I need to run cable between my garage and the consumer unit in the house. There's a small doorway through from the loft space above the garage into the upstairs of the main house, as can be seen in the first picture. The second picture shows the outside of the garage roof joining on to the wall of the house. I'm wondering if it's OK to run the cables up the cavity into the loft space of the main house. To the left of the door there's a space through the external wall where a block has been removed to run the pipework for the boiler into the main house. I've just discovered that the block at the bottom has dropped because there's nothing supporting it anymore. I'm planning to get some wood in there to support it so it doesn't drop onto the pipework. But it means there's access to the cavity there, so I'm thinking of running the cable up there (about 2.5m ish) to the main roof space, so that I don't have to lift all the floorboards in the house and drill all the joists to run the cable across to the other side of the house. It would probably end up being a few cables run like this (new ring main for garage, new lighting radial, plus some networking and speaker cables). Would this cause an issue with bridging the cavity? Should I try and run some flexible conduit or something first? Or would it be better to just go straight across the cavity into the house, then plaster in some conduit to the internal wall and run up there? Although that would require more work I think.