Retaining walls
can be the hardest area to contain water as generally they are constructed with the use of bessablocks that form the structure and then filled with a block fill cement. The blocks are quite porous to begin with and the capillaries in the block are large in nature, therefore the membrane used is quite specific and the application needs to be done correctly. The retaining wall needs adequate drainage and preferably back filled with a layer of sand against the protector sheet (6mm core flute) and back filled with a good grade soil, not a clay base or reused concrete fill.
There is nothing worse than seeing unsightly render falling off due to the wall not being waterproofed correctly or at all. The cost of repairing the drummy render, then painting it, outweighs the price of doing it correctly the first time. A durable and flexible membrane needs to be applied to correct this from happening. Manufacturers specifications is of strict importance and I wouldn't recommend a home handyman try these works or the DIY renovator.
