Why the corners cost more than the runs
A deck around a rectangular pool is not a rectangle. It is a band, and the area of a band of width w around a pool of length L and width W is:
Deck area = 2w(L + W) + 4w²
The first term is the straight run — perimeter times width, exactly what people expect. The second is the four corner squares, and it grows with the square of the deck width. On a 16 by 32 pool a 3 ft band is 324 square feet; a 4 ft band is 448. That is 124 more square feet for one extra foot of width, a 38 per cent jump for what sounds like a small change, and it is why deck width is the single most expensive dimension on the drawing.
Round pools behave the same way, with the same reason wearing different algebra. The ring area is πw(D + w): the πwD is the run, the πw² is the turn. For a freeform pool the calculator uses perimeter × w + πw², which is exact for any convex outline, because all the turning in a closed convex curve adds up to one full circle no matter how the curve wanders. A pool with a genuine inward notch will come out slightly high, which is the direction you want an estimate to be wrong in.
| Deck width | Band around 16 x 32 | Straight run | Corners |
|---|---|---|---|
| 3 ft | 324 sq ft | 288 | 36 |
| 4 ft | 448 sq ft | 384 | 64 |
| 5 ft | 580 sq ft | 480 | 100 |
| 6 ft | 720 sq ft | 576 | 144 |
At six feet the deck is 720 square feet against 512 of water. The pool is now the smaller part of the job.
Coping is a linear item with an unusually bad waste factor
Coping runs the whole perimeter and gets ordered in lineal feet or in pieces. Straight runs cut cleanly and a 10 per cent allowance is generous. Radius ends and freeform curves are a different animal: every piece is mitred to its own angle, offcuts rarely fit anywhere else, and 15 to 20 per cent is ordinary. Corners on a rectangle are usually a separate part number, so four L pieces get ordered on their own rather than coming out of the run.
Cantilevered concrete coping — poured as part of the deck over a form strip — has no pieces at all, which changes the take-off to a forming question. If that is your detail, take the lineal footage from this page for the form strip and ignore the piece count.
The waterline tile band, which sits just below the coping, is a different take-off again, and it is on the pool surface area calculator along with the interior finish.
Fall, and the reason it is an input
Every pool deck slopes away from the water. What the slope has to be is set by the code your jurisdiction has adopted and by the inspector who signs it off, so this page takes it from you rather than telling you. What it does is turn the slope into the number you actually need on site: the drop.
A quarter inch per foot across a 4 ft deck is one inch of fall. Across a 6 ft sun area it is an inch and a half, and that is a real elevation difference to resolve against a door threshold, a retaining wall, or the lawn. Getting it onto the drawing before the coping elevation is fixed is the difference between a deck that drains and one that ponds against the coping for the next twenty years.
Where the water goes once it leaves the deck is the other half, and it usually needs somewhere to go that is not the neighbours yard. The french drain calculator and the rain garden sizing calculator cover the two usual destinations.
What this take-off leaves out
Base preparation. A paver deck sits on compacted gravel and bedding sand, and both are volume items that dwarf the paver cost on a soft site — the paver patio calculator works those out, along with joint sand, and the edge restraint calculator handles the outer edge. Poured concrete needs reinforcement, control joints and an expansion joint at the coping, none of which is area arithmetic.
It also leaves out everything that is not the band: steps down to grade, the equipment pad slab, the walk to the gate, the spa surround. Those are separate rectangles and the extra pad field only holds one of them.
Setbacks, permits, barrier requirements, deck slope, drainage discharge and where equipment may sit are all decided by your building department and, for public or semi-public pools, your health department. Every one of them varies by state, county and city and they change. Take the drawing to them early.
Drowning is the leading cause of death for young children in and around pools, and barriers are the reason the number is not worse. What a barrier has to be — its height, its openings, the gates, the alarms, what counts as a wall of the house — is set by the code your jurisdiction has adopted and by your building department, and this page states none of it. Ask them before the deck is poured, not after.
Questions people ask
How wide should a pool deck be?
That is partly taste and partly what has to happen on the deck, and partly your building department, which in many places has a minimum walking width on at least one side and rules about what can sit near the water. As a planning matter, three feet is a walkway and nothing else — two people cannot pass, and a lounger will not fit. Four feet lets you walk past someone standing. Six to eight feet on one side is what a run of loungers or a dining table actually needs, and the usual answer is a narrow band on three sides with one wide side rather than a uniform six feet everywhere, because the uniform version costs a fortune in corners. Work out the wide area as a separate pad on this page and keep the band narrow.
Why does one extra foot of deck width add so much area?
Because the band grows on both sides of every corner at once. The straight-run part of the area is perimeter times width, which is linear, but the four corners are squares of the deck width, which is not. Going from 3 to 4 feet on a 16 by 32 pool adds 96 square feet of straight run and 28 square feet of corner, for 124 in total on a 324 square foot deck. The same effect makes freeform pools expensive: a wandering outline has more turning in it than a rectangle, and turning is what the squared term is counting.
How many coping pieces will I need?
Divide the perimeter by the piece length and add waste, which is what the calculator does. The part worth thinking about is the waste figure. On a rectangle with straight runs and four corner pieces, 10 per cent covers the cuts at the corners and the odd breakage. On a freeform pool, every piece against a curve gets mitred on both ends to an angle it shares with nothing else, offcuts are not reusable, and estimators commonly carry 15 to 20 per cent. Order the whole job in one delivery if the material is a natural stone: a second batch of travertine or bluestone will not match the first, and the difference shows most where it is wettest.
Do I need a slope on a pool deck, and how much?
Every pool deck is sloped away from the water, and this page will not tell you the number because it is not ours to state. It is set by the code your jurisdiction has adopted, and building departments differ. Enter the figure your department or your contractor gives you and the calculator turns it into the drop across your deck width, which is the number you set forms to. A quarter inch per foot across four feet is one inch. What matters practically is that the elevation gets decided before the coping is set, since the coping is the high point everything else falls away from and it is the hardest thing to move afterwards.
Should I count the equipment pad in the deck area?
Not in this take-off, and usually not in the same pour. The equipment pad is its own slab, sized around what actually sits on it plus the clearance the equipment documentation asks for and the access a service technician needs to get behind it. It is also frequently a different thickness and a different finish, since nobody walks barefoot on it. Enter it in the extra pad field if you want the concrete on one number, but keep it separate on the drawing. What sits on that pad, how it is wired and how far it has to be from the water are questions for your building department and a licensed electrician, and none of them is answered here.