Porthmadog House is a 475-square-metre, two-storey replacement home set on a sloping coastal site in North Wales, overlooking an estuary of the Irish Sea. Designed as a long-term home for a recently retired couple, the project brings the owners back to their roots.

The site was acquired at the end of 2019 after five years of research and preparation. The existing house, which had stood derelict for 15 years, had once belonged to a childhood friend of the clients. The decision to buy the site was based on both personal connection and the opportunity for a new beginning.

The brief called for a home capable of responding to the exposed coastal conditions while remaining warm, comfortable, and closely connected to its setting. Maximising views of the sea and estuary was a priority, alongside creating a sense of shelter and permanence. Beyond a small number of specific requests — including a snug, a gym, and social spaces oriented towards the panoramic outlook — the clients entrusted the overall design direction to Magnus Ström, Founder of Ström Architects.

Site response and form

Ström Architects analysed wind patterns, rainfall, and sightlines to inform the building’s configuration. Located in an exposed setting in North Wales, the house opens towards the Irish Sea while drawing protection from the inland landscape.

The composition is formed by two slate-clad ground-floor volumes and a corten-clad first floor. The lower volumes are positioned to act as windbreaks, shaping a sheltered entrance court and orientating the principal living spaces towards uninterrupted views. Constructed from locally quarried Welsh slate sourced from a quarry approximately 30 minutes from the site, the ground floor anchors the building within its exposed setting while maintaining continuity between exterior and interior surfaces.

Above, the corten-clad first floor pivots towards the sea. Steel fins frame the angled form, providing weather protection, solar shading, and privacy without obstructing views. The upper structure spans across the lower volumes, creating sheltered terraces beneath. The structural design was developed in collaboration with Jensen Hunt Design to ensure resilience in the coastal environment.

Spatial organisation

At ground level, two slate-clad volumes contain enclosed functions, including the snug, gym, and plant room. Between them, the principal living spaces open out through floor-to-ceiling glazing. A courtyard, informed by Japanese spatial principles, introduces natural light into the centre of the plan and provides a calm setting for the gym.

The street-facing elevation remains enclosed and private, while the estuary-facing side opens towards the landscape. The house includes an open-plan kitchen, dining, and living area, a cinema room, and three additional bedrooms for the couple’s children.

On the upper floor, the principal bedroom is positioned on one side of the plan, with guest bedrooms on the opposite side. A central void, staircase, and secondary living room organise the space between them, allowing light and views to extend through the depth of the house.

Material strategy and ageing

Material selection establishes a dialogue between local geology and industrial history. Welsh slate and corten steel reference the region’s slate-mining and ironworking traditions through contemporary construction.

Locally quarried slate grounds the building in its geological context. The slate contains iron, which oxidises over time, bringing warmer tones that correspond with the surface of the corten above. Weathering materials, including corten steel and cedar, were selected for durability and their capacity to change in the coastal climate. Grey-treated cedar gradually silvers, completing a restrained material palette.

“We wanted to create a home that’s beautiful on day one but becomes even more compelling over time,” said Magnus Ström. “The material palette was chosen specifically to achieve that evolution. Welsh slate, corten steel, and cedar were selected not only for their durability but for how they age, settling deeper into the landscape. This combination is rooted in the history and context of Porthmadog. Unlike many houses in the area, often white and interchangeable, this home is designed specifically for its location.”

Interior continuity and inhabitation

Continuity between exterior and interior was central to the design. Slate extends from the external walls into the interior spaces, reinforcing material consistency. Polished concrete flooring grounds the main living areas, while engineered timber introduces warmth. Glazing spans the estuary-facing elevation, maintaining visual connection to the landscape while addressing performance requirements in the exposed coastal climate.

Bespoke oak joinery is integrated throughout the kitchen, snug, and bedrooms. A restrained natural palette allows the surrounding views to remain prominent. Durable, low-maintenance materials support the home’s long-term resilience.

At night, the lighting design alters the character of the house. Viewed from outside, the illuminated interior has been compared by the architect to Edward Hopper’s Nighthawks, with the layered composition of light and shadow revealing the internal arrangement.

For Ström Architects, the idea of “new luxury” is defined by calm and longevity rather than ostentation. Space, light, and acoustic comfort take precedence, supported by tactility and craftsmanship. Heavy slate walls provide shelter and privacy, allowing the principal living areas to open towards the bay through expansive glazing. More enclosed spaces are contained within the protected ground-floor volumes, while shared areas engage directly with the wider landscape.

Delivering both architecture and interior design, Ström Architects developed a fully integrated home shaped by its site, material context, and patterns of daily life.

Large Format Sliding Glass Doors and Structural Glazing for an Exposed Coastal Site

Porthmadog House is a contemporary replacement dwelling located on a sloping coastal site in North West Wales, overlooking the estuary, bay and wider landscape towards Snowdonia. Designed by Strom Architects, the house balances robust material forms with open, light filled spaces.

The IQ Glass was appointed to deliver a comprehensive architectural glazing package, including large format sliding glass doors, frameless structural glazing, slim aluminium windows and opening rooflights. The glazing strategy plays a central role in connecting the internal living spaces to the surrounding coastal landscape while responding to the exposed environmental conditions of the site.

Design Drivers: Exposure, Views and Material Contrast

The architectural concept responds to a site defined by both expansive views and extreme exposure. Positioned along the Welsh coastline, the building is subject to prevailing winds, driving rain and salt laden air, requiring a careful balance between openness and protection.

The design is anchored by two slate clad ground floor volumes that create sheltered internal and external spaces, while a lighter corten steel upper level spans above. Between these elements, glazing is used to open up the primary living areas, framing the surrounding landscape and allowing natural light to penetrate deep into the plan.

For the glazing design, the priority was to maximise panoramic coastal views while maintaining a restrained and minimal architectural language. Large glazed openings with reduced framing were essential to achieving this, but these had to be carefully engineered to perform in a demanding marine environment. At the same time, the glazing systems were required to deliver long-term durability alongside consistent thermal performance and internal comfort, ensuring the openness of the design could be realised without compromising usability or resilience.

Large Format Sliding Glass Doors

The primary architectural expression is defined by a series of large format slim sliding glass door systems, creating wide, open elevations across the main living spaces.

The largest configuration spans approximately 7.1 metres in width and 3.2 metres in height, demonstrating the scale required to match the architectural ambition of the house. These oversized glazed elements allow uninterrupted views across the estuary while enabling a strong visual and physical connection between interior and exterior environments.

To reinforce the minimal aesthetic, the sliding systems were designed with a number of key detailing strategies. Slim aluminium framing reduces the visible structure, allowing the glazing to read as uninterrupted planes of glass, while a glass-to-glass corner detail removes the need for a structural corner post, increasing transparency across the facade.

All frames were finished in marine grade PPC aluminium, ensuring long-term resilience in the exposed coastal location while complementing the restrained palette of slate and corten steel.

Structural Glazing and Integrated Openings

Alongside the sliding doors, a series of frameless structural glazing elements were installed using the Invisio system, allowing for clean junctions and minimal visual interruption across key areas of the facade.

Corner-to-corner glass details further enhance transparency, supporting a continuous visual connection across the building envelope. This approach enables the glazing to sit quietly within the architecture, reinforcing the contrast between solid material volumes and open glazed spaces.

Additional slim aluminium casement windows and doors were integrated throughout the scheme, specified with consistent framing finishes and glass composition to ensure a unified appearance and performance across all elevations.

Rooflights and Environmental Performance

Two ARES automatic opening rooflights were introduced as flush glazed elements within the roofscape, providing both daylight and natural ventilation to internal spaces. The rooflights are engineered using double glazed toughened safety glass with integrated solar control and low-emissivity coatings. Each unit also incorporates a laminated interlayer for additional strength and durability. As opening elements, the rooflights support passive ventilation strategies, allowing fresh air to circulate through the house while maintaining the clean, minimal roof design.

Performance and Coastal Durability

The glazing specification was developed to respond directly to the environmental challenges of the site.

All systems utilise double glazed toughened safety glass with solar control and low-E coatings, balancing daylight transmission with solar gain control and thermal efficiency. Marine grade aluminium finishes were applied to all framing elements, ensuring durability against corrosion and long-term exposure to salt-laden air.

The result is a glazing package that aligns with the wider material strategy of the building, supporting a low maintenance, long-life approach suited to the coastal setting.

Project Details

Project Type: Private coastal residence
Location: Porthmadog, North Wales, UK
Architect: Strom Architects
Glazing Contractor: IQ Glass
Primary Systems: Large-format slim sliding glass doors; frameless structural glazing (Invisio system); aluminium casement windows and doors; ARES automatic opening rooflights
Glazing Specification: Double glazed toughened safety glass with solar control and low-emissivity coatings; laminated interlayers to rooflight elements
Key Elements: Sliding door system up to approximately 7146mm wide × 3266mm high with glass-to-glass corner detailing; flush-glazed opening rooflights
Finish: Marine-grade PPC aluminium

Outcome

The completed Porthmadog House demonstrates how large format glazing systems can be successfully integrated into an exposed coastal architecture, balancing openness with performance and durability.

Through careful coordination of sliding systems, structural glazing and rooflights, the project achieves a high level of transparency while maintaining environmental control and resilience. The glazing plays a central role in delivering both the architectural clarity and long-term functionality required for a modern coastal home.