LWD testing in Manchester.

Same-day and next-day dates are often available, subject to the schedule. Manchester is a long run from our laboratory in Milton Keynes, so next-day is the more realistic ask. An LWD visit needs no reaction vehicle, which makes it easier to schedule than plate bearing. Ring 0161 871 7372 with the postcode and the area to be covered.

The technician seats a loading plate on the prepared surface, lifts a weight to a fixed height on a guide rod and releases it, and a sensor records the deflection of the surface. 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. No reaction load is needed, so one technician can cover a whole shed footprint on foot.

Only with caution. When glacial till is dry and stiff it can give a usable reading. Once it is wet and trafficked, which in Manchester is much of the year, it deforms plastically and the result scatters and means little. At formation level on wet till a CBR with a moisture content is the better test. Use the LWD on the granular layers above.

Less than it affects a CBR on clay, which is one reason the method is popular here. Well graded granular capping and sub-base drain and hold their stiffness in wet weather. Standing water, a saturated layer or a pumping subgrade beneath will still pull the readings down, and that is useful to know before the slab is poured. We note the surface condition at each position.

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. For warehouse floor slabs the engineer normally sets a project value for the sub-base. Give us the target and the report shows every position against it.

A lot. Each position takes a few minutes, so a grid of dozens of readings across a footprint in a day is normal. Because it is a long trip from the laboratory, that productivity is what makes LWD good value in Manchester. Send the slab layout and we will suggest a spacing, or follow the one your specification sets.

Not on its own. An LWD assesses roughly the top 300 to 450 mm. On Chat Moss or Carrington Moss a granular platform of that thickness or more can read well while sitting on very soft peat. The platform should be designed from the ground investigation and proved by plate bearing at the design pressure, with a DCP profile to show what is beneath.

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 comes from the specification, with performance testing of pavement foundations covered by Series 800 of the Specification for Highway Works.

Usually not. Those are designed to a bearing pressure and checked against a plate bearing result. An LWD grid complements it by showing whether the rest of the platform matches the positions that were plate tested. Agree the plan with your temporary works designer before the visit.

It can be estimated, but dynamic stiffness and direct CBR are different measurements and the relationship depends on the material. Any conversion must be appropriate to the material and agreed for the project, and the report should label the value as derived. If the adopting authority wants a CBR, a CBR test is the cleaner route.

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, and at this distance travel is a real part of the price. The way to get value is volume: cover the whole area in one visit and combine it with any plate, CBR or sampling work you need. Send the postcode, the area to be tested and a firm ready date and we will quote.

No. Hixtra has no office, depot, staff or vehicles in Manchester or anywhere in the North West. Every team travels from the laboratory in Milton Keynes, and the 0161 number rings through to the same people as our other numbers. Book with a firm ready date so the trip is not wasted.