Hixtra · LWD testing in Birmingham
Lightweight deflectometer testing for Birmingham sites. On brownfield plots where the formation is recycled fill and nothing is uniform, an LWD lets you check stiffness at dozens of positions in one visit, with no reaction vehicle and results the same day.
Talk to Hixtra →0121 270 6622Same-day and next-day dates are often available for Birmingham, with results normally reported the same day. Call to check availability.
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UKAS accreditation applies to the tests listed in our accredited schedule. Ask us for the current scope before you book.
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Finds the soft spots
Dozens of quick readings across a platform or slab show where the fill changes, which a handful of tests cannot.
No reaction vehicle
The equipment is hand carried, so tight city plots and positions between buildings are testable.
Reported the same day
Results normally reach your engineer the same day as a PDF, position by position.
LWD testing in Birmingham
A great deal of Birmingham is built on somebody else’s fill, and much new work goes down on recycled 6F material and crushed demolition arisings. Those are materials an LWD reads well, and variable enough that you want a lot of readings. It is not a replacement for every other test, so it helps to know where it fits.
The LWD works best on granular and recycled layers with a real elastic response. On Birmingham regeneration sites that means crushed concrete and brick capping, 6F material and Type 1, checked layer by layer as they go down. Explore LWD testing →
Piling platforms and crane bases are designed to a bearing pressure, and designers check them against a plate bearing result. We often run plate tests where the loads act and an LWD grid across the rest of the platform. Explore plate bearing testing →
An LWD sees only the top 300 to 450 mm. Where deep made ground sits below the layer you are testing, a DCP profile shows how strength changes with depth, although brick and slag in the fill can cause false refusals. Explore DCP testing →
CBR testing and plate bearing testing answer different questions from an LWD, and Birmingham’s ground often calls for all three. Through the city and the Black Country the formation is commonly made ground: foundry sand, slag, ash and brick rubble, rarely the same from one bay to the next. An LWD copes with coarse granular fill that a CBR plunger cannot, and its speed lets you map the variation instead of guessing at it. East of the Birmingham Fault, on the Mercia Mudstone towards Solihull, the LWD is unreliable directly on wet clay and belongs on the capping above. West of it, on the dense sand of the weathered Sherwood Sandstone, it can be used at formation level. In the Rea and Tame valleys, a stiff layer over soft alluvium gives a composite reading.
Questions people ask
Practical answers for planning and booking LWD testing in Birmingham.
Ask us about your project →Same-day and next-day dates are often available, subject to the schedule. Birmingham is about an hour and a half from our laboratory in Milton Keynes, and an LWD visit needs only a technician and portable equipment, so it is easy to fit alongside other West Midlands work. We do not guarantee an attendance time. Ring 0121 270 6622 to check dates.
It is a portable device that drops a weight down a guide rod onto a loading plate and measures the deflection of the surface beneath it. A 10 kg weight falling onto a 300 mm plate is typical, with a few seating drops to bed the plate followed by measuring drops that are averaged. The result is a dynamic surface modulus in megapascals, calculated from the force applied and the deflection it produced. On recycled fill it is one of the few quick tests that copes with coarse particles.
Generally yes, and better than a CBR plunger does. The 300 mm plate spans the coarse particles in crushed concrete, brick and 6F material, where a 50 mm plunger would seat on a single fragment. The surface must be reasonably even so the plate beds properly. Very coarse or open textured rubble with large voids is still unsuitable, and we will say so on site.
Because the fill varies. Made ground from two centuries of industry changes in composition, depth and density over a few metres, and a stiffness test reads whatever is under the plate. That variation is information, not error. A grid of LWD readings shows where the weak areas are, so they can be dug out, recompacted or tested further before anything is built on them.
Your specification or designer sets it. For pavements, DMRB CD 225 defines foundation classes by surface modulus, starting at 50 MPa, and the specification says which class applies and how it must be demonstrated. For warehouse slabs and yards the engineer may set a project value. Give us the target and the report shows each position against it.
There is no single British Standard for the lightweight deflectometer. Testing usually follows the equipment manufacturer’s procedure alongside a recognised method such as ASTM E2583. On highway schemes the requirement is set by the specification, with performance testing of pavement foundations covered by Series 800 of the Specification for Highway Works.
About one to one and a half plate diameters, so the top 300 to 450 mm with a 300 mm plate. It tells you about the layer you have placed, not the metres of old fill beneath it. Where the layer is thin, the reading is a composite of the layer and whatever is under it, which on Birmingham made ground is worth remembering.
Not usually. A working platform is designed to carry the rig at a stated bearing pressure, and the designer’s check is written around a plate bearing result. An LWD grid is a good complement, because it shows whether the rest of the platform matches the positions that were plate tested. Agree the testing plan with the platform designer first.
An estimate is possible, but dynamic stiffness and direct CBR are different measurements, and the relationship depends on the material. On variable recycled fill it is particularly unreliable. Any conversion has to be appropriate to the material and agreed for the project, and reported as derived.
Yes, that is one of the strengths of the method. The equipment is carried by hand, so basements, courtyards, plots between existing buildings and positions no vehicle can reach are all testable. Tell us about induction, permits and access times when you book.
Hixtra holds UKAS accreditation to ISO/IEC 17025 under schedule number 8996. Accreditation is granted method by method, not to the company as a whole, so it applies only to the tests listed on our current schedule. Ask us to confirm the accreditation status of LWD testing when you enquire, particularly if your specification requires accredited results, and we will tell you before you book.
Every visit is quoted from the site postcode. With no reaction vehicle and only minutes per position, the cost per test is low compared with plate bearing. The price depends mainly on the time on site, and combining LWD with plate or CBR work on the same visit is the most economical way to do it. Send the postcode, the area and your dates.
No. Hixtra has one laboratory, in Milton Keynes, and every Birmingham visit is run from there. The 0121 number rings through to the same team as our other numbers. The West Midlands is central and well connected, so the drive is well inside a working day.
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