Exploring the Unlimited Possibilities of Concrete Countertops

Andrew Lash doesn’t just make concrete countertops, he’s also a concrete ambassador of sorts helping to educate those in his area about the benefits and possibilities that concrete possesses. I recently had the opportunity to talk with him about his work and some of the challenges he faces as he perfects his craft and builds his business in an area where people think of concrete as nothing more than the gray stuff you use to make sidewalks.Lash Countertop

Educating About the Benefits of Concrete

Speaking about the challenge of attracting clients Andrew said, “In this area here in Florida it seems like most people aren’t aware of concrete as a potential solution for countertops or flooring… When they look at countertops they look at granite, quartz, Formica, laminate type things, not really considering concrete. So right now I feel like I really have to put money and effort into growing a market in this area and showing that concrete is a suitable surface for vanities and countertops. Once I do that, then I can make sure that people know I exist.

When people hear what I do, they so often think that I am referring to a sidewalk that they can put on their cabinets, but when they see pictures and samples that I have they are completely blown away with what concrete can look like.”

Lash Fossil CountertopLash Fossil CloseUp

Working with concrete is exciting and rewarding, but it is a business that often requires customer education in addition to making great pieces.

Unlimited Possibilities

One reason Andrew enjoys working with concrete is the wealth of possibilities this material provides. He often jokes with his customers that concrete’s versatility is one of its biggest advantages and biggest drawbacks. Customers can have literally almost anything they want. They aren’t limited to a few color choices or design possibilities. The difficult part however comes in helping his clients to figure out what they want so he can create a sample and make it happen.

“A lot of times I have customers that they love the idea that they can have what they want, but at the same time they can’t make a decision about what they want.”

Lash Bathroom Cups

Concrete Bathroom Cups

This drive to create unique pieces has pushed Andrew into exploring new possibilities using concrete. Recently he crafted a beautiful set of bathroom cups for his girlfriend and offers similar custom cups to interested clients. A local florist has also contacted Andrew hoping to have custom concrete vases created.

Custom Concrete Bathroom Cups- Side View

Custom Concrete Bathroom Cups- Side View

Taking His Training and Making It His Own

I love seeing my students take the skills they learn and put them into creative, practical and profitable applications. Each student has a unique take on how to use concrete and each creative possibility inspires us. I had the pleasure of training Andrew in October 2011 in my Ultimate Course. In fact one of his biggest pieces of advice for those just getting started in concrete is to find and take advantage of training. Even though he was already working with concrete before attending our training, he found that being able to ask questions and see processes demonstrated was a big help to his career.

One last piece of advice he offers to those new in concrete industry is to avoid the urge to oversell the product.

“I’ve heard a lot of people that try to sell a concrete countertop as… stain-proof or scratch-proof which is definitely not the case and it comes back to bite them when (customer) gets a small scratch. Set expectations for whatever sealer or process you’re going to use.”

What great advice! Marketing the benefits of concrete is essential, but it is important not to sell it as something it is not. When customers know what to expect they will be better able to enjoy their new concrete countertops, and as we all know one happy customer can lead to many more.

Thanks again Andrew for sharing a few of your designs with me and the readers here on the CCI blog.

Andrew Lash Kitchen


Andrew Lash shell sink

How to choose the best diamond pad for concrete countertops

Selecting the right diamond polishing pad (or disc) is the key to getting a good finish for your concrete and getting the most bang for your buck.

There are many different sources, names, styles and prices for diamond pads on the market. This can be very confusing, and what often happens is selection comes down to price. This is unfortunate, because in many cases a cheap pad will cost you more in the long run. However, I’m not suggesting we all go out and spend $100 per pad either. There’s a place for those, and we don’t need to go there (granite folks might though).

Choosing the right pad starts with assessing what you plan on doing with it.

  • Are you using it for heavy stock removal?
  • Is it for general honing?
  • Are you polishing the concrete to a high gloss?

Each of these tasks will influence the choice in pad. I’ll outline some of the variables to consider and then create a general template for selecting the right pad for the right task.


Larger diameter pads (e.g. 7″) are much more stable on large, flat areas than smaller diameter pads (3″ and 4″). However, larger pads become unstable on narrow sections of concrete. A 7″ diameter pad won’t stay flat or cut evenly on a 3″ wide strip of concrete. They are also difficult to use on the vertical edges of countertops.

Small diameter pads are less stable and more likely to gouge when processing large areas on a big polisher, but with a smaller polisher (espcially a pneumatic polisher) they work very well for processing edges and narrow sections.

A good all-around size is a 5″ diameter pad. Many low-cost polisher package deals come with 4″ pads. These can be difficult to control with hand held polishers on concrete. Smaller 4″ pads are really meant for use on hard stone, which is much less prone to gouging than concrete.


Diamond pads come in a variety of thicknesses, from around 2mm thin to 8mm thick.

Thicker pads will last longer, but thicker pads are stiffer, and sometimes are prone to cupping when they dry.

Thin pads don’t last as long (especially when aggressively cutting), but they are more flexible. This is a big advantage when honing or polishing inside curved integral sinks.


The pattern molded into the cutting surface plays a significant role in the lifespan and the cutting quality.

Often pads used for coarse honing (30 and 50 grit) have an aggressive, open pattern with wide and deep channels. Pads with large, open channels allow the abrasive cutting residue to be ejected quickly and effectively. This increases the lifespan of the pad when aggressive stock removal is performed. 

Pads that have many narrower channels are best only for polishing (400 to 3000 grit), where almost no stock is removed. Narrow channels clog more readily when aggressive cutting is performed and when insufficient water flows out from under the disc. 

A good balance of these factors is lots of channels that are large in proportion to the diamond-covered surface. This provides flexibility to the pad while still allowing for effective ejection of cuttings and a large proportion of diamond area. In contrast, pads with very large channels and very large “islands” of diamonds tend to be inflexible.

Diamond Quality

While it’s very easy to see the thickness and channel pattern in a diamond pad, it’s nearly impossible to assess the quality of the diamonds used in the pad, or for that matter, the grading and quantity of diamonds. Ultimately it’s the diamonds that do the cutting, and they are what makes a pad expensive. The better the quality of diamond, the better the grading and the more diamonds in the pad, the more expensive the pad will be.

It’s possible to find $1 pads and $100 pads that look almost identical. What’s not visible are the diamonds, and that’s where you need to trust your supplier to inform you of what you’re getting.

The most expensive pads use the best industrial diamonds. The diamond concentration is high (each manufacturer optimizes the quality and quantity of diamond in their pads), and the gradation is narrow. Like sand and gravel, diamonds come in a variety of sizes. A narrow gradation means almost all of the diamonds are about the same size, so the grit number of the disc is a more precise description of the diamond size gradation. Any variation tends toward smaller diamonds, which don’t affect the quality of the concrete surface.

Cheap pads use low grade diamonds. These tend to have more flaws and much poorer gradation. In addition, fewer diamonds may be used in the pad. Often the gradation is broader, so a 100 grit pad may actually have significant amounts of smaller diamonds and some coarser diamonds (like 70 grit). This results in a lower surface quality (more scratches) and slower cutting (because there are more smaller diamonds in the pad).


The binder that encapsulates the diamonds is just as important as the diamonds, and it has a profound effect on the performance and longevity of the pad. Binder materials range from ceramic to resin, and different materials are used for specific applications. Binder hardness is important. A binder that’s too soft will wear away quickly when processing an abrasive material like concrete.  

Nearly all wet polishing pads use a resin binder, and resins vary. It’s very rare that a pad distributor will describe the binder with any meaningful detail, so here personal observations and reliance on trusted recommendations are necessary to make a good choice. Too often the least expensive pads use soft resin binders that wear away quickly. If you end up using three times as many pads as you would with a pad that costs twice as much, you are not saving money in the end.

Ceramic binders tend to wear better and stand up to higher temperatures than resin pads. Many dry pads use a ceramic binder, which helps to prevent the smearing and glazing that can occur when a resin based dry pad is run at a speed that’s too high.

Recommended Diamond Pads for Concrete Countertops

The Concrete Countertop Institute has developed diamond pads specifically designed for concrete countertops, not granite and not concrete floors.

These pads have all the features you want in a diamond pad for concrete countertops:
– High concentration of diamonds for faster cutting
– Narrow gradation of diamonds for a swirl-free surface
– Thick enough for long life
– Thin enough to be flexible
– Ideal channel design to eject slurry and prevent clogging
– Ideal resin binder for long life without glazing

Click here for pricing.

diamond pads

Diamond Pads

Creating Concrete Countertops Using GFRC

In the last two pieces about glass fiber reinforced concrete I’ve discussed the basics of glass fiber reinforced concrete and the importance of fibers. To finish off this series on GFRC I’d like to move into a few of the technical aspects you will encounter when creating GFRC countertops including mix designs, casting and processing.

GFRC Mix Designs

If you’ve worked much with concrete you know that finding the right mix can be difficult and often requires years of experience. Many different factors impact the ideal composition for concrete, and GFRC is no different. Mix design isn’t a concept that can be tackled in one blog post, but here are some of the basic components in a good GFRC mix:

  • Fine Sand– Sand used in GFRC should have an average size passing a #50 sieve to #30 sieve (0.3 mm to 0.6mm). Finer sand tends to inhibit flowability while coarser material tends to run off of vertical sections and bounce back when being sprayed.
  • Cement– Typical proportions use equal parts by weight of sand and cement.
  • Polymer– Acrylic polymer is typically preferred over EVA or SBR polymers for GFRC. Acrylic is non-rewettable, so once it dries out it won’t soften or dissolve, nor will it yellow from exposure to sunlight. Most acrylic polymers used in GFRC have solids content ranging from 46% to over 50%. Consider trying Smooth-On’s duoMatrix-C and Forton’s VF-774, two reliable acrylic polymer choices.
  • Water– Common water to cement ratios range from .3 to .35.  When determining how much water to use make sure to take the water content from your acrylic polymer into account. This can make calculating water to cement ratios difficult unless the solids content of the polymer is known. With a polymer solids content of 46%, 15 lbs of polymer plus 23 lbs of water are added for every 100 lbs of cement.
  • Alkali Resistant Glass Fibers– Fibers are an essential component of GFRC. If you’re using the spray-up method for casting the fibers will be cut and added to the mix automatically by your sprayer at the time of application. If you’re using premix or the hybrid method for casting you’ll mix the fibers in yourself. Fiber content varies but is typically between 5% to 7% of the overall cementitious weight. Higher fiber content increases strength but decreases workability.
  • Other Admixtures– Some other elements you may choose to include in your GFRC mix include silica fume, metakaolin, VCAS and superplasticizers.

GFRC Casting

I talked a bit about casting in the Introduction to GFRC article. There are a few different methods you can use for casting. Since I’ve already discussed the basic concepts behind casting (if you need a refresher check out Introduction to GFRC) I’d like to take a minute to review the pros and cons associated with each casting method.


A concrete mixture is sprayed into the forms using a special device that chops and sprays a separate stream of long fibers. The concrete and fibers mix when they hit the form surface.

  • Pros: Allows for very high fiber loads using long fibers resulting in greatest possible strength.
  • Cons: Requires expensive, specialized equipment (generally $20,000 or more).


Glass fibers are mixed directly into the fluid concrete. The mixture is then poured or sprayed into molds.

  • Pros: Less expensive than spray-up, although a special spray gun and pump is required.
  • Cons: Fiber orientation is more random than when using spray-up and fibers are shorter resulting in less strength.


The hybrid method for casting GFRC uses an inexpensive hopper gun (the same kind used with drywall) to spray a thin face coat into the forms. Once the face coat dries the fiber loaded backer mix is applied either by pouring or hand packing, just like ordinary concrete.

  • Pros: Affordable way to get started with GFRC. A hopper and air compressor run about $400-$500, much less than the spray guns used for spray-up or premix.
  • Cons: Since the face coat and backer mix are applied at different times careful attention is needed to ensure the mixes have a similar makeup to prevent curling.
Spraying GFRC

Spraying GFRC

GFRC Curing

The high polymer content of GFRC often means that long term moist curing is unnecessary. Cover a freshly cast piece with plastic overnight, but as soon as it has gained enough strength it can be uncovered and processed. Many GFRC pieces are stripped 16 to 24 hours after casting.

GFRC Processing

Your skill level, the composition of your mix and the method used will determine how much processing is needed once your GFRC countertop is removed from its molds. Grouting may be needed to fill in bug holes or surface imperfections. Any blowback (sand and concrete that doesn’t stick to the forms) needs to be cleaned or the concrete’s surface will be open and granular. Achieving a perfect piece right out of the mold is very difficult and requires great skill.

Common Questions About GFRC

  • How Thick is a Typical GFRC Countertop?– Typical concrete countertops made with GFRC range from ¾” to 1” in thickness. This is the minimum thickness that a long, flat countertop can be made so it doesn’t break when handled or transported. Smaller wall tiles can be much thinner.
  • Is GFRC Green?– GFRC is roughly on par with other forms of concrete countertops in terms of the “green-ness”. In comparing 1.5” thick concrete countertops to ¾” GFRC countertops, the same amount of cement is used, since GFRC tends to use about twice as much cement as ordinary concrete. This sets them equal to each other. The use of polymers and the need to truck them does make GFRC less green than using ordinary water, which could be recycled from shop use. Both traditional cast and GFRC can use recycled aggregates, and steel reinforcing is more green than AR glass fibers, since steel is the most recycled material, so its use in concrete of all forms boosts the concrete’s green-ness.

I hope you enjoyed this three-part series on GFRC. Before you go check out this short 7 ½ minute video featuring excerpts from my Comprehensive GFRC Self Study Course. Watching an actual GFRC countertop being constructed will help you better understand many of the topics I’ve covered in this series.

You may also view my FREE, 2.5 hour seminar “Step by Step GFRC with Mix Design” by requesting access here.

Last updated by at .