How to Complete the Form and Pour Concrete for a Vanity Top
DIY pros show how to complete building a form and pour concrete for a customized vanity top.
Following set up of the concrete vanity top for about 48 hours, begin deforming by uncovering the plastic. Clean the concrete residue off tops of the rails and knockouts with a flat bar. Remove all screws from the form, including those which affix the smaller knockouts to the form. To avoid breakage, once each edge is exposed, smooth the corners with a metal file or grinding wheel.
De-form the backsplash shelves first. Remove the rails and pull off the shelves. This may take a little elbow grease as they may be attached to the melamine with silicone. Use caution as you work because the concrete in green form (new and not at its final strength) damages easily. Set the shelves aside.
Remove the curved and side rails of the main vanity piece and double check screws are removed from the knockouts. Flip the form onto the remaining rail and then carefully onto its back. Because of the weight of the form, it's helpful to have several people helping. If the melamine doesn't release easily, gently bend it. If it's difficult to remove remaining knockouts, gently tap them with a hammer and a small wooden block or blunt instrument.
Once you de-form the concrete, allow a few days for set up before grinding to expose the buried glass. Concrete takes 28 days to cure completely, so the glass is still harder than the concrete that surrounds it, which helps in exposing the embedded glass. For this project, we rented a water-fed grinder. If you use one, move to an area where you can work with water and wear garbage bags as it's a wet process (Image 1).
Start grinding the surface with a 50-grit diamond pad on the grinder, using a circular motion under steady pressure (Image 2).
Be careful as you work around the edges as these can still damage easily. Continue to use the 50-grit diamond pad until the buried glass is exposed (Image 3).
Follow up with finer grit pads, working up to 400- or 800-grit diamond pads. You're trying to create a finished surface that will be smooth to the touch with a matte sheen when dry. If your project has backsplash shelves like ours, save yourself time by not grinding the area where they sit.
Let the vanity pieces cure at least another few days before sealing and polishing
Seal the countertop by spraying it with potassium silicate, a densifier. Apply the sealer until the concrete surface and sides are thoroughly wet but not dripping (Image 1). Wipe off excess sealer (Image 2) and allow the surface to dry.
Finish off the vanity top by applying bowling alley wax. Take the applicator and apply the wax in a circular motion. Finish by wiping off excess wax and polishing with a dry terry cloth towel (Image 3).
Once polished to satisfaction, the countertop units will now be ready to install (Image 4).
In our project, we used a pedestal base to support the vanity top against the wall. Set up your pedestal or base where it will stand and then install a wall cleat at the exact same height so the vanity can rest on this for extra support.
Dry set the vanity to make sure that it fits on top of the pedestal and wall cleat then make sure that it is level. If it's not, you can add a small wooden shim. Mark the vanity location on the wall with a pencil. Set the vanity down on top of a blanket or wooden blocks as it will be easier to get your fingers underneath the edges later.
Run construction adhesive on top of the pedestal, against the wall and on the top of the wall cleat. Reset the vanity by lining it up with the mark on the wall. Add any shims and check for level. Set the backsplash shelves with their hardware with silicone caulk to provide a waterproof seal. It's also easier to remove than construction adhesive if you ever need to change the sink's hardware.
The last step is adding the vessel sink and the hardware. Have a plumber come in to hook up the plumbing, as necessary.
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