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DriffieldLand and engineering surveyors based in Lancashire
Impermeable Area Surveys
Impermeable Area Surveys Lancashire and North West
Accurate Impermeable Area Measurement for Drainage Design, SuDS Compliance and Planning
Accurate Impermeable Area Measurement for Drainage Design, SuDS Compliance and Planning
Site Surveying Services delivers accurate, georeferenced impermeable area surveys across Lancashire, the North West and the wider UK. Based in Clitheroe, Lancashire, our directly employed survey team identifies and measures every impermeable and permeable surface across your site – delivering precise, documented data that drainage engineers, planning consultants, developers and local authorities rely on. Whether you are preparing a drainage strategy for a planning application in Preston, demonstrating SuDS compliance for a development in Manchester, or managing an existing site across Cumbria – our surveyors deliver clear, compliant and reproducible impermeable area data tailored to your project stage and requirements. All surveys are OS-controlled, tied to National Grid and delivered in the format your drainage designer and planning consultant need, from day one.
What is an impermeable area survey?
An impermeable area survey is a detailed measurement and classification of all hard and soft surfaces across a site. It records impermeable surfaces – roofs, roads, car parks, footways, hardstanding and any other sealed surface that does not allow rainfall to infiltrate – and permeable surfaces including soft landscaping, grassed areas, gravel, permeable paving and natural ground.
Accurate impermeable area data reduces drainage design risk, supports SuDS compliance, prevents under or over-specified drainage infrastructure, and ensures compliance with planning and regulatory standards. An impermeable area survey from Site Surveying Services forms the reliable foundation for:
Planning applications
OS-controlled, georeferenced impermeable area data that supports drainage strategies within planning submissions and is defensible if challenged by the local planning authority or Lead Local Flood Authority.
Drainage and SuDS design
Accurate measured surface areas that give your drainage engineer verified impermeable area data to calculate runoff volumes, size attenuation storage and design SuDS infrastructure from - not estimated figures.
Discharge of planning conditions
Survey-grade impermeable area measurement and area schedules that satisfy LPA and LLFA requirements for drainage condition discharge on residential, commercial and infrastructure developments.
Existing site management and retro-fit SuDS
Measured impermeable area of existing developed sites - industrial, commercial, highway - for drainage maintenance planning, flood risk management and SuDS retro-fit feasibility.
across Lancashire and the North West
Our Impermeable Area Survey Services
Our Impermeable Area Survey Services
Every drainage design and SuDS strategy begins with the same fundamental question – how much of the site is impermeable? Get it right and the drainage scheme is correctly specified from the outset. Get it wrong – estimate rather than measure, miss a roof slope, overlook a section of hardstanding – and the drainage design is built on a false premise. The SuDS scheme is under-specified. The planning condition is discharged on data that does not reflect reality.
Site Surveying delivers impermeable area surveys across Lancashire, the North West and nationally – for drainage engineers, planning consultants, developers, local authorities and their appointed contractors who need measured surface area data they can build drainage designs on. Our team is directly employed and the surveyor who quotes your project is the surveyor on site. All surface types are classified and measured to the standard drainage engineers and planning authorities require.
Every survey is OS-controlled, tied to National Grid, delivered in AutoCAD DWG and PDF plan format with a full area schedule and methodology statement, produced by the same team from GPS capture through to CAD output, without a subcontractor in the chain. The people who commission impermeable area surveys from us are the people whose drainage design and planning submission depends on the data being right. We understand what that means – and we have done since 1997.
Roofs
All roof planes, roof lights, roof terraces and plant room roofs - measured in plan from survey data.
Roads and Carriageway
All roads, access routes, delivery yards and vehicle circulation areas within the survey boundary.
Car Parks and Parking Areas
All hardstanding used for vehicle parking, including surface material classification where SuDS infiltration assessment is required.
Footways and Pedestrian Areas
All paved footways, steps, ramps and pedestrian surfaces within the survey boundary.
Hardstanding and Yards
Storage yards, service areas, loading bays and all other operational hardstanding.
Permeable Surfaces
Soft landscaping, grassed areas, planted beds, gravel surfaces and natural ground - classified and measured as the balance of the total site area.
Permeable Paving
Where permeable paving systems are present, classified and noted separately for drainage design purposes.
Surface Drainage Features
Gully positions, channel drain positions, soakaway locations and drainage outfall positions recorded and plotted for the drainage designer.
Why Do You Need
An Impermeable Area Survey?
Why Do You Need An Impermeable Area Survey?
An impermeable area survey gives you a comprehensive, measured record of your site’s surface classifications and areas.
Planning applications and drainage strategies
SuDS compliance and attenuation sizing
Discharge of planning conditions
Existing site drainage management
Retro-fit SuDS feasibility
Change of use and intensification assessments
Who Commissions Impermeable Area Surveys From Us
Impermeable area survey sits at the start of every drainage design and SuDS strategy. The clients who commission them include:
Drainage Engineers and SuDS Designers
Commissioning impermeable area surveys at the start of the drainage design process to establish the measured runoff catchment data the calculations depend on. We deliver data in the format your drainage design software requires.
Planning Consultants
Commissioning impermeable area surveys to support planning applications where the LPA’s validation checklist or the LLFA’s SuDS requirements specify measured impermeable area data.
Property Developers and Housebuilders
From initial acquisition surveys through to pre-construction drainage data packages. We have delivered across housing, commercial, mixed-use and brownfield sites throughout Lancashire and the North West.
Local Authorities and LLFAs
Commissioning surveys of existing public highways, car parks and public realm to support drainage maintenance, flood risk management and SuDS retro-fit design programmes across the North West.
Industrial and Commercial Property Managers
Commissioning surveys of existing developed sites where the impermeable area needs to be established for drainage compliance, permitting, insurance purposes or retro-fit SuDS design.
Architects and Project Managers
Commissioning impermeable area surveys as part of pre-application survey packages alongside topographic and measured building surveys for refurbishment, extension and change of use projects.
Impermeable Area Surveys for Your Sector
We provide flexible outputs to suit drainage engineers, planning consultants, developers and local authorities:
What Will You Receive from an Impermeable Area Survey?
What Will You Receive from a CCTV & Drainage Survey?
Georeferenced impermeable area plan showing all surface classifications.
Professionally presented plan for planning submissions and drainage reports.
Structured tabulation of all surface types with individual areas and totals in PDF and spreadsheet format.
Full written record of survey method, equipment, accuracy, coordinate system and date of survey.
(Note: 3D terrain models and contour plans are not included in a standard impermeable area survey - these are topographic survey deliverables. Where ground levels are also required, we recommend commissioning topographic survey and impermeable area survey together as a single coordinated programme.)
Our Services
How Impermeable Area Surveys Integrate With Other Services
How Impermeable Area Surveys Integrate With Other Services
Topographical Surveys
OS-controlled accurate, efficient and cost effective surveys for highways, civils and development. Cad and BIM-ready output.
PAS 128 utility mapping
Providing the location of underground services in 2D or 3D through qualified utility mapping surveys, using advanced GPR and Electromagnetic Location.
Measured building survey
Delivering accurate as-built information that supports design, refurbishment, planning and construction with the latest technology. Producing reliable drawings and digital models.
Laser Scanning
3D laser scanners capture millions of points per second, creating a point cloud which enables the finer details and the physical site to be viewed remotely.
Mobile mapping
For highway engineers, infrastructure managers, local authorities and contractors working on live road schemes, mobile mapping is now the standard for corridor surveys.
3D Machine control
With decades of supporting major earthworks contractors and large-scale infrastructure schemes, we provide reliable machine control across Lancashire and the wider UK.
Setting out engineers
With strong, long-standing relationships across the civil engineering and construction sector, we supply skilled professionals who keep your projects accurate, efficient and on programme.
bathymetric surveys & river surveys
Using modern technology, we capture detailed underwater and river channel information safely and efficiently – delivering reliable data you can trust.
Stockpile surveys & volumetric analysis
Whether a one-off stockpile measurement or regular monitoring, we deliver reliable, repeatable data tailored to your project using advanced technology.
Control Network Installation
Delivering robust and precise site control systems to support every stage of construction in developments, infrastructure schemes or major earthworks.
aerial & drone surveys
CAA-approved drone operations for aerial mapping, photogrammetry and volumetric analysis, providing a comprehensive view of terrain, structures and landscapes.
3D BIM Modelling
Whether you require an as-built Revit model, federated coordination model or detailed digital twin, our team delivers high quality, design-ready outputs.
survey equipment hire
We offer a vast range of surveying and engineering equipment for hire and will always try to beat a comparable quote. Discover the fleet.
monitoring
Providing reliable monitoring surveys across the UK, delivering precise data that supports risk management, compliance and informed decision making throughout a project lifecycle.
Virtual Tour 3D
An immersive experience which instantly transports your clients to your business, guiding them through your space and creating a seamless experience.
Impermeable area surveys
We deliver georeferenced impermeable area data that drainage engineers and planning consultants can work from directly.
CCTV & Drainage surveys
Acoustic & Noise Assessments
We deliver acoustic and noise assessments, supporting planning applications, discharge of conditions and Environmental Impact Assessments.
Why choose site surveying services
On site. On spec. On time.
fast turnaround
Get a quick quote and a survey team prepared for instruction. When the programme window opens, we're ready.
PAS 128 Accredited
British Standard utility mapping. Quality Level B means physical verification of every service - not just surface evidence.
Lancashire-Based
Headquartered in Clitheroe. We know the North West - the sites, the contractors, the programmes. Local knowledge backed by national capability.
Programme-Critical
Data that works in your environment from day one. BIM to your EIR. CAD to your spec. No reprocessing. No delays to the design team.
Frequently Asked Questions
Frequently Asked Questions
What is an impermeable area survey?
An impermeable area survey is a measured record of all hard and soft surfaces across a site – identifying and quantifying every impermeable surface that does not allow rainfall to infiltrate, including roofs, roads, car parks, footways and hardstanding, and every permeable surface including soft landscaping, grassed areas and natural ground. The output is a georeferenced plan and area schedule showing the classification and measured area of every surface type, used by drainage engineers to calculate surface water runoff volumes and size drainage infrastructure.
Why do I need an impermeable area survey for a planning application?
Local planning authorities and Lead Local Flood Authorities require drainage strategies to be supported by measured impermeable area data as part of their SuDS and drainage validation requirements. A drainage strategy based on estimated rather than measured impermeable areas may not satisfy the LPA’s validation requirements, may result in a holding objection from the LLFA, or may produce a SuDS scheme that is incorrectly sized. An impermeable area survey produces the documented, survey-grade data that satisfies both the LPA and LLFA requirements.
What is the difference between an impermeable area survey and a topographic survey?
A topographic survey captures ground levels, boundaries, drainage features and all physical site features for site design and planning. An impermeable area survey classifies and measures the surface types across the site – identifying what is impermeable and what is permeable and producing the area schedule drainage calculations require. The two surveys are best commissioned together – ground levels and surface classifications delivered as a single coordinated dataset from one site visit.
What does the LLFA require for SuDS drainage compliance?
Lead Local Flood Authority requirements vary by local authority area. Common requirements include measured existing and proposed impermeable area, greenfield runoff rate calculation, SuDS attenuation volume calculation and a drainage strategy drawing. We advise on the specific requirements of Lancashire County Council, Greater Manchester Combined Authority and other North West LLFAs at the time of instruction.
What file format will the impermeable area survey be delivered in?
We deliver impermeable area surveys in AutoCAD DWG and PDF plan format alongside a structured area schedule in PDF and spreadsheet format. Where the drainage engineer requires data in a specific format for drainage design software, confirm this at the time of instruction.
Can you survey a large industrial or commercial site efficiently?
Yes. For large sites, we deploy UAV photogrammetry to capture the complete site area – including all roof surfaces – from a single flight programme, combined with GPS ground survey for drainage features and boundary details. For highway-scale sites, our CHCNAV AU20 mobile mapping system captures the complete surface at road speed. We advise on the most appropriate methodology for your site at the time of scoping.
Can you combine an impermeable area survey with a topographic survey?
Yes – and we strongly recommend it on any site where both drainage design and planning are in scope. Combining both surveys from a single site visit produces a complete georeferenced dataset of ground levels, drainage features, boundaries and surface classifications for less total cost and programme time than commissioning each separately. This is the most common combination we deliver for planning application support.
Do you cover the whole of the UK?
Yes. Our head office is in Clitheroe, Lancashire, with additional offices in Matlock, Newcastle and Bristol. We deliver impermeable area surveys across the North West, North East, Midlands, South West and nationally. All work is delivered by our directly employed team – not subcontractors.