How large of a mold can I make from silicone?

Our customers have both molded and cast very large items such as entire walls, bars, museum pieces, sculptures, trees, stairways, and architectural reproductions to name a few. Most of the materials are the same however the processes may change. For instance, you may paint or brush on the silicone mold making rubber rather than pouring. You would then make an outer shell to support the brushed on mold.