Harriet Johnson, working at the Bank Street School in the 1920s and 30s, watched children build with blocks long enough to describe seven distinct stages. Almost every researcher since has come back to her stages with minor revisions. The arc holds because it tracks the child's hands, eyes, and planning ability — not the toys. What follows is a working version of those stages, what they tell you, and what helps. Healthbooq helps families understand what each kind of play is actually building.
Stage 1: Mouthing and Grasping (0–12 months)
The block goes in the mouth. It gets banged on the tray. It gets dropped, watched, retrieved, dropped again. There is no stacking and there shouldn't be. The baby is finding out what a block is — its weight, its temperature, the noise it makes against the floor.
What helps: blocks too big to swallow, soft or rounded edges, supervision when the dropping turns into hurling. Don't try to teach building. The handling is the work.
Stage 2: Knocking Over (12–18 months)
Around a year, children discover that they can make a tower fall. You build, they swing an arm, the tower comes down, they laugh. This will happen forty times in a row. It looks like vandalism; it isn't. They're confirming, over and over, that a small action of theirs reliably produces a big effect — the foundation of cause-and-effect thinking and a real source of confidence.
What helps: build, accept the demolition, build again. A taller stack is more satisfying to knock down than a short one. You can introduce a block here and there into their hand and see if they put it on; sometimes they will, often they won't.
Stage 3: Stacking (18–24 months)
The first deliberate tower. Two blocks. Then three. The tower wobbles, falls, gets rebuilt. Children at this stage are learning balance with their hands — heavier ones go down, the precise centering of one block on another, what happens when the placement is off.
What helps: wooden blocks of similar size are easiest at first because the surfaces are predictable. Don't direct the building; build alongside, slowly, and let them watch what your hands do. Celebrate the attempt and the rebuild, not just the success.
Stage 4: Rows and Towers (24–36 months)
Now the structures start to have variety. Lines along the floor, fences, towers six or eight blocks tall. The placements are clearly intentional. Children start to make decisions before they reach for the next block, even if those decisions still get revised on the fly.
What helps: more blocks, more shapes. Ask "what are you making?" if it's clearly something, but be ready for the answer to be "blocks." Not every structure is a representation; sometimes it's just a structure.
Stage 5: Bridging and Enclosing (around 2–3 years)
Two blocks with a gap, a third one across the top — that's a bridge, and it's a real cognitive jump. So is the enclosure: blocks arranged to make a closed space, often with a toy animal or car inside. These structures require the child to plan in two and three dimensions at once.
What helps: figurines, small vehicles, animals. The structure becomes a setting for play. A horse needs a barn; a barn needs a door.
Stage 6: Named and Decorative (3–4 years)
The tower has a name now. "This is a castle." "This is the train station." Sometimes the name comes after the building, sometimes before — the order is itself a clue about how planning is developing. Children also start to add decorative symmetry, patterns, a block on each corner.
What helps: time. Named structures are often the start of a longer play sequence. Interrupting to clean up before they're done can collapse a half-hour of imaginative work.
Stage 7: Complex, Planned Construction (3–5 years)
The full Johnson endpoint: structures that are designed before they're built, span large areas, take days, and host elaborate small-world play. Children at this stage talk about their buildings, modify them, defend them from siblings, and often build them with a specific other child.
What helps: a generous quantity of blocks (the difference between 30 and 80 is real here), a place where the structure can stay overnight, and props that extend the play — figures, vehicles, fabric for a roof, a basket of natural materials.
Encouragement Without Direction
A few things help across every stage. Build alongside the child rather than for them. Narrate what you see them doing more than what you want them to do. Take a photo when something good gets built — preserving structures teaches that what they make matters. And don't make blocks a "lesson." Children who feel watched for performance disengage; children who feel watched with interest keep going.
Common Snags
"My toddler just knocks everything over." That's stage 2. It is the work, not a failure of it.
"My three-year-old won't stack." Some children are more drawn to small-world or pretend play and come to construction later. Offer, don't push. If by four they show no interest in any constructive activity — blocks, drawing, puzzles, building anything — mention it at a check-up.
"Building gets aggressive." Throwing blocks usually means something else: too tired, too hungry, frustrated at a sibling, overstimulated. Pause the play, deal with the underlying state, come back later.
Materials, Briefly
Wooden unit blocks are the workhorse and the most studied. Foam blocks are forgiving for the early years. Magnetic tiles and plastic interlocking blocks open up structures that don't have to balance, which extends what older preschoolers can build. None of these replace the others; a household with a basket of unit blocks, a tub of magnetic tiles, and a bin of mixed odds and ends is well set up for the entire 0–5 range.
Key Takeaways
Block play moves through a fairly predictable arc — mouthing, knocking down, stacking, bridging, enclosing, naming, then planned construction. Knowing roughly where your child is on that arc is more useful than buying more blocks.
