Which designs do you need to build? (and why they must be coordinated)

A scene every engineer has seen. The slab has been poured, the walls are going up, and the plumber arrives to run the sewage pipe from the upstairs bathroom. The pipe has to come down exactly where a beam is. The improvised solution is to break the concrete and drill through the beam. The problem is that the beam was calculated without that hole.

This happens when each design is produced on its own, or when there is no design at all. Here you will learn which designs a build needs and why they have to talk to each other.

The house in layers

The architectural design is the basis. It defines the form, the rooms and the dimensions. But a building is much more than walls. Inside it there is a skeleton, the structure, and a circulatory system, the installations: water, sewage, rainwater, power, data, gas. And all of it must be protected from moisture.

Each of these systems has its own design, its own technical standards and its own calculations. Together, they are called complementary designs, and the name is exact: they complement the architectural one.

Structural design

Let us start with the skeleton. The structural design defines how the weight of the building reaches the ground safely. It calculates the slabs, beams, columns and foundations, taking into account the building's own weight, people, furniture, water tanks and even the force of the wind.

In houses and buildings, the most common choice is reinforced concrete, sized according to ABNT NBR 6118. In warehouses, mezzanines and large roofs, a steel structure is often more advantageous, and it follows ABNT NBR 8800. The choice depends on the span, the schedule, the cost and the use.

The structural design delivers the formwork plans, which show the dimensions of each element, and the reinforcement details, which show exactly each steel bar: its gauge, length, position and quantity. With that, the site buys the right material, and the steel fixer assembles exactly what was calculated.

And there is one point few people consider: structural design is also economy. A well-calculated structure uses the concrete and steel it needs, no less, which would be a risk, and no more, which would be waste. In practice, the design's quantities become the basis for the construction budget.

Water, sewage and rain

Now, the system everyone uses without noticing: the plumbing and sanitary installations. The design defines how cold and hot water reach each tap, shower and toilet with adequate pressure and flow, and what size the tank should be.

It also defines how sewage leaves the building, with the right slope in the pipes, inspection chambers and the ventilation that stops bad smells coming back through the drains. And it defines the path of rainwater: gutters, downpipes and the final destination, without sending water to the neighbour or into the sewer.

These installations follow their own standards: ABNT NBR 5626 for cold and hot water, ABNT NBR 8160 for sewage and ABNT NBR 10844 for rainwater.

When there is no design, the classic problems appear: a weak shower upstairs, a smelly drain, a toilet that takes ages to fill and a leak nobody can trace.

The plumbing design is also the moment to think about saving water:

• You can plan to use rainwater to water the garden, wash the garage or supply the toilets, with its own tank and a network separate from drinking water, under the standard specific to this use, ABNT NBR 15527.
• You can plan for solar heating, leaving the hot water piping and the space on the roof ready.
• You can position the valves so that a repair in the bathroom does not mean shutting off the water to the whole house.

These are simple decisions on paper and expensive ones once the floor has been laid.

Electrical, automation and gas

Next comes power. The electrical design calculates the load of the whole building and, from that, defines the service entrance with the utility company, the panels, circuit breakers, circuits, wire gauges, sockets and lighting. It follows ABNT NBR 5410, which covers low-voltage electrical installations, and includes life-saving protection such as earthing and the residual-current device, which cuts the circuit in the event of a shock.

An undersized wire heats up, and a wire heating up inside a wall is one of the causes of house fires.

Along with the electrical design, it is worth thinking about data infrastructure and automation: lighting, gates, cameras, irrigation and climate control operated by app or programmed. Automation does not have to be installed on day one, but the conduit for it does. Planning it now costs little; breaking walls later costs a lot.

And gas. The gas design defines the LPG installation or the connection to piped gas, the route of the piping, the ventilation of the rooms and the position of the heaters and the stove. Here, the margin of error is zero: the design follows specific safety standards and, in many buildings, is required by the Fire Department.

Waterproofing and swimming pool

Now, a design that is almost always forgotten and later causes the most headaches: waterproofing. Leaks are among the most frequent complaints in buildings, and most of the time they come from a poorly resolved detail: the drain, the skirting, the joint, the bathroom door threshold.

The waterproofing design, guided by ABNT NBR 9575, defines where to waterproof, with which system (membrane sheet, polymer mortar or liquid membrane) and, above all, how to resolve each detail: upturns on the walls, junctions with drains, pipe penetrations and joints. Slabs, bathrooms, balconies, planters, tanks and foundations have different solutions.

With a swimming pool, the reasoning is similar, only with water under pressure all the time. The pool design combines the structure, the waterproofing and the plant room, with pump, filter and piping sized for the volume of water. A well-designed pool does not leak, does not crack and does not become a structural problem for the house next door.

Design coordination

And so we return to where we began: the pipe that met the beam. Having all the designs is not enough; they must be coordinated.

To coordinate is to overlay all the designs (architecture, structure and installations) and check where they cross:

• a sewage pipe passing through a beam;
• an electrical panel on the wall where a column goes;
• a window that coincides with a tank;
• a ceiling lower than the pipe that has to pass above it.

Each conflict found on paper is resolved on paper, with a planned and reinforced hole in the beam, a pipe detour or a change of position. Each conflict that goes unnoticed becomes rework on site, with demolition, waste, delays and, sometimes, structural risk.

That is why BARRETO.eng develops its designs in an integrated way. The same team that calculates the structure sees where the installations run, and the result is a build that follows the design instead of improvising on top of it.

Common mistakes

• Producing only the architectural design and leaving the installations "for the plumber and the electrician to sort out".
• Hiring each design from a different professional, with no one to coordinate them.
• Forgetting the waterproofing design for wet areas and the slab.
• Not planning the automation and data infrastructure while the walls are still open.

Frequently asked questions

Which designs are needed to build a house?

Architectural, structural (with foundations), plumbing (cold and hot water, sewage and rainwater) and electrical. Depending on the case: gas, waterproofing, automation, swimming pool, fire safety and accessibility.

What is design coordination?

It is the overlaying and joint analysis of all the designs to identify and resolve conflicts (pipe × beam, panel × column…) before construction.

Is a structural design mandatory for a single-storey house?

Every structure must be sized by a qualified professional, according to the technical standards. The documents required for approval vary by municipality.

When should I choose steel over concrete?

For large spans, warehouses and mezzanines, and when time is critical. The decision considers span, schedule, cost and use.

Why have a waterproofing design?

Because most leaks start in details (drains, skirtings, joints, thresholds). The design (ABNT NBR 9575) defines the system and the detail of each point.

Do I need to install automation from the start?

No, but the infrastructure (conduits and points) should be planned in the design to avoid breaking walls later.

Which designs are required to approve a build?

It depends on City Hall and on the type of building. The architectural design is always the basis, and many cities also ask for the ART of the complementary designs.