Collapsed Drain Under Extension

Extensions built over existing drain runs are a common source of collapsed drain problems. The weight of the new structure, foundation work, and changes to ground conditions can damage pipes that were never designed to bear the load.

What to Look For

• Drainage problems that started after an extension was built
• Damp or wet patches on the extension floor
• Cracks in the extension walls or floor slab
• Sewage smells inside the extension
• Slow drainage from extension kitchen or bathroom
• Original drains were not diverted during construction

How We Diagnose the Problem

We use CCTV surveys from external access points to inspect the drain running beneath the extension. Drain tracing maps the exact route under the building, and we assess whether the collapse was caused by construction loading, vibration, or direct damage.

How We Fix It

Where possible, we use no-dig relining from external access points. When excavation is necessary, we work carefully through the internal floor, replacing the damaged section and reinstating the surface. We coordinate with structural engineers if needed.