It was the house that stayed dry. In 2005, a storm and tidal surge devastated the coast of South Uist, damaging homes and taking five lives. But this low building, less than five metres above sea level, somehow escaped the flood.

Cuir na Bhoir is a thatched blackhouse built on a delicate spit of land on the west coast of South Uist, now a holiday cottage. I have travelled here from Devon to help local thatcher Neil Nicholson re-thatch it. We are using water reed from Tayside – not Hebridean, but more local than most thatching reed used in the UK, over 80% of which is imported from as far away as China.

The more traditional material in the Western Isles is marram grass, a spiky plant that grows among the sand dunes, and helps to stabilise them, too. Cutting marram grass for thatching is permitted, but strictly controlled to prevent coastal erosion – a particular concern on the west coast of South Uist, which is vulnerable to rising sea levels due to its large areas of fragile, low-lying machair (sandy, coastal grassland).

Working on the lea side of the roof, we lay the reed over an old layer of marram grass, a technique known as “overcoating”. Beneath the marram sits an older “base coat” of peat turf, hung from nails driven into closely spaced vertical roof timbers known in Gaelic as cabar (as in – yes – tossing the caber). On this almost treeless island, timber was mostly salvaged from the shoreline. A neighbouring crofter, Ian Starkey, tells me he has seen sections of an old wooden loom built into a roof. The inside of this roof has been blackened by smoke from open fires and even now, 20 years after Cuir na Bhoir was converted into a modern dwelling, the attic space still carries the sweet reek of peat smoke.

A quad of whooper swans thwump overhead. Above the darkening machair, a small flock of lapwing turn clumsy pirouettes. And I watch a big spring tide begin to push its way around the dunes, snaking in long pools behind the cottage. By nightfall, Cuir na Bhoir will be surrounded on three sides by water. And once again, for now, the house will stay safe above the sea.