How to Build Sub-Assemblies — Painting Before Full Asse

Sub-assembly means building a model in separate sections (body, arms, head, backpack) so you can paint areas that would be impossible to reach once fully assembled. Use blu-tack or pins to hold pieces during painting, then glue together after.

If you have ever tried to paint the chest of a Space Marine whose bolter is glued across his torso, or the face of a character whose massive shoulder pads create a cave of shadow, you understand the problem that sub-assembly solves. Some areas of a fully assembled miniature are simply impossible to reach with a brush. Sub-assembly — the practice of painting parts of a model separately before final assembly — is the solution.

This guide covers when to use sub-assembly, how to plan your sub-assemblies effectively, what tools you need, and common pitfalls to avoid.

When Should You Use Sub-Assembly?

Sub-assembly is not always necessary. For many models, particularly simple rank-and-file infantry, full assembly before painting is perfectly fine. The areas you cannot reach on a basic infantry model are also areas that no one will ever see on the tabletop, so leaving them unpainted is acceptable.

Sub-assembly becomes valuable — and sometimes essential — in the following situations.

Character models and centrepiece miniatures. When you are investing significant time and effort into a model, you want every visible surface to be painted to the same standard. Sub-assembly allows you to reach areas that would otherwise be hidden or shadowed by overlapping parts.

Models with enclosed areas. Some models have areas that are completely enclosed after assembly — the inside of a vehicle cockpit, the interior of a building or terrain piece, or the chest area beneath crossed arms. If you want these areas painted, you must paint them before assembly.

Models with complex layering. When one part of a model overlaps another — such as a cloak that drapes over a backpack, or a shield arm that covers the torso — painting each layer separately and assembling afterwards produces a much cleaner result than trying to paint behind the overlapping element.

Large models with hard-to-reach areas. Dreadnoughts, vehicles, monsters, and other large models often have recesses and interior surfaces that a brush simply cannot reach after assembly. Painting these areas on the sprue or in sub-assembly is the only option.

Models where different areas require very different techniques. If a model’s skin requires wet blending while its armour uses metallic paints, painting these areas separately prevents cross-contamination and allows you to use the best technique for each surface without worrying about adjacent areas.

How to Plan Your Sub-Assemblies

Planning is the most important step. Before you cut anything from the sprue, study the model’s assembly instructions and dry-fit the pieces to understand how they go together.

Ask yourself the following questions for each piece.

Will this piece block access to another area? If a shield arm covers the torso, or a backpack covers the back of the head, those are candidates for sub-assembly. The blocking piece should be painted separately and attached last.

Does this piece have a clean join? Sub-assemblies work best when pieces fit together at natural seam lines — where armour plates meet, where a cloak attaches to shoulders, where a weapon meets a hand. Joins that cross a smooth surface (like the middle of a thigh or the side of a torso) are harder to disguise and may not be worth the trouble.

How will I hold this piece while painting? Every sub-assembly needs a way to be held. Larger pieces can be attached to painting handles with blu-tack. Smaller pieces may need to be temporarily mounted on cocktail sticks, pinned to cork, or held with self-closing tweezers. Plan your holding method before you start painting.

Where will the glue joint be? You need to keep the glue contact surfaces free of paint. Plastic cement (poly cement) does not work on painted surfaces — it bonds by melting the plastic, and paint creates a barrier that prevents this. Either mask the contact points with tape before painting or scrape the paint off the contact surfaces before gluing.

Common Sub-Assembly Configurations

While every model is different, certain sub-assembly configurations are common across many kits.

Infantry (basic): Body + weapon arm(s) + head. The body is assembled and painted first, then the weapon arms are painted separately and attached, and finally the head is painted separately and glued in. This lets you paint the face without the weapon blocking access, and paint the chest without arms in the way.

Space Marines: Body + backpack + shoulder pads + head + weapons. This is the classic Space Marine sub-assembly. The torso and legs are built as one piece. The backpack, each shoulder pad, the head, and the weapons are painted separately. This configuration lets you paint the chest aquila, the face, and the inner surfaces of the shoulder pads cleanly.

Characters with cloaks: Body + cloak + head + accessories. Paint the body and back first, then paint the cloak separately and attach it. This lets you paint both the inside and outside of the cloak, as well as the back details that the cloak would otherwise cover.

Vehicles: Hull + turret + sponsons + interior details. For vehicles with visible interiors (like Land Raiders with open assault ramps), paint the interior completely before sealing the hull. The turret and any sponson weapons should be painted separately and left removable if possible for transport.

Large monsters: Body + head + arms/wings + rider. Large models benefit enormously from sub-assembly because their size creates deep recesses that a brush cannot reach on a fully assembled model. Paint the body, limbs, and rider separately, then assemble at the end.

Tools and Materials for Sub-Assembly

You do not need specialised equipment for sub-assembly, but a few tools make the process much smoother.

Blu-tack (poster tack): The most versatile tool for sub-assembly work. Use it to temporarily attach pieces to painting handles, to hold small parts during painting, and to mask areas that need to stay paint-free. Blu-tack leaves no residue and can be reused indefinitely.

Painting handles: Citadel makes an official painting handle, but any clip or holder that grips a base works. For sub-assemblies without bases, use wine corks, old paint pots, or blocks of wood with blu-tack on top.

Cocktail sticks or bamboo skewers: Perfect for mounting small parts. Push the stick into a piece of blu-tack on the part, and you have an instant handle for painting tiny components like heads, shoulder pads, or weapon accessories.

Pin vise and brass rod: For more permanent sub-assembly connections, drill small holes in the contact surfaces and insert short lengths of brass rod (0.5mm or 1mm). This creates a mechanical connection that is much stronger than glue alone, and the pins make alignment during final assembly much easier.

Masking tape: Use narrow strips of masking tape to protect glue contact surfaces from paint. This is more precise than blu-tack for flat contact surfaces.

Superglue (cyanoacrylate): While plastic cement is ideal for unpainted plastic, superglue works on painted surfaces. Keep a small bottle of superglue handy for final assembly of painted sub-assemblies. Gel-type superglue is easier to control than liquid.

Step-by-Step Sub-Assembly Process

Here is the complete process from sprue to finished model.

Step 1 — Study the instructions. Read through the entire assembly guide before cutting anything. Identify which pieces block access to other areas and decide on your sub-assembly plan.

Step 2 — Clean and prepare all pieces. Remove all pieces from the sprue and clean the mould lines. Do all of your scraping, filing, and gap-filling now, before any paint touches the model. It is much easier to clean mould lines on bare plastic than on painted surfaces.

Step 3 — Partially assemble. Build the sub-assemblies according to your plan. Glue together the pieces within each sub-assembly (for example, glue the torso to the legs, but leave the arms off). Let the glue cure fully.

Step 4 — Mount for painting. Attach each sub-assembly to a painting handle or stick using blu-tack. Make sure the mount is secure — nothing is more frustrating than a piece falling off its handle mid-paint job.

Step 5 — Prime all sub-assemblies. Prime everything at once to ensure consistent primer coverage across all pieces. If you are spray priming, arrange all the sub-assemblies together and spray them in a single session.

Step 6 — Paint. Paint each sub-assembly to completion. The order typically does not matter, though many painters prefer to start with the body (the largest piece) and work outward to the smaller components. This helps maintain colour consistency and lets you make decisions about smaller pieces based on how the body looks.

Step 7 — Prepare for final assembly. Before gluing, scrape or sand the paint off all contact surfaces. Plastic cement needs bare plastic to create a strong bond. If you are using superglue (which works on painted surfaces), this step is less critical, but roughing up the contact surfaces still improves adhesion.

Step 8 — Final assembly. Glue the sub-assemblies together. Apply glue sparingly to avoid squeeze-out, which can damage the paint job. If any glue does squeeze out, let it cure fully and then carefully trim or scrape it away. Touch up any damage to the paint at the join lines.

Step 9 — Touch up. After assembly, inspect the model for any gaps, visible join lines, or paint damage at the seam points. Fill gaps with liquid green stuff, touch up paint damage, and blend the join lines as best you can.

How to Handle the Join Lines

The biggest challenge of sub-assembly is making the joins invisible after final assembly. No matter how carefully you work, there will usually be a visible seam where the pieces come together. Here are strategies for minimising this.

Choose natural seam lines. Where possible, plan your sub-assemblies so that the joins fall along natural boundaries — where armour plates meet, where fabric overlaps, where different materials change. A seam along the edge of a shoulder pad is invisible. A seam across the middle of a bare arm is not.

Use pins for alignment. Brass pins ensure that pieces align perfectly every time. Without pins, you may find that pieces shift slightly during gluing, creating misaligned surfaces that are impossible to disguise.

Touch up with paint. After assembly, use thin paint to blend the join. If the seam runs along a shadow line (like the junction between an arm and a torso), a thin line of wash or dark paint will hide it completely. If the seam is on a highlighted surface, you may need to re-layer the highlight across the join to make it invisible.

Accept imperfection. On tabletop-quality models, minor join lines are invisible at arm’s length. Do not agonise over a tiny seam that no one will see during a game. Save the perfectionism for display pieces and competition entries.

When NOT to Use Sub-Assembly

Sub-assembly is a tool, not a rule. There are plenty of situations where it adds complexity without proportionate benefit.

Rank-and-file troops. If you are painting 30 Clanrats or 20 Guardsmen to tabletop standard, sub-assembly will triple your assembly time for a marginal improvement in paint quality. Fully assemble, prime, and speed-paint.

Models with minimal overlap. If a model has clear sight lines to all its surfaces even when fully assembled, sub-assembly is unnecessary. Many modern GW kits are designed with painting access in mind, with arms held away from bodies and heads that are easy to reach.

When you are learning. If you are a complete beginner, the additional complexity of sub-assembly can be overwhelming. Learn to paint on fully assembled models first, and add sub-assembly to your workflow once you are comfortable with the basic painting process.

When time is more important than quality. Sub-assembly inevitably takes longer — more priming sessions, more handling, more assembly steps, more touch-ups. If your goal is to get models on the table as quickly as possible, full assembly and painting is faster.

Sub-Assembly for Specific Model Types

Primaris Space Marines: The most commonly sub-assembled models. Separate the head, backpack, bolt rifle, and shoulder pads from the body. The Intercessor kit specifically benefits from this approach, as the bolt rifle crosses the chest and blocks access to the aquila detail.

Age of Sigmar heroes: Many AoS character models have flowing cloaks, large weapons, or complex poses that benefit from sub-assembly. The Stormcast Eternals range particularly benefits because the large shoulder pads and cloaks create significant overlap.

Imperial Knights and Titans: These huge models are painted almost entirely in sub-assembly. The torso, legs, arms, and carapace are all painted separately and assembled at the end. The sheer size of these models makes full assembly before painting completely impractical.

Vehicles with interiors: Any vehicle with a visible interior (Rhinos with open top hatches, Land Raiders with assault ramps) must be painted in sub-assembly. The interior is painted first, then sealed inside the hull, and the exterior is painted afterwards.

Frequently Asked Questions

Can I use plastic cement on painted surfaces?

No. Plastic cement works by chemically melting the plastic surfaces and fusing them together. Paint creates a barrier that prevents this melting process. You must either scrape the paint off the contact surfaces and use plastic cement on bare plastic, or use superglue, which bonds to any surface regardless of paint.

How do I prime sub-assemblies without them falling off their handles?

Make sure the blu-tack connection is firm. For spray priming, apply light, even coats rather than heavy blasts — heavy coats can physically push small pieces off their mounts. Alternatively, hold the piece by hand (wearing a disposable glove) and prime it directly. For pieces that are too small to hold, stick them to a strip of double-sided tape on a piece of cardboard.

How many sub-assemblies is too many?

As a general rule, 3-5 sub-assemblies per model is the sweet spot. More than that and you are spending more time assembling and touching up than you are saving by having better access. The exception is large centrepiece models (Knights, greater daemons) where 6-8 sub-assemblies may be justified by the model’s size and complexity.

Should I varnish before or after final assembly?

Varnish after final assembly. Varnish creates a smooth, sealed surface that superglue does not bond to as well as raw paint. If you must varnish before assembly (for example, to protect a section that might be handled during assembly), scrape the varnish off the contact surfaces before gluing.

Is sub-assembly worth it for competitive gaming armies?

For most competitive players, sub-assembly is only worth it for characters and centrepiece models. The rank-and-file troops should be fully assembled and speed-painted. Your tournament opponents will not notice whether the inside of a Guardsman’s arm is painted, but they will notice if your army looks cohesive and complete on the table.

How to Build Sub-Assemblies — Painting Before Full Assembly