Suitability depends on the slab system, ground conditions, cause of movement, services, loads, access and project-specific engineering assessment.
Void filling
The primary objective is to occupy a confirmed or suspected space and improve contact or support beneath the element. The scope may prioritise stabilising response while limiting deliberate upward movement. Filling a space does not by itself demonstrate that the process which created it has stopped.
Slab lifting
The objective includes controlled upward movement toward an agreed level or relationship with adjacent elements. This requires closer monitoring of levels, joints, connections, finishes, services, equipment and the response across the slab—not only at an injection point.
Questions that decide the pathway
- Is the slab structurally suitable for the proposed response?
- Is the observed level difference historic, active or load-dependent?
- What caused the support change, and is that cause still present?
- Which connected elements or services could restrain or be affected by movement?
- What tolerance and reference define an acceptable result?
- Where must movement be limited or stopped?
Do not define scope from volume alone
Material quantity can be influenced by inaccessible pathways, variable void geometry, fractures, drainage features and ground response. A reliable scope combines zoning, staged delivery, monitoring, hold points and change control.
Verification should match the objective
For support restoration, checks may focus on response, coverage and documented installation. For lifting, controlled survey measurements and movement limits are central. Neither objective should be claimed beyond the actual measurements and agreed acceptance criteria.
When neither is enough
If the main mechanism involves structural deficiency, active water movement, erosion, unsuitable ground beyond the treatment concept or another unresolved driver, additional investigation or a different intervention may be required.