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General · 15 min read

How to Read Architectural Drawings (For Tradespeople)

Stop guessing what the architect meant. A practical guide to reading scales, line weights, abbreviations, and finding the dimensions you need on site.

BuildMetric Engineering

Written & Reviewed

Updated

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If you are a contractor, joiner, or bricklayer, the architectural drawing is your instruction manual. If you read it wrong, you build it wrong.

Architects speak in a visual language built on scales, line weights, and standard abbreviations. While a set of drawings can look incredibly complex at first glance, it is actually a highly organized system. Once you understand the rules, you can find any dimension or detail you need in seconds.

01. Title Block & Scale

Never start measuring off a drawing without checking the title block. Usually located in the bottom right corner of every sheet, the title block is the identity card of the drawing. It tells you:

  • The project name and address.
  • The specific drawing title (e.g., "Ground Floor Plan").
  • The drawing number and revision (e.g., Rev C). Always make sure you are building from the latest revision.
  • The scale.

Understanding the Scale

Drawings are a scaled-down representation of reality. If a drawing is at 1:100, it means 1 unit on the paper equals 100 units in real life (e.g., 1 cm on paper = 100 cm in reality).

In the US, imperial scales are common (e.g., 1/4" = 1'-0", meaning a quarter-inch on paper represents one foot in reality). In the UK and Australia, metric ratios (1:50, 1:100, 1:200) are standard. If you print a drawing and it says "Do Not Scale," it means the printer may have altered the paper size, making physical scaling inaccurate. You must rely on the written dimensions.

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02. Line Weights (Thick vs Thin)

Architects use different line thicknesses (weights) to tell you what is cut versus what is seen from above. This is crucial for understanding what you are looking at.

  • Heavy / Thick Lines

    These represent elements that are physically cut through by the section plane. If you are looking at a plan view, heavy lines are the walls, columns, and structural elements you are cutting through.

  • Medium Lines

    Typically used for elements that are visible but below the cut plane, such as floor edges, steps, or the edges of worktops.

  • Light / Thin Lines

    Used for textures, hatching, grid lines, and elements above the cut plane (like overhead beams or roof lines).

03. Finding Dimensions

Dimensions are usually grouped outside the floor plan, connected by thin lines with tick marks at the ends. Architects use a system called dimensioning strings or chained dimensions.

Typically, the outermost string is the overall building dimension. The next string in shows the room widths and wall thicknesses, and the innermost strings might show specific details like window openings or structural columns.

Golden Rule: Always work from the largest dimension to the smallest. If the overall dimension says 12,000mm, and your internal room dimensions add up to 12,050mm, something is wrong with the drawings (often due to a missing wall thickness or a structural beam). Do not start building until that discrepancy is resolved.

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04. Symbols & Abbreviations

Architects use abbreviations to save space and keep drawings clean. While every office has its own legend, here are the most common ones you will encounter on site:

FFL

Finished Floor Level

SFL

Structural Floor Level

TYP

Typical (applies to all similar items)

NTS

Not To Scale (do not measure this drawing)

CL

Centre Line

DPC

Damp Proof Course

For doors and windows, architects rarely draw every single one in detail. Instead, they use codes like D01 or W03. These codes refer to a "Door Schedule" or "Window Schedule" found elsewhere in the drawing set, which lists the exact dimensions, materials, and fire ratings for each item.

05. Cross-Referencing Drawings

A floor plan only tells you what a building looks like from above. It does not tell you how high the ceiling is, or what the roof looks like from the side. You must cross-reference the Plan with the Elevations and Section Drawings.

  • Sections: Imagine slicing the building in half like a cake and looking inside. Sections show you the layers of the floor, wall, and roof build-ups (e.g., plasterboard, insulation, structural timber, cladding).
  • Elevations: These show the outside faces of the building (North, South, East, West). They indicate external materials, window heights, and roof pitches.

If a detail on the plan seems ambiguous, look for a "detail callout" (usually a circle with a number inside). This tells you to look at another sheet for a larger, zoomed-in drawing of that specific junction.

The Bottom Line

Reading drawings is a skill that improves with practice. Always check the title block for the revision and scale, use a scale rule if necessary, and never assume a dimension—always verify it. If you spot a discrepancy on site, stop and ask for clarification rather than guessing. It is cheaper to ask a question than to rebuild a wall.

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About the Author

BuildMetric Engineering Team

Technical Writing & Code Review

This guide was written by the BuildMetric editorial team and reviewed by a practising structural engineer. We combine field experience with published standards to explain construction math without the jargon. Every article is versioned and dated.

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Frequently Asked Questions

Drawing & Blueprint FAQs

01 What is the most important part of a drawing to check first?

Always check the Title Block (usually in the bottom right corner) first. It contains the drawing title, the drawing number, the revision date (to ensure you are not building from old plans), and the scale. Building from an outdated revision is one of the most common and costly mistakes on site.

02 What does 'NTS' mean on a drawing?

NTS stands for 'Not To Scale'. If a drawing is marked NTS, it means the physical dimensions on the paper do not accurately represent the real world (usually because the drawing was scaled to fit the page). You must rely on the written dimensions provided on the drawing and never measure directly off the paper with a scale rule.

03 What is the difference between a plan, section, and elevation?

A Plan is a view from above (looking down). A Section is a vertical cut-through the building, showing the internal layers of the floor, walls, and roof. An Elevation is a flat view of the outside of the building, showing materials and roof pitches.

04 How do I know if a wall is load-bearing from a floor plan?

On architectural plans, load-bearing or structural walls are usually drawn with thicker, heavier lines or distinct hatching compared to lightweight partition walls. However, you should always cross-reference the architectural plan with the structural engineer's drawings to be 100% certain before removing any walls.

05 What is a door or window schedule?

A schedule is a table, usually found towards the end of the drawing set. Instead of drawing every door in detail, architects label them (e.g., D01, W02). The schedule lists the exact dimensions, materials, fire ratings, and hardware required for each specific labeled item.

06 What do FFL and SFL mean?

FFL stands for Finished Floor Level (the top surface of your tiles, carpet, or timber). SFL stands for Structural Floor Level (the top of the concrete slab or joists before any flooring is laid). Knowing the difference is crucial for calculating door heights and floor build-ups.

07 What is a revision cloud on a drawing?

A revision cloud is a scalloped, cloud-like line drawn around an area of the drawing that has been changed or updated in the latest revision. It is usually accompanied by a triangle containing the revision number, helping builders quickly spot what has changed since the previous issue.

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