Studies and drawings first
Before anyone lays a brick, people plan. An architecture assistant draws the building from the architect's ideas (plans, sections and now digital 3D models). A building economist counts materials and prices (a quantity survey and estimate). A surveyor-topographer measures the land: heights, slopes and exact corner points. All trades work from these drawings.
Public works
Public works are things built for everybody: roads, bridges, water pipes, drains, cables. Their crews dig trenches, lay pipes, compact soil and put down road layers. They work with machines (excavators, rollers) and with surveying tools so the slope of a drain is right and water flows by gravity.
Structural work and masonry
The building technician and mason make the structure: foundation, slab, walls, columns and beams in concrete, brick or stone. Concrete is cement + sand + gravel + water. Blocks are laid in rows with mortar; each row is shifted by half a block (bond) so the wall is stronger. A plumb line checks that a wall is vertical and a spirit level checks that it is flat.
Heritage masonry repairs old stone or lime-mortar buildings with matching materials, so that the old walls can still breathe and look right.
Carpentry and roofing
The carpenter builds frames in wood: roof rafters, beams, floors and stairs. A triangle is a very stiff shape, so roof frames use triangles (trusses). The roofer covers the frame with tiles, slates, metal sheets or thatch. The slope and overlaps send rain away. In heritage work they repair old frames and roofs using traditional joints and matching materials.
Joinery: wood, aluminium and glass
The joiner makes and fits windows, doors, frames and shutters. Wood joinery uses cut joints (mortise and tenon). Aluminium and glass joinery uses metal frames that are light, do not rot and can hold large panes; double glass keeps heat in or out. The fitting must be square, plumb and sealed against wind and rain.
Fit-out, finishing and metalwork
Fit-out trades make the inside ready: partitions, ceilings, floors (tiles, wood), plaster, paint, kitchens and cupboards. Interior fitting design and build plans a space (shops, hotels) and makes the furniture and panels, often in a workshop from wood and wood-based boards (plywood, MDF) cut by machines. Metalwork makes railings, gates, stairs and steel frames by cutting, bending and welding.
Safety, tools and teamwork
Every trade wears protection (helmet, boots, gloves, glasses) and follows rules for ladders and scaffolds. Trades depend on each other: if the mason's wall is not plumb, the joiner's window will not fit. Good teams check each other's work and talk before the next trade starts.
Try it
In the 3D: go to the last step. Slide the stage from 0 to 5 and say aloud which trade is working and which tool it uses.
At home: walk round a building and list 5 trades you can see the work of (a plastered wall, tiled roof, a window frame...). Which trade came first?
Key formulas and definitions
- Floor area = length × width
- Blocks needed = wall area ÷ area of one block (add about 5% extra)
- Rafter length = √(half-span² + rise²)
- Scale 1 : 50 means 1 cm on paper = 50 cm in real life
- Concrete volume = length × width × thickness
Worked examples
1. Which trade works first on a new site: mason, roofer or surveyor?
The surveyor. The corners and levels must be marked before any wall can be built.
2. A wall is 6 m long and 2.4 m high. A block face is 0.4 m × 0.2 m. How many blocks (no extra)?
Wall area = 6 × 2.4 = 14.4 m². Block area = 0.4 × 0.2 = 0.08 m². Blocks = 14.4 ÷ 0.08 = 180.
3. A roof spans 6 m and rises 2 m in the middle. How long is each rafter (one side)?
Half-span = 3 m, rise = 2 m. Rafter = √(3² + 2²) = √13 ≈ 3.6 m.
4. A room is 4 m × 3 m. Tiles are 0.5 m × 0.5 m. How many tiles?
Room area = 12 m². Tile area = 0.25 m². Tiles = 12 ÷ 0.25 = 48.
5. A drawing is at scale 1 : 50. A wall is 6 m long. How long is it on the drawing?
6 m = 600 cm. 600 ÷ 50 = 12 cm.
6. A slab is 5 m × 4 m and 0.15 m thick. What volume of concrete?
5 × 4 × 0.15 = 3 m³.
Common mistakes
- Starting the walls before the surveyor marks the corners and levels. Mistakes are costly to fix later.
- Laying blocks with joints one above the other. Bond (shifted rows) makes the wall strong.
- Forgetting extra material for cuts and waste (about 5% to 10%).
- Thinking the trades work alone. Each trade checks that the previous one left a square, plumb, level surface.