By Roman Ross — Marine Construction Estimator, Shore Protect Construction
The owner of a canal-front home in Jamaica Beach, on the west end of Galveston Island, called about a concrete bulkhead with cracks forming along the top — and then sent photos that told a bigger story. The seawall itself was straight and holding, but the concrete behind it was coming apart: the drive, the patio that runs across the back of the house, and the stepped decks down to the water had all settled, the joints between the slabs had opened, the step edges were crumbling, and the seam where the deck meets the top of the wall had spread wide enough to see down into a hollow underneath. This is a common and misunderstood failure on a saltwater canal, and the fix is not the tear-out most people brace for. Below is the full project — what actually caused a whole concrete deck to sink, why we lift and seal it instead of replacing the wall, the polyurethane slabjacking method, the as-quoted scope and materials, honest 2026 pricing, and what permitting looks like on a Galveston Island canal.
Bottom line: On a saltwater canal in Jamaica Beach (west Galveston Island) in 2026, repairing an 80-foot concrete bulkhead plus the settled concrete deck system behind it — filling the voids, lifting the slabs, and sealing the joints — ran $27,800 as a fixed-scope package. The concrete sank because the tide washed the sandy backfill out from under it, so the real fix is two parts: fill the voids and lift the slabs with structural polyurethane, then seal the wall-to-deck seam and the joints so the washout stops. The seawall itself was sound — this did not need a wall replacement.
The property is a private canal-front lot in Jamaica Beach, on the west end of Galveston Island. This is saltwater — a tidal canal off the bay, with a boat lift and dock — which matters for both why the concrete failed and how the work is permitted. The structure is a poured concrete bulkhead running the width of the lot, roughly 80 feet, with an extensive concrete deck system poured over the backfill behind it: a drive down the west side, a patio that extends across the back of the home, and stepped decks that drop toward the water. The seawall was plumb and holding line. The problem was everything cast behind it.
The tells were everywhere the owner pointed the camera: the seam between the deck slab and the top of the seawall had opened into a visible gap, control joints across the drive and rear patio had spread with weeds coming through, the noses of the steps had cracked and spalled down to exposed aggregate, and the concrete had crushed and cracked where the wood pilings pass through the slab. Every one of those is the same story — soil washing out from underneath and the concrete losing its support. For what concrete and other bulkhead work runs per foot in this market, our Galveston Island bulkhead cost page covers the ranges by material; the rest of this post is one real ticket.
The first honest question on any failing waterfront concrete is whether you are looking at a support problem or a strength problem, because the price gap is enormous. Tearing out and re-pouring a seawall and a full deck system is a massive job; lifting and sealing the existing concrete is a fraction of it. So before quoting, we read the failure. Here the bulkhead was plumb and the slabs themselves were intact — cracked and dropped, but not crumbling from within. The movement traced entirely to the voids washed out beneath them. That pattern says lift and seal, not replace.
What we will not do is lift the slabs and call it finished while leaving the joints open — that is the difference between a repair that lasts and one that fails on the same schedule as the original. The one open item we flagged to the owner up front: until the ground at the waterline is probed, the base of the bulkhead cannot be fully confirmed. If the wall turns out to be undermined at its toe or footing, that is a separate stabilization question, so the quote is written with that contingency stated, not buried. Repairs like this are their own discipline, distinct from new construction. For the same fix-the-cause logic on a concrete wall in a coastal setting, see our concrete seawall cap repair on Copano Bay; for the same washout-and-void failure on a freshwater lake, our Cypress community-lake bulkhead repair; and for how bulkheads are built new on these same West Galveston canals, our Galveston vinyl bulkhead project.
The most important thing to understand about this repair is that the concrete is the victim, not the culprit. On a tidal canal the water rises and falls behind the bulkhead twice a day, and every cycle works a little of the fine, sandy backfill out through the cracks and the open joint at the top of the wall. Year after year that hollows out pockets of unsupported ground under the slabs. Concrete is strong in compression but it cannot bridge an open void; with nothing under it, the drive, the patio, and the step landings settled, their joints pulled apart, and the panels cracked. The widening seam at the wall and the sunken step at the "V" of the lower deck are the same void showing itself in two places.
That is why sealing is half the job, not an afterthought. If we lift the slabs and leave the seam and joints open, the tide simply starts hollowing out the new fill and the concrete settles again. So the repair pairs the lift with a full-length seal of the wall-to-deck seam and every deck and step joint, plus filter fabric and drainage stone where the backfill was lost — a filtered path that lets water drain without carrying soil with it.
The lift is done with polyurethane slabjacking. We drill small ports through the settled slabs and inject a two-part, high-density structural foam underneath. It expands to fill the voids, re-supports the concrete, and raises the sunken sections back toward level. Because this is a saltwater canal and the injection happens near the waterline, we specify a hydrophobic (water-insensitive) formula that cures properly with moisture present — an ordinary foam would not set reliably down there. The advantage over mud or tear-out is precision and speed: the slab comes up in controlled lift, and there is no demolition of concrete that is otherwise fine.
Then we deal with the concrete and the joints so the system acts as one piece. The broken step noses and the spalled edge at the lower deck are saw-cut back to sound concrete and rebuilt with a structural repair mortar and bonding agent, so the edges are solid and square again rather than crumbling. The cracks in the bulkhead and at the pilings are cleaned and repaired with epoxy injection and fast-set hydraulic cement rated for damp, in-and-out-of-water conditions. Finally the wall-to-deck seam and all the slab and step joints are sealed with a self-leveling marine polyurethane over backer rod — roughly 400 feet of joint — which is the piece that actually stops the tide from flushing the fill out again.
Below is the as-quoted material set, straight off the client estimate. Demolition of the failed step edges and the backfill top-off are part of the fixed-scope package total; no individual line-item prices are shown here.
The crew is a foreman, a marine carpenter, and two laborers — four on site. The work runs about five working days, with the waterside crack sealing done at low tide off the existing dock, so no barge is needed. The timeline assumes the repair is confirmed as in-kind maintenance before mobilization. The build breaks into four phases.
Phase 1 — Preparation & Crack Sealing. The crew protects the dock, boat lift, fence, and posts, cleans out the cracks and control joints across the drive, decks, and steps, and cuts away the loose, crumbling concrete at the broken step edges. At low tide the cracks on the water side of the seawall are sealed, closing the path new water uses to get behind the wall.
Phase 2 — Void-Fill & Slab Lift. Small injection ports are drilled through the settled slabs — the drive, the rear patio, and the upper and lower decks. Two-part hydrophobic polyurethane is pumped underneath to fill the voids, re-support the concrete, and raise the sunken sections back toward level, worked in controlled stages so the lift stays even.
Phase 3 — Step Rebuild & Pile-Crack Repair. The broken step noses and the lower-deck "V" edge are formed and patched with structural repair mortar so the edges are solid again, and the cracks where the wood pilings pass through the slab are routed, epoxied, and patched.
Phase 4 — Seal Joints & Restore Backfill. The wall-to-deck seam and all the slab and step joints are sealed with backer rod and self-leveling marine polyurethane. Where soil was lost, filter fabric and drainage stone go in, clean fill sand is placed and compacted, and the crew hauls off all debris and walks the finished work with the owner.
For this Jamaica Beach canal project, the quote came in at $27,800 as a fixed-scope package. The total covers labor, materials, the injection rig and compaction equipment, cutting out and rebuilding the failed step edges, the polyurethane void-fill and slab lift across the drive and decks, the full-length seam and joint sealing, the pile-crack repair, and the backfill top-off behind the wall. It is priced as a package rather than per linear foot on purpose: this repair is spread across an area of concrete and roughly 400 feet of joint, not a straight run of wall, so a per-foot rate would only distort the number. Payment is structured as a simple 50% deposit and 50% on completion.
Because three quantities cannot be measured exactly from photos — how much foam the hidden voids take, how many feet of joint need sealing, and how much broken step edge needs rebuilding — the package is priced to what the site showed, and we confirm those three on a short measure before locking the number, rather than padding the quote or surprising the owner later. Pricing your own wall? Our free bulkhead cost calculator puts a per-foot number on a repair or replacement by material and length. To see how this job fits the wider market, our Galveston Island bulkhead cost page covers per-foot ranges by material, and the Galveston Island bulkhead service overview walks through what we typically deliver on local canals. Broader concrete bulkhead and seawall repairs generally run from $120 to $350 per linear foot; jobs like this one are quoted as a package because the work is area-and-joint driven, not wall-length driven.
The reason this repair is worth doing right is that, done right, it lasts. Slabs sitting on foam that fills the voids, behind joints that no longer let the tide flush the fill out, are a long-term fix — not a seasonal one. The failure mode you are buying out of is not the concrete wearing out; it is the cycle of soil washing out, the slabs settling and cracking, and the patchwork that follows.
On a Galveston Island canal the water is tidal and jurisdictional, so a repair is treated differently from new construction. New or expanded shoreline structures fall under the U.S. Army Corps of Engineers Galveston District under Sections 10 and 404, with the Texas General Land Office over state-owned submerged land, plus the City of Jamaica Beach and Galveston County locally. Repairing an existing bulkhead in kind — same alignment, same footprint, no waterward expansion — and lifting and sealing the concrete behind it typically qualifies as maintenance and does not trigger the full new-structure review. The rule that keeps a project in the maintenance lane is staying landward of the original wall line; the moment work pushes the structure out toward the water, it becomes a new-fill question and the permitting picture changes. We confirm the maintenance status for the specific scope before mobilizing rather than assuming it.
It is almost never the concrete failing on its own — it is the ground washing out from under it. On a saltwater canal like this Jamaica Beach lot, the tide moves in and out behind the bulkhead twice a day, and each cycle carries a little of the sandy backfill out through the cracks and the open joint at the top of the wall. Over years that leaves hollow pockets under the concrete. The drive, the patio, and the steps were poured over that backfill, so once the support underneath them washed away they dropped, the joints between panels opened, and the slabs cracked because they were never meant to bridge an open void. The tell across this property was consistent: every crack and every opened seam pointed back to a hollow under the slab, not to worn-out concrete.
Yes — when the slab itself is sound and only its support washed out, you lift it rather than demolish it, and that was the right call here. The method is polyurethane slabjacking: we drill small ports through the settled concrete and inject a two-part, high-density structural foam underneath. The foam expands to fill the hollow voids, re-supports the slab, and raises the sunken sections back toward level. On a tidal canal we use a hydrophobic (water-insensitive) formula so it cures properly even with moisture present at the waterline. Lifting a slab this way costs a fraction of tear-out and re-pour, keeps your finished concrete, and — critically — it is paired with sealing the joints so the washout that caused the settlement actually stops.
For this job, no. The concrete bulkhead itself was plumb and structurally sound — it was still holding the bank. What failed was the soil behind and under the adjacent concrete, which is a drainage and erosion problem, not a wall-strength problem. Replacing a sound seawall to fix settled backfill would be spending tear-out-and-rebuild money on the wrong thing. The correct scope is to fill the voids and lift the slabs, seal the wall-to-deck seam and the joints so the tide stops flushing soil out, and rebuild the broken step edges. The one condition that would change the answer is if probing at the waterline showed the bulkhead undermined at its toe or footing — then we would stop, show the owner, and quote stabilization separately rather than assume it.
For this Jamaica Beach canal project — an 80-foot concrete bulkhead plus the whole ground-level concrete system that had settled behind it — the quote came in at $27,800 as a fixed-scope package. That covers the polyurethane void-fill and slab lift across the drive and decks, sealing the full-length wall-to-deck seam and all the joints, rebuilding the spalled step edges, repairing the cracks at the pilings, and topping off the lost backfill. It is priced as a package because the work is spread across an area of concrete and hundreds of feet of joint, not a straight run of wall, so a per-foot number would only distort it. Broader concrete bulkhead and seawall repairs in the Galveston area generally run from $120 to $350 per linear foot depending on length and how far the soil loss has spread.
On a Galveston Island canal the water is tidal and jurisdictional, so new or expanded shoreline structures fall under the U.S. Army Corps of Engineers Galveston District under Sections 10 and 404, with the Texas General Land Office over state-owned submerged land, plus the City of Jamaica Beach and Galveston County locally. Repairing an existing bulkhead in kind — same alignment, same footprint, no waterward expansion — and lifting and sealing the concrete behind it typically qualifies as maintenance and does not trigger the full new-structure review. The rule that keeps a project in the maintenance lane is staying landward of the original wall line; the moment work pushes the structure out toward the water it becomes a new-fill question. We confirm the maintenance status for the specific scope before mobilizing rather than assuming it.
Because the cracks and the settlement are symptoms — the cause is the tide washing backfill out through the open joints. Patch the cracks or even re-pour a slab while leaving that path open, and the new concrete settles and cracks on the same schedule as the old, because the ground under it keeps disappearing. This repair fixes the cause: we fill the voids and lift the slabs so they are supported again, then seal the wall-to-deck seam and the control joints with a flexible marine sealant so tidal water can no longer carry fines out from underneath, and back that up with filter fabric and drainage stone where the soil was lost. Stop the washout and the lift lasts; skip it and you are buying the same repair again in a few seasons.
Shore Protect Construction repairs and builds concrete, vinyl, steel, and timber bulkheads and seawalls — and lifts and seals the settled concrete behind them — on the canals of Jamaica Beach, West Galveston Island, and across the greater Galveston and Houston area. We read the failure before we quote it, fix the washout that caused it, and keep repairs in the maintenance lane on permitting. Request a free site estimate and we will put a real number on your shoreline.
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