Rock-filled cofferdams are similar in construction to earth cofferdams. They can be used for comparatively large depths say about 3m depth of water.
They can withstand the effect of swift water currents more successfully. They are economical at places where roc is available easily. Side slope, in this case, may be as steep as 1:1. The biggest drawback of this cofferdam is its poor imperviousness. In case of small heights, a clay puddle larger in required thickness may be laid in the central part of the cofferdam.
For comparatively large or deep cofferdams puddle concrete or steel sheet pile core walls may be constructed. These cofferdams if properly constructed, can withstand the effect of over-topping of water without any serious danger.