How to Read House Plans: Floor Plans, Electrical, Hydraulic and Framing Sheets Explained

A set of house plans is a stack of drawings that each answer one question: what goes where, where the power and water run, how the house is held up, and how high everything sits. Builders read them fluently. Most owners sign a contract on them after a quick look at the floor plan, and find the details later, on site, when they're expensive to change.

This guide explains how to read house plans for a new home or renovation in Queensland: what's in a typical set, how scale and dimensions work, what the common floor plan symbols mean on the architectural, electrical, hydraulic and framing sheets, and what to check before you sign. It finishes with the one thing no set of plans shows: what was actually built.

What's in a set of house plans

Every sheet carries a title block in one corner with the project, the sheet number, the scale, the date and a revision letter. Check that every sheet in your set is the latest revision; plans change during design, and the contract should list the exact sheets and revisions it's based on.

• Site plan. The house on the block: boundaries, setbacks, levels, driveway, services connections and north point.
• Floor plans. One per level, showing rooms, walls, doors, windows and fixtures, usually at 1:100.
• Elevations and sections. The outside of the house from each side, and slices through it showing ceiling heights, roof pitch and floor levels.
• Services sheets. Electrical and hydraulic (plumbing and drainage) layouts on the same floor plan.
• Structural and framing sheets. The engineer's slab, footing and framing details: beams, lintels, bracing and tie-downs.
• Schedules and notes. Door and window schedules, finishes, and general notes that apply across the set.

Scale and dimensions: read the numbers, not the ruler

A plan drawn at 1:100 means 1 mm on the page is 100 mm on site, so a 40 mm line is a 4 m wall. But that's only true on the original sheet size. Printed on the wrong paper, zoomed on a screen or photocopied, the drawing is no longer to scale, which is why most sets say "do not scale".

Read the dimension strings instead. They're in millimetres, run along the walls in chains, and add up to the overall dimensions at the ends. A room marked 3600 × 3000 is 3.6 m by 3 m; the general notes say whether room sizes are measured to the frame or to the finished wall. Levels are shown as a finished floor level (FFL) in metres, and ceiling heights appear on the sections.

Floor plan symbols, sheet by sheet

Each sheet has a legend explaining its symbols, and symbols vary between drafters, so always check the legend on your own set first. The basics are consistent enough to learn once:

• Architectural. Thick lines are walls; a door is drawn with the arc of its swing; windows are thin lines across the wall with a code that points to the window schedule. Section and elevation markers point to the other sheets.
• Electrical. Power points, switches, lights, data and TV points, smoke alarms and the switchboard. Dashed arcs join each switch to the lights it controls. This is also where pre-wiring for home theatre shows up: speaker cable runs, TV conduits and data to the media wall.
• Hydraulic. Hot and cold water, sewer and waste lines, floor wastes (FW) in wet areas, the hot water unit, the water meter, inspection openings and the overflow relief gully.
• Framing. Stud spacing, a lintel over every opening, beams where walls have been left out, and the bracing walls and tie-downs that hold the house against wind.

Pick a layer in the plan viewer below to see what each sheet adds to the same floor plan, and hover or tap a symbol to read it. The last tab shows the one thing the plans don't.

Elevations, sections and the site plan

The floor plan tells you what goes where; the elevations and sections tell you how high. Check the ceiling heights on the sections against what you expect: 2.4 m is the usual minimum for living areas and bedrooms in Queensland, with 2.1 m allowed in kitchens, bathrooms, laundries and corridors. Check window head heights, the roof pitch and the floor level against the ground on the elevations.

On the site plan, check the setbacks from each boundary, where the stormwater and sewer connect, and how the block falls. On a sloping block, the levels on the site plan drive the cut, fill and retaining costs that Before the Slab covers.

What to check before you sign

Read the plans the way you'll live in the house:

• Put your furniture on the floor plan. Check power points against beds, desks, the TV and the kitchen bench appliances.
• Walk the light switches from each doorway. Check you can turn lights on as you enter and off as you leave.
• Check wet areas: shower and vanity positions, floor wastes, and where the hot water unit sits relative to the kitchen and bathrooms.
• Mark anything you'll hang: vanities, TV brackets, shelving, grab rails. Ask for noggings to be shown or noted.
• Check the window sizes, door widths and ceiling heights on the schedules and sections, not just the floor plan.

Every change after the contract is signed is a variation, so changes cost least now. Our building contract guide covers the five business days you usually have to read the whole contract, plans included.

The plans versus the build

Plans show what was intended. During a build, reasonable calls get made on site every day: a nogging moves to clear a pipe, a water line comes in from a different side, a wall shifts a little to fit a cabinet. Each change is sensible on the day. Very few make it back onto the drawings.

That drift matters later. Years on, someone drills or cuts where the plans say it's clear, and the plans are the only record anyone has. The time to check every line of the plans against the frame is before the plasterboard goes on, while the studs, pipes and cables are still in view. The Close-Out Checklist walks the frame room by room with the plans open, with a box for Checked and one for Recorded.

A dated 3D capture of the frame at that stage is the as-built record the plans can't be: where everything actually went, to scale, in every room. Our as-built guide explains how it's captured and used. It's an architectural-grade record, not a survey.

How to read house plans: FAQs