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Picture of How to Build a Polished Concrete Desk
This Instructable documents the construction of my new Modern desk with a polished concrete desktop!
 
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Step 1: Plans!

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Plan and layout the desk. Take measurements of the location you plan to place it. Nothing is worse than building something you wont be able to use. Make sure the concrete is broken up into manageable pieces both to prevent fractures, and to make sure that it is humanly possible to carry it to its final location! Also consider styling and other design elements. I decided to build a relatively minimal and modern corner desk.

Step 2: Buy Materials and Tools

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I used:
about 30-35 board-feet of Lyptus wood,
a sheet of lyptus plywood,
some birch plywood,
2 sheets of 3/4" melamine,
2 94lb bags Portland cement,
6 50lb bags washed plaster sand,
glass fiber,
spray adhesive,
acrylic concrete fortifier,
tube of silicone caulking,
drawer slides,
drawer pulls,

Optional:
Crushed Glass,
Fiber optic cables,
other decorative elements.

Tools:
air powered or waterproof angle grinder,
polishing pad set (from Ebay),
concrete working tools,
woodworking tools


Step 3: Build the wood desk frame

I am not going to describe in depth this part, partly because I did not take enough pictures and partly because my dad mostly did this part. My desk is constructed of lyptus, which i found out is a genetically modified combination of Eucalyptus and Mahogany. It has two shelf/drawer cabinets ant the ends supporting a center frame with a pencil drawer. The main structural parts of the desk are double thicknesses of solid wood. The cabinets are made of panels holding a piece of plywood to cut down on the amount of solid wood necessary for this project.

Step 4: Construct Concrete Form

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for the concrete portion of this project I followed doubleabattery's excellent concrete counter top Instructable here:http://www.instructables.com/id/Concrete-Countertops-for-the-Kitchen---Solid-Surfa/

The form was constructed out of 3/4" melamine sheet, with sides 2" high to ensure the concrete is strong enough. measure your desk frame and make the mold accordingly. make sure to test fit your desk before casting the concrete! It is easier to make changes now than later when it is literally set in stone. Use silicone in the corners to radius the edge of the concrete when it comes out of the mold.

Step 5: Add supports and embedded objects

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Now is the time to add both the wire mesh support (I used K-lath) and any decorative crushed glass or embedded objects you wish to be exposed in the surface of the desk later! Also place any holes you want in the desktop later. wrap a piece of PVC pipe with some thin foam, then cover with packing tape to make a hole form. The pipe will tap free of the foam, then you can peel the foam/tape away. Use wire to suspend the mesh 1" above the surface of the form. this will place it exactly in the middle of the concrete. I wanted some crushed glass, so i bought some green, brown and clear glass, as well as uranium glass blobs. recycled bottles could be a good idea, any other rocks or other coins or other interesting objects can also work well! the possibilities are endless. I also bought some fiber optic cables to embed into the desk. I drilled some small holes through the melamine, inserted a fiber, then hot glued it on the other side. wire down the fibers and cables before pouring. bring the bundle of fibers together at the other end to go into a light box later. when unmolded and polished they will look like stars in the surface of the desk. Use spray adhesive to hold the glass in place in the mold so they dont get pushed around by the concrete.

Step 6: Pour Concrete!

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Once everything is all prepared, mix up 1 part cement to 3 parts sand and mix well. Add water until the texture of thick oatmeal is achieved. Carefully plop into form. Add until about halfway full, and spread mix up sides. Vibrate VERY well to gt rid of air bubbles. now mix the same concrete mix ratio but add a good amount of glass fiber, and fill mold up the rest of the way. Screed over the top with a straight 2x4.
After a day of drying, cover with wet towels to slow the curing process and increase strength. It is safe to unmold after at least 2 days, preferably three. Unfortunately i didn't vibrate nearly well enough and got some major holes in mine, but all is not lost.

To unmold, i took off the sides, then use a shovel and some bricks as a lever to lift some sides. this caused it to peel off enough to get my fingers under the lip and peel it off the rest of the way.

Step 7: Grind and fill holes

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Even if your slab has as many holes and voids as mine, the first thing you need to do is grind away the surface and expose the glass and embedded objects. The point of this is to get rid of the spry adhesive residue and stuff on the surface and to open up the tops of the holes to make it easier to fill them. Don't wear anything you don't want to get covered with concrete mud!
Next, let the slab dry and mix up some pure cement with some pure acrylic fortifier, until it is smooth and about the consistency of a shake. If it doesn't pour easily it is too thick. I found doing it in three stages worked best, as the stuff likes to shrink as it dries. spread one coat evenly over the surface, working it into the holes and voids. let it dry a bit until it has set up pretty well, then scrape all of the extra off of the surface. now repeat this process, filling in any holes you missed or holes that didnt fill all the way. Lastly repeat again, but do not scape off the extra. leave a layer of the mix on the surface in case it shrinks more than expected. let this cure overnight,then grind it off with the roughest polishing pad, probably 50 or 100 grit. inspect for any holes that didn't take the patch material well, and repeat the process if necessary. Surface should feel smooth, and the filled holes may be darker.

Step 8: Polish!

I don't have many pictures of this step since it is hard to hold the grinder, spray the hose, and take pictures simultaneously, but what you want to do is keep the polishing pads wet at all times, and slowly and evenly polish the whole surface with each pad until you reach 1500 grit. The polish pad set comes with a 3000 grit pad, but the sealer needs a small amount of roughness to adhere well. Be careful not to gouge the surface with the grinder or you will be able to tell in the shiny surface when you have finished. When it has been polished completely, apply sealer to the surface and let dry. A few coats may be desired. Buff the surface with paste wax and wipe off with a soft clean cloth or towel when dry.

Step 9: Assemble

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Assemble the desk with bolts to hold the pieces together. set the concrete carefully on top, and add any drawer pulls, power strips, or other things to finish it off. Use zip ties to route wires.
Forthcoming Additions: diy light box build to light up fiber ends in different colors and patterns! also: pictures with less wire clutter visible.
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I'm looking for a computer desk but also one I can do soldering on. is concrete polish heat resistant or would the tinniest burn wreck the whole thing
?

57weld1 month ago

what was the sealer and wax you used to finish the project?

CoolKoon3 years ago
This project sounds like an interesting idea if one wants to have a desk with a polished stone-like appearance. I've seen this project a long time ago (about 1-2 years back) as well, but a question has popped into my mind only now: how much hammering would such concrete board/desk take? And would adding a thicker mesh improve its durability? What do you think?
hivoltage (author)  CoolKoon3 years ago
Do you mean literal hammering? I have not done anything like that on this desk since I built it, but it seems very tough. Thicker mesh might improve the strength but I have not needed it just for use as a computer desk. I think too much impact would probably crack it but I am not really sure. There are other additives like polypropylene fibers and such that are supposed to really increase the strength and plasticity of concrete but was not able to find any locally when I built this desk.

I can't tell you how happy I am that I found this! First off, great design overall and the details (extension, cables hole, glass color selection, etc.) make it that much more beautiful and functional. I'm living in Morocco, remodeling a rundown storage building and trying to find ways of applying polished concrete to the floors and countertops. I'd probably have to apply the concrete directly onto the existing concrete surfaces instead of making a mold separately. I know vibration is important. How exactly did you do this in your case?

Trying to patch a concrete wall or other surface is really difficult. If you want it to last, the fresh batch needs to be bonded to the underlying rebar. This requires jackhammers and expensive contractors to chip it that deep.

Applying what would be called a 'skim coat' just leads to the concrete cracking and becoming unbonded with the original surface, unfortunately. Maybe there are other ways of obtaining your goal?

hivoltage (author)  jake.lipohar3 months ago
This is more akin to filling a nail hole in a piece of wood with putty than it is to repairing damaged building facades or freeway overpasses. The patches seem to have held well over the six years I've been actively using the desk, and are there only for aesthetics anyway. The best thing would have been if i had vibrated the mold well enough to dislodge all the bubbles at casting time, or possibly used a thinner mix of concrete to allow the bubbles to be removed more easily.

You can use a random orbital sander without a sanding pad against the frame as a small vibrator and that will work for smaller projects. Even a larger sander would work, too. It may even be possible to use a reciprocal-saw without a blade against the frame as well, but I haven't tried that. It has enough vibration that I would think it would work, though.

Thank you, I'll give it a try! :)

Yeah, I meant its usage for hammering stuff like you usually do in a workshop. Thanks for the tips though ;)
ericgoetsch9 months ago

COST?

400-500 Dollars, depending on the wood choice. This is assuming you have the woodworking tools to make the desk frame.

Hi! Thank you for tutorial! It's really inspiring.

I have a quick question that may lead to another question. :)

I'm quite interested in the glossy finish of the concrete surface. As from your instructable I understand that the mixture of concrete and acrylic substance is applicable for flat surface only. What should I do if the shape will be more organic? Like flattened big mango 200x200m?

cool

peets1 year ago

it louks goud but i hav mine and chec out my pae if you watn mour. i no i am onley a smal giy but myn louk rilley rilley goud. i noe plees chec out my payge even if i onley hav liek enuff insdutraclbes

GymGeek1 year ago

I made one like this, thanks for the advice on the type of sheets.

mrman171 year ago

To help remove air pockets, you could use an electric sander without the sand paper, hold it at various points around the mold.

This looks awesome! I might just give it a try!

One of the first things I noticed in the pictures, however, is that Fox-body Mustang in the background. Nice job!

chetchez1 year ago

Instead of daisy-chaining the power strips, I really like the Fellowes 10 Outlet Split Surge Protector (Model FEL99082) - Safer and you don't lose an outlet!

this looks very interesting - i have a kitchen counter refurb and granite is v expensive...

sarliaee5 years ago
Windows 7 was my idea. Concrete Desk was yours. Congratulations. Beautiful job!
 So you're to blame for Windows 7.  Widows 7 convinced me to give up and switch to Mac. LOL
i love you. :) ha ha
And Mac convinced me to quit and switch to Vista Ultimate.
I just switched to Linux on my own. lol
then that convinced me to switch to linux since that broke. I post a video sometime. remind me. basically, going to the grub menu, then choosing windows, it says "Loading Windows Vista" along with a progress bar, then when it finishes, the screen turns black and it sits there. I've let it sit for an hour before.
archion hintss4 years ago
And the combination of frustrations from Linux, MAC, and Vista have convinced me to be very thankful for the stability of Windows 7 :)
This is probably my final windows operating system though, I refuse to operate off of a cloud. (Win 8 is cloud based)
It amuses me that 18 months on suddenly people are commenting on a lighthearted comment I made about Windows referring to their TV ad. It did end in LOL which I assumed everyone knows the meaning of. I still posses a laptop running 7 (I don't like the Mac version of MS office) and it crashes quite often.
hintss archion3 years ago
switch to linux soon?
altomic archion3 years ago
aside from instructables i use pen and paper.
*LIKE BUTTON*
agiledesign4 years ago
Just wondering if you poured it on a piece of glass if it would have saved some time polishing it? I've considered doing my kitchen counters in a similar manner. Great looking result. Nice write-up and pics too.
hivoltage (author)  agiledesign4 years ago
Yeah that probably would create a perfectly smooth and shiny surface right out of the mold, if you can manage to shake all the bubbles out of the concrete. I definitely did not anticipate how many bubbles there would be or how difficult they were to get out of the poured concrete. Also, I wanted my embedded glass shards to show in the finished slab, and they were covered by a thin layer of the concrete when I unmolded it. The only way to expose them was a quick grind with the 50 grit polishing wheel. I saw on one of those shows on hgtv they poured some countertops but used a sheet of thin, hard plastic in the bottom of the mold and the countertop came out of the mold ready to go.
I've seen a thick Mylar (brand name) plastic used for glossy slick surface molding. Mylar is the stuff used for model airplane wings and body skins.
hivoltage, where did you buy your glass shards from? Or do you have any recommendations where I might find them? Thanks for your help.
hivoltage (author)  shelycel264 years ago
I don't remember the name of the site, but google doesn't turn up anything familiar, so they may have gone out of business since I published this instructable. I found one site but the minimum order per color is five pounds at 3 dollars a pound
http://www.recycled-rocks.com/Glass-Gravel-p/gravel.htm
I believe I bought five pounds of earth tone mix and a pound each of extra green and teal for my desk.
there is a special sheet of plastic! is shiny and mostly used for columns that can give you a similar finish! also is easier to vibrate with a rubber mallet just hit the form with the mallet several times, this will ensure that all the cement goes down preventing air bubbles so the final product is even and shiny!!
Shiny? I could guess someone could use Polyethylene/Polypropylene sheet since almost NOTHING sticks to it- http://www.usplastic.com/catalog/item.aspx?itemid=23655&catid=705. It's also sold at retail hardware/home improvement centers as plastic drop cloth 4 mil. but this can wrinkle and I've never actually done it this way since it would probably not be very shiny.
pgiambat2 years ago
That is one GREAT looking desk, great job! I so want to try this too. I'm thinking I might start with a workbench top.
nitsuj10982 years ago
Still waiting for the light box instructable and lit up and night pictures...
;-)
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