Miniscule, or what are referred to as hairline cracks, are nearly inevitable in a concrete countertop. They don’t always occur, but they can develop. The cracks tend to be non-structural and are a result of the natural shrinkage of the concrete. It’s important to understand how and why they occur in order to minimize or prevent them.
Common Cause of Cracks
Jeff Girard of Concrete Countertop Institute provides a great overview of the common causes of cracks. Most cracks are caused by the long-term drying shrinkage of the concrete. These are the most common type which are very small and relatively short. They are of no concern to the structural integrity of the concrete. In fact, more often, they are viewed as inherent characteristics of the concrete and not as flaws.
How to Prevent Cracks
Proper reinforcing when the concrete countertop is poured is the best way to reduce the likelihood of cracks. Out-of-level cabinets, improper supports, improper lifting and installation of the countertop can also contribute to cracks. It is wise to discuss how the countertop will be reinforced with your contractor for reassurance as to how they try to prevent significant cracking.
The possibilities of hairline cracks may be inevitable, but it’s certainly not a reason to avoid concrete countertops. With some concrete countertop designs, it is these cracks specifically that are desired for creating a rich, worn-in appeal to the surface. It’s realistic to expect the cracks, but, also keep in mind, that any unwanted minor cracks can be repaired and/or disguised.
Concrete Countertop Heat Resistance
A common question posed about concrete countertops is if they can withstand heat. Overall, a concrete countertop is a durable, tolerant material. The issue lies with the sealer that is used on the concrete countertop. Every concrete contractor has their own preference for countertop sealers, so it is best to discuss with them what they use and how well it holds up to heat.
As a general rule, it is best to avoid placing hot pans on concrete countertops. It is likely there are sealers on the market that now provide protection from heat. But until you know which sealer will be used by your contractor, avoid placing hot items directly on the concrete countertop surface. Concrete is very heat resistant, but the concern is damaging or discoloring the sealer.
Using trivets of stainless steel, brass or copper are the best way to avoid damage to your sealer. Another one of concrete’s versatile features is that you can embed a trivet(s) directly into the countertop, providing an easy access place for setting hot pans without the worry of doing any damage. You can also use hot plates or a hot pad on the counter, but embedded trivets are a unique and functional design option.
| Who would want concrete countertops? |
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| Concrete countertops are the most unique, personal countertop option because they are made from scratch for each client. To determine whether concrete is right for your client, think about whether the client believes that: -- they want something unique and personalized -- they want something that looks natural and has character -- they appreciate high-quality, hand-crafted items -- they think granite is too shiny, too formal, too common -- they think synthetic solid surface materials look and feel like plastic -- they need a color or visual texture that’s not available with other countertop materials If so, concrete countertops may be right for your client. |
| What are the advantages and disadvantages of concrete countertops compared to other countertop materials? |
| Advantages: Custom: Concrete’s biggest advantage is that it is completely custom. You can provide your client with a countertop that is unique to them, and highly personalized. Versatile: Concrete is extremely versatile. It can enhance any style, from French Country to Contemporary. From Arts and Crafts to Industrial. From Traditional to Modern. The possibilities are endless. To read this article, click here. Practical: Contrary to popular belief, concrete countertops do not need to be stain-prone and difficult to maintain. They do not have to "develop a patina". In the past few years, especially in 2004-2005, concrete sealer technology has progressed by leaps and bounds, and sealer manufacturers are recognizing that concrete countertops have unique and stringent performance requirements with regards to staining, heat and scratching. Although there is still no one sealer that all concrete countertop craftsmen use, ask your craftsman what kind of sealer he uses and what its performance characteristics are. Most concrete countertops actually behave similar to granite with respect to staining. Granite countertops are also porous and have to be sealed and maintained. Most people don’t realize this, because granite is usually too dark and patterned to show stains. Imperfections: We believe that this is an advantage. Concrete countertops are hand made and hand finished. Since concrete is a heterogeneous mixture of many different ingredients, subtle variations in color, shade, texture and overall appearance should be expected. All concrete is susceptible to harmless hairline cracks. They will sometimes appear months or years after installation, and are generally a result of seasonal movement of the cabinets and the house itself. These should be considered part of the aesthetic charm of concrete, and not a defect. Concrete exhibits natural beauty rather than plastic perfection. Disadvantages: Unrealistic expectations: Again, ask your craftsman what the performance characteristics of his sealer are. Understand the performance and appearance characteristics and educate your client on what to expect. Lead time: Concrete countertops are a long lead time item. Precast concrete countertops can take approximately 4 to 6 weeks to fabricate. Good concrete countertop craftsmen can be hard to find: The concrete countertop industry is still young, and currently demand outpaces supply. Many design professionals want to use concrete countertops but can't find a qualified local craftsman. The best place to look is ConcreteNetwork.com. Click on the Countertops & Elements category and navigate to your area. Be sure to investigate each craftsman you talk to - ask for references and samples of work. Also make sure that he is a good business person who has a proper contract and product documentation and a history of delivering projects on time. For more help on how to find and evaluate a concrete countertop craftsman, click here. |
| Where can I use concrete countertops in my designs? |
| -- In residential applications, concrete countertops are great for kitchens, bathrooms, fireplace mantles, tables, desks, and anywhere else countertops are required. -- In commercial applications, concrete countertops are frequently used in restaurant bartops, bathrooms, retail counters, reception desks and break rooms. -- Concrete can also be used in vertical applications such as backsplashes, shower surrounds and fireplace surrounds. -- Concrete countertops can be straight, curved, notched, multi-level, etc. With concrete, any shape is possible. -- Integral and vessel sinks are possible. See the section on sinks for more information. -- Concrete countertops can be used both indoors and outdoors. -- Concrete countertops are food safe as long as the sealer is. There is no FDA standard for concrete countertop sealers, but your contractor should use a sealer that is suitable for countertops rather than floors. -- Some specification considerations are: Design your concrete countertops to be at least 1.5” thick. Precast concrete countertops do not require a plywood sub-base. Concrete countertops weigh about the same as granite of the same thickness. For architectural specifications, click here. -- Concrete floors are a completely different application. Your contractor may or may not have experience in concrete flooring. |
| How do I find a contractor to make concrete countertops for me? |
| Many contractors are not listed in the Yellow Pages, but most of them have websites. If you do a web search for "concrete countertops", that returns too many results. Try a more localized search such as "concrete countertops denver co". This site now offers a nationwide directory of experienced concrete countertop professionals. These are paying members of our site and their is no certification involved in having a lisiting so it is still CRITICALLY IMPORTANT to perform due diligence. If you can't find what you are looking for here there are many other sites that offer contractor listings as well. Please read the next question for very important information about how to evaluate a concrete countertop maker. |
| How do I evaluate a concrete countertop maker? |
| Currently demand in the U.S. for concrete countertops outstrips supply. There simply aren't enough competent contractors in all areas of the country. Contractors are seeing the popularity of concrete countertops and getting into the business. This is good, but it also necessitates caution. Not all concrete countertops are created equal. Many decorative concrete contractors, while honestly trying to serve their customers, mistakenly believe that they can elevate a floor on some cabinets, and that makes a concrete countertop. As a design professional or homeowner, you know that the aesthetic and performance requirements of any countertop are different from those for any floor. Many excellent concrete countertop craftsmen get started with floors, but do not assume that because a contractor has experience with concrete floors that he can automatically make a good concrete countertop. You MUST perform due diligence on any contractor who claims to make concrete countertops. Get references, get samples, and see actual projects they've done. Find out how much experience they have or how well they've been trained. Consider the contractor's professionalism and membership in any trade organizations. Concrete countertops are and should be expensive. Do NOT automatically go with the lowest bidder. If a contractor claims that he can make concrete countertops for you for $25 per square foot, he doesn't know what he's doing. Doing a good job at concrete countertops requires a great deal of skill, attention to detail and hard work. Anyone who does concrete countertops for $25 per square foot will put himself out of business very quickly - at your expense. You should expect prices that are higher than granite, in the range of $70 to $200 per square foot or higher in many areas of the country and especially for highly custom and sculptural work. Good concrete countertops are worth it! The Concrete Countertop Institute hears numerous stories of experienced concrete countertop professionals being underbid by someone who thinks that they can elevate a sidewalk and call it a concrete countertop. The results are always disastrous. Imagine having a big, heavy piece of concrete installed on your nice new kitchen cabinets, and then having to have it ripped out and spend even more money on different countertops. Please do not make this mistake! Please help us eliminate bad concrete countertops by not buying them. How to recognize good concrete countertops. To help you understand what constitutes acceptable versus unacceptable quality of concrete countertops, we have created photo galleries with many examples. -- Click here to see great examples of concrete countertops. -- Click here to see the "Hall of Shame" gallery that shows what can happen if you hire just anybody to make concrete countertops for you. Click here for a form that will help you evaluate a concrete countertop maker. Do your due diligence, find a good concrete countertop maker, pay him or her what the product is worth, and you will have a beautiful, unique countertop that will serve you well for years to come. |
| What's the difference between concrete and cement? |
| "Concrete" and "cement" are NOT synonyms. Cement is the glue that holds concrete together. Calling concrete "cement" is like calling cake "flour". Concrete starts with rocks, sand and cement. Cement is a powder. When water is added, a chemical reaction occurs that causes the cement to harden or "cure". This is what creates the durable, stone-like concrete. So please, don't say "cement countertops"! A cement countertop would be powder! |
| How are concrete countertops made? |
| When it comes to concrete countertops, there are two basic processes: cast in place and precast. Some contractors do one or the other; some do both. Neither is superior to the other, but there are some differences in the final product. Cast in place concrete countertops are done right on the cabinets or millwork. The forms are built on the cabinets and the concrete poured in the forms. The countertop surface is troweled until smooth and free of pinholes. Many coloring effects are possible, including integral colors and acid stains, and talented craftsmen can do amazing things with stencils or other techniques. Achieving a fine finish with cast in place countertops requires a high degree of skill with a trowel, and cast in place countertops often have more of a handmade or rough look. The process for precast concrete countertops is just like granite, as far as the general contractor or homeowner is concerned. You may be more familiar with and comfortable with this process. Your contractor will make a template from the installed cabinets, go back to his shop to make the countertops, then come back and install the slabs. As far as looks, precast countertops are more versatile. Depending on your contractor’s methods and skills, precast concrete countertops can have a fine, smooth finish or an exposed aggregate finish achieved by grinding. Your contractor can use decorative stone or glass aggregate in any color or size you want. He can embed decorative accents such as bits of copper, or even tiles to match a backsplash. There is no one right answer for the type of concrete countertop that is best for your application. Talk to your contractor about the type of work he or she does, and get creative! |
| What is the lead time? |
| Although countertops are one of the last items to be installed, concrete countertops should be selected as early as possible. Here is an outline of the process for: Precast concrete countertops: 1. Color selection (3 weeks) Because concrete countertops are completely custom, you may want to allow time for custom color development or matching. Your contractor will submit samples for your client’s approval. Allow about 3 weeks for this process. Off the shelf colors that are selected without a proof sample eliminate this step. 2. Templating from finished cabinetry (1 day) Templating is done from finished and installed cabinetry, and it takes less than one day. This is exactly the same as the process for granite. 3. Creation/Fabrication (4-6 weeks) The typical time required to craft most concrete countertops, depending on their size and complexity, is 4-6 weeks. Note that the actual creation process may not start immediately after templating depending on how full our production schedule is. A good guideline is to contact your contractor at the beginning of the project, or at the latest one month before cabinetry is scheduled to be installed, both to allow time for custom color samples and to secure a spot on the production schedule. In the case of a residential project such as a complete kitchen remodel, homeowners are usually willing to wait longer for their custom-made, handcrafted concrete countertops. However, temporary countertops can be a way to minimize inconvenience. Temporary plywood countertops are one possible solution. Or, the contractor can preserve parts of the old countertop to provide some work surfaces. 4. Installation (1 day) Because precast concrete countertops are prefinished, installation generally takes less than one day. This is almost exactly the same as the process for granite. Cast in place concrete countertops: The process for cast in place concrete countertops involves just as much craftsmanship and work, but it is compressed into a tighter timeframe: 1. Color selection (3 weeks) Again, allow time for your custom color development. 2. Site preparation, forming and reinforcing (1 to 2 days) Your contractor will take great care in protecting the job site and great precision in building the forms and preparing the reinforcement. Allow at least a full day for this process. 3. Pouring and troweling (1 day) This is the messy and exciting part. Your contractor will mix multiple batches of concrete and place the wet concrete into the forms. Concrete cures at different rates, and it takes training and practice to recognize when it is time to start troweling the concrete. There are multiple skilled steps involved, and this can be a very long day that goes well into the night if necessary. 4. Post casting work (1 to 2 days) Depending on the exact process your contractor is using, he may need to come back the next day to do some work on the edges or do other touchups. 5. Curing (1 week or more) Your contractor will protect your fresh concrete with curing covers. It is very important not to disturb the concrete during this period - do not lift the covers, and do not touch the concrete. Do not allow the concrete to be used as a workbench or storage table. 6. Polishing (1 to 2 days) If the concrete is to be polished, then a certain period of curing time is required before polishing can begin. This depends on the concrete mix used by your contractor. Some post-polishing work may be necessary that adds an additional day or two. 7. Acid staining (1 to 2 days) If the concrete is to be acid stained, all physical work must be completed before acid staining is performed. Acid staining can add a day or two, depending on the acid used and the length of time it must be left on for. 6. Sealing (1 day) Depending on the type of sealer used, your contractor may recommend that you wait a certain time period before using your countertops. There may be a required drying period after curing but before sealing. Additional time after sealing may be required to allow the sealer to cure so that the countertops may be used. These are both dependent on the sealer used. |
| Will concrete countertops stain? |
| Contrary to popular belief, concrete countertops do not need to be stain-prone and difficult to maintain. They do not have to "develop a patina". In the past few years, especially in 2004-2005, concrete sealer technology has progressed by leaps and bounds, and sealer manufacturers are recognizing that concrete countertops have unique and stringent performance requirements with regards to staining, heat and scratching. Although there is still no one sealer that all contractors use, ask your contractor what kind of sealer he uses and what its performance characteristics are. To find out more about evaluating a contractor, click here. Most concrete countertops actually behave similar to granite with respect to staining. Granite countertops are also porous and have to be sealed and maintained. Most people don’t realize this, because granite is usually too dark and patterned to show stains. |
| Will they scratch? |
| Depending on the type of sealer used, cutting on the concrete may compromise the integrity of the sealer and allow stains to permeate the concrete matrix. Ask your contractor about the scratch resistance of his sealer. If you do scratch the countertop sealer, ask whether the scratch can be repaired, because this depends on the sealer used. Even if the sealer will not scratch, cutting on the concrete will also ruin knives, requiring a professional resharpening to reshape the damaged edge. Remember, concrete is made with stone, the same thing used to sharpen knives (and will therefore dull them just as easily). No material is scratch proof. Bare concrete is generally a bit softer than granite, but if the concrete is made with granite aggregates, then the overall hardness is very similar to granite. |
| Can I put hot pots on the countertops? |
| As with almost all types of countertop surfaces, it is generally best to use trivets. Most often it is the sealer that is heat sensitive. And some sealers can tolerate much more or much less heat than others. Additionally, concrete can microcrack if exposed to high heat, and some types of sealer are not elastic enough to “absorb” these microcracks. The surface will appear “crazed”, especially when it is wet. However, again this depends on the sealer, and you should ask your fabricator how his sealer will perform. For comparison, some granite will exhibit quartz "pops", where heat causes the quartz grains to expand and pop out. And solid surface materials can crack because of their generally poor thermal expansion characteristics. |
| Are concrete countertops sanitary? |
| Yes! Read this article for information about sanitation and cleanability of concrete countertops. |
| How much do concrete countertops cost? |
| Concrete is a completely custom material, and as such it is priced on the high end of countertop materials, ranging from a retail price of about $70 to well over $100 per square foot and beyond. Some people mistakenly believe that concrete countertops should be cheap because concrete itself is inexpensive – it’s just sand and cement, right? Not quite, and the material cost has very little to do with the cost of the finished product. Violins and 2x4s are both made out of wood, so should they have similar costs? You are a design professional who understands that you don’t pay the same for an original Picasso as you would for a print purchased at Bed Bath and Beyond. Then why would you pay the same for a handcrafted countertop as you would for Uba Tuba granite that is available in Home Depot? Help your clients understand that a tremendous amount of craftsmanship and experience goes into creating a beautiful concrete countertop custom-designed by you for your client. They are paying for your design as well as your fabricator’s skill. |
| What colors are available? |
| Any color! There are thousands of color possibilities including every color on the spectrum. Your fabricator may offer a small set of standard colors, or he may leave it wide open. Some fabricators can even color-match another design element such as tile or paint. Any color can be produced in a solid, speckled or variegated pattern, depending on the fabricator’s methods. And with precast countertops you can specify embedded stone, glass, or other objects. You can specify the color, size and density of embedments. Coupled with the many color choices, you have myriad design options. Concrete is the only material that allows you to offer your clients truly infinite color options. |
| How much color variation can occur? |
| Concrete is not a homogenous, uniform material. Just like natural wood or stone, the finished concrete's appearance can have subtle aesthetic variations of shade, color or pattern, depending on the materials used, the casting and curing process and the processing and finishing techniques. Concrete is a natural, handmade material. Many factors such as humidity, sand lot and cement lot can affect the final appearance of the concrete. Even if color formulas record the type of sand, type of cement, and exact measurements of pigments to 1/10th of a gram, colors can still vary because of the aforementioned factors. Variation, especially color and visual texture, almost always occur to some degree or another. The greatest degree of variation is often seen between old samples and newly finished concrete, because the ingredients used were not identical. However, if carefully executed, all of the concrete within a particular job should look the same, even if the countertops looked subtly different from the sample. In other words, all of the variations will be similar so that the finished product looks alike. Another factor that contributes to perceived variation is simply the size of samples. A 3” x 3” sample, or even a 6” x 6” sample, will look different than a whole countertop simply because the small sample does not capture all of the natural, random variations that will occur over a large surface. The color in a 3” x 3” sample may appear completely uniform, but a whole countertop in that exact same color will not appear as uniform. The same situation occurs with other natural materials such as granite. If your client prefers perfect uniformity, solid surface might be a better countertop option. |
| What edges are available? |
| For concrete, edging is usually formed and cast rather than cut like granite or solid surface. Therefore, edge choices depend on the availability of appropriate trim moulding. For example, your fabricator may offer pencil, beveled, concave and reverse cove edging, and other custom edges may be available. Edging may be placed on top or bottom of the countertop. Concrete is the only material that allows highly decorative edges at a reasonable cost. For example, check out the following floral edge design:  This is possible in granite, but it would take a skilled stonecarver! |
| What kind of sinks can be used with concrete countertops? |
| Both precast and cast in place concrete countertops can accommodate all types of sinks including drop-in, undermount and apron front. With cast in place countertops, finishing the inside of an undermount sink hole is more challenging. And integral cast in place sinks are by far the most challenging to pull off. Concrete can also accommodate drop-in cooktops. Integral concrete sinks of almost any shape are possible, but make sure that your fabricator is experienced at sinks. Bathroom vanities are an excellent application of integral concrete sinks. Concrete vessel sinks are possible, and concrete’s versatility means that the sink can be any color and shape. Integral concrete kitchen sinks are also a possibility, but they can be challenging for engineering reasons. Kitchen sinks are deep and wide, and could have corners and angles that would put large stresses on the concrete and thus have a higher potential for cracking. Also, the size of kitchen sinks generally dictates thick concrete for the walls and sink bottom, and that can sometimes be a problem with standard plumbing and cabinetry. Integral concrete kitchen sinks can be challenging for aesthetic reasons too. The kitchen sink is just about the most heavily used area in the house, with near-constant wetness, impacts, scratches and so forth. If you do specify or purchase a concrete kitchen sink, be aware that it will most likely develop a “patina” that shows the effects of this wear and tear. |
| Are there any size limitations? |
| Horizontal countertops should be at least 1.5” thick. Thicker countertops are possible, or your fabricator may use edge returns to give the look of thick slabs without the extra weight. For vertical applications, concrete panels are generally 1” thick. The maximum slab length for standard 25” deep precast kitchen countertops is generally about 8 to 12 feet long. This is because of weight and installation considerations. Your fabricator may have specific limits based on his fabrication capacity, installation machinery or staffing. For precast concrete countertops, the maximum slab length is most often dicated by the site conditions. Stairs, corners, angled hallways, cabinet configurations, etc. all impact the ability of the fabricator to safely maneuver and install a long countertop slab. Remember, concrete does not bend! For cast in place countertops, the concrete is poured in place, so handling large rigid slabs is not an issue. However, the practical maximum continuous run of cast in place concrete countertops is generally on the order of 20 to 30 linear feet. Keep in mind that the length limitation is dictated by the concrete's physical properties. Concrete that exhibits less drying shrinkage and has a higher flexural strength can be cast in longer seamless runs than a mix that has high shrinkage and low flexural strength. |
| How much do they weigh? |
| Although concrete countertops are heavy, they are not much heavier than granite when made to standard countertop thickness of 1.5”, even with a standard non-lightweight concrete mix. Concrete countertops that are 1.5" thick weigh about 18 pounds per square foot; solid 2" thick concrete weighs about 24 lbs per square foot. These numbers may even be lower depending on the concrete mix design. For comparison, 3 cm granite weighs about 16.5 pounds per square foot. |
| What about seams? |
| Seams for precast countertops are almost always located around sinks and cooktops, or wherever required for structural reasons. Your fabricator will work with you to design seam placement that is both structurally sound and aesthetically pleasing. Seams are typically 1/16” wide, similar to tile grout lines. However, it is important to realize that concrete countertops are hand made and hand processed; they are not machine cut, so tolerances for seams can be more generous than with granite. Seam appearance is minimized by using color-matched caulk. Seams are not necessarily a drawback. Not only do they provide the ability of the countertops to flex and move (thus reducing cracking), seams can be incorporated into the overall design. Seams can be filled with color contrasting caulk. And they don't have to run in straight lines. Interlocking, or "puzzle" seams can add a great deal of interest and offer a precaster flexibility in seam layout. Cast in place countertops often don't have any seams at all. Generally long continuous runs of 20 to 30 linear feet are possible simply because the concrete is poured in place. |
| What about backsplashes? |
| Precast backsplashes are cast and finished separately and deck mounted after the countertops are installed, very similar to how granite backsplashes are installed. Backsplashes are nominally 1 inch thick and can be from 3 inches high to full height. Outlet openings are cast in, not cut on site. For cast in place projects, backsplashes can be cast as a single integral piece with the countertop, but this involves a great deal of skill and will cost significantly more than deck mounted backsplashes. Integral backsplashes are also harder to finish smoothly, and tend to have a “rougher”, less finished look. |
| How are templates made? |
| Precast concrete countertops are templated just like granite. Templating is done after any existing countertops are removed, or after new cabinets are fully installed. Your general contractor may need to arrange for existing countertop removal, or your countertop contractor may offer this as an additional service. Almost all concrete countertops require physical templates from the finished and installed cabinetry. In some cases, such as small or freestanding pieces, or islands without sinks or other holes, the contractor can use CADD drawings instead of physical templates. You will need to run full size plots for your contractor, and he can use those to create the forms. All fixtures that penetrate the concrete, such as sinks and faucets, must be physically available at templating time. Because concrete countertops are formed exactly to shape, not cut, field modifications are problematic. Provide your contractor with all of the fixtures ahead of time to insure a precise fit. |
| How are the countertops installed? |
| Precast concrete countertops are handled and installed just like granite. Seams are caulked with a color-matched caulk. The general contractor needs to arrange for plumbing and electrical hookup no earlier than 24 hours after the countertop installation. |
| Do I need to reinforce my cabinets? |
| A square foot of regular 1.5” thick concrete weighs about 17 to 18 lbs; a square foot of 3 cm granite weighs about 16.5 lbs. Typically, no special considerations are necessary for standard kitchen or bathroom vanity countertops. Cantilevered slabs, bartops on kneewalls and similar situations sometimes require brackets or other structural supports for the countertops. This is not a specific requirement of concrete, rather it is a general structural consideration that is largely material independent. Your contractor can advise on support requirements. |
| Where can I get more information about concrete countertops? |
| Concrete Network (www.concretenetwork.com) has lots of information about concrete countertops as well as decorative concrete flooring and other topics. |
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