The Mercia Mudstone that underlies much of Leicester doesn't give up its secrets easily. We see it on borehole logs every week: that weathered zone where the claystone turns to something softer, and suddenly water moves through it in ways the desk study never predicted. A standard lab test on a small sample misses that entirely. That's where the in-situ permeability testing we run, using Lefranc or Lugeon depending on depth, gives the design team something they can actually work with. Around the Soar valley, with its alluvial silts and pockets of sand, the contrast between one borehole and the next twenty metres away can be stark. Getting a field value rather than a lab estimate changes the dewatering strategy and the earthworks spec from day one. The team carries out tests to BS 5930:2015 across residential, commercial and infrastructure sites in Leicester, and what we've learned is that local geology always has the last word.
A field permeability test in Leicester's Mercia Mudstone weathered zone often returns a value an order of magnitude higher than the intact rock — a difference that dictates whether a basement slab stays dry.
Local considerations
Leicester sits inland but its weather does not lack drama: a wet winter can push the Soar over its banks and saturate the floodplain silts for months. The clay-rich glacial till across the eastern suburbs tightens up in summer and softens in winter, changing the near-surface permeability by a factor of two or three. Running a field permeability test in August tells you one story; running it in February tells you another. The biggest risk we see is a test done too quickly, in a borehole that hasn't been properly developed, giving a k value that looks safe but isn't. That leads to undersized drainage or dewatering systems, and water where the structural engineer never expected it. A second test at a different depth or in an adjacent borehole often reveals the variability, and we would rather flag that uncertainty early than let it become a contractual headache later.
Common questions
What does a field permeability test in Leicester typically cost?
For a single Lefranc or Lugeon test in an existing borehole, you are generally looking at £500 to £740. The spread depends on depth, packer setup and whether we are mobilising to a remote part of the site. If the borehole still needs to be drilled, that cost is separate and we can quote the full package once we have the ground profile.
Which method is right for my site: Lefranc or Lugeon?
It comes down to the ground. In Leicester, we use Lefranc in the softer alluvial silts, sands and gravels where the borehole wall stays open and the permeability is moderate. Lugeon is for rock: the weathered and fractured Mercia Mudstone that underlies much of the city. If you are deeper than about 15 m and hitting mudstone, Lugeon is almost certainly the way forward.
How long does a field permeability test take on site?
A single Lefranc test might take thirty to sixty minutes once the borehole is prepared. A Lugeon test with multiple pressure stages can run two to three hours for one test interval. The real variable is borehole stability and how quickly the water level stabilises. We budget a full day on site when several tests are needed across the footprint.
Can I use the results for a basement waterproofing design?
Yes, but with a caveat. A field permeability test gives you the mass permeability of the ground at one location and depth. For a basement, you also need to understand the groundwater regime across the seasons. We normally recommend at least two tests at different depths and, for larger excavations, a piezometer monitoring period to see how the water table moves before finalising the waterproofing and drainage strategy.
