Basement Impact Assessments for Planning Applications
Planning-ready Basement Impact Assessments covering flood risk, groundwater, surface water and land stability — prepared to London borough and local planning standards.
Basement Impact Assessments (BIA)
Many local planning authorities — particularly London boroughs such as Camden, Westminster, Kensington & Chelsea and Hammersmith & Fulham — require a Basement Impact Assessment for new or extended basements. A BIA demonstrates that the excavation will not increase flood risk, disrupt groundwater flow, cause land instability or harm neighbouring properties.
We prepare the flood risk, groundwater and drainage elements of the BIA using the standard screening, scoping and assessment approach adopted by most borough guidance (based on the widely used Arup / GSD methodology). Where a structural or geotechnical input is also required, we co-ordinate with your engineer so the assessment reads as one coherent document.
What a BIA covers
- Screening against borough BIA criteria
- Groundwater flow & levels
- Surface water flood risk
- River & sewer flooding context
- Subterranean (basement) flood resilience
- SuDS & drainage strategy
- Impact on neighbouring properties
- Scoping for structural/geotechnical input
When you need a Basement Impact Assessment
Most new-build and retrofit basements in BIA boroughs require one at planning stage.
New basement or extension
Excavating a new basement, lightwell or lowering an existing cellar typically triggers a BIA where the borough has adopted basement policy.
London boroughs
Camden, Westminster, RBKC, Hammersmith & Fulham, Islington and others require a BIA screening and, where flagged, a full assessment as validation.
Near watercourses or high groundwater
Sites over sensitive aquifers, near rivers, or with a history of groundwater or surface water flooding need careful groundwater and flood assessment.
Flood-resilient design
Basements are highly vulnerable to flooding — the BIA sets out resilience, pumping, and safe-access measures to satisfy the EA and LLFA.
Frequently Asked Questions
Related services: Flood Risk Assessments • FRA London • SuDS Drainage Strategies
Trusted by Developers, Architects & Planning Consultants
★★★★★ 5.0 from 6 Google reviews
“Antony was great to work with when we needed a Flood Risk Assessment and Emergency Flood Plan. As an architect I would definitely use FRE Consultants again… his report went a good way in helping us get planning permission on a tricky site. Highly recommended.”
“Antony carried out my Flood Risk Assessment and has done a great job. My architect commented that the report was professionally drafted and very easy to follow. I highly recommend Antony's services.”
“Antony carried out a SuDS report for one of our projects and provided an excellent service throughout — quick to respond, clear communication, and a thorough, detailed report within the agreed timescale. We will certainly be using his services on all future projects!”
“Extremely helpful, prompt and friendly service carrying out a Flood Risk Assessment for a home project that required planning permission in a flood risk area… the price was reasonable and given up-front, and the final report was highly professional and exactly as required.”
“I had an extension completed on my house and needed a Flood Risk Assessment for planning. The service received was great and at a competitive cost. We were granted planning after first submission.”
“Nice and quick service. Recommend A++”
Planning a basement? Get your BIA sorted.
Send us your address and proposals for a fixed-fee Basement Impact Assessment quote within 24 hours.
Get a Free QuoteOr contact us directly: 07826 705389 •