Outdoor porcelain paving needs a solid base, a full mortar bed and a slurry primer on every slab. We'd always recommend a professional landscaper, but these are the key steps for laying 20mm porcelain paving:
- Prepare a solid base. For a patio or path, dig out the area to a depth of around 150mm, then lay a sub-base of MOT Type 1 at least 100mm deep. Compact it thoroughly with a plate compactor (wacker plate) to give the paving a firm, stable foundation. The finished patio should also sit at least 150mm below your home's damp-proof course.
- Plan a slight slope. The patio should fall gently away from your house, so rainwater drains off rather than sitting on the surface. A fall of around 1 in 60 is ideal for porcelain, which works out at roughly 1.7cm for every metre.
- Use a full mortar bed. Lay each slab on a full, even bed of mortar, not on dots or dabs, so it's supported across its whole area. A good mix is 4 parts sharp sand to 1 part cement, laid around 25–40mm deep. Use sharp sand rather than soft building sand, as it gives a stronger bed.
- Always use a slurry primer. Porcelain absorbs almost no water, so mortar can't grip it on its own. Brush a slurry primer, such as our Ultra Scape Pro Prime Slurry Primer, onto the back of every slab just before laying it. This is the most important step: without it, slabs can work loose over time.
- Leave even joints. Use spacers to leave joints of at least 5mm between slabs.
- Clean as you go. Wipe any mortar or primer off the surface straight away, before it sets, to avoid grout haze.
Leave the paving to set before walking on it or pointing the joints.