How To Mosaic a Patio Table

Replace Glass Top With Concrete Board

Glass-top metal patio tables can be used to make a mosaic table by replacing the glass top with 1/4 inch concrete backer board. The concrete backer board is roughly the same thickness as the glass top it is replacing, and it can rest on the rim of the metal table just as the glass top did. However, the thin concrete backer board can sag if unsupported, so marine plywood or pressure-treated plywood should be laminated to the underside of the backer board to stiffen it.

Note that the plywood should be slightly smaller in diameter than the concrete backer board so that it doesn’t interfere with the metal rim of of the table. Only the concrete backer board rests in the inside of the rim where the glass rested. If the plywood were to rest there, then the table top would be too thick and stick up above the rim instead of fitting inside it like the glass.

Steps For Replacing The Glass Top With Reinforced Concrete Mosaic Backer

  • buy 1/4″ concrete backer board from building material store.
  • measure glass top being replaced.
  • cut 1/4″ concrete backer board into a circle the same size using jig saw.
  • cut pressure-treated plywood into slightly smaller circle using jig saw with fresh blade.
  • glue plywood to concrete backer board using Weldbond or other PVA glue.
  • paint underside of plywood and its outer edge with multiple coats of outdoor paint.
  • insert table top into metal table base.

Repairing Edges of Concrete Backer Board

Concrete backer board sometimes has bubbles and voids that aren’t exposed until you cut across them and leave a weak spot or rough crumbly spot at the edge of the piece. You can also damage the edges of the concrete backer board during transport and handling. If this happens, you can repair and reinforce these weak crumbly places with the same thinset mortar that you use to attach the tiles.

Use Thinset Mortar Instead of Glue

Outdoor and wet mosaic should always be done with thinset mortar instead of glue. Thinset mortar is concrete with polymers added for strength and adhesive properties. You can also use the thinset for grouting the finished mosaic. An outdoor mosaic made with thinset will last many times longer than a mosaic made with glue, and that is why they use thinset for attaching tiles in swimming pools.

Using Thinset

We use Versabond brand thinset by Custom Building Products and add 1/4 pound of water per pound of thinset. Thinset comes in big bags that are inconvenient. We keep the bag of thinset in a 5-gallon plastic bucket with a lid. We slide the whole bag into the bucket and cut the top off the bag and scoop out what we need. Never try to pour it unless you like big clouds of dust that is dangerous to breath.

Finding The Right Table Is Easier Than Making The Wrong Table Work

I have always disliked the subject of mosaic tops for metal patio tables because I receive too many emails from lunatics who think the most important thing about the table to be mosaiced is that it is what they already happen to have on hand. It doesn’t matter to them if the table is broken or rusting to pieces or made of wood or already has an expanded metal mesh top welded in place.

For these people, it isn’t about finding a table that is appropriate for a mosaic top, it’s about making whatever they happen to have work, no matter how flawed or problematic or downright dangerous it might be. What’s worse is that when I take valuable time to email back explaining why the table is a poor candidate, they usually email back proposing some farcical method of making it work and wanting further comment.

These proposals show a lack of understanding of basic concepts, but what really makes them insufferable is that they are usually posed as questions asking me to explain why it would not work or why it wouldn’t make the process quicker or easier, usually in a pleading way. (As if my agreeing with them could somehow alter laws of physics or other aspects of objective reality… )

Reading their emails always brings to mind an expression used in the military, one that is blunt, crude and profoundly apt, like so many military expressions: You cannot polish a turd. How many times have I longed to type those words into an email reply!

Inspect Table For Strength And Stability

A mosaic table top can weigh significantly more than the glass top it is replacing. Before doing anything else, inspect the table to make sure it can hold the weight. Look for broken welds in particular, but also keep an eye out for the gauge of materials used for the table. Most metal patio tables are much heavier and stronger than they need to be, but factories make things lighter, cheaper and more disposable each year. If the table in question appears to be light-gauge and weaker than most wrought iron you have seen, then think twice before using it as the base for a mosaic table top.

Bistro Tables

If you use a small metal bistro table, then make sure that you don’t create a safety problem by putting a very heavy top on a table that is taller than it is wide. This can make the table unstable and easy to tip over. The heavy table top could easily injure someone if the table were knocked over by a casual bump. The solution is to anchor or weight the feet of the table, and a sock filled with sand and tied in a knot is often all that is required. Using wire to twist tie the table to the railing of a balcony is another quick solution.

Glass Mosaic Tile Is Best For Outdoors

Glass in nonporous and therefore impervious to moisture and freeze damage. Ceramic tile and stone are porous, and thus water can penetrate inside and freeze and crack the tile over time, sometimes very rapidly depending on where you live. Sure we have a lot of Roman stone mosaics from 2000 years ago, but those mosaics are in the dry warm Mediterranean basin and not west Michigan…

Remember To Seal Outdoor Mosaics

A few days after grouting, you should seal your mosaic with a tile and grout sealer. Tile and grout sealers are invisible pore sealers and not coatings that form a separate layer over the top of the mosaic. You wipe them on with a rag, and then wipe away the excess with a clean rag and allow to dry for ten minutes. Apply it 3 times or whatever the manufacturer instructions recommend.

36 thoughts on “How To Mosaic a Patio Table

  1. Cheryl Regehr

    Do you have suggestions of where I could purchase a suitable table? I am going to attempt to do this for class art project for the school auction.
    Cheryl

    Reply
  2. Stacy Sims

    I am on the fence about using mosaic tile on my patio table. The glass top broke this winter and a new piece is more than I want to spend. I have a whole matching set so I would like to use my table. Problem is the glass sat inside a 1 inch rim. I read your article and I can cut the wood to fit in the table but I am worried that the once I put my tile and grout, it will be substantially higher than the edges. Do you have any ideas?

    Reply
    1. Joe Moorman

      Stacy,

      I might be interpreting your information incorrectly, but a 1-inch rim seems ideal for mosaic patio table. Glass mosaic tile is usually roughly 1/8″ thick. If you were to use 1/4″ concrete backer board glued to 1/2″ plywood, then you should be just under the height of the rim. However, you would need to thoroughly paint the edge and underside of the plywood with several (3+) coats of oil-based paint to prevent warping over time due to humidity. My preference would be to bolt or weld some metal supports (angle iron) across the top of the frame/table base to support the center of the table top and mosaic on 1/2″ concrete backer board. Of course, you should make sure that the table top is adequately supported and all the structural issues are addressed (look for sagging) before starting the actual mosaic work.

      I hope this helps some!

      Reply
    2. Miller

      I am rather excited to try this. I “found” a wonderfully unique table curbside! it appears to be from the fifties, oval in shape, a metal base with scrolls. It is in wonderful condition except for the top. The wood is solid and true but it is covered in a vinyl material which is completely secure. I also have left over tiles from a bath and kitchen project that are earth-tone in color. I also want a new set of dishes for the kitchen to be able to have a full set for guests this summer and to have a dark blue in the design.
      I love the background of this page. It inspires me to include some small trinkets that have memories attached to them. “Winter time”, it sure does mess with the phsyceeee! That’s kinda of the point, to give yourself to create and thus relax with. Too much today is about do it now!, do it this way!. You can use your common sense and your creativeness together to create something wonderful and long lasting so that perhaps you can hand this one piece down through the generations to come. It could be your “something to remember me by” thing while you enjoy it and tells stories about it to others.
      As for Stacy of last year, do it! What is the worst that could happen? You spend a little time with yourself to spend a lot of time with others later and you save some garbage from being garbage.
      Let’s all get started today and have a blast!

      Reply
  3. Betty Richardson

    I just purchased a palapa for our backyard and they mentioned we could get an untreated pine table top so that i can mosaic it… Sooo my question is whats the best way to go about doing it? should I put a moisture barrier underneath before I use thinset and glass tiles or should it be fine just using the thinset directly on the pine? or maybe can coat the pine with something before i start using the thinset?

    Reply
    1. Joe Moorman

      Salesmen will sometimes tell you anything to make the sale, and sometimes they are just plain mindless. Wood is not an appropriate backer for an outdoor or wet mosaic (as discussed in many places on this website). This article discusses some of the options.

      Reply
  4. Ramona

    Can a glazed porcelain tile be the base for mosaic project on a small 12″ table? It fits exactly into my table. My husband says it’s not porous so thinset and tiles won’t stick to it properly. Thanks and appreciate your expertise.

    Reply
  5. Susan

    I have a Wrought iron fire pit base perfect for a mosaic top. It has a ring around the top that I think would be perfect for the plywood layer to fit into. If the backer board is 2-3″ wider all around will the edges be too fragile? If I don’t have a frame for the edge how do you recommend to finish the edges?

    Reply
    1. Joe Moorman Post author

      Some of the main points I try to make in this article is that plywood doesn’t make a good backer for a mosaic patio table. The other main point is that it makes more sense to find a table base that works well than it does to try to make whatever you have work. If you are determined to make what you have work, then you need to weld things like edging and supports as needed to it.

      Reply
      1. Susan V

        I am going to make the mosaic top with the concrete backer board in a diameter of 36″. The supporting plywood layer will be 30″ in diameter. Will the outer 3″that are mosaic be too heavy? That overhanging amount will have a 1/2″ metal support at each quarter. Do you think that a 3″ overlap. Will have too much sagging? If so, I could probably. Put some additional plywood underneath.

        Reply
  6. Guilty Granddaughter

    Referring back to Miller’s Feb 2015 comment of “perhaps you can hand this one piece down through the generations to come”… I have a 48″x48″ mosaic table my grandmother designed and grandfather built that is 40+ years old. It was used in their enclosed sunroom in Pennsylvania. Fast forward to it’s life on my humid South Carolina screened porch. The original plywood backing has begun to warp and delaminate, but the mosaic tiles and grout are still in seemingly excellent condition on the top.
    Is there a way to secure the tiles in their original positions, flip the table top to carefully remove the plywood backer, and then re-secure the tiles to a new outdoor-friendly backing? The individual tiles are tiny – no more than ½”x½” – and most smaller than that, so I am trying to avoid completely reconstructing from scratch. I fully realize I will have to re-grout after the bulk transfer. Will the packing tape/contact paper method discussed on another thread work on a project this large?
    Fix or toss? I’d prefer to fix if at all possible, but I know the limits of my craft skills and patience. Many thanks in advance for any words of wisdom.

    Reply
    1. Joe Moorman Post author

      Repairing a mosaic can be a labor of love, especially if the backer is warping, but it isn’t impossible, and it doesn’t have to be tedious. It all depends on how easily the tiles come off the plywood, and there are techniques for that, even if the adhesive is stubborn.

      The first step is to get the mosaic securely attached to mosaic mounting tape.

      Then you need to remove the plywood from underneath. To do that, I would take the table apart so that I had the mosaic on the backer board.

      If the adhesive is old and failing you might be able to firmly but gently scrape the mosaic off with a paint scraper.

      If the adhesive is still strong, then what you do next depends on the condition of the plywood backer and how flat it is. One option would be to use a power planer to shave off the excess layers of plywood down to the last 1/4 inch and then laminate that onto a new piece of plywood using glues and weights during drying to ensure flatness.

      Another option would be to place the mosaic in a shallow layer of water, such as children’s pool until the glue delaminated from the plywood. Again, you would have to use weights on a second piece of plywood to keep it flat as it soaked, and you would need to make sure that the water was just right: up to the backer but not up to the mounting tape.

      I hope this helps!

      Reply
      1. Guilty Granddaughter

        Thanks for the speedy suggestions and encouragement – had not thought of a water bath to loosen the old adhesive!

        Reply
  7. Julie

    I am a little confused about using plywood in an outdoor table application and am hoping for a little clarification. I understand that using plywood as a base is a bad idea due the surface being unstable. However, if a concrete backer board is used as the base but plywood is used underneath to support it, wouldn’t that plywood also disintegrate over time? I just want to make sure I understand before I proceed! Thanks so much for your blog and information, it’s incredibly helpful!

    Reply
    1. Joe Moorman Post author

      Thanks Julie! By using concrete backer board on top of the plywood, the tiles are less likely to pop off, but warping is still possible, and the plywood will still disintegrate over time. For that reason, the plywood needs to painted with three coats of outdoor paint, especially the edges. Seal the face of the mosaic with multiple applications of a tile and grout sealer. Instead of concrete board laminated to plywood, I have been wanting to try a product called Hardieboard for my next mosaic table. Hardieboard is a tile backer board that has fibers mixed in with the concrete to make it stronger and less crumbly at the edges. I haven’t had time to soak a piece and see if moisture affects it, but I think even if it had some slight issues, it would still be fine if I painted to bottom and side edges with three coats of outdoor paint.

      I hope this helps!

      Reply
  8. Veronica

    Hi Joe,
    I have just recieved a lovely cement mosaic table from the 70’s. Much of the grout has worn away from the edges which feel sharp when you rest. Your arms on the table. The gaps in grout range from 1/4 (or more) Between the tiles on the edges of the table top to 1/16th or less where the grout is still thick on the flat part of the table. Can I regrout? Would I use a combination of sanded grout on the sides and areas of wide grout lines and non sanded on the top?
    Many thanks for a great site.

    Reply
  9. Neil Razdan

    I have seen some of Neille Olson’s mosaic table tops. I want to make one myself. Of course my own design. I am willing to go to a Iron workshop and have an anodized/powder coated, backed base (my design). My question is, well I guess her tabletops have grout all around the edges too. Does she grout the back of the board she uses to mosaic on? Does she use hard wood base/board? Designing/mosaicking I can handle, I just want to have a 48″ round table top that is weatherproof, and wouldn’t crumble. Is it just the usual grout which covers the edges around. How do I make sure that the tiles wont cut somebody’s arm when they rest their arms on the table edge.

    Reply
    1. Joe Moorman Post author

      Neil,

      Some people mosaic the sides of bar counter tops and table tops, but the top needs to be built with sides to support the mosaic on them. That usually means plywood, which is extremely problematic outdoors. If you do use plywood as a backer for outdoor mosaics, then the sides and bottom need to be sealed with multiple applications of an outdoor sealer, such as used for decks. The have to smooth the edges of cut pieces of tile with the fine side of a marble file.

      Reply
  10. Lauren

    Hi I have been wanting to make a mosaic round top
    that would be larger then a heavy round metal table.
    I am thinking that I could make new table top and just
    put it on top of original table.
    The table is one piece with all metal top , sides and
    legs. I thought maybe there could be 2inch hangover
    so table would now seat more people.
    Is there a way to make independent top and just let
    it sit on top of old table ?
    Thanks !!

    Reply
    1. Joe Moorman Post author

      Hi Lauren,

      People make table tops separate from table bases or pedestals all the time, and so it is possible. However, you need to make sure you aren’t making something heavier than the base can support or something that is unstable and could fall over. Consulting with a local handy person or welder is the way to go.

      Reply
  11. Maya

    Hi Joe, Could you please tell me if marine plywood would be a good base for an outdoor table? I’m wanting to use a heavy iron base from a pub table. I’ve read your comments re; warping and we do get a lot of rain here in the UK. Thanks.

    Reply
    1. Joe Moorman Post author

      Maya,

      You should be able to get a foam-core tile backer board such as the Wedi product, and that would be a much better choice.

      Reply
      1. Maya

        Thank you for your reply, Joe. Would the foam-core tile backer board such as the Wedi be preferable to the hardie board? Do I put it onto the marine ply base before tiling? Or would it be better to find a different material for the base. Many thanks.

        Reply
        1. Joe Moorman Post author

          The foam-core board can be bought in different thickness, and so you should be able to use foam-core without plywood underneath. People use the board to build walls all the time. If you still need plywood for some reason, you can attach the foam core board to it using an outdoor construction adhesive, such as the Liquid Nails Outdoor product sold in the USA. Thanks!

          Reply
          1. Maya

            I’m not bothered about using ply if the foam core will hold up without warping. The table top needs to be 28 inches square to fit the base so is quite large. I have no experience of foam core , so welcome your advice on it. Thank you.

          2. Joe Moorman Post author

            If you got 1-inch thick or used 2 sheets of 1/2-inch, I think you should be fine. People use this for fabricating bathroom surfaces.

            Thanks,

  12. Traci Prescott

    Two questions: Is Concrete Backer Board the same as Permabase Cement Board from Menards? and second question is how thick should the first grout layer be that we first lay the tiles into when designing the mosaic?

    Reply
    1. Joe Moorman Post author

      We don’t have Menards down here, but concrete board should be the same everywhere. The only thing to check out is to see if it looks like it has cellulose fibers in it like Hardibacker. If so, I would avoid it for outdoor use, but I suspect what Menards is selling is ordinary concrete board.

      Grout is not mortar and cannot be used to attach tiles. You want to use thinset mortar instead. How think you put it on depends on the size of tile and your working preference. You will figure that out by a little experimentation when you get started.

      Reply
      1. Traci

        One more question: do you have any recommendations about where I could purchase glass tiles to make my outdoor bar table top? I just need some direction about where to get good tiles and then I think we are ready to get going. We already cut and painted our plywood base, will be installing the concrete backer board this weekend and then we are ready to start tiling with the thin set versa bond. Oh except, we need tiles. 😊

        Reply
          1. Traci

            We were planning on putting the concrete backer over the sealed plywood and then tiling on top of the concrete backer. There was nothing underneath the concrete backer that we could secure the backer to without having to use plywood underneath it. But the plywood should not get any direct moisture since the back room will be on top of it

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