I first heard of "modular" in the Lego world about the series of modular buildings in sets produced from 2007 onward. The architecture seems to be 1800s to late 2000s.

Then read that the Lego system as a whole is considered modular. "This modular system is a set of basic building blocks that can be combined in different ways to build numerous varying creations.

But sometimes the people talking about their modular buildings are talking about MOCs or medieval villages. Is the term being used to mean something more?

6 Answers 6


Generally speaking "Modular(s)" refers to sets in the Creator Expert theme that are designed with common proportions and common attachment points to allow them to be strung together neatly. Mostly this takes the form of Technic-pin connectors and socket bricks in the same places on each set. It's made somewhat simple by all the sets being built on the same size baseplates, sometimes paired up the half-width version for larger sets.

They're also generally designed so that each floor of the building is itself a module. They have no cross-floor connections, allowing higher levels to be cleanly lifted off lower floors and separated to see what's inside.

While most of them are in the Creator Expert series, and that's generally what people mean when they talk about "Modulars" as a group, there are sets in other themes designed to a compatible specification. Off the top of my head:

There are some sets built with similar techniques (plate size, easily lifted floors) that are not directly/fully compatible with the other "Modulars": 71741 Ninjago City Gardens comes to mind. It doesn't have the sidewalks of the other sets, nor does it have all the attachment points.

From My Living Room, 2021-08-09

Lastly... in the eyes of Lego themselves, "Modular" is not a theme. You can't shop explicitly for sets by their modular nature. List of Themes from Lego.com There's a few more themes than those listed above, but "Modular" isn't among them.


To add to the answer given by Alex when building a MOC some people also make their creation modular to make it transportable and/or to make it flexible in usage. For landscaping there are some standards created by the community. One example is called MILS(Modular Integrated Landscaping System). In the case of MILS one of its primary objectives is to create a set of standards so that 2 or more people can work together on 1 large creation while not in the same location and make sure it will all fit together.

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    MILS is commonly used, but it is not the standard. There is at least one other option - Moduverse.
    – Alex
    Commented Nov 30, 2022 at 18:09
  • I didn't know about that one. I have edited my answer to make it clearer that MILS is just 1 of the standards created by the community. Commented Nov 30, 2022 at 20:01
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    In some parts of the community "modular" in relation to a MOC means it's designed to attach to the official modulars. Commented Nov 30, 2022 at 23:31

"Modularity" is an attribute, that like for example "flexibility" can be applied on different scales. A water droplet is considered flexible, but a larger volume of water is definitely not. Whereas a meter of 1mm diameter copper wire is clearly flexible, but a 5mm piece of it will easily pierce skin.

When people talk about LEGO bricks being modular, they mean they (i.e. the individual bricks) can easily attach to each other in various different configurations (barring some combinations of course). When the same is said about buildings, they mean essentially the same, just on a different scale: that the individual buildings can be attached to each other easily and in various ways. Inbetween, a single LEGO set can be modular as well, meaning it consists of multiple modules that can be connected in different ways, like for example 6973: Deep Freeze Defender, 7633: Construction Site or 60349: Lunar Space Station


I would say term "modular system" is the basic idea behind the LEGO itself. It is the reason there is so much variety in the ways you can attach parts to make your won creations.

"Modulars", on the other hand, is the term commonly used for particular Creator Expert sets of buildings that, once completed, can be attached one another to form a larger exposition. This is because these buildings are modular (have sort of a standard) - they are roughly same scale, have attachment points in the same place, sidewalk is the same width (+- a stud or two depending on a building). All of this makes them look consistent and easily interchangeable i.e. modular. Unlike previously sets with buildings which were standalone or didn't keep to the same "standard".


We are not limited to the modular buildings from LEGO. You can design your own based on documented standards for modular buildings. And the community has designed many modular buildings that you can get instructions for on rebrickable.

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    Your first link is super helpful, thank you! I guess that though I will probably not build in the modular 'style', having the proportions at least, will help to make my buildings compatible to each other.
    – MocBird
    Commented Dec 5, 2022 at 23:59

The standard Lego modulars (the ones designed to resemble 19th century to early 1930s urban centres) all are part of the Lego Expert line, but there's Lego modular sets from other themes. The unifying features with the Lego Expert sets are 19th and early 20th century architecture, two or three removable floors, and a system of Technic pins that allow multiple of those buildings to be "locked" together to make a defined town scape. A few Lego modulars fall into the Ninjago series. The Ninjago City Gardens set is modular in that it can physically connect to other Lego modular buildings, though the Lego Ninjago City set differs from any of the Lego Expert modulars in its architectural style (a contemporary Japanese style) and the fact that it has more storeys than any of the Expert modular buildings ( 7 floors as opposed to the standard 2 or 3).

  • Looks like "LLM answered".
    – LKBricks
    Commented Jun 7 at 15:12
  • 1
    The style of the answer is indeed fishy but the content is there for it to be considered a proper answer.
    – zovits
    Commented Jun 10 at 9:37

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