Most people meet a house as a floor plan: walls, door swings, a dimension string. But the walls are the last thing an architect decides about a room, not the first. Before them comes a quieter drawing in which each room is only an area and a position. That drawing is the space plan, and the thinking behind it is what this page explains.
Four stages, in order
A building design passes through several levels of precision, and each level answers a different question. Space planning is the second of four. The names vary between countries (the brief is called the program in North America), but the sequence does not.
| Stage | Question it answers | Output | Precision | Typical medium |
|---|---|---|---|---|
| Programming (the brief) | What does the building need, and how big? | A room list with target areas | Square metres per room | Spreadsheet, list, brief |
| Space planning | Where does each space sit, how big is it, and what does it touch? | Sized blocks arranged inside a footprint | Blocks to about 100 mm; areas to the m² | Diagram or planning tool |
| Floor planning | What are the walls, doors and windows? | Walls with thickness, openings, derived rooms | Millimetres | CAD or a drafting tool |
| Detailed drafting | How is it built and documented? | Dimensions, schedules, sections, details | Millimetres, to a print scale | CAD, sheets, exports |
The stages are not watertight. A space plan often reveals that the brief asked for more than the footprint holds, and the brief is revised. A floor plan often reveals that a corridor is too narrow once doors swing into it, and the space plan is revised. But the direction of travel is always from area to geometry, because area decisions are cheaper to change than geometric ones.
What a space plan contains
A space plan is deliberately incomplete. It records a handful of decisions and leaves the rest open on purpose.
- Named spaces. Kitchen, Main bedroom, Hall, Utility. Each is a single block, usually a rectangle, occasionally an L or a polygon where the footprint forces it.
- A target area and a current area for each. The target comes from the brief; the current area is whatever the block measures right now. The gap between them is what you are managing.
- Position and proportion. Where each space sits in the footprint, and whether it is a usable shape or a strip.
- Adjacency. Which spaces share an edge. Sharing an edge is how a space plan says "these connect" without yet drawing a door.
- Boundary intent. Whether a shared edge is meant to become a wall or stay open, as a kitchen and dining space might.
- Circulation as a space. The hall, the landing and the corridor drawn as blocks with their own area, not left over as whatever the rooms did not take.
- The footprint. The outline everything must fit inside, when there is one.
What a space plan does not contain is just as defining: wall thickness, door positions and swings, window positions, structure, services and, for the most part, furniture. Those belong to the floor plan. Adding them early makes the drawing look finished and makes it slow to change, which is the opposite of what this stage is for.
Why the stage exists
Three things make space planning worth doing as a separate step rather than sketching walls straight away.
Area is the scarcest resource. A house has a fixed number of square metres, and every one given to the hall is taken from a bedroom. A space plan puts that trade-off in front of you as numbers, before the geometry hides it. See how to allocate floor area between rooms for the method.
Relationships are cheaper to change before walls. Moving a bedroom to the other side of the house in a space plan is dragging a block. In a floor plan it is redrawing four walls, three doors, a window and every dimension that touched them. The plan that gets tested most is the plan that gets better, so the cheap version should be the one you test.
It separates the decision from the drawing. A finished-looking floor plan invites comments on door swings and tile layouts. A block plan invites the question that matters at this point: is this the right amount of space in the right place?
Bubble diagram, space plan, floor plan
Architects use three drawings on the way from a brief to a building, and they are often confused with each other.
- A bubble diagram shows relationships only. Rooms are circles, lines join the ones that should connect, and nothing is to scale. It answers "what goes near what" and nothing else.
- A space plan adds area and position. The bubbles become sized blocks inside a footprint, so the diagram can now be wrong about fit, which is the whole point.
- A floor plan adds construction. Blocks become rooms enclosed by walls of real thickness, with openings.
Each step makes the drawing more committed. You can skip the bubble diagram for a small project; the relationships fit in your head. Skipping the space plan is riskier, because fit does not fit in anyone's head. It has to be measured.
How precise a space plan should be
Precise enough to be wrong about fit, and no more. In practice that means blocks placed and sized to about 100 mm, areas read to the square metre, and no attempt to chase millimetres. Real wall thickness will later take a few percent off every room (a 120 mm partition centred on a planning line costs each side 60 mm), so a space plan that balances to the last 0.1 m² is spending effort that the next stage will erase. The arithmetic is in how to turn a space plan into a floor plan.
Width matters more than area at this stage. A 12 m² bedroom drawn 2.4 m wide fails as a bedroom no matter what its area says. Use the working minimums in the room sizes and clearances guide as the floor under each block's short dimension.
Space planning in houses and in offices
The same word covers two slightly different jobs. In commercial work, space planning is largely arithmetic: workstation counts, area per person, meeting-room ratios, and the plan is judged on efficiency. In a house the arithmetic is smaller and the judgement larger: whether the entrance protects the bedrooms, whether the kitchen sees the garden, whether the one bathroom is reachable from every bedroom without crossing the living room. A house space plan is still counted in square metres, but it is decided by those relationships.
When to stop space planning
When every required space is present, the areas balance against the footprint, the route from the entrance reaches every room, and every shared boundary has a decision behind it. At that point the arrangement is worth committing to walls. Stopping earlier means drawing walls around a plan that does not yet fit; stopping later means polishing blocks that the wall thickness will change anyway. The full method is in how to plan rooms before drawing walls.
How this works in Gridsnap
Gridsnap's Space tool is a space planner in exactly this sense. A Space is a named block with a target area and a current area, drawn as a rectangle or polygon. Adjacent Spaces snap edge-to-edge, and a shared boundary can be dragged to move area from one Space to the other. An Envelope marks the footprint, and the plan summary reports overlaps, unassigned area inside the envelope and any Space that sits outside it. Each shared boundary is set to Wall, Open or left as Auto.
When the arrangement works, Build plan converts it into ordinary walls and detects rooms from them. The space plan is kept as a read-only source that can be viewed or reopened as an editable variation. What Gridsnap does not do in the current release is arrange the spaces for you or judge the relationships between them: it makes the allocation exact and the trade-offs visible, and the designer decides.