I'm going to get my house rewired but want to save some money on the electrician so will chase out the boxes and cable runs myself.
For a full rewire (so Part P notifiable) how deep and wide do I need to chase for the cable into a brick wall? Can I just remove the plaster and go back to the brick?
The minimum possible cuts and chases is the best answer! Building Reg's has a section regarding 'Structural' and I have seen too many cut well over halfway into a brick (or even knock a brick into a cavity) thereby reducing the load bearing capacity of the wall... Now imagine 3 double socket outlets, an aerial outlet and a telephone outlet grouped together and the cutting/chasing undertaken by an "house-basher" (as opposed to a person minimising disturbance...).
Chases... I use capping to mark out chasing required. This way the width is sufficient without being excessive. It's good practice to chase below the tops of skirting boards with the view to enabling cables to be removed from the back box to alter the circuit later... Maybe an additional socket will be required later.
Chasing machines... I utilise a dust extractor when using chasing machines and dust still seems to go everywhere? In an occupied home "by hand" with a large bolster saves an equal amount of time (if not a lot more) in cleaning!
With traditionally constructed homes I do not use the old cable routes - I prefer to ensure I can get under the floor boards (sometimes making an "hatch" in the under stairs cupboard) and plan from here... Chasing walls to get the cables upstairs is also very messy and not user-friendly when future maintenance is to be considered. My normal approach is to widen the chimney breast by a couple of inches with a frame and plasterboard. The cavity provided enables a length of trunking to be run up the inside into the upstairs floor void. The same plasterboard void may also be utilised for a double socket outlet or other accessories and provides a excellent route for co-ax cables, telephone cables, alarm cables and data cables WITHOUT HAVING TO CHASE OR CUT OUT BRICK WALLS!!!!
The way the floor boards run upstairs contributes a lot to positioning of sockets and other accessories. I want to lift a floor board at either side of the room only, but I am a specialist! If socket outlets or other accessories are required along the 2 walls where the floor boards haven't been lifted, then I cut circular access holes through the floor boards (and batten underneath) to provide points at which cables can be accessed. There is normally a flooring support joist just off the wall at this point and so a notch is required to insert cable(s) through - I would normally clear the area behind the skirting board at this point to "fish" the cable up and fill with polystyrene or similar prior to making good. Maintenance, maintenance, maintenance...
With a floor board up at either side of the room either a pendant light or down lights may be installed. For Pendant lights I cut out a 3" hole to use a dry-ling box to mount the pendant on - this also facilitates feeding cables through the ceiling void to the edge where the floor board has been lifted.
A room-by-room approach minimises disruption and disturbance to decor.
Room lighting switches, where possible, are mounted back-to-back, so just one chase is required to cable both rooms lights. The ring main circuit, where possible, exits one room and enters the adjacent room back-to-back. Where bathroom floors are concerned, any electrics beneath I install from the adjacent room - this saves having to remove tiled floors for access later
Where possible, I would also run the trunking from the first floor void up into the loft space either up the inside of a cupboard or using the bit on the side of a chimney breast approach.
Electrician's hourly self-employed rates are between £20 - 25. For those who choose to liaise closely with the builders' work aspects of a home's electrical installation refurbishment the savings not only in time and money, but in heartache and misery, can be most advantageous.
I have undertaken works on the above basis from the North of England to the South of England and what I appreciate most about such is home-owners and/or others assisting obtain a knowledge of home electrics - even the testing procedure to verify the safety of each circuit - which, at the least, enables the determination of the many Indians whom the Cowboys disguise themselves within.
Apart from Part P of the Building Regulations, there are also other Parts to consider including energy efficiency, fire safety, access...
A good electrician will meet the needs of a customer... I find arriving on a Wednesday/Thursday enables the customer to take a Friday off of work and assist with the electrical refurbishment of their home on the Saturday/Sunday too.
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