Need a little bit of help. I would like to build a timber deck on a concrete pad. The problem is that I only have 9cm drop from the sliding door to the concrete pad. The dimensions of the patio are aprox 11m x 2.7m. I was thinking of using L brackets dynabolted to the concrete so the timber is not sitting in moisture. I was going to have the joists 450 mm apart. Will this work Do I need any support along the 2.7M span.