A newcomer looks at a drawing and sees lines. Someone who can read drawings sees a brick wall, a door opening inwards, a 220×400 beam, a socket mounted 300 mm above the floor. The difference is a table of construction drawing symbols carried in the head.
This article is that table, written to be looked up: 110 symbols, each with its figure, grouped from line types, materials, architecture and furniture through structure, steel sections, services, roads and earthworks, closing with the abbreviations table. All figures were drawn by the Institute, so you may reuse and print them freely. A printable PDF sits at the end.
Jump to a building element: doors and windows · stairs · furniture · reinforcement and members · steel sections · electrical and plumbing.
Jump to a drawing convention: line types and grids · materials in section · roads and earthworks · abbreviations.
The reliability of each group differs, so the article says so up front. The line-work and architecture groups are checked against the standards, with sources cited. The electrical and plumbing groups are not: they follow common practice in Vietnamese project sets rather than a verified standard.
If what you need is the reading order for a full document set rather than individual symbols, start with How to read construction drawings. And for guided practice on real document sets, the Institute runs a six-session drawing-reading course.
The symbols and the standards behind them
Drawing conventions in Vietnam follow the national system of design documentation standards. The table below names the standard currently in force for each group, checked against the national standards portal:
| Symbol group | Standard in force | Notes |
|---|---|---|
| Line types, grid lines | TCVN 5570:2012 | Replaces the 1991 edition. Thick lines 0.5–1.4 mm depending on scale; thin lines 1/3–1/2 of that |
| Title blocks | TCVN 5571:2012 | Replaces the 1991 edition |
| Materials in section | TCVN 7:1993 | Hatching at 45°, minimum spacing 0.7 mm. Concrete alternates solid and chain lines |
| Doors, stairs, building elements | TCVN 4614:2012 | Replaces the 1988 edition; a revision is planned and the National Institute of Architecture has published a draft |
| Reinforced concrete | TCVN 5572:2012 and TCVN 6084:2012 | Construction drawings and rebar representation |
| Electrical | TCVN 7922:2008 (IEC 60617) | The familiar TCVN 185:1986 has been withdrawn since 2008 |
| Plumbing and equipment | TCVN 6077:2012 | TCVN 4615:1988 has been withdrawn |
The most useful fact in that table: the two standards most often cited online — TCVN 185:1986 for electrical and TCVN 4615:1988 for plumbing — were both withdrawn long ago. The figures below were checked against the original TCVN 7:1993 and the draft revision of TCVN 4614.
One rule outranks every chart, including this one: the general notes sheet and the legend of the actual document set always take priority. Company sets may differ from the standard in details. Use the tables below when a set has no legend, or when its legend has gaps.
One thing to grasp before looking anything up, especially as a beginner: the same object can carry different symbols depending on the type of view it appears in. A plan is seen from above, through the conventional horizontal cut. A section is a vertical cut through the building. An elevation looks straight at a face. Each table below therefore states which representation its symbols belong to, with exceptions noted per row.
| Symbol | Name | What it means |
|---|---|---|
| Thick solid line | Visible outline of a cut element: walls and columns on a plan | |
| Thin solid line | Uncut outlines, dimension lines, extension lines, hatching | |
| Dashed line | Hidden edges: beams below the slab, footings below grade | |
| Thin chain line | Grid lines and centre lines | |
| Thick chain line | Position of a cutting plane | |
| Wavy line | Break line, limit of a partial view | |
| Zigzag line | Also a break line, common on long members | |
| Numbered grid | Grid in one direction, usually across the plan | |
| Lettered grid | Grid in the other direction | |
| Intermediate grid | A grid line inserted between two main ones | |
| Datum level | The ±0.000 mark, usually the finished ground-floor slab. Filled triangle: the surface is cut | |
| Level, seen | Level relative to datum, in metres to three decimals. Open triangle | |
| Dimension line | True size in mm. Oblique tick terminators are the common Vietnamese style | |
| Repeated dimension | Four equal bays of 900, totalling 3600 | |
| Section mark | Position and viewing direction of section A–A | |
| Detail reference | Detail number 3, drawn on sheet KC-05 |
Two traps in this group. First, on Vietnamese drawings dimensions are in mm but levels are in metres, so +3.600 and 3600 are the same distance. Second, grids and levels must be read together with the general notes, because every project chooses its own ±0.000.
A question that comes up often: how is thickness marked? Thickness has no figure of its own. It is always written out, and the way it is written changes with the element. Walls carry the dimension directly on the plan, where 110 or 220 is the masonry thickness before plaster. Slabs and flat members use h, as in h=100. Plate steel uses δ or t, so δ10 is a 10 mm plate. Build-ups in section are listed layer by layer with a thickness against each, read from the top down. Anything unfamiliar belongs in the general notes, because this is where office conventions differ.
Material symbols
This group appears in section. The first column comes straight from TCVN 7:1993, the materials standard still in force. In practice, though, many document sets use more pictorial hatches from software libraries, and most drawing readers know those better. So where the two commonly diverge, the table puts both side by side: whichever you meet, you recognise it.
| Per TCVN | Commonly seen on drawings | Material | How to read it |
|---|---|---|---|
| — | Metal | Section left empty. Narrow sections may be filled solid | |
| Natural ground | TCVN draws short stroke clusters along the boundary only; real sets often hatch solid with dots | ||
| Stone | TCVN uses broken-line hatching; real sets often scatter triangles in the section | ||
| — | Brickwork | 45° solid hatching, the same on both | |
| Concrete | TCVN alternates solid and chain lines; real sets often use dots and triangles from software libraries | ||
| — | Reinforced concrete | Like concrete, closer spaced | |
| — | Timber | Grain arcs, drawn freehand if need be | |
| — | Glass, transparent materials | Pairs of short oblique strokes, scattered evenly | |
| — | Liquid, water | Broken horizontal lines, staggered | |
| — | Plastics, insulation, sealing materials | Cross hatching |
Two conventions few people know sit in TCVN 7:1993's own footnotes: the natural-ground symbol is drawn along the section boundary only, and the wood-grain arcs may be drawn freehand. When two materials on one drawing carry near-identical symbols, the material name is written beside the figure.
If this table looks different from most charts online, here is why. The charts in circulation mostly reproduce the hatch library of foreign software, where concrete is dots and triangles, or scan one company's own CAD library — some even paste two different hatches under the same word "concrete". The table here is redrawn from the original TCVN 7:1993, still in force, so the difference is deliberate.
Architectural symbols
This group appears on the plan, except where a row says otherwise. Sill and door heights belong to sections and elevations.
| Symbol | Object | How to read it |
|---|---|---|
| Brick wall, cut | Two thick lines with 45° hatching. Thickness as dimensioned, typically 110 or 220 | |
| Concrete wall or column | 45° hatching alternating solid and chain lines, closer spaced than brickwork. Foreign software often draws dots and triangles, but TCVN 7:1993 specifies this hatch | |
| Partition, glazing | Thin parallel lines, non-loadbearing. Material noted in text | |
| Single door | The arc shows the swing. The arc's centre sits at the hinge, not the latch | |
| Double door | Two symmetrical arcs | |
| Sliding door | Leaf drawn offset from the wall face, tied back with a thin dashed line | |
| Folding door | Leaves drawn as a concertina, quite different from a slider | |
| Four-leaf door | Four arcs in a row; lobbies and wide living rooms | |
| Double-swing door | The arc sweeps both ways; sprung doors on shared circulation | |
| Roller shutter | The roller box drawn above, slats below. Nearly every Vietnamese shophouse front has one | |
| Window | An opening with two or three thin lines. Sill height is on the section | |
| Stair | Treads are thin lines. The dot marks the first riser, the arrow from it points up. The oblique line is the break, cut 1 m above floor level | |
| Lift | Rectangle with both diagonals | |
| WC | Simplified block, not to detailed scale | |
| Basin | The centre dot is the waste position | |
| Floor drain | In bathrooms and balconies; the floor falls towards it | |
| Shower | Cross-check the pipe stub-out heights on the plumbing set | |
| Fall of a roof or floor | The arrow points the way the water runs, downhill | |
| Service shaft | Where pipes and cables pass between floors. Cross-check the services plan |
Doors and windows on the plan
This is the most looked-up group, and the one most often misread.
The quick test: a door has an arc, a window does not. Every door carries an arc showing which way the leaf swings. A window is an opening in the wall drawn with two or three thin parallel lines, contained within the wall thickness. An opening with neither an arc nor parallel lines is a void or an unleaved opening, not a window.
The trap in the door swing is the centre of the arc. It sits at the hinge, never at the handle. Misreading it puts the hinge on the wrong side, and the light switch ends up behind the open door — the classic clash between the architectural and the electrical set.
A window on plan says nothing about height. The plan gives its width and position only. Sill level and window height come from the section or the elevation.
Doors and windows also carry lettered codes. Doors are D1, D2, windows S1, S2, or whatever the office convention says. The code carries no dimension: sizes, materials, glass type and quantities live in the door and window schedule, usually the last sheet of the architectural set. Do not scale the plan to get a door size.
Stairs: the dot, the arrow and the break line
A stair on plan is three marks read together. The treads are thin parallel lines. A dot marks the start of the first tread. An arrow runs from that dot and always points up.
The arrow is where mistakes happen. It points up on every floor, so on the second-floor plan it continues to the third, it does not descend to the first. Newcomers read it backwards and conclude the flight is drawn wrong.
The third mark is the break line across the flight, conventionally cut about 1 m above the floor being drawn. Everything above that line is cut away by the plan's own cutting plane, so it is not drawn.
Furniture symbols on the plan
This group has no mandatory standard. Furniture is drawn in plan view, with the conventional cut taken at about 900 mm above the floor, so each symbol reads like the object seen from above. They crowd the furniture layout plan, the sheet a homeowner studies most.
| Symbol | Object | How to read it |
|---|---|---|
| Double bed | Two pillows face the headboard, headboard against the wall | |
| Wardrobe | Hanging rail along the middle, short strokes are hangers | |
| Sofa | The seat divisions count the places | |
| Dining table | Chairs drawn around it match the seat count | |
| Hob | Two or four circles are the cooking zones | |
| Refrigerator | Leave door-swing clearance on the handle side | |
| Washing machine | The circle is the drum. Cross-check the water stub-outs | |
| Bathtub | The dot is the waste. The floor around it needs waterproofing |
None of this needs memorising: the figures mimic the objects' real shapes. Their value lies elsewhere — furniture positions dictate the socket, switch and water stub-out positions on the services sheets that follow.
Furniture closes the architectural set. The three groups that follow — structure, services and infrastructure — each use a symbol system of their own, tabulated below.
Structural symbols
This group mixes two representations: footings, piles, columns, beams and walls appear on the plan; longitudinal bars and stirrups appear in the member section; end hooks belong to the bar bending detail.
| Symbol | Object | How to read it |
|---|---|---|
| Bored pile | Numbered, with a pile coordinate schedule | |
| Square driven pile | Distinguished from bored piles by shape alone | |
| Column on plan | Coded C1, C2. Section written width × depth, e.g. 300×500 | |
| Beam below slab | Dashed, because it sits under the cutting plane. 220×400 is 220 wide, 400 deep | |
| Shear wall, core | Long filled rectangle, thickness noted | |
| Longitudinal bars in section | Each solid dot is one bar cut through. Count the dots | |
| Stirrup | Closed loop around the main bars, hooked at the corner | |
| Bar call-out | Four bars of 16 mm diameter. Ø and ϕ both mean diameter | |
| Stirrup call-out | Diameter 8 at 150 mm centres. a is the spacing | |
| End hooks | 90° or 180° bends, shown on the bar bending detail |
The rest of a structural set is lettered and numbered notation, with no figure but just as necessary.
| Written on the drawing | Meaning |
|---|---|
S1 (h = 120) | Slab type 1, 120 mm thick |
M1, M2 | Footing marks, see the matching footing detail sheet |
LT, GT | Lintel, tie beam |
B20, B25, B30 | Concrete strength class, current notation |
M250, M300 | Old concrete grade notation, still met on renovation sets |
CB240-T, CB300-V, CB400-V | Rebar grades to TCVN 1651. T is plain round, V is ribbed |
AI, AII, AIII | Old rebar notation, roughly CB240, CB300, CB400 |
a = 25 | Concrete cover, mm |
30d, 40d | Anchorage or lap length, in bar diameters |
Steel sections
Pre-engineered steel buildings and the metalwork in ordinary houses add the rolled-section set. Each section carries its shorthand on the drawing.
| Symbol | Section | Written on the drawing |
|---|---|---|
| I and H sections | I200 is 200 mm deep; H sections carry both sides, e.g. H300×300 | |
| U and C channels | U120; a paired member reads 2U120 | |
| Angle | L50×50×5: both legs 50 mm, 5 mm thick | |
| Hollow box | ☐100×50×2: 100×50 section, 2 mm wall | |
| Circular hollow | D60×3: 60 mm outside diameter, 3 mm wall |
Roads, earthworks and infrastructure
Infrastructure sets, internal roads and grading plans carry a symbol set that building drawings rarely show. This group appears on the plan, except the drainage channel, which comes with its own section.
| Symbol | Object | How to read it |
|---|---|---|
| Fill slope | Long strokes alternating with short, rooted at the top edge of the slope | |
| Cut slope | Same convention, rooted at the toe of the cut, pointing the other way | |
| Contour lines | Joining points of equal level. Index contours are drawn heavier and labelled; the closer the lines, the steeper the ground | |
| Alignment centreline | Chain line with chainage in the form KM 0+250, meaning 250 metres from the origin | |
| Survey marker | Setting-out and level markers for grading, with a coordinate schedule | |
| Grading fall | The arrow points the way water runs, with the design gradient | |
| Drainage channel | A trapezoid in section; on plan, two parallel lines following the run |
Estimators and quantity surveyors live inside these two tables. What is quantity take-off? covers the mistakes people make when lifting numbers from structural drawings.
One convention that is easy to forget and directly changes quantities: structural dimensions are bare concrete sizes, smaller than the architectural dimensions at the same spot, which include render and finishes.
Electrical and plumbing symbols
Services symbols vary between firms more than the two groups above. The tables show the common forms. Always check the legend on the first sheet of the services set before relying on them.
Electrical — fixture symbols sit on the plan; the board schematic is a separate drawing, not to scale.
| Symbol | Object | How to read it |
|---|---|---|
| Distribution board | The board's schematic is on its own sheet | |
| Single socket | Mounting height in the general notes, e.g. +300 | |
| Twin socket | The tick count gives the number of gangs | |
| One-way switch | One stroke, one way | |
| Two-way switch | Two strokes; stairs and corridors | |
| Luminaire | Type and wattage in the equipment schedule | |
| Fluorescent batten | Drawn at its true length | |
| Recessed downlight | Cross-check the ceiling plan for position | |
| Fan | Type and flow in the equipment schedule | |
| Cable run | 2×2.5 + E2.5: two 2.5 mm² conductors plus a 2.5 mm² earth | |
| Cable tray | Written width × height, mm | |
| Earth | Three bars, shortening | |
| Air-conditioner indoor unit | Outdoor unit and insulated pipework on their own sheet | |
| Water heater | Has its own switch, typically 20 A | |
| Data and TV outlet | Run in separate conduit from power, against interference | |
| Door bell | Paired with the push button at the door | |
| Circuit breaker | Rated current written beside it, e.g. MCB 32A. Lives on the board schematic | |
| Pendant light | Dining tables and feature lighting. Drop height in the notes | |
| Extract fan | The arrow points the exhaust direction. Bathrooms and kitchens | |
| Camera | Position and field of view; signal cable in its own conduit | |
| Wi-Fi access point | Power and data stubbed out at the mounting point |
One thing to know before looking anything up: electrical symbols diverge between document sets more than any other group. Residential sets from design firms tend to use in-house libraries, where a socket may be drawn like an umbrella and a switch like a musical note whose strokes count the gangs. The table below follows IEC 60617, the symbol set the current TCVN 7922:2008 adopts, which is also what large projects use. On a residential set, check its own legend sheet first.
A solid run is in the ceiling or wall; a dashed run is buried in the slab. Note that the dashed line means something entirely different here than on a structural plan, so do not carry the habit across disciplines.
Plumbing — pipe runs and fixtures sit on the plan; drains and manholes carry their own sections.
| Symbol | Object | How to read it |
|---|---|---|
| Supply pipe | CL cold, CN hot. D25 is the 25 mm nominal diameter | |
| Drainage pipe | TX soil, TR waste, TM rainwater | |
| Vent pipe | Marked TH, run up to the roof | |
| Gate valve | Two opposed triangles, the commonest valve | |
| Check valve | The filled triangle points the permitted flow direction | |
| Manhole | Invert and cover levels noted | |
| Water meter | The metering point, usually at the supply boundary | |
| Pipe gradient | i = 2% means 20 mm of fall per metre of run | |
| Pump | The filled triangle points the pumping direction | |
| Roof tank | The liquid symbol drawn inside; capacity noted | |
| Union | A demountable joint, placed where equipment must come out for repair | |
| Reducer | Where the pipe changes size, say D32 down to D25 | |
| Tee | A branch taken square off the main run |
One principle covers both systems. The plan gives position, the schematic gives connection, the equipment schedule gives type and rating. Read all three or you have a third of the story.
When a document set moves into a BIM model, these symbols become real objects with measurable properties. What is BIM? explains that step.
Common abbreviations on drawings
Beyond graphic symbols, drawings carry a great many abbreviations. No standard collects them all, since most are trade convention passed down. The table below holds the ones met most often on residential sets. They are Vietnamese abbreviations, so this is chiefly useful when reading a Vietnamese document set.
| Abbreviation | Meaning |
|---|---|
MB, MĐ, MC | Plan, elevation, section |
TL 1:50 | Drawing scale |
CT | Detail. CT-03 is detail number 3 |
KT-01, KC-01, Đ-01, N-01 | Sheet codes: architecture, structure, electrical, plumbing |
BTCT | Reinforced concrete |
VXM M75 | Cement mortar, grade 75 |
LT, GT | Lintel, tie beam |
WC | Toilet |
LG | Loggia |
SHC | Family room |
TT | Void. On plan, an opening looking down to the floor below |
CL, CN, TX, TR, TM, TH | The pipe runs, see the services table above |
For any abbreviation not listed, check the set's general notes. A carefully produced set always defines its own abbreviations there.
Putting them together: reading a fragment of plan
Knowing symbols one at a time is not enough. A real drawing stacks many of them into one figure.
Reading a fragment like this takes four steps. Find the grid first, to locate yourself in the building. Then separate structure from partitions by the hatching. Then read the openings — doors and windows, with their swings. Last, find the section marks to know which sheet to turn to for heights.
Download the printable chart
The tables above are collected into a seven-page PDF, figures included, sized for A4.
**Download the construction drawing symbols chart (PDF)**
A chart helps you recognise symbols. Reading a full document set, and catching where the disciplines disagree, takes practice on real drawings with someone marking your work. The Institute's six-session Construction Drawing Reading course does exactly that for people from outside the industry. Those who want to produce drawings to the conventions take the AutoCAD course.
Frequently asked questions
Are drawing symbols the same from one firm to the next?
Architecture and structure mostly are, because they follow TCVN. Services vary more, partly because the old standards were withdrawn and the current IEC-based set does not cover every local habit. Always read the set's own general notes and legend before using any generic chart.
What does Ø8a150 mean?
Stirrups or slab bars of 8 mm diameter at 150 mm centres. The a is the spacing. Near beam ends you often see a100: closer stirrups where the shear is higher.
In 220×400, which comes first — width or depth?
Width first: 220 wide, 400 deep including the slab. Some sets write it the other way, so check against the beam section whenever a number looks odd.
What does a dashed line mean on a plan?
It depends on the discipline. On a structural plan it is usually a beam below the slab or an element on the floor below. On an electrical plan it is a run buried in the slab. Read it with that sheet's own notes.
Are the figures standard-compliant, and may I reuse them?
The line-work, materials and architecture groups were checked directly against TCVN 5570:2012, TCVN 7:1993 and the building-element symbol set. The structure, electrical and plumbing groups follow common Vietnamese practice; the standard in force for each group is named at the top of the article, and the set's own legend always comes first. Every figure was drawn by the Institute, copied from no book or project set, so print them, project them in class or reuse them in internal documents freely.