First fix for an intruder alarm is pretty straightforward but if you ask an electrician to do it at an early stage, i.e. electrical first fix, he should be able to route the wires in the most efficient, tidy manner. For example cables for detectors on windows can be routed through window frames very unobtrusively by an experienced installer. Cable route to garage will obviously need mechanical protection in the form of a conduit or trunking. But the distance from the house to the garage is a factor as the greater the length of cable the more electrical resistance there is and this is a factor with more modern alarms which use resistance to monitor for alarm and tamper. Again an experienced electrician/ installer will be able to advise. Expect to pay around €300 for first fix only for a largish house and garage.