Rupert McKelvie’s latest creation sits somewhere between architectural statement and wellness refuge. The Aquila, a mobile sauna from his Devon-based studio Out of the Valley, transforms the traditional Finnish ritual into something you can tow behind a truck. It’s taking heat therapy to lakesides, coastal cliffs, and forest clearings across the United Kingdom, proving that proper bathing culture doesn’t need permanent foundations.
Built on a double-axle trailer measuring just 3.8 meters in length, this compact structure seats six people and runs entirely off-grid. Black larch cladding covers the exterior, treated using yakisugi, the Japanese charring technique that both protects the wood and creates that striking carbonized finish. The roof folds down using a mechanical system that took multiple prototypes to get right. McKelvie admits it was the hardest part of the build, requiring constant testing to ensure the mechanism could handle repeated setup and breakdown without fail.
Designer: Out of the Valley
McKelvie started Out of the Valley six years ago after building his first timber cabin as a personal escape near Dartmoor National Park. That project sparked something bigger, evolving into a full design-build practice focused on handcrafted structures that work with natural materials rather than against them. The Aquila marks the studio’s most ambitious output so far, earning recognition this year with a longlisting at the Dezeen Awards 2025 in the Product Design category for Health, Wellbeing and Wearables. It competed against over 4,300 entries from 89 countries.
Inside, thermally modified alder lines the walls, chosen specifically because it can handle extreme temperature shifts without warping or splitting. A 16-kilowatt Narvi wood-burning stove anchors the space, delivering the kind of authentic heat that electric alternatives struggle to replicate. Solar panels power subtle LED lighting throughout, keeping the unit functional wherever it gets parked. At the rear, a panel drops down to form an entrance deck, while an integrated cold shower completes the traditional contrast bathing experience that sauna purists swear by.
The design packs in clever details without feeling overworked. Perforated storage at the hitch end holds firewood for multiple sessions. The folding roof protects everything during transport and creates visual drama when deployed. The compact footprint gets into remote locations while maintaining comfortable capacity inside, which isn’t an easy balance to strike when you’re working with trailer dimensions.
Over recent months, Out of the Valley has partnered with lifestyle brands Passenger Clothing and Canopy & Stars to tour the Lake District National Park. Another unit spent a season with Unique Homestays, giving vacation rental guests an unexpected amenity. McKelvie and his team handcraft each unit in their workshops, with a current lead time sitting at four months. Pricing is available on request, reflecting the bespoke nature of every build and options for customizations, including door orientation and heating preferences.
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