Seawall material calculator
100 feet of anchored wall with 4 feet showing above the water comes to 100 vinyl sheet-pile panels of 8 feet, 4.9 cubic yards of cap concrete before waste, 13 tiebacks at 8 feet on center, and 62 tons of toe rock. Change any input below and every line moves, including the arithmetic underneath it.
Updated August 2026
The arithmetic
What each line is doing
Panels. Wall length divided by covering width, rounded up. Sheet pile interlocks, so the covering width is already net of the overlap and there is no separate waste allowance. What does bite is the ends: a run that has to return into a neighbor's wall or around a boat lift piling costs you cuts, and cut panels are not reusable at the other end.
Panel length. Exposed height plus embedment, rounded up to the next even foot because that is how vinyl sheet pile is stocked. Embedment here is 1.0 times exposed for an anchored wall and 1.5 times for a cantilever. Those are planning multipliers for ordering, ours, and they are the first thing a geotechnical report will overrule. Soft organic layers under Naples canal fill are common and they push embedment up, not down.
Cap concrete. Section width times section depth times length, then divided by 27 for cubic yards. The ordered figure adds 10% and rounds up to the quarter yard, which is how a plant takes an order. Bag counts use the yield printed on the bag: 0.60 cubic feet from an 80-pound bag, 0.45 from a 60, 0.375 from a 50.
Tiebacks. Wall length divided by spacing, plus one, because there is a rod at each end. The count is rods and it is also deadmen if each rod gets its own anchor. Some designs run a continuous concrete deadman instead, in which case the number you want is linear feet of anchor rather than a count.
Riprap. Apron width times thickness times length, converted at 1.4 tons per cubic yard placed. That figure includes voids, because rock in a pile is not solid rock. Quarries publish their own tested unit weight and it varies by a few percent with the stone.
Reference: quantity by run length
Every row assumes 4 feet exposed, anchored, 12-inch panels, a 12 by 16 inch cap, tiebacks at 8 feet, and the standard riprap apron. Computed by the same code the form above runs.
| Wall run | Panels | Panel length | Cap, neat | Cap, ordered | Tiebacks | Riprap |
|---|---|---|---|---|---|---|
| 40 ft | 40 | 8 ft | 2 cu yd | 2.25 cu yd | 6 | 25 t |
| 60 ft | 60 | 8 ft | 3 cu yd | 3.5 cu yd | 8 | 37 t |
| 80 ft | 80 | 8 ft | 4 cu yd | 4.5 cu yd | 11 | 50 t |
| 100 ft | 100 | 8 ft | 4.9 cu yd | 5.5 cu yd | 13 | 62 t |
| 150 ft | 150 | 8 ft | 7.4 cu yd | 8.25 cu yd | 19 | 93 t |
| 200 ft | 200 | 8 ft | 9.9 cu yd | 11 cu yd | 26 | 124 t |
Reference: what exposed height does
Height is the input that moves the job most, and it moves two quantities at once. Every extra foot showing above the water adds a foot of panel above the mudline and another foot or a foot and a half below it.
| Exposed | Embedment, anchored | Panel, anchored | Embedment, cantilever | Panel, cantilever | Deadman setback |
|---|---|---|---|---|---|
| 3 ft | 3 ft | 6 ft | 4.5 ft | 8 ft | 6 ft |
| 4 ft | 4 ft | 8 ft | 6 ft | 10 ft | 8 ft |
| 5 ft | 5 ft | 10 ft | 7.5 ft | 14 ft | 10 ft |
| 6 ft | 6 ft | 12 ft | 9 ft | 16 ft | 12 ft |
| 8 ft | 8 ft | 16 ft | 12 ft | 20 ft | 16 ft |
Read the last two columns together. A wall showing 8 feet needs 24-foot panels if nothing ties it back, against 16-foot panels if something does. That is why almost every seawall in Naples above four feet of exposure is anchored, and why a failed tieback on such a wall is not a small problem.
What this take-off is not. It is a shopping list, not a design. It says nothing about panel section modulus, rod diameter, cap reinforcement, or whether your soil will hold any of it, and all four of those are decided by a Florida licensed engineer looking at a boring log. Use these numbers to read a bid, not to build a wall.
Questions about the numbers
How many vinyl sheet-pile panels do I need per foot of wall?
One per foot with 12-inch panels, two per three feet with 18-inch, one per two feet with 24-inch. The number that matters is covering width, which is what the panel holds once the interlock is engaged, not the width of the extrusion lying on the ground. 100 feet of wall in 12-inch panels is 100 panels, and there is no waste factor on that count because sheet pile is cut to length rather than trimmed to width.
How long do the panels have to be?
Exposed height plus embedment, rounded up to the next even foot. This take-off uses an embedment of 1.0 times the exposed height for a wall carrying tiebacks and 1.5 times for an unanchored cantilever, which is planning practice for loose coastal sand and is our stated assumption, not a design. At 4 feet exposed and anchored that gives 8-foot panels. Real embedment is a geotechnical number that moves with soil density, the surcharge sitting behind the wall, and how deep the water is in front of the toe.
Should I buy bagged concrete or ready-mix for the cap?
Ready-mix, unless the pour is a patch. A 100-foot cap at 12 by 16 inches is 4.9 cubic yards, which is 245 eighty-pound bags with the waste allowance in. That is a pallet and a half, several hours of mixing, and a cold joint every time the mixer stops. The bag count is here because it is the right answer for a six-foot section of cap knocked out by a boat, and the wrong answer for anything longer.
How far behind the wall does the deadman go?
At least twice the exposed height, and never less than 6 feet, which for a 4-foot wall means about 8 feet back from the face. The anchor has to sit outside the wedge of soil that would slide if the wall let go, so an anchor set too close is carried by the same soil it is supposed to be anchoring into. This is the constraint that sends Naples retrofits to helical anchors instead: on a lot with a pool deck at 10 feet, there is nowhere to bury a deadman.
Is riprap at the toe worth it?
On a canal with deep water in front of the wall, usually. Toe rock does two things: it armours the mudline against the scour that undermines the sheeting, and it adds weight in front of the toe where the wall needs passive resistance most. The standard apron in this take-off is 6 feet wide and 2 feet thick, which on 100 feet of wall is 62 tons of quarry rock at 1.4 tons per cubic yard placed. Confirm the unit weight with the quarry, because they all quote off their own tested figure.