Marine Grade Concrete Works on Jubilee Pool, Penzance
Concrete work delivered on a Grade II listed 1930s seawater lido, in marine grade concrete and rapid set concrete, scheduled around low tide windows. A structure that takes the full weight of Mount's Bay in a storm sets the specification, not the contractor.
What a Grade II Listed Seawater Lido Demands of a Concrete Contractor
Cornwall Civils was brought in to assist on this project rather than to lead it. A specialist concrete formwork contractor held the works, and we were called in to work alongside them and help deliver the job on site, inside the windows the tide allows. What follows is the work as it was built, and what a structure like this demands of everyone on it.
Jubilee Pool is a Grade II listed art deco lido, built on the Penzance promenade in the 1930s and one of the largest surviving seawater lidos in Britain. It sits where the town meets Mount's Bay, and in a storm it takes the sea head on.
That is the whole brief before anyone opens a drawing. Concrete in a tidal splash zone is not the same material problem as concrete on an inland site. Salt water carries chlorides, chlorides work their way through the cover to the reinforcement, and once steel begins to corrode it expands and pushes the concrete off itself. Specification and cover are what decide whether a repair lasts a generation or a couple of winters.
The listing sets the second half of the brief. On a listed structure the method follows the fabric. You work to what is already there and to what the consents allow, rather than re-detailing a 1930s building to suit a programme.
The Work: Marine Grade Concrete, Rapid Set Concrete and Low Tide Windows
The work carried out on the pool used marine grade concrete, rapid set concrete, and a programme built around low tide windows. Each of those three is a direct answer to a condition the structure imposes.
Marine grade concrete is a mix designed for chloride exposure rather than a standard structural mix used near the sea. It is denser and less permeable, and it is placed with enough cover over the steel to hold chlorides away from the reinforcement for as long as possible. Get the mix or the cover wrong in a splash zone and the repair becomes the next defect.
Rapid set concrete exists for the tide. Where a working window closes in hours, an ordinary mix is the wrong tool, because it will still be green when the water comes back over it. Rapid set concrete gains strength inside the window, so the repair is stable before the sea returns to test it.
The low tide window is the programme. The tide decides when work can happen and for how long, which means setting out, cutting, mixing and staging all happen before the water drops. The window is spent working rather than preparing, and nothing is left where the sea can take it.
None of that is discretionary. On a listed marine structure the exposure sets the specification, the listing sets the method, and the tide sets the hours. The same three disciplines govern every coastal job we take on in west Cornwall.
The Constraints We Solved on a Tidal, Listed Structure
Three constraints run through the whole job, and they pull against each other.
The same discipline applies on any exposed Cornish site, where the weather closes the window as often as the tide does.
The tide is a fixed programmeIt cannot be extended, moved or negotiated with, so the only variable left is how well prepared you are when it drops.
The listing narrows every method choiceMaterials, finishes and repair methods have to sit with the original fabric, so the easy modern shortcut is usually not available.
Marine exposure is permanentSalt does not stop after handover. Anything specified for a structure like this is specified for what the sea will do to it over decades, not for what it looks like on the day.
On a tidal site the programme is not yours. You set out, mix and stage everything before the water drops, because the window closes whether you have finished or not. Matt Richards, director
The Services This Project Demonstrates
Work like this sits inside two of our core disciplines. Specification, placement and cover in an aggressive exposure are concrete services. Working to a fixed window on a constrained site, with everything staged before it starts, is groundworks discipline applied to the coast. More of the same thinking sits across our completed projects.
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If your site is exposed, tidal, listed, or all three, tell us what the drawings say and what the access looks like, and Matt will come and see it. Coastal work is priced off the exposure and the window, not off an inland rate.
Call Matt Richards on 07958 102538 · Get a free quote online
14 The Strand, Newlyn, Penzance, TR18 5HN
Phone: 07958 102538
Email: info@cornwallcivilsandconstruction.co.uk
Hours: Mon to Fri 07:00 to 17:00 · Sat 08:00 to 12:00
Sunday: emergency call out only
Last updated: 22 September 2026