I have a flat roof with low wall around all sides. I want to turn it into a roof terrace, but would need to install railings for safety. Is it advisable to drill into the brickwork to make holes for the metal railings, or will this cause the roof to leak?
If the wall extends up beyond the roof and the top of it is not covered by the roof covering (felt/rubber/fibreglass) then drilling into it should not cause the roof to leak. Its easier here to have a plate welded to each upright with holes dilled in it. The plate sits on the brickwork and is screwed down. This also allows you to put a rubber packing piece (3 or 4mm) thick between plate and wall which acts as a seal between the two and stops any water penetration into the brickwork through the screw holes. This is not to stop leaks but to stop water getting into the brickwork and freezing/thawing which will eventually rust the screws and crack the brickwork. See our project on freeze/thaw action.