Concrete casting in residential architecture is not a structural decision with aesthetic consequences. It is a design decision with structural requirements. Every surface that will remain exposed — interior walls, floor slabs, exterior facades — must be specified with the same care as any other material in the building.
Why Cast-in-Place Concrete Requires Design Specification
A cast-in-place concrete wall records everything: the texture of the formwork, the placement of the pour joints, the location of tie holes, the size of the aggregate at the surface. These are not construction variables — they are design variables that must be specified before the pour begins.
In MÉTODO, we approach concrete casting in residential design as a material composition. The formwork pattern is drawn. The joint locations are placed. The tie hole grid is part of the elevation composition. The mix design — including pigmentation if applicable — is specified with the same precision as the stone or wood that will be adjacent to it.
This is what materialidad honesta — honest materiality — means when applied to concrete. The material shows what it is and how it was made. The design should be in control of both.
Formwork Options and Their Visual Effect
The formwork is the mold that gives the concrete its surface texture. Common formwork options in residential work in Mexico:
Smooth steel formwork. Produces a nearly uniform surface with minimal texture. The concrete reads as a monolithic plane. High-quality steel formwork minimizes bugholes (voids) and produces a consistent sheen. Most appropriate for interior surfaces where the design calls for a refined, controlled appearance.
Plank formwork. Each board leaves a horizontal or vertical texture in the concrete surface. The grain of the wood transfers to the concrete in relief. The resulting surface has warmth and directionality — the concrete reads as a material that remembers what it was formed against. Common in residential architecture with a warm or contextual material palette.
Plywood formwork. The standard in most construction. Produces a smooth, slightly varied surface depending on plywood quality and oiling protocol. With good oiling and tight joints, it is a reliable background surface. With poor oiling and gaps, it produces bubbling and color variation.
Custom or textured formwork. Inserts can be placed in the form to create patterns — aggregated texture, geometric relief, or irregular surface profiles. These are used sparingly in residential work because they require a specific formal language to avoid appearing arbitrary.
Pour Joint Design
Pour joints — the lines where two separate pours of concrete meet — are unavoidable in large surfaces. In exposed architectural concrete, they must be designed, not accepted as a construction necessity.
A horizontal pour joint in a wall reads as a thin shadow line. If it is placed at the same height as a window sill or a ceiling height, it reads as an intentional compositional element. If it is placed randomly, it reads as an error.
In a MÉTODO residential project, pour joint locations are drawn on the elevation drawings as part of the construction documents. The contractor is required to place the joint at the specified location. Field substitutions require architect approval.
Pigmentation in Mexican Residential Work
Natural concrete in Mexico tends toward a grey-blue tone because of the lime content and aggregate composition of the standard cement mixes available in the country. For many residential projects, this tone is not the desired result.
Integral pigmentation — adding iron oxide pigments directly to the mix — shifts the concrete color. Common directions in Mexican residential work:
- Warm grey (iron oxide at 1 to 2 percent of cement weight)
- Near-white (titanium dioxide pigment in a white cement base)
- Terracotta warm tones (combinations of red and yellow iron oxide)
Batch control is the critical requirement for pigmented concrete. Each batch must be mixed with the same pigment ratio, the same water-cement ratio, and the same admixture dosage. Variations between batches produce visible color bands in the final wall. This requires either factory-batched ready-mix with strict QC or careful on-site batching with calibrated equipment.
Sealing Exposed Concrete in Mexico City Climate
Mexico City experiences a pronounced wet season from May through October and a dry season from November through April. Exterior concrete exposed to this cycling must be sealed to prevent:
- Water absorption leading to efflorescence (white mineral deposits on the surface)
- Moss and algae growth in shaded areas during the wet season
- Staining from urban pollution
Penetrating silane or siloxane sealers are appropriate for exterior concrete in Mexico City — they penetrate the concrete matrix rather than forming a film, which means they do not trap moisture or peel. Application in two coats during dry season is standard. Reapplication every 5 to 7 years depending on exposure.
Interior concrete in kitchens and bathrooms requires a different sealer: a polyurethane or epoxy topcoat that resists cooking oils, cleaning products, and sustained water contact. Matte and satin topcoat finishes are available.
Próximos pasos
Exposed concrete in residential design requires detailed specification before the pour. The decisions made at that stage determine whether the surface reads as designed or as built.
Conoce el método de MÉTODO to understand how concrete casting is specified and coordinated in a MÉTODO residential project in Mexico City.