Construction project organisation
A construction job needs many people to work as one team. The usual roles are:
- Owner (client): pays for the work and sets the aim.
- Designer / engineer: makes the drawings and specification and answers technical questions.
- Contractor: the firm that builds. Inside it: the project manager (runs the whole job, money, time), the site engineer (checks the work against drawings), the foreman (leads the crews daily), skilled workers (masons, carpenters, bar benders) and helpers.
- Supervisor / inspector: checks quality for the owner.
An organisation chart shows who reports to whom. Clear lines stop confusion: a worker takes orders from one foreman. Good communication means a short daily meeting, a site diary, and written instructions for changes.
Process control (time)
Process control (progress control) keeps the job on schedule. Each day or week we do four things:
- Measure what was really done (metres of wall, m³ of concrete).
- Compare with the plan on the bar chart: planned bar against actual bar.
- Find the cause if late: rain, material not delivered, too few workers, mistakes needing rework.
- Correct: add workers or shifts, bring materials sooner, change the order of tasks that do not depend on each other, or update the plan.
A delay on a task that other tasks wait for (the critical path) delays the whole job. In the 3D, walls took 2 days more and the roof had to wait, so the whole job was 2 days late.
Work and workers: days = total worker-days ÷ number of workers. 48 worker-days with 6 workers takes 8 days. Doubling the crew roughly halves the time, but a very crowded site loses speed.
Quality control
Quality control checks that materials and work meet the specification. The idea is: inspect and test before it is too late, and keep records.
- Check materials when they arrive: cement bags unbroken and dry, sand clean, bars without heavy rust, bricks not cracked.
- Check the work as it goes: size with a tape, level with a spirit level, straightness with a string, bar spacing and cover before pouring.
- Test concrete: the slump test checks how workable the fresh mix is. Concrete cubes (usually 150 mm) are cast, cured in water, and crushed at 7 and 28 days. Strength = load ÷ area. Example: 562.5 kN on 150 mm × 150 mm = 22 500 mm² gives 25 N/mm².
Most common cause of weak concrete: too much water. Extra water makes the mix easy to pour but leaves tiny holes when it dries, so the strength falls. Other causes: poor mixing, poor curing, dirty sand.
If a test fails, the part must be checked, fixed or rebuilt. Quality is cheaper when done right the first time.
Safety management
Safety management prevents injury and harm. Steps: find the hazards (things that can hurt), judge the risk (how likely and how bad), then control it. Best controls first:
- Remove the hazard if possible (cover the pit, fill it).
- Guard it: railings, barriers, signs, supports in trenches, covers on machine parts.
- Train and organise: short safety talks, safe ways of lifting, no one works alone, clear rules.
- Personal protective equipment (PPE): helmet, boots, gloves, glasses, mask, ear plugs, harness at height. PPE is the last line, not the first.
Common farm-site hazards: open trenches and pits, falling from height, moving vehicles and tractors, electricity and cables, heavy lifting, dust and cement burns, and heat. Trenches deeper than about 1.5 m need supports or a sloped side. Keep a first-aid box, know the emergency number and where to go, and write down every accident and near miss so that it does not happen again.
Try it: classroom site audit
Walk round your school or farm and spot five hazards (an open drain, loose wire, slippery step, uncovered pit, a heavy object on a shelf). For each, write: the hazard, who may be hurt, and the best control (remove, guard, train, PPE). Then test quality: build two small clay cubes, one with a lot of water and one with less. Dry them and press with your fingers. Which is stronger?
Key formulas and definitions
- Days = total worker-days ÷ workers
- Delay = actual days − planned days
- Progress % = work done ÷ total work × 100
- Cube strength = load ÷ area (N/mm² = N ÷ mm²)
- Risk = chance of harm × how bad the harm is
- Control order: remove → guard → train → PPE
Worked examples
1. A job needs 48 worker-days. With 6 workers, how many days?
48 ÷ 6 = 8 days.
2. The same job must finish in 4 days. How many workers are needed?
48 ÷ 4 = 12 workers.
3. Planned time is 11 days and actual time is 13 days. Find the delay and the delay as a percent of the plan.
Delay = 13 − 11 = 2 days. 2 ÷ 11 × 100 ≈ 18%.
4. A 150 mm concrete cube fails at a load of 562.5 kN. Find its strength.
Area = 150 × 150 = 22 500 mm². Load = 562 500 N. Strength = 562 500 ÷ 22 500 = 25 N/mm².
5. Another cube fails at 450 kN. The required strength is 25 N/mm². Does it pass?
450 000 ÷ 22 500 = 20 N/mm². 20 is less than 25, so it fails.
6. A channel job needs 120 m of lining. After 6 days 30 m is done. What is the progress? How long at this rate for the whole job?
Progress = 30 ÷ 120 × 100 = 25%. Rate = 30 ÷ 6 = 5 m/day. Total = 120 ÷ 5 = 24 days.
7. A safety audit found 12 hazards and 9 were fixed. What percent are fixed? How many remain?
9 ÷ 12 × 100 = 75%. 12 − 9 = 3 remain.
Common mistakes
- Thinking quality can be judged by looking. Concrete strength needs a test.
- Adding water to make concrete easier to pour. It makes the concrete weaker.
- Using a helmet as the only safety measure and leaving the open trench unguarded.
- Checking progress only at the end, when it is too late to catch up.