Patio sizes and layouts

Almost every patio that disappoints is the right area and the wrong shape. The area was decided by what was left of the garden, and the furniture was chosen afterwards. Reverse those two decisions and the same square footage does twice the work, because a patio is really a set of nested rectangles: furniture inside a clearance band, the clearance band inside a circulation route, the route inside the paving. Everything else in outdoor room dimensions follows from getting those four rectangles in the right order.

The rectangle that counts is not the paved one#

Patios get quoted as slab sizes. The number that decides whether the furniture works is the clear furniture rectangle, and it is smaller than the paving on every side that is not a wall.

At a free edge, allow a 6 in (15 cm) set-back before any furniture leg. A chair leg on the outer 2 in (5 cm) of a paver levers the unit and tips the sitter, and it is the single most common reason a chair goes over backwards on a new patio. Where the edge has a drop of more than about 4 in (10 cm) to a lawn or a bed, make it 12 in (30 cm). Against the house, allow 3 in (8 cm) so a chair back does not scuff render, and check the door threshold: the door swing belongs to the patio, not to the room, and it is measured the way door swing and approach clearance sets out.

Run that through a real slab. A 12 x 14 ft (3.7 x 4.3 m) patio with the house on one long side and two free edges gives a furniture rectangle of 11 ft 6 in x 13 ft 6 in (3.5 x 4.1 m). That is 155 sq ft (14.4 m2) inside 168 sq ft (15.6 m2), a loss of 8 per cent that never appears on a plan. On a small patio the loss is proportionally larger: a 8 x 10 ft (2.4 x 3.0 m) slab loses 13 per cent the same way.

Measure the paving from the finished face of the wall, not the render line or the cladding, and take the diagonal as well. Paving is set out on the ground rather than between walls, so it is easy to build a patio 2 in (5 cm) out of square without noticing until the furniture sits crooked. The method in how to measure a room properly applies outdoors unchanged.

Where 12 x 9 ft comes from#

Start with the table. Dining allows 24 in (61 cm) of table edge per person, so six people on the long sides need 3 x 24 = 72 in (183 cm) of length, and the width that lets two people face each other without knees touching is 36 to 40 in (91 to 102 cm). That gives the standard six-seat table of 72 x 36 in.

Now the band. A dining chair has to travel back far enough for the sitter to clear the table edge and stand. Chair depth is 18 to 20 in (46 to 51 cm), and the getting-up movement needs another 16 to 18 in (41 to 46 cm) behind the rear legs. Rounded, that is the familiar 36 in (91 cm) minimum from table edge to obstruction, which is the same figure that governs dining room clearances indoors.

Add them:

• Length: 36 + 72 + 36 = 144 in (366 cm), or 12 ft
• Depth: 36 + 36 + 36 = 108 in (274 cm), or 9 ft
• Area: 12 x 9 = 108 sq ft (10.0 m2)

The two 108s are a coincidence, but a useful one to remember. The dining table size calculator runs the same addition for any seat count and then tests it against a room, which is the check that matters once the paving is drawn. If anyone has to walk behind a seated diner, that side goes from 36 to 44 or 48 in (112 to 122 cm), turning the 9 ft depth into 9 ft 8 in or 10 ft. Outdoors that side is usually the one against the house, because that is where the door is.

Eight footprints, from a 49 sq ft bistro to a 225 sq ft fire pit#

Every row below is the clear furniture rectangle, not the slab. Add the edge set-backs to get the paving.

The fire pit row is the one that surprises people. Working outwards from a 42 in (107 cm) pit, the seat fronts sit 36 in (91 cm) back from the pit edge for radiant comfort, so the seat front radius is 21 + 36 = 57 in (145 cm), and a 30 in (76 cm) deep chair puts the outer radius at 87 in (221 cm). That is a 14 ft 6 in (4.4 m) circle, and the arithmetic behind the spacing is set out in fire pit clearances and seating dimensions. A fire pit is not a small addition to a patio. It is the largest single furniture group most gardens contain.

Loungers behave in the opposite direction: two side by side need only 52 sq ft (4.8 m2), because a person lying down needs no clearance band at all on three sides. The full range of outdoor seating depths appears in outdoor sofa and lounger dimensions.

Why a second zone costs 13 ft, not 10#

A route across a patio is held to the same widths as one inside a house, and for the same reason: shoulder breadth plus a swing allowance. Use 36 in (91 cm) for anything that carries traffic to a gate, a door or a second zone, and treat 30 in (76 cm) as a dead-end width only, exactly as walkway and circulation widths does indoors. Outdoors there is a case for adding a few inches rather than removing them, because people carry trays across patios and the surface is rarely as flat as a floor.

The route cannot be borrowed from a clearance band. A 36 in pull-back is the space a chair occupies when someone stands up, so a person walking through it at that moment collides. This is why two zones on one patio cost more than the sum of their footprints:

Set the zones side by side rather than end to end wherever the garden allows. Two zones stacked need 22 ft (6.7 m) of depth from the house, which most gardens do not have. The same two zones placed along the house need 12 ft (3.7 m) of depth and 27 ft (8.2 m) of length, which many do. The logic is the same one that separates zones in an open plan room indoors, and it is just as unforgiving about the strip in the middle.

The 1 in 48 fall, and the level the house dictates#

Paving is never flat. It is laid to a fall so that water leaves, and the usual figure is 1 in 48, which is 2 per cent, or 1/4 in per foot. Across a 12 ft (3.7 m) patio that is 2.9 in (73 mm) of drop, and across 16 ft (4.9 m) it is 4 in (102 mm). Some references accept 1 in 80 (1.25 per cent) on a rigid, accurately laid surface, and many contractors build 1 in 40 (2.5 per cent) to be sure. All three are invisible to the eye and all three matter to the furniture.

The finished level is set from the building, not the garden. UK practice finishes paving at least 150 mm (6 in) below the damp proof course. Everywhere else the constraint is the door threshold and the sill. Because a patio build-up is typically 200 mm (8 in) of unit, bedding and sub-base, the level decision commits you to an excavation depth before a single slab is bought, and it is also what decides whether the transition at the door is level or a step, which is covered in floor transitions and threshold heights.

Three worked plans: 100, 192 and 320 sq ft#

10 x 10 ft (3.0 x 3.0 m), 100 sq ft (9.3 m2). One four-seat table at 48 x 36 in, centred, with 36 in all round and nothing else. The 6 in edge set-back on two sides means the furniture rectangle is 9 ft 6 in x 9 ft 6 in, so the table has to sit within 3 in of centre. This is the smallest patio that is genuinely a room rather than a landing, and it holds one thing.

12 x 16 ft (3.7 x 4.9 m), 192 sq ft (17.8 m2). Six-seat dining occupying 12 x 9 ft at the far end, a 3 ft (91 cm) route across the middle, and a 12 x 4 ft (3.7 x 1.2 m) strip against the house for a grill run and a bench. The strip is 4 ft deep because a 24 in (61 cm) counter plus a 24 in standing zone is 48 in, and the working aisle in front of it is the same 3 ft route, shared. The counter depths and clearances are in outdoor kitchen dimensions.

16 x 20 ft (4.9 x 6.1 m), 320 sq ft (29.7 m2). Eight-seat dining in a 14 x 9 ft zone, a 3 ft route, and a 14 x 8 ft lounge group of two facing sofas at 8 ft (2.4 m) apart. The 2 ft (61 cm) margin on the width absorbs the edge set-backs and a run of planters. The facing distance comes straight from living room seating geometry, which does not change because the ceiling has gone.

Six 600 mm slabs measure 3,630 mm, not 3,600#

Patio dimensions want to be whole numbers of paving units, and paving units are not whole numbers of feet.

Six 600 mm slabs plus their joints measure 3,630 mm (11 ft 11 in), not 3,600. Fix the patio at 3,630 mm and every course runs full; fix it at 3,600 mm and you have a 30 mm strip to cut along one edge, which is too narrow to cut cleanly and too wide to hide. The same near-miss arithmetic that ruins cabinet runs is at work here, and it is set out in imperial and metric dimension systems. Put the cut course against the house wall, where furniture and planters cover it, never at the free edge where the eye follows the line.