Start Small to Polish Your Concrete Countertop Skills
Concrete countertops are becoming more popular, and they fit well in many old homes. They can complement the rustic ambiance of a classic old house, yet they also can bring elegance akin to granite. But even if you are a confirmed DIYer, you may have some consternation over trying to make your own polished concrete countertop.
Why not take some mini-steps to get the hang of it? Try making a couple small, polished slabs first. You might use them for small tabletops for your patio, or maybe mount your house numbers on one to hang at the driveway entrance.
Tips to Start
Here are some tips to get you started on a small-scale project:
- Size. For easier handling, you probably don't want anything bigger than 2' X 3' and a couple of inches thick. That will use two 80-pound bags of concrete, more than you may want to lift.
- Mix. Investigate buying bags of special countertop mix. If you can't find a special mix, just get a couple bags of ready-mix to play with.
- Forms. Keep it simple, using a chunk of plywood and two-by-fours, or rip a two-by-four to give you a 2" depth. Be sure to use a release agent on the forms--a thin coat of vegetable oil will do.
- Steel. 3/8" rebar or 3/16" steel reinforcing wire can be used to strengthen the slab. For small slabs such as this, the reinforcing wire actually does a better job.
For proper polishing, you should use a variable-speed polisher with water feed for wet polishing. You can purchase a set of diamond-embedded polishing disks (grits of 50, 100, 200, 400, 800, 1500, and 3000) for around $200.
If you don't have these items, don't despair. You can fake it for your small slabs, using a belt sander and reciprocating sander--you're just going to burn through a ream of sandpaper.
If your finished product will have exposed aggregate, you can start grinding down the top layer (grits 50 through 200) with your belt sander four days after pouring the concrete. Wait until ten days to begin the polishing (400 grit and up) with the reciprocal sander.
At the 400-grit level, you can coat the slab. Make a slurry of cement and water (add some fine sand if you'd like) to fill pin-holes and achieve a truly glistening surface. Let it dry a couple of days before resuming the polishing. Work your way up to the 1500 or even 3000 grit. The local box store may not have anything finer than 400 grit, but you can buy the finer grits at stores that sell auto-body repair supplies.
Be patient. Do a thorough job with each grit and don't skip a level, and you should be amazed by the luster. Add a couple of coats of a glossy sealer to, well, seal the deal.
Multiply the effort of your test run by several times and you will get an idea of whether you want to tackle a full countertop. It's a huge project, but it also can be hugely rewarding.
Jim Mallery, a semi-retired journalist and onetime registered contractor, has extensive experience remodeling, repairing, and rebuilding homes.