It starts on the A3216 just to the south of the tangle of railway lines around Queenstown Road Battersea station. It heads south along Silverthorne Road before crossing the A3036 at a set of traffic lights.
It continues on to meet the B303 on the edge of Clapham Common, where the B224 becomes one-way southbound. Soon after, the road splits. The left fork reaches the eastbound A3; the right fork is for the westbound A3 and A24. Interestingly, the original route of the A3 here followed what is now the B303, so the right fork was at one time detached from the main body of the B224.