The Roundhouse, Park Lane, Old Knebworth, SG3 6PP

Set amid open countryside near the rural hamlet of Old Knebworth in Hertfordshire, this remarkable five-bedroom house was built on the site of a disused above-ground water tank.

The circular Roundhouse radiates ergonomically around a majestic central tree-like core from which its three levels and sweeping irregular roofline are suspended.

Designed with handcrafted natural materials and sustainability at the forefront, it extends over 4,820 sq ft, with generously proportioned spaces for living and working.

Despite the secluded feel, the house is within easy reach of Cambridge, St Albans and under 30 minutes by train from London King's Cross.

The Building A tapestry of reclaimed and local materials was used for the construction, firmly rooting the building in the region's vernacular.

The concrete reservoir lid was crushed to create the cladding for the façade, and its striking Edwardian steel struts now support the balcony.

The entirety of the wood was sourced from local larch, ash and oak trees, harvested and milled less than a mile away on the neighbouring historic Knebworth House estate.

The rest of the predominantly reclaimed materials were carried by hand to the grounds to protect existing trees.

The house can operate almost entirely off-grid, with a clear water septic tank, a wood-fired/electric range cooker, roof-top solar panels and an uneven shape that allows it to collect rainwater from the conical roof.

Thermally broken Crittall windows enhance energy efficiency, while lightwells deliver abundant natural light to all floors.

The central tree-trunk core, a towering 14-metre reclaimed steel pipe, serves as the main chimney, allowing warm air to circulate from the biomass boiler.

The house has underfloor heating on all levels, 10kw of battery storage and is wired for high-speed internet connection.

The Tour The house lies off a country lane with established trees setting a tone of tranquillity and seclusion from the moment of arrival.

A paved pathway meanders across wooded grounds, leading to a moated entrance gate for pedestrian access, while a gated driveway provides access by car and parking for several vehicles.

The façade is defined by a jigsaw of stone, Lutyens-inspired red-brick and Edwardian concrete, interspersed with bee bricks to encourage pollinators to nest.

The house is topped by a weathervane and a striking cone-shaped reclaimed tiled roof, while expansive glass panels wrap all around, contributing a sense of lightness.

The main entrance is on the first floor, reached via an external staircase.

Past the front door lies the inviting porch, characterised by a soft palette and natural light washing down from the skylights above, and stone slabs extend underfoot.

There is plenty of storage space provided by hand-crafted joinery and a wooden staircase leading to an upper mezzanine floor.

The top floor is entirely occupied by the sweeping open plan reception area, where floor-to-ceiling glass panes remove the boundaries with the surrounding landscape, for an overwhelming impression of openness.

Soaring vaulted ceilings and expansive skylights flood the space with abundant natural light throughout the day.

Harmoniously integrated with their leafy surroundings, the interiors are characterised by a neutral palette and an emphasis on natural materials.

Solid larch floorboards run underfoot, with large glass panels in circular formation offering glimpses to the landing below.

Anchored by the majestic central core, which serves as a central chimney and circulates warm air across the spaces, the open plan radiates outward to include the kitchen, dining, and living areas.

The kitchen has its focal point in a red electric/wood-fired Thornhill range cooker topped by a tiled zellige splashback.

Made of solid wood, bespoke units are complemented by a generous oak-topped island with seats for casual dining and underneath storage space.

Above the sink, a porthole window frames leafy views of the garden.

Tucked to one side, a secondary kitchen provides additional storage and houses the integrated appliances, a dual-door plumbed American fridge (Samsung) and 15 15-setting dishwasher (Samsung).

Two distinct lounging zones cater to different moods: One is oriented toward the gardens, where expansive trifold doors lead to a generous balcony with panoramic views and space for outdoor dining; the other is nestled in a more secluded part of the open plan and warmed by a wood burning stove.

Also on this floor are the playroom and a separate WC room. The open plan is crowned by the light-filled mezzanine, the perfect space for a crow’s nest office/study.

A striking, spiral open-tread steel and ash staircase wraps around the central columns as it descends toward the levels below, with subtly painted flowing handrails.

There are five bedrooms on the first floor, all accessible from the landing.

Finished in a neutral palette, the peaceful principal bedroom opens directly onto the side garden, perfect for stepping out in the fresh morning air.

Solid larch floorboards ground the space in soft warmth.

The natural clay plaster ensuite is well appointed with decorative encaustic tiles in a graphic pattern and fitted with a roll-top bathtub and a shower.

The guest bedroom has its own encaustic tiled and clay plaster ensuite shower room.

There are three additional natural carpeted double bedrooms with access to a shared bathroom, finished with decorative pink and green tiles and fitted with a walk-in shower, a bathtub, and a vintage wash basin.

Solid ash stairs lead down to the versatile lower level, divided into distinct living zones.

A reclaimed brick archway gives way to a fully functioning oak bar with counter space for seating and a generous dining area, perfect for easy entertaining.

From here, doors open into the home gym/studio/theatre, with a wall of built-in cabinetry and cork flooring underfoot, and a separate WC.

A wine cellar/utility room leads to the spacious laundry, fitted with Samsung appliances and linen storage cupboards.

At the opposite end of the plan is a substantial log store, workshop, and storage area that connects to the plant room and biomass boiler.

Outdoor Space An enchanting natural landscape wraps around the house, offering ever-changing views across the seasons.

Wonderfully private, the landscaped gardens are bordered by hedgerows and established oak and fir trees, interspersed with terraced areas, shingled paths, and grassy lawns.

To the rear, a paved terrace is arranged with a generous outdoor dining area looking out toward the country, sheltered from the sunlight by mature oak trees.

From the open-plan reception area on the first floor, trifold doors lead out to an expansive balcony, surrounded by the dense canopy of treetops and perfect for unwinding or outdoor dining.

The Area The Roundhouse sits on a quiet country road within walking distance of the iconic Grade II*-listed Knebworth House, a Tudor stately home with a wide programme of events including live music, open-air theatre and classic car shows.

The area is surrounded by lush greenbelt countryside.

The house has direct access to a range of woodland and open country footpaths, from which local dining favourites The Lytton Arms and The Robin Hood, two classic country pubs, can be reached via a gentle 20-minute stroll.

The historic Stevenage Old Town’s centre is a short 10-minute drive from the house, well served with a wide range of supermarkets, independent pubs and restaurants.

Schooling options include Knebworth Primary and Nursery School, Heathmount School, Dame Alice Owen’s School in Potter’s Bar, Haileybury College and St Albans High School.

Knebworth rail station is a 14-minute walk from the house and provides direct services to London King's Cross in 40 minutes.

Stansted airport is a 50-minute drive away, with daily flights to many international destinations. Council Tax Band: H