York yards hold water when the fall is wrong. A terrace behind the walls has nowhere for rain to wander off to a field. The outlet is a gully, a channel, or a border that can actually soak. The ground under the city changes from street to street. Clay and moraine sand are the two characters to know.
Falls in a walled yard
A fall is a slight slope built into the paving so water moves. The low side must not be the house wall. A gentle fall is enough. Too steep, and a table rocks. Too flat, and a puddle sits at the back door. Our team sets that fall from the threshold outward, then checks it against the gully that already exists. If the gully lid is higher than the new surface, the water cannot enter it. The lid, or the paving levels, have to be reconciled before the slabs go down. South Bank yards show this often. The plot is short, the walls are high, and the only low point is a grating by the step. Shade from those walls keeps the slab wet for longer, so the fall has to be real, not a hopeful skim of sand.
Gullies and trapped terraces
A trapped yard is a terrace with walls on the sides and a house at one end. No lawn takes the overflow. No side gate lets water out to a lane, unless a ginnel happens to be there. Holgate has many of these short rectangles behind a rear offshoot. The offshoot adds another wall and another corner where water stalls. The gully is often the original one, sized for a yard of bare soil, now asked to take a whole patio. If that gully connects to a combined drain, the connection has to be a lawful one. Our team does not send patio water into a foul pipe on a guess. A second gully, or a channel that feeds the existing grating, is the usual repair when one outlet is in the wrong corner. Leaves from a neighbour's tree will find that grating. A silt bucket that can be lifted is worth more than a hidden trap nobody can reach.
Clay and moraine
Clay and moraine are both under York, and they do not drain alike. The vale, including much of Heslington and Dunnington, sits on till and glacial clay. Rain stays in the top of that clay. A soakaway drawn on a plan may fill and stay full. Moraine ground, the sandy ridge under parts of South Bank, Holgate and Acomb, can take more water, yet clay lenses sit inside the sand. If a hole in one half of the yard is firm and the other half smears on the spade, the soft half comes out. Crushed stone goes back in thin layers and is packed until it stops moving. The geology viewer is the map of that contrast. It is not a substitute for the hole. A patio on clay still needs an outlet even when the base is sound. The base stops the slabs sinking. The fall stops the rain sitting on top of them.
Channel drains and air bricks
A channel drain is a narrow slot or a small grated run set into the paving. It earns its place across a doorway, along the low edge of a trapped yard, or where a rear extension has removed the old gully from the corner it used to occupy. The channel has to fall to a point that can take the water, and it has to be possible to lift the grate and clear the silt. Porcelain works well beside a channel because the slab is regular and the joint can meet the metal edge cleanly. Stone flags can do the same if the cut is straight. Air bricks are not a place to gain an extra row of paving. Covering them asks the wall to stay damp. The surface stays 150 mm below the damp course, and the air bricks stay in the open air. A gravel margin is the neat way to finish against an old wall when the slabs should not touch the brick. If the national rules for a raised platform are in play, because someone wants the yard about 300 mm above the existing ground, drainage and consent are one conversation, not two. A quote for a walled yard should say where the water goes now, and where it can go.
Patio FAQs
Where should a trapped yard send its water?
To a gully or a channel that connects to a drain allowed to take it. A wall on every side means there is no lawn to share the rain.
Does moraine sand drain like vale clay?
No. Sand on the moraine can take more water. Clay in the vale, and clay pockets in the moraine, hold it. The outlet still matters on both.
Can the new patio cover an air brick?
No. Air bricks stay open. The paving stays 150 mm below the damp course, with a gravel margin if the slabs would otherwise meet the wall.
When is a channel drain the right outlet?
When the only gully is in the wrong place, or a doorway needs a line the water cannot cross. The channel still has to reach a real drain and stay clear of silt.