Building a Modular MOC – Where do I start?

Sanctum Sanctorum v1 - Facade 45 deg left
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Starting a Modular MOC, or My Own Creation is not easy. Many people shy away because they often do not know where or how to start. In this series, I will attempt to point you in the right direction using my last two years of experience as the basis.

A little history

When I started down the modular road from many years of building Technics sets, I had no intention to create MOCs, let alone write about it. When I began, I honestly thought it would take me months to build my first. Since I had a neurological event and could no longer use my right hand, I had to learn to do a lot with one hand, and building was one of these things. I found the first few very difficult but persevered, and nearly two years later, I write about LEGO designs, go figure.

It has been therapeutic in its own way; there is a sense of satisfaction in completing a set as complex as the Dinner or Assembly Square, to name a few. I still can’t use my hand beyond positioning it to support things but it has not stopped me from progressing forward in my life.

I tell you this because I want you to know if I can do it, anyone can.

Where to start?

Firstly, I highly recommend that you build a few LEGO Modular buildings; these will teach you invaluable building techniques. I will write about these techniques in future posts but for right now, learn all you can by understanding why LEGO chose to do things the way they did. Their approach to building walls with overlapping bricks, placement of support beams, doors and windows and even brick types are often as important as if it was a real building.

From the exterior aesthetics to the details in the interior decorations, everything has a purpose.

Your first MOC

I bought and built LEGO 76108 Marvel Super Heroes Sanctum Sanctorum Showdown and soon released that it would fit perfectly into my little village. The set has near-exact proportions to modular buildings, with a 16 studs long facade. You will find many MOCs based on Sanctum Sanctorum for that very reason; I have one here.

Because it is ideal to begin creating your own creation, I highly recommend it.

If you cannot find Sanctum Sanctorum, get a similar set where the facade is done for you.


Let us talk of essential considerations before you start building a Modular MOC.

Choosing a baseplate

You have the choice to use the following sizes

    • 16×16 studs baseplate for small buildings that will not connect to the city.
    • 16×32 studs baseplate for small modular buildings that will fit in a modular city.
    • 32×32 studs baseplate for standard modular buildings that will fit in a modular city.
    • 48×48 studs baseplate for large modular buildings, these will need special placement considerations.

You can also use a 16×32 and 32×32 to create a 48×32 baseplate as used by the Assembly Square.

A straight or corner building type?

For your first few modular MOCs I would not recommend corner buildings like the Brick Bank, they are more complex and are susceptible to more errors.

Tip: Sizing of buildings

This is one that is highly important; I have made the mistake of ignoring it too often.
Ensure your floor area is of even brick sizes. Do not have walls that are of uneven brick sizes; building the next floor becomes very difficult.
This is because all the LEGO plates above three studs are in even numbers 4, 6, 8, 10, 14, 12 and 16, this is also the case for most other bricks.
When building LEGO models always think in even numbers, it will make your life easier.

Modular building standards

I use some standards when building modulars, some are set by Lego such as the building connection bricks, others are more personal or simply by observation.

Building connection bricks

On a 32 studs side, start by positioning 2 Technic Bricks 1×2 with a hole at the 10th stud from either side of the base plate on both the right and the left of the plate as shown on the right. This is a LEGO standard for connecting modular buildings. For corner buildings, use the perpendicular side.

This is the first thing I do when I start a new modular.

Sidewalk and building lines

The sidewalk should be eight studs deep directly followed by the building line, though this is more a guideline than a rule I have not seen building lines exceed the 8th stud.

As the Parisian Restaurant (LEGO set 10243) so aptly showed, the sidewalk can be extended upon but leave space for minifigs to walk past.

It is also a good idea to add a lamp post at the end of the plate or every 30 studs and water evacuation grids every 14 studs right behind the curb.

Floor dividers and locks

On the top the last row of bricks I add a row of 1 by x plates, I am very careful to ensure they overlap the bricks by one or ideally more studs. I then add a row of 1 by x tiles, these also making sure they overlap, in this row I also add 1×4 modified pates with two studs strategically situated at each corner to stabilise the next floor.

I also add a row of 1 by x plates bellow the floor plates of the next floor. This avoids bending and helps with the locking of the floor below.

Lastly, every plate joint should have a two by x plate to reinforce its shown below.

In the next post, I will explain how I prepare the foundations and walls.

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  1. Todd

    Awesome help. Thank you.

    1. Pascal Parent


  2. Matt

    Fantastic – I can’t wait for the next installment!

    1. Pascal Parent

      Thanks, Matt. I am working on it.

  3. Jon

    Where can I find the next one about the wall preparation? This post was so helpful!

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