Why Site Supervision Matters in Construction

Drawings and contracts describe what a building should be. Supervision is what makes sure it is actually built that way. On many projects that go wrong, the design was sound and the builder was willing, but no one was checking the work as it happened. Defects in foundations, concrete or reinforcement are hidden once covered, and they can cost many times more to correct, or can threaten the safety of the building itself. This article explains what good site supervision involves and why it is worth paying for.

What does a site supervisor do?

A supervisor represents the owner’s interests, or the contractor’s management, on site. Their job is to compare the work with the drawings and specification, check materials, organise and direct workers, keep records and report problems. A good supervisor is on site every day, knows the drawings well and has the authority to stop work that is wrong.

Stages that must be checked before they are covered

• Setting out. The building’s position, levels and dimensions must be correct before excavation begins. A mistake here carries through to every other stage.
• Excavations. Check depth and width of trenches, the condition of the ground at the bottom, and that loose or soft material has been dealt with.
• Reinforcement. Before concrete is poured, check the size, number, spacing, cover and lapping of bars against the engineer’s details. Reinforcement should be clean and held firmly in position.
• Formwork. It must be strong, tight and correctly aligned, so that it does not move or leak when concrete is placed.
• Concrete. Check the mix proportions, the water added, the way the concrete is placed and compacted, and that it is cured afterwards by keeping it damp.
• Blockwork. Check the quality of the blocks, the mortar, the level and line of the courses and the reinforcement at lintels and columns.
• Roof. Check timber or steel members, fixings, and the overlaps and sealing of roofing sheets.
• Services. Inspect pipework and conduits before they are buried or plastered over, and test them.

Common defects that supervision prevents

Experience shows the same problems appearing repeatedly on poorly supervised sites. Concrete is mixed with too much water or too little cement. Reinforcement is moved, left too close to the surface or replaced with smaller bars. Concrete is not cured, especially in hot weather, and cracks. Blocks of poor quality are used. Mortar is thin and joints are not filled. Foundations are not taken to a suitable depth. Roof drainage is poorly planned, leading to damp walls. Each of these can be avoided if someone is looking at the work as it is carried out.

Materials control

Supervision includes checking what comes onto the site. Compare deliveries with the order, check that cement is fresh and has been stored dry, that steel is the specified size and that sand is clean. Reject materials that do not meet the specification, and record what was rejected and why. Controlling materials also reduces waste and theft, which is a real cost on many sites. Read our materials cost control tips for more.

Records and communication

A daily site diary, with notes on who was on site, what was done, what was delivered, the weather and any problems, becomes valuable evidence if there is a disagreement later. Photographs of hidden work before it is covered are equally useful. A supervisor also passes instructions from the architect or engineer to the workers and reports back to the owner, keeping everyone informed.

Safety

Supervision also means protecting people. Check that scaffolding and excavations are safe, that workers have suitable footwear, helmets and gloves where needed, that electrical equipment is properly connected and that visitors are kept away from hazards. A site with good order tends also to be a site with good quality.

If you are an owner supervising yourself

If you cannot afford a full-time supervisor, at least visit the site often and unannounced, carry a copy of the drawings, and have a qualified professional inspect the critical stages above. Ask questions, and do not be afraid to stop the work and have something checked. It is better to cause a short delay than to build in a mistake. Never allow concrete to be poured until the reinforcement has been inspected.

Supervision is an investment

The cost of competent supervision is small compared with the cost of the building and very small compared with the cost of putting right a major defect. At Fani Nigeria Limited, supervision is part of our project management and construction services. You may also want to read about project management for building on time and within budget. To discuss supervision for your project, please contact us.