The air of the Bay works on your house, even when nobody is in it

There is a sentence I hear often, the first time an owner shows me round: "the house hasn't moved since we bought it." It has moved. It simply moved slowly, and nobody was there to see the movement.

Coastal buildings age differently from inland ones. Not faster in themselves, but by other mechanisms, and with failure points that surprise people who do not know them.

I. Salt: corrosion that never sleeps

Sea spray deposits a fine film of chlorides on every exposed surface. That film is hygroscopic: it draws moisture from the air and keeps metals permanently wet, even in dry weather.

The result is corrosion that never stops, including at the height of summer. Around the Bay, exposure varies with distance from the shore and with orientation: a west elevation three hundred metres from the water receives deposits on a wholly different scale from an east elevation sheltered by forest.

What suffers, in order:

• Zinc-plated screws in decks and cladding. They rust, they swell, and they split the timber around them.
• 304 stainless, very widely used, which pits in marine air. On the Bay the grade to specify is 316 — "marine" stainless, containing molybdenum, far more resistant to chlorides. About 30% more expensive, with roughly four times the service life.
• Sliding door tracks and rollers, which seize as salt and sand accumulate. A door that is forced eventually goes out of adjustment altogether.
• Hinges, locks and cylinders, whose wear goes unnoticed until the key will not turn, generally on arrival, at ten in the evening, on a Friday in August.
• Outdoor air-conditioning and heat pump units, whose aluminium exchangers degrade and lose efficiency. Coastal models with anti-corrosion treatment exist and are entirely justified here.

II. Condensation: the fault you create yourself

External humidity is not the real problem. The real problem is the meeting of humid air and a cold surface.

A house closed in November, unheated, with its air inlets carefully sealed, is a condensation machine. Interior air stays loaded — floors, masonry and furniture slowly release their moisture — and meets walls at 8 °C. The dew point is reached. Water deposits on cold surfaces: north corners, the backs of wardrobes, behind curtains, window reveals.

Three months later you open up. There are black patches in the corners, a cellar smell, wallpaper cockling. The owner concludes there is a weatherproofing problem. In nine cases out of ten there is none: the house simply breathed into a void.

The countermeasures are known and inexpensive:

• Hold 8 to 12 °C in the body of the house rather than switching off.
• Keep mechanical ventilation powered, always.
• Never block low-level vents or trickle vents in the joinery.
• Pull furniture ten centimetres clear of cold walls.
• Put a dehumidifying box in each windowless room and empty it at every visit.

III. Rising damp, a local speciality

The subsoil around the Bay is sandy, often with a shallow water table. Many older buildings — oyster village houses, échoppes, pre-war villas — were built without a damp-proof course, or with systems that have aged out.

Water then rises through the masonry to an equilibrium height determined by the material's porosity and by ventilation at the wall base. It carries salts, which crystallise at the surface as it dries and blister the render.

Two classic mistakes make it worse.

First, applying an impermeable cement render at the wall base. The water does not stop; it rises higher, until it finds somewhere it can evaporate. You move the problem up by a metre.

Second, raising the ground level against the façade during landscaping — a terrace, a bed, a driveway. The drainage layer disappears, and so does ventilation at the wall base.

The right instinct is the opposite: clear the wall base, let it breathe, prefer breathable lime renders, and treat the source with perimeter drainage where that is justified.

IV. Sand, the agent everyone forgets

Nobody lists sand among the threats. It should be there.

Driven by the westerly, it settles everywhere and acts as a mild abrasive. It scratches exposed glazing, dulls stainless steel, accumulates in tracks and joinery grooves, blocks terrace outlets and fills gutters mixed with pine needles.

It is also what prematurely wears sliding door gear: the roller runs on a bed of grains, and the track hollows out.

None of this is irreversible, provided things are cleaned regularly. On front-line houses, a monthly pass over tracks and outlets is routine maintenance, not heavy work.

V. What it looks like over ten years

Take two identical villas, built the same year at Piraillan, four hundred metres from the water.

The first is maintained to a calendar: ironmongery rinsed twice a year, gutters cleared in autumn, frost protection held, ventilation running, timber re-coated every three years on the west side, joinery seals checked.

The second is "looked after" — opened in summer, closed in September, and visited by a kindly neighbour.

At ten years the difference does not show in photographs. It shows in the quotation: the second house needs cladding repairs, two sliding doors replaced, mould treatment in the north bedrooms and terrace waterproofing renewed. That is tens of thousands of euros, against a few thousand a year of routine maintenance.

Arithmetically it is the same money. Except that it is spent all at once, under pressure, with trades chosen by availability rather than competence — and often at the moment one had hoped to sell.