Before any foundation is poured comes excavation, and sometimes soil replacement, levelling and compaction. This work is buried and invisible after pouring, but it decides the building's safety for decades; many cracks and settlement that appear years later come from excavation that did not reach the right layer, or replacement fill that was not compacted properly. This guide explains the role of the soil report, when replacement is required and how it is done, the related permits, safety precautions, and the acceptance points that must not be skipped.
The Soil Report Is the Starting Point
A soil investigation report is a requirement of the building permit on Balady. It sets the foundation depth, the need for replacement, the foundation type, the soil's bearing capacity and the groundwater level if any. See our structural design service, and read: The soil investigation report.
What Is Soil Replacement, and When Is It Required?
Soil replacement means removing an unsuitable soil layer and replacing it with material compacted in layers. It is required when the soil report recommends it, as with weak soil, soil containing waste, or old fill.
| Soil condition | Usual treatment |
|---|---|
| Old fill or waste | Full removal down to natural soil, then replacement |
| Weak surface soil | Replacement to a thickness set by the report |
| Good soil at shallow depth | Founding directly on it with levelling |
| Expansive or collapsible soil | Special treatments set by the report and designer |
How Is Replacement Done Properly?
- Excavate to the level the report specifies.
- The supervisor accepts the excavation bottom before backfilling.
- Backfill with material meeting the specifications, in layers of set thickness.
- Compact each layer with suitable equipment and moisture.
- Test compaction (field density) before the next layer where needed.
Related Permits
- Preparing and levelling the site before construction: The site preparation permit.
- Excavating for foundations: part of carrying out the building permit. Read: The building permit.
Safety During Excavation
- Follow the construction safety precautions (Chapter 33 of SBC 201).
- Secure excavation sides with safe slopes or supports, and prevent collapse.
- Protect neighbours' foundations in deep excavation. Read: Shoring.
- Fence the site and prevent passers-by from falling in.
- Keep equipment and excavated soil away from the edge.
The Role of Supervision
Supervision verifies that excavation and compaction match the report's recommendations before pouring. This is one of the stages that must not be passed without documented acceptance. See our supervision service, and read: Stages where concrete must not be poured without the supervisor.
Common Mistakes
- Founding on old fill without removing it.
- Placing thick layers at once without enough compaction.
- Using unsuitable fill material from the site.
- Starting to pour without the excavation bottom being accepted.
Frequently Asked Questions
Can soil replacement be skipped to save cost?
If the soil report recommends it, skipping it exposes the building to settlement and cracking later.
Who sets the excavation depth?
The soil report and the structural design.
Is a compaction test required?
The report and specifications decide; it is the reliable way to verify replacement quality.
What if water appears during excavation?
Stop and consult the designer; dewatering and special foundation treatment may be needed.
Does levelling need a permit?
Levelling the site before construction is done under the site preparation permit.
How Abak Engineering Consultancy Helps
Abak is an accredited engineering office in Riyadh that designs foundations based on the soil report and supervises excavation and soil replacement, accepting it before pouring. Learn about our structural design service, or Learn more about our Sidewalk Occupancy Permit service. contact us.
Regulatory information is based on the Balady platform and the Ministry of Municipalities and Housing, and procedures may be updated by the competent authority. Last reviewed: October 2026.
