Cables are easy to replace if the containment is right and impossible if it is not. This is the first fix sequence, including the earthing work that must be done early.
Electrical first fix installs the routes, boxes and protective conductors that the finished installation will live in. Containment is the part that lasts: conduits, trunking, trays and draw boxes decide whether a cable can ever be replaced or added without breaking a wall. Earthing is the part that protects people, and much of it has to be installed before the concrete is poured, which means it cannot be left to the electrician who arrives at second fix.
Before stage one
Nothing should be fixed before the electrical layout has been coordinated with the plumbing, the air conditioning and the structure. The usual collisions are a conduit crossing a beam where the structural engineer will not allow a hole, a socket on a wall that will be covered by a wardrobe, and a ceiling route occupied by a duct that was drawn later.
- Approved electrical layouts with socket, switch and light positions coordinated against furniture and joinery drawings.
- A coordinated services drawing showing routes shared with mechanical and plumbing services.
- An approved earthing design showing the electrode arrangement and the bonding points.
- Approved conduit, trunking and tray materials with fixings suited to the location.
- An inspection and test plan naming the hold points before concrete pours and before plaster.
Stage 1: Install the earthing electrode system and the foundation connections
The earthing system starts in the ground, with electrodes and with connections made to the reinforcement or to a dedicated conductor in the foundations where the design requires it. This is done before concrete is cast, so the window is short and it closes permanently. Connections must be accessible for testing afterwards, through a test point or inspection pit.
- Deliverable: An earthing installation record with electrode positions, connection details and photographs before casting.
- Owner: Electrical subcontractor, witnessed by the supervising engineer.
- Approval gate: Earthing inspection completed before the relevant concrete pour.
Stage 2: Cast in conduits and boxes within the structure
Conduits that run inside slabs and walls are fixed to the reinforcement before the pour, positioned so they do not reduce cover or cluster in a way that weakens the section. Boxes are set flush to the eventual finish level, which means knowing the plaster and screed thickness before the pour, and they are plugged so concrete cannot fill them.
- Deliverable: A pre pour electrical inspection record with photographs of conduit and box positions.
- Owner: Electrical subcontractor with the site engineer.
- Approval gate: Pre pour inspection signed by both the structural and electrical supervisors.
Stage 3: Install surface containment in voids and risers
Trays, ladders and trunking in ceiling voids, risers and plant rooms carry the cables that will be installed later and the ones nobody has thought of yet. Size them with spare capacity, support them at the correct spacing, and keep separation from other services, particularly from hot pipework and from data cabling that is sensitive to interference.
- Deliverable: Installed containment with support spacing, segregation and spare capacity recorded.
- Owner: Electrical subcontractor.
- Approval gate: Containment inspected before ceilings are closed.
Stage 4: Chase walls and install conduit to the specified limits
Chases in blockwork follow the depth and direction limits that keep the wall sound, which usually means vertical drops rather than long horizontal runs and no chases cut back to back. Conduits are continuous into boxes, with bends that allow a cable to be drawn in and, critically, drawn out again in ten years time.
- Deliverable: Chased and conduited walls inspected before filling, with a photographic record.
- Owner: Electrical subcontractor with the blockwork supervisor.
- Approval gate: Chases inspected before they are filled and plastered.
Stage 5: Install bonding to metalwork and services
Protective bonding connects metallic services and structural metalwork to the earthing system so that no conductive part can sit at a different potential. Typical points include incoming metallic pipework, water tanks, structural steel and metal frames. Bonding to a pipe that is later replaced with a plastic section needs the connection to be reviewed, not abandoned.
- Deliverable: A bonding schedule listing each bonded item, the conductor size and the connection point.
- Owner: Electrical subcontractor.
- Approval gate: Bonding verified before the installation is energised.
Stage 6: Pull cables and label everything as you go
Cables are drawn in once the building is weathertight and the containment is complete, with draw strings left in spare conduits. Every cable is labelled at both ends as it is installed, because labelling after the fact is guesswork. Leave the conduits genuinely spare rather than filling them, since that spare capacity is the point.
- Deliverable: A cable schedule with labelling at both ends and spare capacity recorded per route.
- Owner: Electrical subcontractor.
- Approval gate: Labelling checked before boards are terminated.
Stage 7: Test the earthing and continuity before closing anything
Earth electrode resistance, continuity of protective conductors and bonding connections are tested and recorded while they are still reachable. These results are the evidence that the protective system works, and they are required for the completion documentation. Recording them early also catches a poor connection while it is cheap to correct.
- Deliverable: Test results for earth resistance, continuity and bonding, with instrument details and dates.
- Owner: Electrical subcontractor, witnessed by supervision.
- Approval gate: Results accepted before the installation progresses to final testing.
Handovers between stages
The handover from first fix to the trades that follow is the point where containment gets damaged, boxes get buried under plaster and draw strings disappear. Agree with the plasterer how boxes will be kept clear and at the right depth, and have the electrician return to check after plastering rather than at second fix. The second handover is to whoever installs ceilings, because a closed ceiling over incomplete containment is reopened at somebody expense.
How you know it is finished
First fix is finished when every route is complete and testable, the earthing and bonding are installed and measured, the boxes sit at the correct depth for the finished surface, spare capacity genuinely exists, and the whole lot is photographed and recorded. The test of a good job is simple and arrives years later: can a new circuit be added without opening a wall?
Domira builds and supervises projects across Saudi Arabia, and this is the level of detail its site teams work at. Send the drawings or the site, and Domira will tell you what the specification has to say before anyone prices it.
Frequently Asked Questions
Why is earthing installed before the concrete is poured?
Because part of the system is connected to the foundations and the reinforcement, and that connection can only be made while the steel is exposed. Once the concrete is cast, the opportunity is gone and alternatives are more intrusive and often less effective. The connections must also be left accessible for testing, which means planning test points before the pour.
What is the purpose of conduit if the cable could be buried directly?
Conduit protects the cable mechanically, allows it to be replaced or added to without breaking the structure, and keeps heat and moisture away from it. A directly buried cable in a chase is effectively permanent, and when it fails or when a new circuit is needed, the wall is opened. Conduit with real spare capacity is one of the cheapest forms of future proofing.
How deep can electrical chases be cut into a block wall?
Depth and direction limits exist to keep the wall sound and are set by the design and the block type, with horizontal chases generally more damaging than vertical ones and back to back chases particularly dangerous. Take the limits from your specification and confirm them with the structural engineer where walls are loadbearing, since requirements vary between projects and codes are periodically revised.
What is the difference between earthing and bonding?
Earthing provides a path for fault current to flow so that protective devices operate and disconnect the supply. Bonding connects metallic parts together so that they stay at a similar potential, which prevents a dangerous voltage difference between, for example, a tap and an appliance. A safe installation needs both, and both are tested and recorded.
Have a Property Question?
Domira can help you navigate property, financing and investment decisions in Saudi Arabia. Speak with our team for an initial consultation.
