A Guide to External Tiling

External tiling is becoming more and more popular. This is partly due to the increase in availability and popularity of 20mm porcelain tiles. Over recent years, homeowners have become inspired by seamless indoor outdoor living spaces and by using 10mm internal and 20mm external tiles, this beautiful design trend is now very achievable.


Traditionally, when tiling externally a concrete base is required. A typical concrete base is made up of 100mm of type one compacted stone. Once the stone has been compacted, a 200mm concrete screed should be poured over the base. It is really important that the screed is left to fully cure – we recommend leaving a concrete screed to cure for at least 6 weeks in dry conditions, prior to applying an adhesive bed).

A level, fully cured screed will not only provide a solid base, but it will also provide a foundation to create ‘falls’ – a slight gradient in the adhesive bed that will allow water to run off.

An alternative method for external tiling would be a sub-base of 100mm of type one compacted stone. This is made up of one 50mm layer of compacted stone, followed by a second 50mm layer. Once this has been achieved, 20mm porcelain tiles can be applied onto a bedding mortar.


Fixing 20mm porcelain external tiles depends on the type of sub-base.

Option One – Concrete Base

Fixing using an adhesive

  1.  Ensure that the concrete is dry.
  2.  Clean the base, removing any loose and weak areas.
  3.  Prime the area with two coats of UltraTile ProPrimer (first at 1:3 followed by a second coat at 1:1).
  4.  Apply the adhesive to the floor using UltraTile ProFlex SP, ProFlex SPES or ProFlex S2.
  5.  Once the adhesive is set, the area can be grouted using UltraTile ProGrout Flexible.

Option Two – Compacted Stone

Fixing using a bedding mortar

  1.  Mix and apply a minimum 30mm bed of UltraTile ProPave Mortar Sharp Sand at a 1:6 Ratio .
  2.  Prime the back of the 20mm porcelain tile using UltraScape pro-prime slurry primer then bed into the wet bedding mortar.
  3.  Once the mortar is set, the area can be grouted using UltraTile ProPave.

Before using any of the above products, please refer to the corresponding datasheets which can be found by visiting instarmac.co.uk.

For further advice on external tiling, or for more information on any of the products mentioned, please contact our Technical Team by calling +44 (0) 1827 254402 or emailing enquiries@instarmac.co.uk.

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