A full How-To on building concrete countertops
This project was one that I had been waiting on for 10 years to do. The house my wife and I were in, having concrete countertops, really didn't fit the look of the house. What you will find here is the final executed approach I took to make beautiful countertops and vanity top. ...And if you choose to DIY you will find that the cost is around that of a standard Formica top... even with buying the tools needed to build it.
There is a lot of details that go into making concrete countertops. This document is organized in a way to take you through the correct order of planning and building your masterpiece. (This page is in process of being built, we will remove this message when complete. Document is complete through "Install" and is currently being proof read.)
- Tape Measure
- Circular Saw
- Impact Driver
- Countersink Drill bit set
- Fine point sharpie
- Utility Knife
- Scraper Blade
- Putty Knife
- Speed Square (12-in recommended)
- Orbital Polisher with Wet/Dry Shroud, 4in to 5in Velcro Backer Pad and water pump
- Orbital Sander w/ Shop Vac hookup
- Shop Vac w/ bag (The bag is important as you will be collecting fine dust)
- (8x-12x) 5 Gallon Buckets (1 clean water bucket, 1 dirty water bucket, rest are for cement prep which is explained later in this page)
- 10lb digital scale with OZ option measurements (Typically these are kitchen scales)
- Concrete Mix (Details See "Picking Your Concrete")
- Base concrete mix or separate components
- Sand (If you are looking for a light color, silica pool sand is a good choice)
- (2x-4x) 2x4x8 Premium Board (Straighter = flatter countertop)
- (2x) 3/4" MDF 4x8-ft Sheet
- 3/4" Melamine Bull-nose Shelving (Qty depends on how many surfaces/size you will be creating)
- Blue Painters Tape
- Vinyl Tape (Width >= Thickness of the countertop)
- DAP Black Silicone
- Paste Wax
- Paper Towels
- Screws for Edging - Vertical (Length = Countertop thickness + 1/2")
- Screws for Edging - Horizontal (1-1/2")
- Composite Shims
- Sandpaper for Orbital Sander (100 grit)
- Foam Sanding Pad (100 grit)
- Wet/Dry Diamond Polishing Pad Set (4"-5" -- 50 grit to 3000 grit set)
- 2-in Extruded Polystyrene Foam Board Insulation (Sink Cutout Areas)
- Sink Mounting Hardware (See "Mounting Sinks" section under "Planning the Build" for hardware options)
- Color Additives
Basic Rule of Thumb when making concrete countertops... Do test runs and practice pieces! No two concrete mixes or brands are the same and have the same look. This is why it is important to pick your concrete before you start pouring your countertops. With countertops you are striving for a higher PSI concrete but that doesn't mean you have to buy the concrete that is rated at a higher PSI, the mixture that I will include in this post will include a pre-mix concrete with the additions to the mix that will make it more to the grade you are seeking.
Some Concrete Pre-Mixes I have tried and feedback...
- Quickcrete 110180 (80lb) Concrete Mix
- This concrete is very consistent bag to bag. It has a Medium grey tone naturally with a normal amount of small aggregate. You pay a little more per bag but you are paying for quality and consistency.
- Handi-crete 80lb Concrete Mix
- This concrete is made by the Quickcrete company but it is not the same consistency as your standard Quickcrete. Over about 40 bags of this stuff I have seen 2 bags of just sand and aggregate (5% failure rate). This concrete is cheap per bag but you may run into a bad bag here and there. Now this is the concrete I used for my kitchen countertops and they are beautiful and were completed March 2019.
- Mastercraft 60lb Concrete Mix (Menards)
- This concrete is a similar story to the Handi-crete. Consistency isn't 100% but usable. Example... Just helped a neighbor pour a concrete pad behind their house with this stuff and it looks like a semi-professional concrete professional did it. (Kinda) Aka... it does the job just pay attention when mixing a bag.
- Mastercraft 60lb 5000psi Concrete Mix (Menards)
- This stuff was a bit of a surprise. So much so that I almost scrapped all the other pieces I had already poured to re-pour in with this stuff and I was 75% done with the kitchen tops. This stuff has a really neat color naturally. It is a deep grey with a hint of blue. Consistency was good with the 5 bags I used. With doing a test run if you are looking for a darker look and don't want to use pigments.
- Mix your own concrete
- If you want to guaranteed quality and consistency then this is your only true option. This will add a little more measuring to your prep work but it will get you good consistent results. See "The DIY Mix" below for the mix I used on the bathroom vanity. And oh BTW you might want to get a higher capacity scale.🤓
Rule of thumb... the flatter the table, the flatter your countertops will be. Keep in mind too the amount of weight that this table will be holding so do not cheap out on the saw horse you use. This is my recommendation for a 4-ft x 8-ft pour table.
- 1.Take 3 saw horses and space them out about 3.5-ft apart.
- 2.Place two 2 x 4 x 8-ft boards in the board slots between the 3 saw horses
- 3.Place a 3/4-in x 4ft x 8ft MDF board on the saw horses and 2x4's
- 4.Secure down with wood screws the MDF Board to the 2x4's
- 5.Place a second 3/4-in x 4ft x 8ft MDF board on the first MDF board.
- 6.Secure down with wood screws the second MDF board to the first MDF board with just 4 screws, 1 screw in each of the 4 corners
Once the table is setup, this will be the base that you will place the melamine sheet on top of and build your mold on top of the melamine sheet.
Note: The melamine is something that concrete will not attach to and will create a very smooth surface.
Remember that concrete is a fluid material and when you pour countertops the mixture tends to be wetter than if you were pouring a floor or sidewalk. With that leveling the table will help in things spreading equally and at a consistent thickness naturally.
To help work out the bubbles vibrating the table is the key, otherwise you could get large number of air bubbles on the downward surface which will eventually be the top. I have included a link in the tools section of this document for a purchased table vibrator. (Do this at your own risk) One DIY way you can make a table shaker is with an old treadmill motor. The nice thing with treadmills are the motor controller system is variable. Meaning you can control the speed of the motor. One additional thing to add is a weight on one side of the motor to put the motor out of balance creating the vibration when it turns. PLEASE, PLEASE, PLEASE be careful, you can tear apart the table and mount by doing this and increasing the speed too high.
Initial testing of the treadmill motor as a table shaker. BE CAREFUL! Try at your own risk!
Treadmill Motor running (White box is the motor controller and speed control)
PLAN YOUR BUILD!!!!!! It is best to draw out your countertops and measurements. Don't just make a mold blindly. I'm a huge Fusion 360 user so if you have the skills with a parametric design software, drawing up countertops are easy. If you don't have these skills, grab a piece of paper, a ruler, and pencil and draw things out.
Example of Countertop Drawings
Vanity Top Depth: 22-in Kitchen Countertop Depth: 25.5-in Back-splash Depth: 1-in Sink: Sinks come in all shapes and sizes, pick out your sink and typically they come with cutout dimensions regardless if they are an under mount or top mount sink. Kitchen Sink Faucet Placement: From back of countertop... 2.75-in (It really depends on the sink you choose as the correct placement and with some sinks they will tell you where to place the faucet in relation to the sink) Vanity Faucet Placement: From back of sink opening... 3-in (It really depends on the sink you choose as the correct placement and with some sinks they will tell you where to place the faucet in relation to the sink)
This is always a creative part of the build for under mount or farm sinks. If you can build a frame in the cabinet for the sink to sit on, this is the most reliable means for mounting a sink. Other ways are using epoxy clips or cabinet mount clips. Just make sure you figure this out before you start pouring sink molds. I thought of clips after the fact and I had to do in place mods which is never fun, easy, or convenient.
Molds can give some added character and functionality to any countertop. From Edge Molds to Soap Molds to Drying Boards. Molds come with a price though. If you are doing this professionally mold costs can be spread out over many tops. Visit Expressions-LTD for a site that has a good selection of molds.
When it comes to edge molds, remember to account for edge mold added dimension when designing your molds. Visit Expressions-LTD for a site that has a good selection of edge molds. If you want a square edge with a rounded corner this can be done with just the edge of the mold, silicone, and a metal ball caulking tool. This will be addressed later but worth noting here so you plan for the right look. Using a square edge with a rounded corner adds no extra cost to the build.
Mold for creating a Square edge with rounded corner look. (Silicone spill over shown)
This is upside-down but shows you a top made with an edge mold
Remember that you are pouring the countertop up-side-down. So what is left is right when setting up the mold... sink fixtures, corners, etc are flipped.
Cutting the Edge Strips: If you were wondering why you were buying bull-nose melamine shelving, well you are gong to cut this into strips at the thickness of the countertop you are wanting to pour. Use a table saw or circular saw to cut your edges.
Marking the Mold: Marking your surface before you start setting your edges is highly recommended! Using a fine point sharpie, mark out the melamine sheet and where your edges will be placed. Make sure your measurements and angles are square, the last thing you want is a countertop that isn't square.
Securing your Edges: There are a couple rules to live by when setting your edges.... 1. Set one edge first and then work from that 1 secured edge. 2. Double check you are square, edges are straight, and your dimensions are correct as you secure things. 3. Pre-drill and countersink all your holes so the screw head sits below the surface of the top edge. 4. Connect the boards at the corners so the entire mold is tied together.
This is going to be the most challenging part of the mold making process depending on the tools you have available... specifically sinks and cutout with inside rounded corners. Personally I have a 3D Printer and a CNC router which gave me some options for this category.
Sinks and Cutouts: If you are doing this by hand or have a CNC router, cutting the sink opening in extruded polystyrene foam would be the easiest solution. If you have a 3D Printer the models for the inside corners are posted for download. Once you have cutouts / sink edges set, wrap the area (edges) that will make contact with the concrete with Vinyl Tape. (3D Printed corners) The vinyl tape will help smooth the surface between the printed part and the melamine. (Foam) The vinyl tape will help smooth the surface and seal off the foam where it would contact the concrete.
Faucets: Faucet biggest challenge is proper placement because there really isn't a hard and fast rule on where a faucet needs to be placed. Once you have picked a place for your faucet to be then you need to place your plug. Plugs typically are made out of silicone and you can buy them at Expressions-LTD. If you are like me and have a 3D printer you can print plugs that I have designed and are pictured below.
Cutout area with 3D printed corners and Sink faucet molds
Cutout for a Kitchen Sink made out of Extruded Polystyrene and Edge taped with Vinyl Tape
This category of prepping the mold is pretty easy... To attach any molds to the form use silicone on the back of mold and press against the surface of the mold you wish it to be placed. Just make sure you clean any silicone up that may protrude on a surface that might create a flaw in the surface of the concrete.
Before you seal the countertop mold you will want to make sure that any edge molds and/or misc molds used are secure... aka the silicone used to secure them has solidified.
Sealing the mold is necessary regardless if you want a rounded edge or not. You are welcome to pour without sealing (Water proofing) your mold but I wouldn't do it. All the work up to this point is worth the extra step of sealing the mold.
Step 1: Waxing your Mold
Now this one took me a while to figure out. All the videos I watched and sites I visited never really emphasized this step or they said to do it but never were specific as to what really to use. And after pealing off gobs of silicone stuck to the surface of the melamine using a putty knife and scraper knife. I caught a video of "This Old House" which has a couple second blip that showed the can... it happened to be SC Johnson Paste Wax. This is the magic that makes silicon-ing the edges of the mold so much easier when cleaning up.
Taking a rag wipe down the inside of the mold with Paste Wax everywhere silicone will be applied to an edge or where the silicone might spill over.
Step 2: Sealing the Mold
Using the black silicone, run the silicone around all the sharp edges in the mold and potentially at the base of any edge molds that require a finish rounded edge.
Step 3: Finishing the Silicone
Using the Metal Ball Caulk tool (Whatever ball diameter you desire), run the ball over the silicone you laid in "Step 2". The excess silicone will spill over the sides of where you run the tool. This is normal, we will clean it up later. If your ball gets too much build up of silicone use paper towels to periodically clean it off. Once you are done let the silicone fully cure, even the spill over.
Step 4: Cleaning up the Mold
Once the silicone laid in Step 2 and 3 is fully cured, peel away all of the spill over created in Step 3. Fix any areas that need fixed, repeating step 2 through 4 until you are satisfied with the mold.
Step 5: Taping your screw holes
All of your screw holes, take painters tape and cover the screw heads. When you de-mold your countertop and you don't have to dig dried concrete out of a screw head you will thank me for this step.
Now these are my cheesy descriptions but you will get the point... A.k.a. What look are you going for? Do you want the natural rock in the cement to show? Do you want a smooth, unblemished look? Do you have some cool stone, glass or whatever to show through the surface? And hey, What about something other than Grey?
The Sections to Follow will collectively make up the look of your countertop. Understanding the look you are going for is important.
Are you wanting to see the natural aggregate in the concrete? During the wet polishing step during finishing you are going to want to start with a heavier grit diamond polishing pad. Polishing until you get the desired look.
A smooth consistent surface with little to no blemishes... Muwah Perfect! (I'm Italian... its like making the perfect dish or desert. That comfort food that just hits the spot every time.)
This look can be achieved 2 different ways. One way is a higher guarantee of look than the other but with a higher guarantee comes more work.
Easier but a lower guarantee: In the wet polishing process you start at a higher grit of diamond polishing pad (around 400 grit). The idea here is you do not want to remove as little of the surface as possible so you do not expose the aggregate directly below the surface.
Harder but a higher guarantee: When you are mixing concrete you mix 2 different batches. One batch you mix is a mortar mix with no aggregate. Instead of mixing the entire counter at once you mix the mortar first and lay it, let it set (harden) Once it has set, then mix the rest of the concrete with aggregate and pour the rest of the countertop. This will ensure that the top surface of your countertop has no aggregate regardless of how low of a grit of diamond you start with.
So yeah... I don't even know where to begin. Have you ever picked out paint colors for your house? ...yeah this is kinda like that. Just like picking out paint colors, pigments for concrete are about as plentiful. All I am going to say is start HERE. (If you need to calculate how much pigment you need, Direct Colors have calculators for their pigments and how to documents to use their pigments. Oh and psst they sell samples too!!!!)
Looking for that aggregate to compliment the room or compliment the color you chose for the concrete. Or maybe you want to embed something in the surface of the concrete. Now embedding something in the surface is a level above moderate skill level but all these are possible.
Doing custom aggregate (Crushed Glass or Granite) means mixing your own concrete and doing a similar process to what I spelled out in "The Silky Smooth Look" - "Harder but a higher guarantee" but to minimize the amount of aggregate needed you place the aggregate in empty mold and pour mortar over the mortar. This places the aggregate at the surface so when polishing you expose the custom aggregate.
Note: I am playing around with using spray adhesives to find the right adhesive that makes the aggregate stay in place when pouring but pops from the mold. More to come on this technique.
Your mixture is key to a good countertop pour. Just like its takes just the right cake mixture to make the perfect wedding cake... too wet and the cake will sink, too dry and well let's be honest not many people like dry cake. Just like a cake mix concrete needs the right mix of elements for it to turn out the way you want. Make sure with all mixes you account for humidity as this will change the amount of water you use in your mix.
Also, If you want to make it easy on yourself... GET A CEMENT MIXER!
This concrete mixture is designed for an 80lb bag of pre-mix concrete. (Yield 633sqin @ 1.5in thickness, 994.5sqin @ 1in thickness, Yield 474sqin @ 2in thickness, Yield 316sqin @ 3in thickness):
- 4-liter of water @ 50% Humidity, 4.5-liter of water @ 35% Humidity
- 80-lbs bag of pre-mix concrete (I used Handi-Crete which is made by Quickcrete)
- 5-lbs Portland cement (Grey or White)
- If you have clumps in your portland cement use a flour sifter to break it up and sift it into a fine powder.
- 1-oz (weight) Plasticizer/Water Reducer
- 2-oz (weight) Chopped Glass Fibers (Optional)
This is a custom mixture of concrete that I have used for both a mortar style mix (No Aggregate) and concrete mix on countertops. (Yield 664sqin @ 1.5in thickness, 1044sqin @ 1in thickness, Yield 497sqin @ 2in thickness, Yield 331sqin @ 3in thickness):
- 4.25-liter of water @ 50% Humidity, 4.75-liter of water @ 35% Humidity
- 20-lbs Portland Cement (Grey or White)
- 30-lbs Sand
- 40-lbs Aggregate (optional)
- 1-oz (weight) Plasticizer/Water Reducer
- 2-oz (weight) Chopped Glass Fibers (Optional)
** If you haven't obtained a cement mixer at this point you will have to figure out the best way to mix without a mixer. I will be talking only to the order of mixing for a cement mixer. **
- 1.Pour all the water and plasticizer in the cement mixer.
- 2.Slowly add the Cement Mix / Portland (Portland, Sand and Aggregate in that order for the DIY mix) in the cement mixer.
- 3.If you are adding fiberglass reinforcement, Add the Chopped Glass Fibers in the mixer.
- 4.Let it mix thoroughly for a period of time. Add portland if the mix is too wet. Add water if the mix is too chunky or dry.
Before you mix a bag, pour it, and mix another bag, pour it... STOP! This was a huge mistake I made when I poured the first large area countertop that required more than 1 batch of concrete.
Step 1: Mix all your concrete and pour into buckets until you have all the concrete your need, then pour all the buckets one after another into your mold. You will get better results and a more consistent pour. If you plan on inlaying mesh or steel reinforcement this is the time to do it.
Step 2: Once you have poured all your concrete spread the concrete to the areas of the molds to get a consistent thickness throughout.
Step 3: Turn on your table vibrator. If you have large areas of standing water you can pour dry sand and portland in these areas to soak up the water and fill the areas. This is also the time to smooth the bottom of the countertop. (Do your research on proper forms of smoothing / finishing concrete. I honestly did a little smoothing as it cured but didn't spend a ton of time and they still turned out great.)
This will not be addressed in this blog post but do some research it is a really cool technique for creating countertops. You are spraying the concrete into the mold to either create a consistent surface or to seal specialty aggregate at the surface of your countertop. Once you spray the surface and it sets you then fill in the rest of the mold with standard concrete.
Patience is a virtue... The slower the cure the better. As a general rule you should not move your piece for 5-7 days. If the piece has a sink cutout, do not move it. On day 3-4 you can de-mold your countertop.
Planning the flip is important, especially if you have a cutout of some sort. The use of boards and clamps to keep the countertop from twisting during the flip is critical. You do not want to throw away 5-7 days of work.
Using boards and clamps to keep the countertop from cracking during the flip.
This is where you are going to achieve the look you desire but just like woodworking you can mess up a project in one over sanding or measure-once-cut-once bad cut. You are polishing a rock that could expose unexpected things. It is highly recommended to make a test piece and practice your finishing techniques. You don't want hours of pouring and days of curing to be wasted by over finishing the countertop.
The Graveyard... Where test countertops went to die (And great reinforcement under my porch)
(This is the process where you can expose the aggregate in the concrete)
- Orbital Polisher with Wet/Dry Shroud, 4in to 5in Velcro Backer Pad and water pump
- Wet/Dry Diamond Polishing Pad Set (50 grit to 3000 grit)
- 5 Gallon Bucket with clean water
- Diamond Hand Polishing Pads Foam Back
This process is just like sanding or polishing anything. You start with a coarser grit (50-400 grit depending on how much aggregate you want to expose) and work your way down to a finer grit (3000). Make sure to do at least 2 passes per grit and each pass direction 90 degree from the previous pass.
Using the concrete mixture you used for your countertops, separate the aggregate from the sand/portland. We are separating the mix so we can get the same color concrete as we did in our initial poured mixture.
In a solo cup, mix together the sand/portland with water until the cement is a thinner paste consistency. Pour on the surface of the countertop and spread with a 6-in to 8-in drywall taping knife. The goal here is to fill any small bubble holes in the surface.
Let Dry. Repeat if needed.
Once the slurry is dry using an orbital sander with 100 grit sand paper and a shop vac, sand the surface. You are trying to sand down all the excess slurry that is not filling an air bubble hole. Do not worry, you will not hurt the surface. Make sure you wear a respirator during this process even though you have your sander hooked up to the shop vac.
- Orbital Polisher with Wet/Dry Shroud, 4in to 5in Velcro Backer Pad
- Wet/Dry Diamond Polishing Pad Set (400 grit to 3000 grit)
This process is just like "Step 1: Wet Polishing" just without the wet part. This time start with a finer grit (400 grit) and work to a finer grit (3000 grit), doing the 90 degree offset per pass. Just like in step 1 each grit gets at least 2 passes.
As much as you want to install the countertops and revile in the beauty you need to seal your work. There are 2 different ways to apply sealer, Foam roller or HVLP Spray gun.
Foam Roller Application:
This application process is going to appeal to most people because not everyone has the air supply to run a HVLP Sprayer let alone have one. By far, if you have the equipment to run a HVLP sprayer, do it! It will give you an exceptional finish.
The goal with using a foam roller is to apply thin coats of sealer. You may need to sand between coats using 400 grit sand paper. Apply at least 5 coats.
This application process takes less coats since each layer is thicker with a sprayer than if you foam roll the sealer. Apply 2-3 coats.