Hi All, I know this is hard to believe, but I have never had to put a system in a house that is decorated. I was wondering how the hell you would hide cables. If you have to lift carpets how do you stretch them again.
Any room with stick-on plaster coving (not original Victorian coving;-) effectively has trunking all around the ceiling, and in many cases, all around the house in this way. You can drill through the face of it with an old 1" spade bit to gain access to the channel, and draw cables through using a proper electrician's draw wire, an expanding tape measure, or similar. When finished, just polyfilla over the access holes, and if the coving is painted matt white, you probably don't even need to paint over the polyfilla. I've done this lots of times with all sorts of data cables.
It's also quite easy to get door contact wiring up to this 'trunking' without damaging decorations (depending on age/state of plastering). Using a masonary drill which is long enough to drill from the door frame up to the ceiling (450mm/18" long 6mm bit), drill up vertically through the frame about 1/2" behind the plaster face (plaster depth), all the way up to just short of the ceiling (don't use hammer action). Then drill horizontally through the front of the coving (as above) continuing 1/2" into the wall behind (which you can easily do with the same spade bit with thermal block walls), and you will meet the
6mm hole up from the door frame, and you can easily push a 4 or 6 core alarm cable through.
With any of these schemes, there's scope for things to go wrong, e.g. a large chunk of plaster to fall off, coving to become detached, etc, so you need to think through what you'll do if the worse does happen.
cj has it. If you can't easily conceal the cables sometimes it is more cost effective to use wireless. Got to weigh up the difference in cost of equipment opposed to labour content to try and wire. I use gardtec wireless a fair bit as it is normally reliable and the panels are hybrid. Wire the zones you can and use wireless for the difficult ones.