I am embarrassed to admit this, but there are a lot of unfinished projects hanging over my head: unglazed planters, unframed wall hangings, and of course, ungrouted mosaics. I find I have bursts of inspiration and my excitement propels me to complete maybe 90% of the project before my interest wanes and I move onto something else. It’s a bad habit, I know. And all these unfinished projects are constant reminders of the long list of to-do items cluttering my studio. So, every once in a while I make the resolution to complete at least one of my orphan projects. Every piece deserves a chance to reach its full potential, right?
My neglected mosaic pieces, waiting patiently to decorate a tabletop.
|
A couple years ago I picked up a small end table with a metal base from a thrift store ($4, yeah for thrift stores!), and decided to replace the original grubby tabletop with a custom-made mosaic. I created my design, cut out all the tiles, bisque fired them, glazed them and fired them a second time before my momentum petered out. All that remained was to set the mosaic pieces into the tabletop, but at that point I could not be bothered with the effort – I had moved on to something much more exciting (and now unremembered). My husband commandeered the end table for his own purposes, and there the situation stood for two years or so. Recently, as I was cleaning out the hard-to-reach recesses of my studio, I came across the pieces to the mosaic tabletop and decided time enough had passed. The day had come to finish the project!
Project:
Creating a Mosaic Base for a Custom Tabletop
I really wanted to cram everything into one post: creating the base for the mosaic, setting the mosaic and grouting the mosaic. In the beginning it didn't seem like too much information to discuss at once. But, apparently, I tend to ramble on a bit, and this post was getting a tad long, even from my perspective. So, in the interest of size, I have decided to split it into two posts. The first part will deal with prepping the base for the mosaic from cement board. The second post (Piece by Piece (Part 2): Setting and Grouting a Mosaic Tabletop), will cover - can you guess? Ding, ding, ding! Setting and grouting a mosaic. So, enjoy!
A Note on Mosaic Substrates
A variety of substrates can be use as a base for mosaics, such as cement board, Hardiebacker, custom mixed cement, and Wedi Board. Each material has its advantages and its drawbacks.
Cement board, used as a water resistant material in bathrooms, can be found at home improvement stores in common thicknesses ranging from ¼” to ½”. The backer board is sold in large sheets, usually 4 feet by 8 feet, and is basically a layer of cement sandwiched between mesh to hold it together. It can be cut to the desired dimensions for the project at hand, and used for indoor and outdoor applications.
Cement board, used as a water resistant material in bathrooms, can be found at home improvement stores in common thicknesses ranging from ¼” to ½”. The backer board is sold in large sheets, usually 4 feet by 8 feet, and is basically a layer of cement sandwiched between mesh to hold it together. It can be cut to the desired dimensions for the project at hand, and used for indoor and outdoor applications.
Cement backer board (Durock, brand name)
|
Stacked 1/4" cement backer board
|
HardieBacker is a brand of cement backer board which can also be picked up at your local home improvement store. While traditional cement board is comprised of cement, HardieBacker is made of a mixture of cement and cellulose fiber. Is it somewhat water resistant, but not to the extent of traditional cement board, and therefore should only be used for indoor projects. However, HardieBacker, in my opinion, is easier to cut and generally easier to use since it is lighter than traditional cement board.
Stacked Hardiebacker board.
|
Hardiebacker board with cutting grid visible.
|
|
Wedi Board is another variation on the traditional cement board. It is comprised of a foam core wrapped in a mesh and coated with cement. Like cement board, it is water proof and can be used indoors and outdoors. However, since the bulk of the board is the foam core, it is significantly lighter than regular cement board as well as HardieBacker board. The main drawback is that I have not found Wede Board at my local home improvement store, and thus have never used it myself, though I have heard great reviews.
|
Wedi board (various thicknesses).
|
Mosaics can also be set on (or directly into) a poured cement surface. Poured cement is water and weather proof, and can be used both indoors and out. It holds an advantage over the cement boards in that it can be easily formed (without cutting) into basically any imaginable shape, including three-dimensional forms. There are also ways to mitigate the weight of the cement by using armatures for 3-D constructions, or adding peat moss to the cement to form what is called hypertufa.
Tip: Sometimes you will see mosaics set on pieces of wood. However, even manufactured wood tends to expand, contract and warp over time when exposed to moisture and temperature changes. I prefer cement backer board as a base for mosaics since bases of a cement-based material are waterproof and thus more stable and do not tend to warp.
Since this end table will be used exclusively indoors, I chose ¼” Hardiebacker for the base of the new tabletop since it is easier than cement board to manipulate. Since my tabletop is relatively small, the ¼” board should provide enough support for the mosaic. For larger mosaics, it is wiser to use a ½” cement backer board that is well supported. As mentioned above, Hardiebacker is not for use outdoors since heavy, sustained moisture can damage it. If your project will be used outdoors, choose a traditional cement board instead.
|
Materials:
|
My $4 thrift store end table find, complete with metal base (good) and grubby tabletop (bad).
|
Safety Note: When drilling and sawing, be sure to wear the appropriate personal protective equipment, including safety glasses, respirator and ear plugs.
Step 1: Remove the Old Tabletop
Sometimes it is possible to set your mosaic directly on the existing tabletop, depending on the material of the tabletop. My tabletop was thick and heavy, of indeterminate material. Since my mosaics would add a significant amount of weight and thickness, I decided to remove to old tabletop and start fresh.
The bottom of the thrift store table. 6 metal flanges allow the tabletop to be attached to the base with screws.
|
Closeup of the flanges and screws attaching the old tabletop to the base of the table.
|
The top of my tiny end table was quite easy to remove. Six metal flanges allowed for screws to be drilled through the base of the table and directly into the bottom of the table top. I merely unscrewed the screws, and the tabletop lifted off.
Unscrewing the old tabletop from the base of the table.
|
The separated base and old tabletop.
|
Step 2: Cut the Mosaic Substrate to the Size of the New Tabletop
♦ Measure.
The old tabletop measured 11” x 17”, and I decided to use these measurements to create the base for the new one. Using a measuring tape and straight edge, I marked my measurements on a piece of HardieBacker.
The old tabletop measured 11” x 17”, and I decided to use these measurements to create the base for the new one. Using a measuring tape and straight edge, I marked my measurements on a piece of HardieBacker.
Measuring out the new tabletop on HardieBacker board, based on the measurements from the old tabletop.
|
♦ Score and snap.
Both HardieBacker and traditional cement backer board can be cut using the score and snap method. HadrieBacker has the advantage of a grid incised into one side of the board to act as a cutting guide (we will be mosaicing over this side, so it does not show on the bottom of out final tabletop). After marking my measurements on the HardieBacker, I scored the board with a utility blade, using a straight edge as a guide. I like going over the initial cut a few extra times to ensure the depth of the score.
Both HardieBacker and traditional cement backer board can be cut using the score and snap method. HadrieBacker has the advantage of a grid incised into one side of the board to act as a cutting guide (we will be mosaicing over this side, so it does not show on the bottom of out final tabletop). After marking my measurements on the HardieBacker, I scored the board with a utility blade, using a straight edge as a guide. I like going over the initial cut a few extra times to ensure the depth of the score.
Scoring the HardieBacker board with a utility knife. Use a straight edge as a cutting guide.
|
Snapping the scored HardieBacker board using downward pressure on the edge of a table.
|
To snap the score, align the score with the edge of the table. Brace the portion of the board on the table with one hand, while firmly pressing down on the portion of the board that is hanging off the table. With enough pressure, the board should snap along the score line. If the board does not break completely, fold it back along the score line and use the utility knife to easily cut the rest of the way through the board.
Cutting through the back of the break with a utility knife.
|
Scored and snapped edge of the HardieBacker board. The edge is a bit messy, but will be covered by my mosaic tiles.
|
♦ Jigsaw option.
The score and snap method works really well for straight cuts, but the resulting edges can be a bit rough. If you want your edges to be perfectly smooth, or for more difficult rounded cuts, a jigsaw is a great cutting option. Fit your jigsaw with a diamond grit blade when cutting cement board. In addition to eye protection, definitely wear a dust mask rated for fine particles as cutting cement board generates a lot of dust which can contain silica.
The score and snap method works really well for straight cuts, but the resulting edges can be a bit rough. If you want your edges to be perfectly smooth, or for more difficult rounded cuts, a jigsaw is a great cutting option. Fit your jigsaw with a diamond grit blade when cutting cement board. In addition to eye protection, definitely wear a dust mask rated for fine particles as cutting cement board generates a lot of dust which can contain silica.
Using a jigsaw to cut the HardieBacker board.
|
The edge of the HardieBacker board cut with a jigsaw. Notice that the finished edge is much smoother than with the score and snap method.
|
Note: I have attempted to use a regular wood blade in my jigsaw to cut my HardieBacker. It worked really well for the first 10” or so of the cut, until the blade began to slow and I began to smell a bit of smoke. I took a look at the blade, and the teeth had all been worn down to innocuous nubs – hence the need for a diamond grit blade.
Look, Ma, no teeth! The consequence of using a standard wood-cutting jigsaw blade for cutting cement board.
|
Step 3: Affix the Fasteners
The old tabletop was attached to the base using screws screwed directly into the base of the top. This is definitely an option. However, I wanted to attach the top to the base in a way that has less potential to cause damage to the mosaic substrate. Screws can only be unfastened a finite number of times before the screw hole becomes unusable. Also, normal movement of the table creates stress at the joining points, and can work the screws loose, marring the screw holes. Therefore, I decided to use pronged T-nuts as a base for the screws.
A pair of pronged T-nuts.
|
Note: For this project, I used #8-32 x ¼” pronged T-nuts. Since the HardieBacker I used is ¼” thick, once installed, the shanks of the T-nuts will sit flush with the top of the backer board. T-nuts are also available with longer shanks that will accommodate thicker substrates.
♦ Mark the position of the screw holes.
Since my table base has flanges for attaching to the table top, the screw holes in the top must be aligned to match these flanges. I set my cut HardieBacker mosaic base on the work table underside up, and then centered the end table (legs up) on the mosaic base. With a pencil, I marked the flange positions on the HardieBacker.
Since my table base has flanges for attaching to the table top, the screw holes in the top must be aligned to match these flanges. I set my cut HardieBacker mosaic base on the work table underside up, and then centered the end table (legs up) on the mosaic base. With a pencil, I marked the flange positions on the HardieBacker.
Marking the screw hole positions on the HardieBacker board using the table base flanges as a guide.
|
♦ Drill sink holes.
Using a drill bit a bit larger than the width of the T-nut shank (in this case 3/16"), drill sink holes for the pronged T-nuts. I support the cement board on a piece of thick scrap wood so that I can drill all the way through my mosaic base and not mar my work table. Since the drill tends to leave a bit of a rough exit hole, I drill through the back side of the HardiBacker (the smooth side). After the holes have been drilled, I set the table base back on top of the backer board to ensure that the holes for the t-nuts are aligned with the base flanges.
Using a drill bit a bit larger than the width of the T-nut shank (in this case 3/16"), drill sink holes for the pronged T-nuts. I support the cement board on a piece of thick scrap wood so that I can drill all the way through my mosaic base and not mar my work table. Since the drill tends to leave a bit of a rough exit hole, I drill through the back side of the HardiBacker (the smooth side). After the holes have been drilled, I set the table base back on top of the backer board to ensure that the holes for the t-nuts are aligned with the base flanges.
Drilling the sink hole for the T-nuts in the HardieBacker board. The board is placed textured-side down.
|
♦ Set the T-nuts.
With the backer board sitting with the side to be tiled facing up, place the stem of a T-nut into one of the sink holes. Using a hammer, pound the T-nut into the sink hole until the prongs of the T-nut are embedded into the backer board. The mosaic will be affixed over the flat face of the T-nut, ensuring the T-nut will not pull loose.
With the backer board sitting with the side to be tiled facing up, place the stem of a T-nut into one of the sink holes. Using a hammer, pound the T-nut into the sink hole until the prongs of the T-nut are embedded into the backer board. The mosaic will be affixed over the flat face of the T-nut, ensuring the T-nut will not pull loose.
Sinking the T-nuts into the pre-drilled holes in the HardieBacker board.
|
Closeup of a T-nut installed in HardieBAcker board. The face of the T-nut sits tight against the board, and the prongs are embedded in the board.
|
The T-nuts installed in the HardieBacker board (mosaic side).
|
T-nut reinforced screw holes in the HardieBacker board (back side). The bottom of the shanks of the T-nuts sit flush with the back of the board.
|
Tip: If instead you sink your T-nuts with the face of the T-nut on the bottom of the backer board (the non-mosaic side), coat the inside of the sink hole and the bottom of the skirt of the T-nut with a little glue for added strength.
Now that we actually have something on which to mosaic, it's time to move forward to the fun part. Check out Piece by Piece (Part 2): Setting and Grouting a Mosaic Tabletop for the continuation of the project.
