Modern residential architecture increasingly relies on hybrid structural systems that combine materials to achieve striking visual effects while maintaining structural integrity. The Casa Miravent project, designed by Julio Gomez-Perretta de Mateo and completed in 2017 in Godella, Valencia, exemplifies how large horizontal concrete planes can define a home’s character. Spanning 600 square meters, the house uses broad concrete roof slabs that appear to float between glass panels, creating a seamless connection between interior spaces and the surrounding landscape. This approach to residential architecture demonstrates how concrete, glass, and open planning work together to produce homes that feel both substantial and inviting.
Structural Design of Cantilevered Concrete Roof Planes
The most distinctive feature of the Casa Miravent design is its use of large horizontal concrete planes that extend well beyond the building’s enclosed volume. These cantilevered slabs serve as both roof and sun-shading devices, projecting outward to shelter outdoor areas while reducing solar heat gain on the glass walls below. Architects and engineers designing such features must account for the full range of structural loads while preserving the thin, floating appearance that defines the aesthetic.
Engineering Principles Behind Cantilevered Concrete Slabs
Cantilevered concrete slabs transfer their load back to internal support columns and walls through continuous steel reinforcement. The top reinforcement mat carries tension forces generated by the cantilever moment, while the concrete below handles compression. For residential applications, cantilever spans typically range from 2 to 4 meters beyond the last support point, though engineered solutions using post-tensioning can extend this range significantly. The embodied carbon reduction strategies used in modern concrete construction have introduced supplementary cementitious materials that replace 20 to 50 percent of Portland cement content, lowering the environmental footprint of each cubic meter of concrete.
Recommended Span-to-Depth Ratios for Residential Cantilevers
For cantilevered concrete roof slabs, engineers commonly specify a span-to-depth ratio between 10:1 and 15:1. A 3-meter cantilever requires a slab depth of 200 to 300 millimeters, depending on the reinforcement design and concrete strength grade. The expansive planes in projects like Casa Miravent typically require detailed finite element analysis to optimize both structural performance and the thin visual profile the architect seeks. Factors that influence the final slab depth include:
- Dead load from the concrete self-weight and any superimposed finishes
- Live loads from snow, maintenance access, and potential roof terrace use
- Wind uplift forces that can reverse the direction of bending
- Thermal movement stresses from direct sun exposure on the top surface
- Creep and shrinkage effects that increase long-term deflections
| Roof Structural System | Maximum Span | Typical Depth | Material Cost per m2 | Thermal Performance |
|---|---|---|---|---|
| Reinforced Concrete Slab | 6-12 m | 150-300 mm | $80-120 | High thermal mass |
| Post-Tensioned Concrete Slab | 10-18 m | 180-350 mm | $100-140 | High thermal mass |
| Steel Frame with Metal Deck | 8-20 m | 250-500 mm (beam depth) | $100-150 | Low (requires insulation) |
| Timber Truss System | 8-15 m | 300-600 mm (truss depth) | $50-80 | Moderate |
| Hybrid Concrete-Steel Composite | 10-18 m | 200-400 mm | $90-130 | High with detailing |
Concrete slabs offer the advantage of monolithic construction with inherent thermal mass that stabilizes indoor temperatures. This passive benefit can reduce heating and cooling loads by 10 to 25 percent compared to lightweight framing systems, particularly in climates with significant diurnal temperature swings like the Mediterranean region where Casa Miravent is located.
Glass Panel Systems Integrated With Concrete Structures
The Casa Miravent plan uses glass panels that fill the spaces between concrete roof slabs and floor plates, creating walls that visually disappear. This approach requires careful detailing at every intersection point where glass meets concrete. The junction between these two materials must address structural support, thermal performance, water-tightness, and aesthetic continuity simultaneously.
Types of Glass Systems for Concrete-Frame Homes
Three primary glass systems work with concrete structures in residential applications:
- Frameless glass systems where panels are held by discrete point fittings attached to the concrete above and below. This produces the cleanest aesthetic but requires thicker tempered glass, typically 12 to 19 millimeters, and precise embedment of anchor points during concrete placement.
- Semi-frameless systems using slim vertical mullions between panels. The mullions, typically 50 to 80 millimeters wide, provide intermediate support that permits thinner glass while maintaining a relatively transparent appearance.
- Curtain wall systems with aluminum frames that span between concrete floor slabs. These systems offer the best thermal performance through thermally broken frames but add more visual structure between interior and exterior.
Thermal Break Requirements at Concrete-Glass Interfaces
Where glass meets concrete, thermal bridging can cause significant heat loss and interior surface condensation. Engineers specify thermal break materials to interrupt this conductive path. Common solutions include structural thermal clips made from high-strength polymer composites, insulated aluminum framing with polyamide thermal breaks rated for the structural load, and continuous insulation wraps applied at slab edges before cladding installation. Double-glazed units with low-emissivity coatings used in these applications typically deliver U-values between 1.0 and 1.6 W/m2K, depending on the gas fill and coating specification.
Open-Plan Interior Layouts Within Concrete-Framed Buildings
Concrete frame construction allows interior layouts that are not constrained by load-bearing wall positions. The structural loads travel through columns and slabs, leaving interior partitions free to be positioned anywhere on the floor plate. This freedom gives architects and homeowners significant flexibility in configuring living spaces.
Advantages of Column-Free Interior Spaces
The primary benefits of concrete frame construction for residential interiors include:
- Flexible room configurations that can adapt as family needs change over time
- Larger window openings not limited by wall-supported structures above
- Reduced material use for interior partitions since fewer load-bearing walls are needed
- Better natural light distribution across the floor plate because obstructions are minimized
- Simplified future renovations since interior walls can be moved without structural work
Integrating Vertical Circulation in Open Concrete Plans
The Casa Miravent incorporates a spiral staircase visible through the glass facade, serving as both a functional element and a central visual anchor. When designing vertical circulation in open-plan concrete homes, architects must consider several factors:
Open-plan layouts in concrete homes typically achieve 15 to 30 percent better space utilization compared to traditional compartmentalized floor plans of the same gross area. The elimination of corridor space alone can recover 5 to 10 percent of the floor plate for usable living area.
Outdoor Living Spaces and Pool Deck Integration
The transition from interior to exterior space in the Casa Miravent is handled through covered terraces formed by the projecting concrete roof planes. The pool deck sits adjacent to the living areas, with the roof overhang providing partial shade during peak sun hours. This integration of hardscape and structure requires careful attention to drainage, material transitions, and thermal movement.
Concrete Deck and Patio Construction Methods
Outdoor concrete surfaces adjacent to pools require specific construction methods that differ from interior slabs. Key requirements include reinforced concrete slabs with control joints every 2.5 to 3.5 meters to manage cracking from thermal and moisture movement, surface texturing for slip resistance using broom finish or exposed aggregate techniques, proper drainage slope of 1.5 to 2 percent away from the house foundation, and sealing with penetrating sealers that resist chloride exposure from pool water and deicing salts.
| Finish Type | Slip Resistance | Maintenance Frequency | Cost Premium | Best Application |
|---|---|---|---|---|
| Broom Finish | High | Low (seal every 3-5 years) | +0% | Pool decks, walkways |
| Exposed Aggregate | High | Low (seal every 3-5 years) | +15-25% | Patios, entertainment zones |
| Stamped Concrete | Moderate | Moderate (reseal every 2-3 years) | +30-50% | Decorative patios, driveways |
| Polished Concrete | Low (wet) | Low | +20-40% | Covered outdoor rooms only |
| Acid-Stained Concrete | Moderate | Moderate (wax every 1-2 years) | +15-30% | Indoor-outdoor transition zones |
For coastal projects such as Casa Miravent, concrete mixes should include air-entrainment admixtures to improve durability against salt exposure, even in Mediterranean climates where freeze-thaw cycles are less frequent than in northern regions. The air content target for exterior flatwork typically ranges from 4 to 7 percent by volume.
Material Selection for Architectural Concrete Finishes
Achieving the smooth, consistent finish seen in the Casa Miravent requires careful material selection and construction sequencing. Architectural concrete, sometimes called fair-faced or exposed concrete, demands tighter tolerances and higher quality materials than standard structural concrete.
Concrete Mix Design for Architectural Exposed Finishes
Architectural concrete mixes differ from standard structural mixes in several important ways. Maximum aggregate size is limited to 20 millimeters for better surface uniformity and reduced bug hole formation. Cement content is higher, typically 350 to 400 kilograms per cubic meter, to produce denser, more consistent surfaces. The water-cement ratio is kept between 0.40 and 0.45 to minimize surface voids, and superplasticizers are added to maintain workability without requiring additional water.
Formwork Selection for Visible Concrete Surfaces
The quality of visible concrete depends primarily on the formwork system. Plywood forms with phenolic resin coating produce smooth surfaces with consistent texture. Steel forms provide consistent panel alignment and can be reused many times, amortizing the higher initial cost over multiple pours. Controlled permeability formwork liners improve surface density by allowing excess water and air to escape during vibration. Form-release agents must be selected carefully to avoid staining the concrete surface.
Formwork costs for architectural concrete typically run 30 to 60 percent higher than standard structural formwork due to tighter tolerances and higher quality materials. Joints between formwork panels must be aligned precisely to avoid step-offs, and tie-hole layouts should follow a planned grid pattern that becomes part of the finished aesthetic. For projects like Casa Miravent where large plane surfaces dominate the visual experience, the formwork specification is as critical to the final appearance as the concrete mix itself.