Modern coastal architecture has moved beyond the single-box structure with a few windows facing the water. Split-level designs that cascade down a shoreline site create multiple view terraces, each oriented toward the ocean at a slightly different angle. The Atlantic Beach project by Martin Architects shows this approach in practice: a series of half-levels that spill over one another, each with its own private patio and panoramic Atlantic view. The building is clad in thermally-modified radiata pine, kebony wood rainscreen, weathered wood siding, concrete, bluestone, and glass. Understanding the material vocabulary for specifying these cladding options helps architects and builders communicate clearly during the design and procurement phases.
Split-Level Floor Plans for Sloped Coastal Sites
Split-level plans work well on sites that slope toward the water. Rather than excavating a flat pad or building tall retaining walls, the architect can step the building down the slope in half-floor increments. Each level aligns with the natural grade at that elevation, reducing cut-and-fill earthwork by 20-40% compared to a fully excavated basement or slab-on-grade foundation. The floor plan terminology used to describe split-level configurations includes terms such as bi-level, tri-level, and raised ranch, each describing a different arrangement of the half-floor offsets.
How Split-Levels Create Multiple View Corridors
Each half-level in a split-level coastal home can rotate its floor plate slightly relative to the levels above and below. A 5 to 15 degree rotation per level means that the living room, dining level, and master bedroom each face a slightly different slice of the horizon. This multiplies the usable view area from a single house. On a narrow lot where a single long facade can only face one direction, this rotation strategy can double or triple the number of rooms with direct water views.
| Floor Plan Type | Number of Levels | Typical Lot Slope | Earthwork Reduction | View Multiplier |
|---|---|---|---|---|
| Single-story slab | 1 | Flat to 2% | Baseline | 1x |
| Two-story on slab | 2 | Up to 5% | 10-15% | 1.5x |
| Split-level | 3-4 half-levels | 5-15% | 20-40% | 2-3x |
| Walk-out basement | 2 + daylight basement | 10-25% | 15-25% | 2x |
| Staggered terraced | 3-5 full levels | 15-30%+ | 30-50% | 2.5-4x |
Structural Considerations for Split-Level Framing
Split-level construction requires careful structural coordination where the floor levels offset. The framing at the transition between half-levels must transfer lateral loads from the upper portion of the building to the lower portion and down to the foundation. Steel moment frames or engineered shear walls at these transition points are typical. The cost premium for split-level structural engineering runs 8-12% above a conventional two-story design, but the savings in site excavation and retaining walls often offset this entirely.
Thermally-Modified Wood and Modified Wood Cladding Systems
The Atlantic Beach project uses thermally-modified radiata pine as its primary cladding material. Thermal modification is a process where wood is heated to 390-430 degrees Fahrenheit in a low-oxygen environment, changing the cellular structure of the wood. The process improves dimensional stability by 50-60% and increases resistance to fungal decay without using chemical preservatives. Diversity and education programs in the architecture field are helping train the next generation of specifiers who will work with these advanced material systems.
Comparing Modified Wood Cladding Options
The project also uses kebony wood rainscreen, which is a modified wood product treated through a different process. Kebony uses a bio-based liquid derived from agricultural waste that is impregnated into the wood and then heat-cured. The result is a material with hardness and durability comparable to tropical hardwoods but made from sustainably sourced softwoods. Side-by-side comparisons help architects choose the right system for each application.
| Wood Cladding Type | Modification Process | Janka Hardness | Decay Resistance | Service Life | Cost per sq ft |
|---|---|---|---|---|---|
| Thermally-modified radiata pine | Heat treatment 390-430F | 1,200 lbf | Class 1 (very durable) | 30-50 years | $6-10 |
| Kebony modified wood | Bio-liquid impregnation + heat cure | 1,800 lbf | Class 1 (very durable) | 40-60 years | $8-14 |
| Accoya acetylated wood | Acetic anhydride treatment | 1,500 lbf | Class 1 (very durable) | 50-60 years | $10-16 |
| Ipe (untreated hardwood) | None (natural durability) | 3,500 lbf | Class 1 (very durable) | 40-75 years | $12-20 |
| Cedar (pressure treated) | Chemical preservative | 700 lbf | Class 3 (moderately durable) | 15-25 years | $4-8 |
Rainscreen Installation Details for Wood Cladding
Wood cladding on coastal homes should be installed as a rainscreen system. A rainscreen creates a ventilated cavity between the cladding and the building wrap, typically 3/4 inch to 1-1/2 inches deep. This gap allows any moisture that penetrates the cladding to drain out and dry before it reaches the weather-resistant barrier. For thermally modified pine and kebony, the cavity also provides ventilation that keeps the wood surface temperature lower, reducing the rate of UV degradation. Stainless steel furring strips and hidden clip fasteners prevent corrosion staining that would appear on the wood surface over time.
Weathered Wood Siding as a Design Element
The Atlantic Beach project layers weathered wood siding alongside the thermally-modified cladding. Weathered wood carries a gray-silver patina that signals age and integration with the coastal environment. Architects can achieve this look through three methods: natural weathering over 2-5 years, chemical accelerating solutions applied to new wood, or pre-weathered siding purchased from specialty mills. Understanding who holds the design rights is important when specifying proprietary weathering finishes that a subcontractor may need a license to replicate.
Accelerated Weathering Techniques for New Coastal Siding
- Iron acetate solution: Mix steel wool with white vinegar for 24 hours, strain, and apply to bare wood. The iron reacts with tannins in the wood to produce a gray-silver color. Results appear within 2-4 hours.
- Tea and vinegar wash: Steep black tea bags in hot water, cool, apply to the wood, then follow immediately with a diluted vinegar solution. The tannic acid in tea supports the color change.
- Commercial wood stain: Water-based acrylic stains formulated to mimic 5-10 years of natural weathering. These offer the most consistent color across a large facade.
- Sandblasted finish: Light sandblasting removes soft earlywood, leaving the harder latewood ridges exposed. This creates a textured surface that weathers faster and more evenly.
Concrete, Bluestone, and Glass in Coastal Minimalist Architecture
The materials used in the Atlantic Beach design overlap in various tones and textures. Concrete provides a neutral structural anchor, bluestone adds a dark blue-gray horizontal plane for patios and walkways, and glass creates transparent vertical surfaces that dissolve the boundary between interior and exterior. The professional credentials and expertise that senior project architects bring to material selection ensure that these diverse surfaces work together thermally, structurally, and aesthetically.
Concrete Detailing for Coastal Environments
Architectural concrete in coastal projects requires specific mix designs to resist salt attack. Key specifications include:
- Low water-cement ratio: Target 0.40 or lower to reduce permeability. Every 0.05 reduction in w/c ratio cuts water absorption by roughly 25%.
- Air entrainment: 5-7% entrained air protects against freeze-thaw damage in northern coastal climates.
- Supplementary cementitious materials: Fly ash at 20-30% replacement or slag cement at 40-50% replacement improves resistance to chloride ion penetration.
- Curing period: Extended wet curing for 7-14 days is mandatory for coastal architectural concrete. Premature drying creates surface cracking that accelerates salt damage.
Bluestone Patios as Thermal Mass Elements
Bluestone is a dense sandstone that absorbs solar heat during the day and releases it slowly in the evening. A 2-inch thick bluestone patio adjacent to south-facing glass can raise the outdoor surface temperature by 5 to 10 degrees Fahrenheit in the evening, extending the usable hours of the patio during cooler months. The stone should be sealed with a penetrating silane-siloxane sealer to prevent salt staining from ocean spray.
Private Patios at Each Level for Outdoor Living
One of the strengths of the split-level configuration is that every half-level can open onto its own private patio. The master bedroom level accesses a patio directly from the sleeping area. The living room level steps out onto a larger terrace. The lower-level recreation room connects to a bluestone patio at grade. Each outdoor space feels separate and oriented toward the water, even though they are part of the same building footprint.
Minimum Patio Sizes for Functional Outdoor Spaces
Outdoor patios in coastal homes need minimum dimensions to be usable. A private master suite patio should be at least 6 by 8 feet to accommodate two chairs and a small table. The main living level terrace needs at least 10 by 14 feet for a dining table and seating. Lower-level patios near a pool or hot tub should provide 200 square feet minimum. All patio surfaces draining toward the ocean should slope at 1/8 inch per foot minimum to prevent standing water.
Sourcing and Specifying Mixed Material Facades
Specifying a facade that uses thermally-modified pine, kebony, weathered wood, concrete, and bluestone in a single composition requires careful coordination. Each material has different expansion rates, substrate requirements, and attachment methods. The transition details between materials must be designed to accommodate differential movement while maintaining water tightness. Aluminum-framed interior wall systems offer a complementary approach for the interior side of these facades, providing dimensional stability and thermal break performance that matches the exterior cladding investment.
Architects are increasingly being called on to consider the ethical dimensions of their material and project choices. Specifying sustainably sourced thermally-modified wood and durable natural stone aligns with the growing expectation that coastal buildings contribute positively to their environment rather than consuming resources that cannot be replaced.