Building near the sea: materials that survive salt air
A sea view is one of the reasons people pay a premium for houses in Sea Point, Camps Bay, Bantry Bay, Llandudno or along the False Bay coast. The same location is hard on buildings. Salt carried on the wind settles on every surface, attracts moisture and attacks metals, coatings and concrete. Choosing the right materials at the start saves a lot of maintenance later.
Metals: the first thing to fail
Salt corrodes ordinary steel quickly. On the coast, you will see rust stains running from balustrade fixings, gate hinges and light fittings within a few years if the wrong materials are used.
- Stainless steel: use marine grade 316 for exposed balustrades, fixings and fittings. Grade 304, common in kitchens, will tea-stain and pit in salt air.
- Mild steel: if you use it, it needs hot-dip galvanising and a proper paint system on top, and it still needs regular maintenance.
- Aluminium: should be powder-coated or anodised to a coastal or marine specification. Ask your supplier what specification they offer and what the warranty covers near the sea.
- Fixings: the screws and bolts matter as much as the material they fix. A 316 balustrade held on with zinc-plated bolts will still rust.
Concrete and plaster
Salt and moisture penetrate concrete over time and attack the steel reinforcing inside it. When the steel rusts, it expands and cracks the concrete off (“concrete cancer”). Coastal structures need enough concrete cover over the steel, a good concrete mix, and repairs made early, before cracking spreads.
Plaster on coastal walls should be sound and well cured, and painted with a system made for exterior use. Cracks should be repaired before they let salt-laden water in.
Windows and doors
Wind-driven rain is a bigger risk on the coast than in sheltered suburbs. Choose windows and doors rated for the wind loads at your site, with good drainage in the frames and seals that can be maintained. Sliding doors on exposed elevations need proper sills and drainage, or water will be driven under them in a north-westerly storm.
Timber
Timber decks, screens and doors weather quickly in sun and salt. Hardwoods and treated timbers suited to exterior use last longest, but they all need regular oiling or sealing. If you do not want the maintenance, consider composite decking or let the timber go silver deliberately.
Paint
Use a paint system made for coastal conditions, and do the preparation properly. On the coast, walls should be washed down before painting to remove salt. We wrote a separate guide on painting coastal homes.
Maintenance is part of the design
Even the best materials need care near the sea. Rinse balustrades and window frames with fresh water a few times a year, check sealants annually, and repaint before the coating fails, not after. A maintenance plan at handover is worth more than a long list of guarantees.
Our work on the coast includes a villa in Sea Point and Pembroke on the V&A Waterfront. If you are building near the sea, get in touch.
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