How to draw a house plan to scale
A plan is only useful if the numbers on it are real. This is the order to work in, what to measure before you start, and how to get a drawing a builder can work from.
What "to scale" actually means
A scaled drawing is one where a measured distance on the paper stands for a fixed distance in the building. At 1/4" = 1'-0", a quarter of an inch on the sheet is a foot on site, so a 12 ft room is drawn 3 inches long. Put a ruler on the paper and you can read a dimension that was never written down.
A sketch that is not to scale can still be useful for talking about a layout, but nobody can build from it, price it, or check whether the sofa fits. The moment you want any of those, the drawing has to be scaled.
Before you draw: what to measure
Every mistake at this stage is one you will find again at the end, so it is worth being slow here.
- Room by room, wall to wall. Measure at floor level, not at waist height where furniture gets in the way, and write the figure down immediately.
- Wall thicknesses. Measure at a doorway, where you can see through the wall. A 9-inch block wall drawn as a line will throw every room out.
- Openings, with their positions. Each door and window needs a width and a distance from the nearest corner. "There is a window in that wall" is not a measurement.
- An overall check. Measure the full outside length of each face. When you add the rooms and the walls together, they should come to the same figure. If they don't, something is wrong now rather than later.
Choosing a scale
The scale you pick decides how much of the building fits on a sheet. These are the ones a drawing set normally uses:
| Scale | Metric equivalent | Suits |
|---|---|---|
| 1/8" = 1'-0" | 1:96 | A whole house on A4 |
| 3/16" = 1'-0" | 1:64 | A house on A3 |
| 1/4" = 1'-0" | 1:48 | The usual working scale for a house plan |
| 1/2" = 1'-0" | 1:24 | One room, or a kitchen layout |
| 1" = 1'-0" | 1:12 | Details — a stair, a window head |
The order to draw in
1. The outside walls first
Start at a corner and work round the outside of the building, entering each wall length exactly rather than dragging it to look about right. Keep going until the run closes back on the corner you started from. If it doesn't close, your measurements don't add up — and it is far better to discover that now.
2. Then the internal walls
Divide the shell into rooms. Snap each partition to the walls it meets so the junction is solid rather than two lines that nearly touch; a plan with gaps at the junctions will not produce a sensible floor area or a usable 3D model.
3. Doors and windows
Place each opening in its wall at the width you measured. Get the swing right — which side the door is hinged on and which way it opens — because it decides whether furniture fits behind it and whether two doors clash in a hallway. See standard door and window sizes if you are designing rather than recording.
4. Stairs
A stair is set out from the floor-to-floor height, not guessed. Give it the total rise and the number of steps follows; see stair dimensions for the riser and going rules and a worked example.
5. Dimension it
A drawing without dimensions is a picture. Work outwards in tiers, the way a drawing set does: openings jamb to jamb on the inside line, the walls that set out the rooms next, and the overall size furthest out. Decide whether you are dimensioning to wall centre lines (the drafting convention) or to wall faces (what a builder sets out to on site) and stay consistent.
6. Check before anyone builds
Add the room dimensions along one face and compare the total against the overall figure you measured. Do the same the other way. Two minutes here saves an argument on site.
Printing so the scale survives
This is where most home-printed plans go wrong. In the print dialog set margins to None and scale to 100%. Anything labelled "Fit to page" silently shrinks the drawing by a few per cent, and a scale rule laid on that sheet will lie to you all the way through the job.
DrawHousePlan does all of this in the browser. You type a wall length in feet and inches and the wall is drawn exactly that long, doors and windows go into the walls with real swings, the stair works its own riser out from the floor-to-floor height, and the sheets print at a true architectural scale with the dimension chains and a door and window schedule. It is free, needs no account, and the drawing stays on your machine.
Common mistakes
- Drawing walls as lines. A wall has a thickness, and it eats floor area. Draw it at its real thickness from the start.
- Not closing the outline. If the walls don't join, areas and roofs cannot be traced from them.
- Measuring to the wrong face. Decide early whether a room dimension is between finished faces or between structure, and keep to it.
- Forgetting the door swing. A door that opens the wrong way is one of the cheapest mistakes to fix on paper and one of the most annoying on site.
- Printing "fit to page". It destroys the scale.