Project Description
Protecting Steelwork in Coastal Environments: Remedial Structural Solutions for Seafront Properties
This project was first published in August 2023 and updated in May 2026.
This project highlights the importance of protecting steelwork in coastal environments, carrying out regular inspections, and ensuring structures are designed and maintained to withstand harsh marine conditions.
Properties located near the coast face unique structural challenges, particularly when it comes to the long-term durability of exposed steelwork.
At SWJ Consulting, we were recently appointed to assess and design remedial works for a mixed-use 1960s steel-framed commercial and residential building on the South Coast, in Christchurch, where severe corrosion and structural deterioration had compromised an external terrace structure.
Structural concerns with existing steelwork on the coastline
The property featured a cantilevered first-floor terrace attached to residential units above commercial premises. While residents had been regularly using the space as a balcony terrace, our initial structural assessment identified that the steel structure had not originally been designed to support this type of load.
It quickly became apparent that the terrace was originally intended as a lightweight canopy rather than a load-bearing balcony. However, over time, the addition of access doors and continued residential use had placed additional stress on the structure.
Project Team
Client: Private Client
Contractor: SER Ltd
The impact of coastal conditions on steel structures
One of the most significant issues affecting the building was the deterioration of the external steelwork. The steel beams had not been adequately protected against corrosion, resulting in extensive rusting and delamination.
The building’s proximity to the sea had accelerated the rate of deterioration due to constant exposure to salt-laden air and windblown spray. Coastal environments are particularly aggressive for exposed steel structures because airborne chlorides can rapidly break down protective coatings and initiate corrosion.
In this case, failed drainage systems compounded the issue. Rainwater had been allowed to collect within beam flanges and drainage channels due to:
- Poor maintenance over many years
- Failed and blocked drainage systems
- Deflection of the cantilevered structure under increased loading
- Standing water within the drainage and pipework leaking directly onto the steel sections
These conditions created the ideal environment for accelerated corrosion.
Why protecting steelwork in coastal environments matters
Steelwork located close to the shoreline requires enhanced protection measures and ongoing maintenance to ensure structural integrity over time.
According to guidance from Premier Guarantee, steelwork within 500 metres of the shoreline should typically have a minimum galvanising coating of 710g/m² to provide adequate corrosion resistance in marine environments.
Without suitable protection systems, steel structures near the coast can experience:
- Premature corrosion
- Structural weakening
- Water ingress and leakage
- Increased maintenance costs
- Safety risks to occupants and the public
Regular inspections and preventative maintenance are essential for extending the lifespan of coastal steelwork.
Remedial steelwork design and structural repairs
Following our detailed assessment, SWJ Consulting designed a remedial structural solution to restore the terrace safely while accommodating its continued use as a residential balcony.
The works included:
- Removing delaminated and heavily corroded steel sections
- Splicing new protected steelwork into the existing structure
- Improving drainage, falls, and water management
- Reinforcing the cantilevered structure for residential use
- Reinstating the terrace with appropriate corrosion protection systems
Working closely with the contractor team, we delivered a practical solution that allowed the existing structure to be strengthened without complete replacement.
Designing steel structures for coastal environments
When involved at the early design stages of a project, SWJ Consulting can help identify potential corrosion risks before they become costly structural problems.
Effective strategies for protecting steelwork in coastal environments include:
Selecting appropriate protective coatings – Choosing suitable galvanising systems, specialist marine-grade coatings, and corrosion inhibitors can significantly extend the lifespan of exposed steelwork.
Improving drainage design – Ensuring water cannot pond or collect around structural steel elements is critical. Proper drainage falls, outlets, and maintenance access should always be incorporated into the design.
Considering building geometry – The shape and detailing of a structure can influence how moisture and salt accumulate. Designing to minimise water traps and exposed vulnerable areas can reduce future corrosion risks.
Using suitable materials and backfill – Where steelwork interfaces with the ground or buried structures, selecting appropriate backfill materials and corrosion-resistant detailing can help prevent long-term degradation.
Structural Engineering support for coastal properties
At SWJ Consulting, we regularly assist clients across the South Coast with structural inspections, remedial steelwork design, and corrosion-related structural repairs.
Whether you are dealing with an ageing coastal structure, exposed balcony steelwork, or concerns regarding corrosion in a marine environment, our team can provide practical engineering solutions tailored to your property. Give our Southampton-based team a call on 02381 920656 or email mail@swjconsulting.co.uk
