Ground-bearing slab assessment

The project

A commercial unit in Parsons Green has an existing ground-bearing concrete slab, and the question is whether it can take the proposed new use. We are inspecting the slab, assessing its capacity and preparing drawings and recommendations. This kind of check is often needed when a unit changes hands or use, because the slab was designed for whatever the building was originally meant to do.

Ground-bearing slabs rest directly on the ground beneath them, so their capacity depends on the slab thickness, any reinforcement, and the quality of the fill and ground below. A change of use can bring heavier concentrated loads from equipment, shelving or new partitions. The slab needs checking for those local loads as well as for the general floor loading spread across the whole unit.

Checking a slab for a new use

We are starting with an inspection of the existing slab, looking at its condition and for signs of cracking or settlement that would affect its capacity. Where the slab's make-up is not known from records, it may need confirming by coring or a small break-out, since thickness and reinforcement drive the result more than anything else. The ground beneath matters too, because a slab on poorly compacted fill can crack under a load it could otherwise carry, even when the concrete itself is sound.

The capacity assessment then compares what the slab can carry with what the proposed use will put on it. Our drawings and recommendations set out the findings in a form that the tenant or landlord can act on directly, whether that means using the slab as it is or planning for local strengthening. Our structural calculations guide explains what an assessment like this involves.

Planning something similar?

Before signing a lease or ordering heavy equipment, check that the floor can take it. A slab assessment is far easier to do at the start than dealing with cracking or settlement later. See more of our work in Hammersmith and Fulham.