DTAC, PTh, DDE: the phases of an architecture project, explained

When you discuss a project with an architecture studio, three acronyms come up quickly: DTAC, PTh, and DDE. They are not jargon for its own sake — they describe the natural phases a project passes through, each with a different level of detail and a different role. Below we explain them one by one and show why their order matters.

Why a project has several phases

An architectural project is not drawn "once, completely." It develops in stages: first only as much as is needed to obtain the permit, then as much as is needed to build it correctly on site. Each phase answers a different question — "is it allowed?", "how is it built?", "what does the exact detail look like?" — and is addressed to a different recipient (the authority, the contractor, the site team).

DTAC — the technical documentation for the building permit

DTAC (documentația tehnică pentru autorizarea executării lucrărilor de construire, the technical documentation for the building permit) is the phase on the basis of which the building permit (autorizație de construire, AC) is obtained.

• What it is: the technical documentation that demonstrates the project complies with urban-planning regulations (the POT and CUT indicators, the height regime, the setbacks set out in the certificat de urbanism, the urban-planning certificate) and the applicable technical standards.
• Level of detail: sufficient for authorisation. DTAC establishes the overall solution — functions, dimensions, placement on the plot, appearance — without yet going down into the fine details of execution.
• Who produces it: the architect, together with the specialist engineers (structure, building services), to the extent needed for the permit.
• What the client receives: a coherent, permittable project that clearly shows which building will be approved: plans, elevations, sections, and the layout on the plot.

In essence, DTAC answers the question: "is what we want to build allowed?"

PTh — the technical project

Once the permit has been obtained, the project must be developed to a level at which it can be executed. This is the PTh phase (proiectul tehnic, the technical project).

• What it is: the development of the solutions across all disciplines — architecture, structure, and building services (electrical, plumbing, heating, ventilation) — coordinated with one another.
• Level of detail: far higher than DTAC. The technical project describes how the building is actually constructed: assemblies, materials, technical solutions, and dimensioning.
• What the client receives: a project on the basis of which the construction can be organised, comparable price offers can be requested from contractors, and the cost of the works can be estimated realistically.

PTh answers the question: "how is it built?"

DDE — the execution details

DDE (detaliile de execuție, the execution details) completes the technical project with the detailed drawings needed directly on site.

• What it is: the execution details — large-scale drawings that clarify the sensitive points: construction joints, connections, finishes, and non-standard elements.
• Role: they remove ambiguities on site, where a general solution is not enough to build correctly.
• What the client receives: a more predictable execution, with fewer improvised decisions on site and, by extension, fewer errors and additional costs.

DDE answers the question: "what does the detail look like exactly, in execution?"

The logical order and why it matters

The phases follow one another naturally, not by chance:

1. DTAC → the building permit is obtained;
2. PTh → the solutions are detailed for execution;
3. DDE → the details are clarified for the site.

The table below summarises the differences:

This order follows an economic and a technical logic. There is no point in developing the execution details for a building that has not yet been authorised and that might still change. And, conversely, you cannot build well with only the level of detail of DTAC.

What happens if you skip phases

The temptation to "save money" by dropping the full technical project or the execution details comes up often, but as a rule it merely shifts the cost further down the line, onto the site. Without a well-developed PTh and DDE:

• contractors' offers become hard to compare, because each one assumes something different;
• technical decisions are improvised during execution, without coordination between the disciplines;
• the risk of errors, rework, and unforeseen additional costs increases.

In other words, the phases are not bureaucratic boxes to tick, but the instrument through which a project moves from "approved" to "built correctly." Understanding them from the start helps you anticipate what you receive at each step, and why each one is worth it.