Schonox southeast regional business manager, stated, “After the surface is vacuumed and any loose pieces are removed, the surface is primed and AP is designed to be poured over any existing substrate without the need for shot blasting or scarifying.” After the product is poured, gauge rakes are used to move the material to the correct height and break tension creating a smooth, flat subfloor.
Added HPS Schonox president Enos Farnsworth: “Installers who use these products help fast-track projects, enabling other trades to get in the next day while ensuring a very smooth, strong subfloor.”
Keene Building Products. Daniel Gibson, Keene Building Products sales and development, noted, “A good sound underlayment is one that installs quickly and easily. The best practice of installation is always the one specified by the manufacturer.”
To that point, he added, “Keene’s QQ Step Soft underlayments can be glued down or adhered by use of a latex modified thin-set. It is not recommended that the use of any mechanical fasteners such as staples and nails be used either during the installation of the product or the finished flooring. The use of such fasteners can severely diminish the overall product, but without the full understanding of the science behind the product the installer may say, ‘What’s the big deal?’”
MAPEI. James Longo, national account manager for Specified Surfaces, specifies a range of MAPEI products. “We have utilized MAPEI Planiseal and Ultraplan 1 Plus or Novaplan on over two million square feet of projects in the last two years,” he said.
The company works with many large facilities that demand immediate results, so often recommends products geared toward fast-track construction. “When mission-critical facilities need to implement rapid build-occupancy schedules there is simply not enough time to wait for concrete to dry to the flooring manufacturer’s requirements,” Longo noted.
However, even systems designed to stand up to fast-track conditions will need a little prep. “Unlike floor coverings, these types of products do not have to go into an acclimated space. However, they need to be in an area that is compliant with recommended ambient conditions. This requires understanding the surface and the environmental, and making the proper preparations,” he said.
MP Global Products. Duane Reimer, MP Global Products technical director, can’t emphasize enough the importance of prep. “Clean the subfloor,” he stressed. “Microscopic debris can be a food source for mold. Do whatever you think is necessary to get that last bit of dust and debris off the surface.”
He also said installers should always take time to read instructions. “There are new products coming out every day in this industry, so reading instructions is absolutely critical. I can’t tell you how many times a day I get phone calls from professional installers asking questions that are answered in the first paragraph of the instruction sheet.”
NAC Products. Bob Scavone, Sr., president of Total Flooring Contractors, swears by NAC Products’ ECB membrane when working on mall projects. “In renovating existing mall projects, most of these renovations are overlays, which means when placing new flooring over existing there is no way for the new tile to fall exactly on the existing expansion joints. ECB membrane allows you to shift the existing joint one way or another. Also all of your stress cracks in the existing tile would be resolved by using the membrane over these areas,” he said.
He also uses the product when installing a mud bed. “Sometimes when running your screeds and then applying your mud bed, you often get a  crack between the screed and the mud bed. If you do not apply a membrane, this could become a problem area.”
QEP/Roberts. Stephen Seltzer, QEP director of retail marketing, said there are several choices for installers when choosing underlayments for laminate floating floors. “The best-selling big box underlayment is the two-in-one variety, usually constructed out of LDPE foam with a moisture barrier attached.  Roberts Unison 2 in 1 includes an attached overlap with adhesive for fast, easy installation.”
Regarding membranes, Michael Venturelli, QEP vice president of sales, added, “Professional installers use trowel applied waterproof or cleavage membranes such as Homelux waterproofing underlayment or D-Lux Gold Crack and Moisture Barrier. Use TCNA tested and approved products and always refer to the manufacturer’s recommendations for primers and adhesives.”