PORCELAIN SLABS - WHAT'S THE BEST WAY TO LAY THEM?

Porcelain has become a popular option for garden patios. Sometimes referred to as vitrified paving, it’s a great low maintenance choice for customers and looks particularly good in modern gardens. But if you’ve never laid a porcelain patio before, where do you start?

For most gardens, a sub-base of 100mm should be sufficient for laying porcelain slabs, but make sure you take into account the particular ground conditions. If excavation is needed, the depth should be based upon the thickness of the sub-base plus the sand, mortar and paving flag thickness. If you’re laying the patio up to an existing structure make sure it’s minimum of 150mm below the damp proof course to prevent problems with rising damp.

Your sub-base material, as with other paving types, should be well graded (40mm to dust) Type 1 quality material and placed in layers no more than 75mm thick, or twice the nominal maximum aggregate size.

Edge restraints should be sufficiently robust and installed prior to the installation of the sub-base. Alternatively, and a good design idea for a quality finish, you could create a border using an alternative product or material to frame the project and enhance the overall finish.

Flags should be supported on a full ‘wet’ workable mix mortar bed (1:4 cement/sharp sand), you should lay the mortar bedding to give a thickness between 15mm and 30mm. To increase adhesion to the mortar bed and prevent separation, a paving primer or similar flexible bonding agent compound should be applied to the back of the flag prior to installing onto the mortar bed. Gently tap down onto the mortar bed using an appropriate rubber mallet. Adjustment may be necessary to ensure that the units are fully supported and do not rock or move, and that desired levels and falls are achieved.

Another area where the practice differs a little from other materials is jointing. Good suppliers will supply a vitrified jointing material with the product, and this should be used to full fill the joints. Joint widths should be 3-5mm wide, you could use spacers to achieve uniform joints.

Under no circumstances should dry or semi dry sand/cement mixes be brushed into the joints as this doesn’t give a rigid joint and can cause the paving to become stained.

Once you have laid the paving on the mortar bed, rake out any excess mortar between the joints to the base level of the flag with a suitable tool. This will ensure the jointing material fills all joints to the entire depth and width of the flag joint. The joints should then be filled using the supplied jointing compound following the instructions supplied. Saturate the paved area with water prior to expelling the product onto the paving then brush diagonally into the joints. Remember, different jointing compounds need to be used in different ways, so always make sure you follow the guidelines specific to the product you are using.

To finish the installation, gently spray the surface of the paving with water before sweeping off any excess jointing material with a soft bristled brush.