Sitting directly across from the St Francis Yacht Club on Marina Boulevard in San Francisco, this luxury property now boasts a multi-level 1,200 square foot roof terrace, offering waterfront views. The roof terrace offers a glorious outdoor space, whilst the Glazing Vision Flushglaze walk-on rooflights, imported from the UK, and interspersed in the decking, ensure that the bedroom suite floor below is bathed in diffused daylight.
Structural challenges of adding a roof terrace to this period property
Built in the 1920’s in the Spanish Mission style, this three-storey property already offered an impressive 4,000 square feet of space, but the homeowner wished to extend the house further, particularly looking to unlock the potential of the unused, run-down flat roof by adding a fully-operational outdoor kitchen as well as spacious dining and living areas. A viewing platform to take advantage of the views out over the marina was also on his wish list.
ODS Architecture was appointed by the homeowner in 2012 to undertake this ambitious project. The brief to build a stylish roof terrace as well as to reconfigure the master bedroom floor posed a number of significant structural challenges. Firstly, changes to the historic façade of the property were not allowed by the State of California, plus any new construction had to be out of view of the street as much as possible. Furthermore, the close proximity of the neighbours’ houses on both sides compromised the amount of natural light entering the client’s home, and the inability to install windows because of insufficient clearance to the property line meant a regular upper floor extension in a traditional masonry sense was not going to be appropriate. Building a roof terrace, or deck, is never an easy task but at Marina Boulevard, this was going to be particularly challenging as the silver-painted rooftop was in a state of disrepair.
ODS’s design for a new multi-level, multi-functional roof terrace, incorporating a modernization of the third floor of the house, demanded creative construction techniques. General building contractor, Jeff King & Company, working in close collaboration with ODS, re-framed the roof with new wooden supports, metal connectors and hardware to ensure that it could take the weight of the planned roof terrace. Vertical cables on the side of the house were made to fit.
Large roof terraces always require careful attention to waterproofing, and at Marina Boulevard, where old and new systems needed to be finely tuned in order to create a completely waterproof envelope, a high-tech waterproof system had to be devised. Additionally, the deck was laid with durable chip, fade and crack-resistant porcelain tiles that could be easily removed and replaced should there be a leak, or water damage in the future. They are also fire-proof, an important feature given the type of appliances installed on the roof terrace and the closeness of the neighbouring properties to either side.
Multi-level layout for roof terrace design
The lower tier of the roof terrace contains the outdoor kitchen, resplendent with stainless steel Viking appliances and concrete counter tops, which are a nod to the stucco plaster walls of the old house. The dining area, complete with a large dining table, is adjacent to the kitchen and on the next tier there is small bar and a fire pit for alfresco entertaining. The “crow’s nest”, the viewing platform, is reached by a glass and timber stairwell, and was created by the contractor where the original roof was sloped. This level deck, based on a pedestal system that reaches up to 24 inches, is split into four quadrants to ensure proper drainage and is waterproofed to protect the sitting room below, which is accessed from both the master bedroom and the main deck. This room provides a contemporary, yet intimate space in which to relax and retreat should the weather prove inclement. It can be closed off by glazed sliding doors, yet it is bright and airy, and offers a quiet peaceful zone to observe the marina.
Unlocking daylight to living space below the roof terrace
A key consideration, however, for the architects and contractor in the design of the roof terrace was the need to unlock the daylight to the lower bedroom and bathroom suite floor, whilst simultaneously protecting the privacy of these intimate quarters. The original roof had four square-shaped skylights, which had allowed for natural light to enter the living space below. As the old roof was being covered with the new roof deck, and the old skylights removed, a glazing solution was required that would guarantee a direct source of daylight and could utilise the original skylight apertures. Additionally, the glazing had to be sufficiently robust to be walk-able so as to not compromise the structure or the practicality of the deck itself, and it had to be able to cope with inclement weather conditions, including heavy rainfall. Safety too was a critical factor in the selection of the glazing – it had to be safe underfoot.
After extensive research ODS specified a series of Flushglaze walk-on rooflights, manufactured in England by Glazing Vision. Unlike skylight products available in the USA, the Glazing Vision Flushglaze rooflights were designed and tested to withstand heavy foot traffic whilst maintaining watertight integrity. Architect, contractor and client all felt that these rooflights best met their exacting criteria.
The Flushglaze walk-on rooflights had the advantage of being able to be installed flush with the porcelain floor tiles used on the main roof terrace, making for a perfectly flat surface. A lack of any visible internal framework meant that, crucially, these rooflights would not spoil the visual effect – on the contrary they would enhance the contemporary appearance of the roof terrace, adding a distinct wow factor.
Safety and privacy considerations
For the three rooflights located on the main deck, the glazing had been specifically ordered with a sandblasted finish. This would result in a more diffused light entering the bedroom suite below, but would also improve obscurity, thereby offering greater privacy too, an important factor for the client given that the roof terrace would be used frequently for entertaining guests.
Additionally, the sandblasted finish provided better slip-resistance than standard glazing. Slip resistance is measured using mean Pendulum Test Values (PTV), with values of 25-35 deemed as having moderate slip risk and 36+ as a low slip risk. Glazing Vision’s sandblasted glass achieves a PTV of 50 as standard, well above the threshold of PTV 36 to be categorized as having a low-slip potential, and it was considered ideal for use at Marina Boulevard.
“Crow’s nest” at the top of the house
The fourth of the Glazing Vision Flushglaze walk-on rooflights, and the largest at 67 x 34 inches, was installed on the viewing platform, and unlike the other three rooflights, its glazing had a fritted finish. A screen-printed frit, that included particles within the ink to create a rough texture, was applied to the glass in a unique pattern to provide 40% coverage, significantly increasing the slip resistance of the glass. Indeed, fritted glass generally achieves a PTV of 60, thus providing an even better slip-resistance than the sandblasted.
The size of the Glazing Vision Flushglaze walk-on rooflight on the viewing platform also ensured that daylight flooded the narrow walkway underneath, from which the adjacent master bedroom sitting room also benefited. Complimenting the contemporary staircase leading up from the main deck, this almost frameless rooflight stylishly combined with the IPE wood flooring to create a kind of nautical feel, a perfect environment from where to watch the Americas Cup race!
Whilst this challenging project took two anda half years to complete, the resulting roof terrace is testament to extraordinary teamwork. The roof terrace design is convincing in its simplicity, and the sensitivity to colour and materiality ensures it blends seamlessly with the rest of the house, so that when walking into the living space on the master suite floor.