Cantilevered structures push building elements beyond their supporting columns, creating dramatic overhangs that open floor plans to surrounding views. The Adrisa Residence on Koh Samui demonstrates how 7 meter cantilevers on the second floor remove corner obstructions for uninterrupted panoramic sightlines. This approach requires careful coordination between concrete and steel structural systems. A well designed cantilevered stair follows similar load distribution principles, transferring weight through concealed stringers rather than visible supports. Both applications rely on the same engineering logic: extend structure selectively while maintaining a clear load path to the foundation.
Structural Systems for Cantilevered Construction
Long cantilevers place unique demands on building materials. Concrete performs well in compression but has limited tensile strength without reinforcement. Steel offers higher strength to weight ratios that reduce the mass of the cantilevered section. The Adrisa Residence uses a hybrid approach: concrete for the underground and first floor structures, steel trusses for the second floor. The second floor cantilever reaches 7 meters, made possible by a truss configuration that distributes forces across multiple members rather than relying on a single beam. Proper flashing techniques for cantilevered deck joists address the waterproofing challenges at these structural penetrations, preventing moisture intrusion at the transition points.
Cantilever Load Path Fundamentals
Every cantilever transfers load back to a support point through a reversal of moment forces. The top of the cantilever experiences tension while the bottom experiences compression, the opposite of a standard simply supported beam. This reversal determines where reinforcement must be placed. In concrete cantilevers, top reinforcement is the critical element and must extend past the support into the backspan by at least the length of the cantilever itself.
Steel Truss Configuration for Extended Spans
Steel trusses achieve longer cantilevers than solid beams of equivalent weight. A Warren truss with diagonal members in alternating directions distributes loads efficiently for cantilever applications. The truss depth is typically 1/10 to 1/12 of the span length. For a 7 meter cantilever, a truss depth of 600 to 700 millimeters is common. Connections use bolted gusset plates rather than welded joints to simplify field assembly and allow for inspection.
| Cantilever Material | Maximum Practical Span | Depth to Span Ratio | Relative Cost Factor |
|---|---|---|---|
| Reinforced Concrete | 3 5 meters | 1:6 to 1:8 | 1.0 (baseline) |
| Prestressed Concrete | 5 10 meters | 1:10 to 1:15 | 1.4 1.8 |
| Steel Beam (Wide Flange) | 3 6 meters | 1:8 to 1:12 | 1.2 1.5 |
| Steel Truss | 6 15 meters | 1:10 to 1:14 | 1.5 2.0 |
| Composite Steel Concrete | 5 12 meters | 1:8 to 1:12 | 1.3 1.7 |
Site Planning for View Maximization
Building on a hillside with panoramic views requires careful site analysis before structural design begins. The Adrisa Residence sits on Bophut Hills on Koh Samui, with eastern and northern ocean views and western mountain views. The architects shifted part of the building to the second floor level and moved service areas underground. An open courtyard sits in the middle of the house, creating a visual sequence from the south entrance through the interior to the view beyond. For those evaluating similar projects elsewhere, the process from plot selection to residence approval follows comparable steps across jurisdictions.
Solar Orientation and View Corridors
Eastern and northern orientations receive gentler morning light and avoid the harsh afternoon sun that generates cooling loads in tropical climates. The main living spaces and bedrooms on the north west corner capture both the ocean panorama and the later afternoon mountain light while the building mass shades interior spaces. Three view corridors should be preserved: a primary corridor centered on the main living area, secondary corridors from each bedroom, and a tertiary corridor from the pool deck.
- Primary view corridor: 30 to 45 degree cone from living room centerline
- Secondary corridors: 20 to 30 degree cones from bedroom windows
- Tertiary corridor: 180 degree horizontal from pool deck level
- Service areas: positioned underground or behind the view axis
- Structure points: reduced to 3 per room to minimize visual obstruction
Pool Integration with Architectural Massing
The L shaped pool at the Adrisa Residence combines a 25 meter lap pool with a 16 meter family pool and jacuzzi. The pool is positioned in front of the living room, extending the visual plane of the interior toward the ocean horizon. This placement creates a reflective surface that expands the perceived size of the outdoor space. The trail creek mountain residence uses a similar approach with pool placement along the primary view axis to extend the living area visually.
Lap Pool Design Parameters
A 25 meter lap pool requires a minimum clear length of 82 feet with a depth of 4 to 5 feet for safe turning. The width should be at least 8 feet for single lane swimming or 12 feet for two swimmers side by side. Pool water temperature for lap swimming is typically 78 to 82 degrees Fahrenheit. The family pool and jacuzzi section operates at a warmer 86 to 92 degrees. The L shape allows both pools to share filtration and heating equipment while maintaining different temperature zones.
Pool Structural and Mechanical Integration
Pools placed near cantilevered structures require careful foundation coordination. The pool shell must be independently supported on compacted fill or piles, not tied to the building foundation, to prevent differential settlement from cracking either structure. The mechanical room for pumps, filters, and heaters is ideally located within 50 feet of the pool edge to minimize head loss in circulation piping. Variable speed pumps reduce energy consumption by 30 to 50% compared to single speed models.
Underground Service Area Planning
Moving service areas underground freed the north west corner of the Adrisa Residence for open plan living spaces. Underground placement also buffers mechanical equipment from tropical heat, improving efficiency. The service zone includes the kitchen back of house, laundry, storage, and mechanical systems. A modernizing midcentury ranch approach often relocates service functions in similar ways to open floor plans for better living space allocation.
Waterproofing and Ventilation Requirements
Underground spaces require below grade waterproofing systems rated for hydrostatic pressure. A combination of bentonite panels, liquid applied membranes, and drainage boards directs groundwater away from the structure. Mechanical ventilation is mandatory for underground service areas. The system should provide at least 6 air changes per hour for laundry and storage spaces, and 10 air changes per hour for any occupied below grade areas. Sump pumps with battery backup handles groundwater infiltration during power outages.
- Excavate to required depth with 3 foot clearance around foundation walls
- Install drainage board and waterproofing membrane on exterior walls
- Place concrete walls with continuous waterstop at construction joints
- Install interior drainage system connected to sump pump
- Backfill with granular material to promote drainage away from walls
Interior Layout for Panoramic Living
Removing corner structure in each bedroom and living area opens the panorama to the landscape. With only three structural support points per room, the layout achieves nearly 270 degrees of glazing on the view side. The open courtyard inserted in the middle of the house creates an interior center point and organizes the circulation from the south entrance through the house to the view. Bedrooms and living areas sit on the north west corner to capture the best sightlines. The kreiger residence design build approach demonstrates similar interior organization strategies with open layouts oriented toward primary views.
Glazing Selection for Panoramic Windows
Large expanses of glass in tropical climates must balance thermal performance with structural loading from wind. Low iron glass with a solar heat gain coefficient of 0.25 to 0.30 reduces cooling loads while maintaining clarity. Tinted or spectrally selective coatings control glare without blocking the view. The glass thickness increases with span: 6 millimeter monolithic glass for spans up to 4 feet, 10 millimeter for spans up to 7 feet, and laminated glass for spans exceeding 7 feet where wind loads are significant.
Landscape Integration with Architecture
Piet Oudolf handled the landscape design for the Adrisa Residence, using naturalistic planting schemes that blend with the surrounding hillside. The landscape acts as a foreground to the ocean view rather than competing with it. Low growing grasses and ground covers near the pool maintain sightlines while taller trees frame the property edges. The stumpf residence design lessons show how landscape buffers between indoor and outdoor spaces create transitional zones that extend the perceived size of compact floor plans.
Plant Selection for Tropical Hillsides
Native and drought tolerant species reduce irrigation demands on hillside properties. Ornamental grasses, ground covers, and small flowering shrubs near the building foundation prevent soil erosion while maintaining open views. Trees are placed at the perimeter of the property to frame the view without obstruction. A 15 to 20 foot buffer of low vegetation between the pool and the view edge maintains safety while preserving sightlines. The root zones of trees near cantilevered foundations must be setback at least 10 feet from the structure to prevent root damage to waterproofing membranes.