Outdoor sofa, lounger and cushion dimensions

Everything about an outdoor sofa that a catalogue tells you is a frame dimension. Everything you experience is a cushion dimension. The gap between the two is about 5 in (13 cm) of foam that behaves differently when it is new, when it is wet and when it is four summers old, and it is the reason a set that measured correctly on paper can be uncomfortable on delivery.

Seat height is measured to a compressed cushion#

An outdoor seat height is the vertical distance from the finished paving or decking surface to the top of the seat cushion with an adult sitting on it. Three faces are wrong and all three are quoted: the top of the bare frame deck, the top of the uncompressed cushion, and the top of the arm.

The frame deck is the hard platform the cushion sits on, and it is usually 12 to 14 in (30 to 36 cm) above the ground. Sit on it bare and it is a bench for a child. The uncompressed cushion top is 17 to 20 in (43 to 51 cm) and it is the number that appears on most spec sheets, because it is the one you can measure with nobody in the way. The number that matters is the third one, and it lands between the other two.

Take a typical aluminium frame: a deck at 13 in (33 cm), a 5 in (13 cm) cushion of quick-dry reticulated foam. Empty, the seat measures 18 in (46 cm). With an adult of average weight on it, the foam gives up about a quarter of its thickness, so 5 in becomes roughly 3.75 in (10 cm) and the finished seat height is 16.75 in (43 cm). That is a good number, and it is 1.25 in (32 mm) below the one on the label.

Where 16 to 18 in comes from outdoors#

The constraint is popliteal height: the distance from the floor to the underside of the thigh at the back of the knee, sitting. Panero and Zelnik put the fifth percentile adult female at roughly 14 in (36 cm) barefoot and the ninety-fifth percentile adult male at about 19.5 in (50 cm). A seat taller than the shorter user's popliteal height presses on the underside of the thigh and cuts circulation, which is why seat heights are set near the bottom of the range rather than the middle. The full derivation sits in seat height, depth and angle, and it is the same arithmetic that produces the indoor sofa band in sofa dimensions.

Outdoors, two things push the answer up rather than down.

• Shoes. Almost nobody is barefoot on a terrace, and a shoe adds 0.75 to 1.25 in (19 to 32 mm) of effective leg length. That moves the comfortable band up by about an inch.
• Standing up from a hard surface. Indoors you rise from a seat onto carpet with a coffee table you can push against. Outdoors the ground is often a wet slab with a fall on it. A seat at 15 in (38 cm) means the hips start below the knees and the whole body weight has to be lifted before it can be moved forward.

Against those, one thing pushes down: outdoor seating is designed to be reclined in, and a lower, deeper seat with a raked back is more comfortable for an hour of sitting still than an upright one. That is the whole argument for deep seating, and it is why an outdoor sofa is typically 33 to 38 in (84 to 97 cm) deep against 36 to 40 in (91 to 102 cm) indoors but with far more of that depth given over to cushion.

Cushion thicknesses: 5 in seats, 4 in dining pads#

Outdoor foam is not indoor foam. Reticulated polyether foam has its cell walls burned out so water passes straight through, and the density that comes with that is typically 1.5 to 2.0 lb per cubic foot (24 to 32 kg per cubic metre) against 2.5 to 3.0 lb (40 to 48 kg) for a good indoor high-resilience foam. Less material per unit volume means more compression under the same body, which is where the 25 per cent working figure comes from. Cushions wrapped in a polyester fibre layer compress more again in the first season as the fibre collapses, typically another 0.25 to 0.5 in (6 to 13 mm) permanently.

The sizes of scatter cushions and the oversize rule for inserts are set out in cushion, pillow and throw sizes, and they do not change outdoors: the insert is still 2 in (5 cm) larger than the cover.

The 24 in cushion module that fixes the length#

Outdoor sofas are not sized from the body. They are sized from a cushion, and the cushion comes from a small set of stock plan sizes because foam is cut from stock buns and covers are cut from 54 in (137 cm) wide fabric. That gives a module of 24, 25 or 27 in (61, 64 or 69 cm) square, and every frame dimension follows from it.

The corner is the module that costs money. A corner unit is square in plan, so its side is the full frame depth: a 34 in (86 cm) deep range has a 34 in square corner. It joins two runs but seats one and a half people at best, because the two seats meeting at 90 degrees share the same cushion. When you cost an L-shaped arrangement per seat, the corner is the most expensive seat in the set and the one nobody chooses. The same geometry, and the same penalty, appears in sectional sofa dimensions.

Loungers, daybeds and the space behind them#

A sun lounger is 76 to 80 in (193 to 203 cm) long and 26 to 30 in (66 to 76 cm) wide, with the seat platform at 13 to 16 in (33 to 41 cm). The width comes from shoulder breadth plus room for the arms to rest beside the body: a ninety-fifth percentile male shoulder breadth is about 20 in (51 cm), and 26 in leaves 3 in (8 cm) each side.

The dimension that gets missed is behind the head. A reclining back needs the backrest to fall through its arc, and on most ratchet frames that sweeps 10 to 12 in (25 to 30 cm) beyond the end of the frame. Wheeled loungers need more, because tipping the frame onto its wheels rotates the whole thing about the axle. Allow a 92 in (234 cm) strip for a 80 in (203 cm) lounger and it will always work.

Two loungers side by side want 12 to 18 in (30 to 46 cm) between them: enough for a side table of 16 to 18 in (41 to 46 cm) square and enough to swing your legs off without hitting the neighbour. Three loungers on a 12 ft (3.66 m) run of terrace works out at 30 in each plus two 15 in gaps, which is 120 in (305 cm), so a 12 ft terrace takes three and a 10 ft (3.05 m) terrace takes two.

Paving falls, deck gaps and the 72 in balcony#

The ground has a fall on it. Paving is laid to shed water, typically at 1 in 80, which is about 1/8 in per foot (12 mm per metre). Across the 34 in (86 cm) depth of a sofa that is 0.43 in (11 mm) of drop, and the sofa either tips backwards into the fall, which feels fine, or forwards down it, which feels wrong at a fraction of an inch. Face the seating uphill where you have the choice.

Decking gaps swallow feet. Deck boards are laid at 5.5 in (140 mm) wide with gaps of 1/8 to 1/4 in (3 to 6 mm), and a furniture glide of 1 in (25 mm) diameter spans that comfortably. A slim tapered leg with a 3/8 in (10 mm) tip does not, and it also concentrates load: check the guard heights and board spans in deck sizes and railing heights before loading a deck with a full sectional.

The balcony case. A 34 in (86 cm) deep sofa plus a 36 in (91 cm) walkway is 70 in (178 cm), and a great many balconies are 60 to 72 in (152 to 183 cm) deep in total. That single sum is why deep seating does not go on a balcony and why the sizes in balcony dimensions and the furniture that fits are a different family of products.

Getting it there. An 84 in (213 cm) sofa frame is delivered assembled far more often than an indoor one, and it usually has to pass through a side gate. The clear width arithmetic is the same as indoors and is worked through in measuring the delivery path.

Setting out: 110 in of terrace for one group#

Outdoor conversation geometry is the indoor geometry with a small penalty applied. Facing seats want 6 to 9 ft (1.8 to 2.7 m) between the cushion faces, slightly wider than the indoor range because outdoors there is background noise and because people speak across an open space rather than into a room. Beyond about 10 ft (3 m) conversation stops.

The coffee table gap goes to 18 to 20 in (46 to 51 cm) rather than the indoor 16 to 18 in explained in how far the coffee table should be from the sofa, for two reasons: outdoor cushions push the sitter forward as they compress, and outdoor tables are often heavier and less easily nudged. The table top belongs at 16 to 18 in (41 to 46 cm), level with the finished seat, not at the 18 to 20 in of an indoor tray table.

Circulation behind and around the group follows the standard bands set out in walkway and circulation widths: 36 in (91 cm) for a route people use, 30 in (76 cm) where they only pass occasionally. On gravel, add 6 in (15 cm), because people walk wider on loose material. The full worked layouts for a terrace, including how the seating group sits against dining and circulation, are in patio sizes and layouts, and the seating ring around a fire is a different geometry again, covered in fire pit clearances and seating dimensions.

The whole seating group above needs a terrace 110 in (279 cm) deep before anything else happens, which is a useful number to hold against the rest of the outdoor dimensions section when a plan starts to feel tight. If you want the arrangement checked against a specific room or terrace rectangle, the sofa and seating fit checker runs the same clearances.