Patios and paving

Two numbers decide whether a patio works. Finished paving must sit at least 150mm below the damp proof course, two brick courses down, so rain splashing off the slabs never reaches wall above the membrane. The surface also wants a fall of roughly 1 in 80 running away from the building, about 12mm in every metre, enough to shift water without being felt underfoot. Paving laid dead level, or worse still tipping back towards the house, is a common cause of damp patches indoors.

Excavation goes to around 250mm below the intended paving face where foot traffic is all that is expected. Into that hole goes 100mm to 150mm of compacted Type 1, then a full mortar bed. Full bed means exactly that: a continuous 30mm to 50mm of wet mix under every slab, not five dabs at the corners. Spot bedding leaves voids that fill with water, freeze and crack slabs from underneath, and it remains the most frequent fault in cheap paving.

Porcelain behaves nothing like stone. Vitrified tiles are effectively non-porous, so mortar will not grip them without a slurry primer painted onto the back of every slab, and skipping that step is why porcelain terraces lift in year two. Natural sandstone and limestone arrive calibrated or uncalibrated, and uncalibrated stone means the bed gets adjusted slab by slab. Jointing comes last, either a brush-in resin compound or a pointed mortar mix, and both want the paving dry and the air above 5 degrees to cure.