What Mosaic Base Should I Use?

March 11, 2015

What Mosaic Base Should I Use?

Mosaics can be applied to practically any surface including bowling balls and styrofoam forms. This article looks at common mosaic bases, their pro's and con's and what adhesives can be used. Ultimately the choice of a mosaic base or substrate is determined by many factors, including the mosaic's intended use, location, type of project, cost and individual choice.  

MDF (Medium Density Fibrebroad)

  • Made from compressed and glued pieces of sawdust, it is dense and heavy and will not warp.
  • Not a great choice for a mosaic based due to its venerability to water, should not be used on outdoor mosaics.
  • The bonding agent used to make MDF pose health risks
  • Popular for craft projects because it's easy to use and cheap
  • If used as a mosaic base keep inside and away from moisture
  • Adhesive: PVA, Weldbond, Cement based adhesives
  • Needs to be primed or sealed first


  • Plywood is made from thin sheets of wood that are laminated together.
  • Types of plywood suitable to mosaic on:
  • Exterior plywood - is high quality and it is a non structural type of plywood. It can be used in full or semi exposed areas. The glue in exterior plywood is much more moisture resistant than interior ply.
  • Marine - this is the type of plywood to use when you need it to be moisture resistant. This type of plywood uses the best glues and is the best manufactured.
  • Susceptible to water damage and not recommended in areas exposed to water.
  • Plywood needs to be sealed. Seal the mosaic well and paint all surfaces that aren't mosaiced.
  • Easy to cut and screw, able to be shaped into different forms, cost effective, resistant to splitting and warping
  • Adhesive: PVA, Weldbond, Cement based adhesives
  • Needs to be primed or sealed first


  • Not a good material to mosaic on because of its vulnerability to moisture and decay. Do not use it on an outdoor mosaic.
  • Can be used on small indoor mosaics such as mirrors or plaques
  • To prepare wood - seal back and edges or paint
  • The bigger the mosaic the thicker the wood must be to prevent it warping
  • Adhesive: PVA, Weldbond, Cement based adhesives
  • Needs to be primed or sealed first


  • A good choice for a mosaic base due to its weather resistance
  • Ensure that the surface is thoroughly cleaned and a coat of sealer is applied. Sealing the terracotta will help stop it absorbing water from the adhesive and the grout drying out too quickly.
  • Adhesive: Weldbond, Cement based adhesives
  • Needs to be primed or sealed first


  • Great surface to mosaic especially exterior mosaics
  • Strong, rigid and weatherproof
  • Often used to make stepping stones, wet cement poured into molds
  • Tiles, tesserae can be laid directly into wet cement
  • Adhesive: Cement based adhesives
  • Needs to be primed or sealed first


  • Is extremely effective when using transparent tiles
  • Clean glass with methylated spirit prior to mosaicing
  • Make sure the glass tiles are adhered with smooth side onto glass with plenty of clear silicon. Wipe away excess with skewer, press down well to ensure there are no air bubbles.
  • Adhesive: Clear silicon, Weldbond glue, Mac Glue


  • The surface needs to be roughed up by lightly scoring or sanding before adhering tiles
  • Check for rust
  • Consider to weight of the mosaic when finished
  • Metal can expand and contract under temperature extremes, which may cause the grout to crack and tiles to fall off. Consider covering the metal with a wire mesh which is fixed with screws and then applying a coat of cement.
  • Adhesive: Two part epoxy, araldite
  • Needs to be keyed or roughed up and primed


  • High density fibre cement sheet
  • Difficult and messy to cut
  • Great for outdoor murals and tabletops
  • Tough durable substrate, will not warp, weather resistant
  • Apply a coat of primer to help adhesive take hold
  • Adhesive: Cement based adhesive (Thinset)


  • A lightweight economical substrate.
  • Made from waterproof extruded polystyrene, faces with a fibreglass mesh embedded into a cement polymer on each side
  • It is light and tough but can be cut with a sharp knife, no power tools needed.
  • Not prone to warping and waterproof, suitable for outdoors.
  • To make Marmox it waterproof, coat the edges in either cement or a cement based adhesive.


  • Great for creating 3 dimensional shapes
  • Don't use adhesives that contain solvents as it will dissolve the styrofoam
  • For indoor smaller sized projects Weldbond works well as an adhesive, with the tiles and tesserae being directly applied
  • For outdoor projects or larger projects wrap the styrofoam form in wire mesh, then apply a layer of cement to serve as a base for the mosaic. The cement can also be applied directly to the form in smaller projects. A cement based adhesive can then be used as the adhesive.
  • Can be coated in a layer of cement based adhesive to give it extra rigidity and durability (important for outdoor mosaics)

Surface Preparation Tips

  • Make sure your surface is clean before you start
  • Check if you surface needs to be sanded and primed, to allow the adhesive to grip to the surface correctly.
  • A primer works to reduce the porosity of a substrate, it doesn't eliminate it. It helps to stop the adhesive drying out too quickly and destabilising it. It also creates a clean surface for the adhesive to stick to.