BRE365 Percolation Testing in Farnham & Surrey.
Ensure your surface water drainage meets building regulations with our expert BRE365 infiltration testing. We provide accurate soil permeability data essential for designing effective soakaways and sustainable drainage systems (SuDS).
Why Choose Clever Works?
- Fully compliant with BRE Digest 365
- Detailed infiltration rate calculations
- Comprehensive reports for planning
- WRC-approved & SafeContractor accredited
Expert Infiltration Testing for Building Compliance
If you are planning a new build, an extension, or upgrading your property's surface water drainage in Farnham or the wider Surrey area, you will likely need a BRE365 percolation test. This specialised infiltration testing is a strict requirement under UK Building Regulations to ensure that the ground can safely absorb rainwater runoff without causing localized flooding or subsidence.
At Clever Works, our WRC-approved engineers provide comprehensive BRE365 percolation testing for homeowners, architects, and developers. We conduct precise, methodical trial pit testing to calculate the exact soil infiltration rate of your site. This data is essential for the accurate sizing and design of soakaways and Sustainable Drainage Systems (SuDS), ensuring your project passes building control without costly delays.
What is a BRE365 Percolation Test?
In simple terms, a BRE365 percolation test measures how quickly water drains away into the soil on your specific plot of land. When you build a new roof or lay a new driveway, rainwater that would normally soak into the ground is displaced. Building control requires that this surface water is managed on-site, typically via a soakaway.
However, you cannot simply dig a hole and hope for the best. The BRE Digest 365 outlines a rigorous scientific method to determine the soil's permeability. By excavating a trial pit, filling it with water, and timing the drainage rate over multiple cycles, we calculate the soil infiltration rate (v). This calculation dictates exactly how large your soakaway needs to be to handle a severe storm event.
Why Choose Clever Works for Your Infiltration Testing?
When it comes to building compliance, guesswork is not an option. Clever Works brings over a decade of drainage engineering experience to every site survey. We are SafeContractor accredited, JIB-PMES certified, and BSI tested, meaning our testing protocols adhere strictly to industry standards.
Unlike generic groundworkers, our specialist drainage engineers understand the nuances of the BRE365 methodology. We don't just dig a hole and pour water in; we provide the detailed, mathematically sound reporting that local authority planning departments and building control officers demand. With over 250 five-star reviews and more than 550 successful surveys completed, you can trust us to deliver accurate data that keeps your project moving forward.
The Percolation Testing Process: What to Expect
Our BRE365 testing process is thorough and fully compliant with building regulations. Here is what happens when you book a test with Clever Works:
Site Assessment & Excavation
We arrive on-site and excavate a trial pit to the exact dimensions required by the BRE Digest 365 guidelines, ensuring it represents the proposed depth of your soakaway.
Pre-Soaking the Ground
We fill the pit with water and allow it to drain completely. This crucial step saturates the surrounding soil, mimicking the conditions of a heavy, prolonged storm.
Timed Drainage Cycles
The pit is refilled, and we meticulously record the time it takes for the water level to drop from 75% full to 25% full. This process is repeated to ensure consistent, reliable data.
Calculation & Reporting
We use the recorded times to calculate the soil infiltration rate. You receive a comprehensive, professional report containing all the data, calculations, and trial pit logs required by building control for your soakaway design.
Local Expertise for Farnham & Surrey Soils
The geology of Farnham and the surrounding Surrey towns—such as Godalming, Guildford, and Haslemere—presents unique drainage challenges. The area features a complex mix of highly permeable sandy soils (like those around the Bourne and Frensham) and dense, impermeable London Clay and Weald Clay.
If your property sits on heavy clay, a standard soakaway may fail, and building control will reject your drainage design. Our local experience means we understand these varying soil types. If a BRE365 test reveals that your soil is unsuitable for a traditional soakaway, we have the expertise to advise on alternative, compliant surface water drainage solutions, such as attenuation tanks or controlled discharge to a watercourse.
Frequently Asked Questions About BRE365 Testing
How long does a BRE365 percolation test take?
The testing process usually takes between one and two days. The exact duration depends entirely on the permeability of your soil. Sandy soils drain quickly, allowing us to complete the required cycles in a single day, whereas heavy clay soils drain very slowly and require more time.
Can I do a percolation test myself to save money?
While the concept seems straightforward, building control and local planning authorities almost always require the test to be carried out and certified by a competent, qualified professional. An incorrectly performed test can lead to an undersized soakaway, flooding, and rejected planning applications.
What happens if my soil fails the percolation test?
If the soil infiltration rate is too slow (typically in heavy clay areas), a standard soakaway will not be permitted. In these instances, we will detail the failure in our report and can advise your architect or builder on alternative SuDS solutions, such as rainwater harvesting systems or attenuation crates with a restricted outflow.
Do I need a BRE365 test for a small extension?
Yes, if your extension increases the impermeable area of your property and you plan to manage the new surface water via a soakaway, building control will require a BRE365 percolation test to prove the soakaway is adequately sized for the new roof area.