External Porcelain Installation Advice and information for installing porcelain paving.

How To Install Porcelain Paving Slabs

Last Updated 18th June 2019

Porcelain is very different from traditional paving materials like natural stone or concrete, therefore it needs to be treated differently. We have outlined some of the most popular fixing methods below, including some of their benefits and disadvantages. Care should be taken when fixing over problem conditions such as clay. In these situations, a reinforced concrete system is recommended.

All the fixing methods mentioned below have a common preparation which involves removing the top soil to the sub base, laying a geotextile and then laying a compacted and suitable aggregate such as MOT Type 1 to an appropriate depth.

Solid Concrete Base & Adhesive

A 75-100mm bed of concrete is laid, and the porcelain slabs are stuck down with a solid bed of polymer modified cement based tiling adhesive. This method can be used for both patios and driveways.

This method works well when fixing over problem sub bases such as clay, however it does have disadvantages. Concrete slabs need to be left to cure and shrink before tiling. This will typically take 6-8 weeks. It is also difficult to lay a concrete slab to accurate falls which can require a lot of adhesive to make good any undulations in the surface and will take extra laying time. This type of installation will require expansion joints running through the screed and tiles at perimeters with walls and at approx. 6 metre intervals across the tiling.

Shop our range of outdoor tile adhesive and grout online.

PorcelQuick Adpeds

Plastic Adped formers are positioned at the intersections of the where the porcelain slabs are to be fixed and filled with a screed mix. This is allowed to set and the porcelain slabs are then fixed to the Adped adhesive pedestals using polymer modified cement based tiling adhesive.

Only suitable for areas subject to foot traffic, but uses 80% less fixing material, 80% less carbon footprint and is a quicker fixing solution. Not suitable for roof terraces and balconies.

Shop for PorcelQuick Adpeds online here.

Height Adjustable Plastic Support Pedestals

Height adjustable plastic pedestals such as Eterno Ivica can be used to support porcelain slabs on balconies and roof terraces. This is a simple fixing system that allows for the slabs to be lifted and to run services underneath. The joints are left open which allows for drainage, but means it is best to use rectified tiles as the edges are unprotected by grout.

Shop for Eterno Ivica adjustable pedestals online here.

Sand & Cement Wet Bed Method

This method involves laying a wet mix of sand and cement to a thickness of 50-75mm. The porcelain slab would then be bedded into the mix and tapped down to meet the required levels. Traditionally used to fix riven concrete slabs and stone with wide joints. Engineered rectified** porcelain fixed with narrow joints requires much tighter fixing tolerances and will take longer to fix.

Porcelain slabs are impervious so it is critical the bed mix has a suitable volume of polymer admix added to the mix, or polymer bridging coat (primer) is applied to the back of the slab. If the correct mixes are not added or applied the mortar will not bond correctly and the installation may fail.

Wet bed installations will rarely achieve a solid bed underneath the slab as the system will commonly leave voids. As the porcelain slabs are impervious any residual moisture in the bed will tend to collect under the tile and condense in cold weather (unlike stone and concrete will allow moisture to slowly escape from under slabs over time). Even if the installation has been correctly laid it is possible the water in the voids will freeze and the pressure of the expanding ice could be sufficient to overcome the bond strength and the installation may fail.

A solution to this problem can be to lay a level semi-dry screed and apply a porcelain primer or polymer modified cement based tiling adhesive to the back of the porcelain and fix to the screed mix thus avoiding any voids.

Bitumen, Damp Proof Membranes or Roofing Grade Asphalt

Previously tiling onto these substrates was complicated and avoided, but with a combination of Norcros Ultim8 B+ adhesive and Marmox Sloping Board you can fix porcelain paving slabs to bitument, damp proof membranes or roofing grade asphalt. All surfaces should be dry, clean and strong enough to support the weight of the overall tiled system. All traces of dirt, dust, laitance and other contaminants must be removed. Substrates should be true and flat to allow Marmox Board to be fixed without leaving any voids beneath the boards. Porous or dusty surfaces must be sealed using Norcros Prime Bond diluted 1:4 with water. Stir the contents before use.

Using a suitable notched trowel, apply the adhesive to the substrate in an even layer. Lay Marmox Board of a suitable thickness into the adhesive bed and press firmly to collapse the ribs. Allow the adhesive to dry. In areas which may be subject to wetting, tape joints between the boards using Norcros Waterproofing Tape. Once the adhesive beneath the boards has dried, tiles may be fixed using any of the Norcros Adhesives flexible cement-based adhesives. The adhesive has an open time of approximately 20 to 40 minutes at 20ÂC. Do not use below 5ÂC.

*18mm and thicker porcelain slabs

** Rectified tiles have their edges ground so that each tile is exactly the same as another within a batch. Non-rectified tiles can vary in size by a small percentage within a batch.

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