A floor plan can look simple until you try to picture living in it. Lines, symbols and numbers hide a lot of information. DADU plan reading is a skill any owner can learn, and it helps you compare designs before you commit to one.

This guide explains the basics in plain terms. It covers scale, room sizes, doors, windows, stairs, circulation and furniture, and it ends with questions to ask about any plan.

DADU Plan Reading Starts With Scale

Every plan shows the real building at a reduced size. The scale tells you how much. According to SDCI’s tip on general standards for plans, permit plans must clearly state the scale and show it as a graphic. For small residential projects, the minimum scale is a quarter inch on paper for each foot of building.

Dimensions matter more than the drawing itself. Look for strings of numbers along walls, which give exact lengths. If a plan has no dimensions, treat it as a sketch rather than a design.

Check the drawing set as a whole too. A floor plan shows the layout from above, while elevations show each outside wall and sections slice through the building. Good DADU plan reading means looking at all three, since a window or ceiling height may only make sense once you see the elevation or section.

Reading Room Sizes and Labels

Each room should carry a label, and permit plans must state how each room will be used. Many marketing plans also list room sizes, such as a width and a length. Check whether those figures measure to the wall surface or to the wall center, since that changes the usable space.

Code sets a floor for room size. SDCI’s residential code tip states that habitable rooms, except kitchens, must be at least 70 square feet and at least 7 feet in any horizontal direction. A room that barely meets the minimum may still feel tight once furniture goes in.

Doors and Windows in DADU Plan Reading

Doors show as a line with an arc that traces the swing. That arc tells you how much floor the door needs when it opens. For example, a bedroom door that swings into a closet door can cause daily frustration.

Windows show as thin breaks in the wall, often with a tag that links to a schedule. Permit plans list the width and height of each window and door. Each bedroom also needs an emergency escape window or door, so check that every bedroom has one on an outside wall. In addition, SDCI’s tip calls for at least one swinging exit door per unit that is 3 feet wide.

Stairs and Level Changes

Stairs appear as a series of parallel lines with an arrow that points up or down. A break line often cuts the stair where the floor above takes over. Look for the stair on both floor plans, since it uses space on each level.

Stairs follow code limits on width, step size and headroom. As a result, a stair that looks narrow on a marketing plan may grow during design. Ask whether the stair already meets the residential code, and whether the headroom works under the roof above it.

Circulation and Flow

Circulation means the paths people take through the home. Trace a few common routes with your finger. Walk from the entry to the kitchen, from a bedroom to the bathroom and from the living room to the yard.

Good plans keep paths short and clear. However, a path that cuts through the middle of the living room or past the kitchen work area can make both spaces harder to use. Also watch for dead space, such as a long hall that serves only one room.

Furniture and Real Life Fit

Many plans show furniture, but the pieces may be smaller than real ones. So measure your own bed, sofa, table and desk. Then sketch them to the same scale on a copy of the plan. Paper cutouts work well for this.

Leave room to move around each piece. In particular, check space beside beds, in front of closets and around the dining table. Our guide to DADU bedroom count explains how bedroom choices shape the rest of the floor plan.

Comparing Plans With DADU Plan Reading

Once you can read one plan, you can compare several. Start with total floor area and how it fits the size cap, which our guide to Seattle ADU size explains. Then compare storage, light, privacy and how each plan fits your lot.

Preapproved plans deserve a careful read too. They have already passed some city review, but they still need to fit your site. Our post on the Seattle preapproved DADU program covers what that review does and does not include.

Questions to Ask About Any Plan

A short list helps you get clear answers from a designer or seller.

• Does the plan state its scale, and does it dimension every room?
• Where do the heating equipment, water heater and laundry go?
• Does every bedroom have a code compliant escape window?
• How would the plan change to fit my lot, setbacks and height limit?
• Which changes would need new structural design?

Asking early can prevent costly surprises later, as our guide to DADU design cost explains.

Overall, a floor plan becomes much clearer once you know what to look for. Scale, dimensions, door swings, windows, stairs and paths all tell a story about daily life in the cottage.