We have already written about whether you need a building permit for a container. The answer was honest but necessarily general: it depends. This time we go a level deeper and explain what exactly it depends on. In practice it almost always comes down to a single question — how your structure is classified by construction complexity.

What follows is practical guidance with sources, not legal advice. Slovenian legislation and municipal acts change, so your administrative unit (upravna enota) or municipality always has the final word.

Four categories that decide everything

The Slovenian Building Act (GZ-1) sorts structures into four groups: demanding, less demanding, non-demanding and simple. The detailed criteria are set by the Regulation on the Classification of Structures (Uredba o razvrščanju objektov). For something as small as a container unit only the last two matter — and the difference between them is the difference between “just put it up” and “administrative unit first”.

Two numbers worth memorising

For a “majhna stavba” — the small-building category that covers sheds, workshops, garages and similar ancillary structures — the threshold is set by floor area:

• up to and including 20 m² — simple structure (enostavni objekt)
• up to and including 50 m² — non-demanding structure (nezahtevni objekt)
• above 50 m² — as a rule the structure becomes less demanding (manj zahtevni objekt)

Two further conditions apply on top of area. The structure has at most one storey, and its height must not exceed 4 m for a simple structure or 6 m for a non-demanding one. For a single-storey container the height is practically never the problem — storeys and square metres are.

What this means for each model

• ContBlox 3×3 — approx. 9 m², comfortably under the 20 m² threshold.
• ContBlox 3×6 — approx. 18 m², still under 20 m², but close to the line.
• ContBlox 3×9 — approx. 27 m², so in the 20–50 m² band.

These areas are approximate and refer to external footprint dimensions. If you are near the 20 m² line it is worth asking how the area is counted in your case — that detail can decide which category you land in, and whether you file anything at all.

The catch people miss most often

By its legal definition, a simple structure is one that is not intended for dwelling. That matters more than the square metres, and it is almost never mentioned. Nine square metres where you keep tools and nine square metres where you sleep are not the same structure in law — even though it is the identical container on the identical base.

So answer one question honestly at the very start: what will you use it for? A garden shed, a hobby workshop or storage is a different thing from a weekend place with a bed in it. If the purpose is living, expect to be talking about a non-demanding structure at minimum — and expect the municipal spatial plan to have the final say.

Stacking and lining up units changes the category

The ContBlox system lets you place 3×6 units side by side to any length, or stack up to three high. For classification that cuts both ways:

• Upwards. The criterion for simple and non-demanding structures is at most one storey. Two units on top of each other are two storeys — which puts the structure outside both categories regardless of its height.
• Sideways. Two 3×6 units side by side are not 18 m² but 36 m². Still under 50 m², but already outside the simple-structure band.

If you plan to expand in stages, say so at your first visit to the administrative unit. It is far easier to know up front what will apply to the finished layout than to sort out the paperwork twice — the second time retrospectively.

What each category requires

• Simple structure — no building permit is required, and no construction-start notification either.
• Non-demanding structure — a building permit is required, but in simplified form: documentation for a non-demanding structure (DNZO) is enough, and it does not have to be prepared by an authorised designer.
• Less demanding structure — a full building permit with project documentation prepared by an authorised designer.

One important caveat: not needing a permit for a simple structure does not mean you may put it anywhere. The municipal spatial plan — permitted land use, setbacks from boundaries, protection corridors — applies to it as well.

Before you order anything

1. Check the permitted land use of your plot and the municipal spatial plan rules at the municipality.
2. Decide honestly what the structure is for — dwelling or not.
3. Add up the final area and number of storeys, not just the first unit.
4. Take those three facts to the administrative unit and ask one question: how is this structure classified and what do I need?

Where to check this

• Building Act (GZ-1) and the Regulation on the Classification of Structures — pisrs.si
• Classification of structures by construction complexity — pis.eprostor.gov.si
• Technical guideline TSG-V-006 on classification — gov.si

Once you know the category, the rest is mechanics. If you are missing technical data for that conversation — dimensions, structural build-up, weight — tell us which model you have in mind and where it is going, and we will send it over.