Garage/Workshop conversion
Garage-workshop conversion
HOME PAGEPHASE 1. Back door removal & window replacement. PHASE 2. Construction of a stud framework supporting eight joists. PHASE 3. Plasterboard ceiling construction. PHASE 4. Partition construction with relocated door. PHASE 5 Construction of mezzanine floor. PHASE 6. Installation of wall insulation & OSB sheathing.

PHASE 7. Electrical Re-Wiring.
(This page)

Garage/Workshop conversion
Garage/workshop conversion
APPENDIX 1. Measurements & materials.

Phase 7. Electrical Rewiring.

Details of Electrical Work.

If modifying/installing electrical circuitary/lights/sockets/cabling then the recommended option is to get the work done by a qualified electrician as (in the UK), it is essential that the modifications comply with current Building Regulations. In any case a qualified electrician should be consulted at the outset as regards the implications of using an existing electrical circuit with new wiring and equipment.

I decided after the initial consultation to do all the installation myself but get the same electrician to thoroughly check my work and sign it off when finished. It is very important to get any DIY electrical work inpected and signed off as complying with Building Regulations.

The Original Electrical Circuit.

Original electrical components, July 2015.

Original Components, July 2015.
The main photograph shows the very basic existing electrics. This consisted of three lights comprising one four foot fluorescent lighting unit and two bayonet light fittings fitted with two 60watt tungsten filament light bulbs, and a cable feeding a single switched power socket.

The left inset shows the wire-fused distribution board with a feed coming into the garage from the house (lower cable), and cables for the three lights and single socket, exiting from the top of the board and running behind the rafters, clipped to the roof ties and walls. The board was fitted with a main switch and fuse wires for one lighting and one power circuits. Such a distribution board is totally inadequate for a workshop and needed replacing with a small consumer unit fitted with RCD (residual-current device) switches instead of fuse wire. Allan, my consultant electrician, very kindly supplied a suitable second hand unit free of charge!

The right inset shows the single plastic switched socket which originally supplied power to all equipment in the garage and (with an extension cable reel), supplied external power (via the window), for an electric lawn mower and hedge trimmer!

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Out With The Old!

The existing electric lights, power socket and associated cabling systems were completely dismantled from the workshop area to facilitate the installation of the stud walling, insulation and OSB sheathing. A temporary supply system was then set up to enable the use of power tools and electric light (See below for details).

Temporary lighting and power supply.

Using Temporary Lighting and Power Circuits, August 2015
Using the existing cabling, the 4 foot fluorescent lamp was relocated to a new permanent position attached to a rafter in the vestibule area. A new metal clad double socket was installed in the vestibule area, again using the existing cabling from the consumer unit. Both the light and the socket (visible in the photograph), were prepared for use with conduit for later integration into new conduit-based cabling. This provided temporary light and power for power tools used for re-modelling the garage into a workshop.

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In With the New!

With the building work near completion, it was time to commence the permanent rewiring and installation of new power sockets and fluorescent lighting units.

Garage/workshop electrical circuit diagram.

Garage/workshop electrical circuit diagram
This shows how the electrical supply was modified in the garage to provide lighting and power for the workshop, vestibule, mezzanine floor and externally for garden appliances. At 12, the number of switched double sockets may seem excessive, but they give a functionality to the workshop which is, in my view, essential and mitigate the use of multi-socket adaptors with trailing wires.

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Electrical work in progress, 27th August 2015.

Electrical work in progress, 27th August 2015.
Work in progress installing a new consumer unit and conduit wiring to two sets of lights and a ring main of double sockets. Note that the original supply cabling for the garage has been used which comes from the utility room of the house and which uses the old twin & earth cable with red (live) and black (neutral) instead of the new colour coding brown (live) & blue (neutral). In the longer term it may be necessary to run a new feed between the main consumer unit in the house and the new consumer unit in the garage. Such an undertaking (involving the supply to the house) is definitely outside the remit of a DIY project and should only be carried out by a qualified electrician.

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Tools, Techniques & Fittings.

Running the Cabling, Why Use Conduit?
Having wired up three workshops, I am a conduit convert and here are some of the reasons why. If the cabling is done on a DIY basis rather than employing an electrician, it pays to surface mount (on walls and ceiling), so that it is easy for the signing off inspection (also to correct any faults that the inspection may pinpoint). If the walls and ceiling are insulated, then it is very difficult to conceal the cabling as it is against Building Regulations to run cabling in wall or ceiling insulation (because of the danger of the cables overheating and the potential fire risk). Surface mounting also makes it very easy to make any changes such as adding additional lights and sockets or re-routing cables, as usage may require at a later date.

Cabling could have been simply clipped to walls and ceilings, but when using such a method and connecting to a surface mounted switch or socket, the entry point of the cable is not air-tight and thus allows ingress of dust into the fitting, which, in a woodworking workshop, is universally present. Conduit connects to switches, sockets and fluorescent light battens via dust resistant adaptors which neatly enter the boxes through knockout apertures. Single core (not the usual twin and earth) cables are best used with conduit and this is much easier to wire into switches, lights and sockets (but see notes below).

Problems Obtaining Single Core Cable.
Most of the electrical components used in this project can be easily purchased from the large DIY outlets such as B & Q or Wickes. There is one exception which should be mentioned here. For this project, 20mm diameter plastic conduit was used for cabling both the lighting and power circuits, and this can be purchased readily in 2 or 3 metre lengths at the retail outlets mentioned above. Although it can be used (with difficulty), to run lengths of twin & earth cable, it is really designed for use with individual reels of single-core live (brown), neutral (blue), & earth (green and yellow striped) cables, and this is what was used in this project. Perversely, although selling conduit (and reels of twin & earth cable), none of the main outlets mentioned above stock the associated individual reels of single-core cable.

One of the cheapest on-line sources for reels of single-core cable (and other electrical equipment), is TLC-Direct. Items can be purchased on-line for delivery throughout the UK or for collection from one of their 27 branches.

Three reels of single core cable. Reels of Single Core 6491X cable

The three 2.5mm 2 reels of single-core cable shown here were used for wiring the metal-clad double-sockets in the workshop (brown coloured cable = live, blue coloured cable = neutral, green/yellow cable = earth. 6491X cable is PVC Insulated and suitable for power circuits, lighting circuits and building wiring. It is designed for use with conduit or trunking instead of the twin & earth grey or white sheathed cable.

Three reels (brown, blue and yellow/green) of 1.5mm 2 single core cable were similarly used to power the lighting circuits.

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Conduit & cutter. Conduit & Cutter.

20mm diameter plastic conduit was used for cabling both the the lighting and power circuits. Also shown is an adjustable pipe cutter which is ideal for accurate clean cutting of plastic conduit. This is quicker and preferable to cutting with a hacksaw which tends to leave a jagged and uneven cut, which makes the push fit into the conduit accessories difficult.

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Installing Metal-Clad Sockets with Conduit
As well as the metal-clad sockets, white 20mm diameter conduit can be interfaced with knock-out cable entry apertures in switches, fluorescent light battens and consumer units but it is well to check before purchasing that the knock-outs are present and of 20mm diameter.

The example (described below), of connecting sockets with 20mm conduit also applies to the other fittings with knock-outs, used in this project.

Metal-Clad Box with associated Conduit Fittings. Metal-Clad Box with associated Conduit Fittings. 5th October 2015.

The metal-clad box has a total of 8 knock-out apertures to choose from. These are fitted to 20mm conduit via the plastic male adaptor, secured with the lock-nut (adaptor & lock-nut shown on the right of the photograph).

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Removing a knock-out. Removing a Knock-Out. 5th October 2015.

Using a hammer and nail-punch to remove a knock-out to enable insertion of a conduit adaptor.

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Two knock-outs removed, two adaptors fitted in the apertures. Two Knock-Outs Removed & Two Adaptors Fitted. 5th October 2015.

Here, two knock-outs have been removed and two conduit adaptors fitted in the knock-out apertures, held in place with locking nuts.

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Push-fitting the conduit into the adaptor. Push-Fitting the Conduit. 5th October 2015.

The 20mm diameter conduit is a simple push-fit into the open end of the adaptor.

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Screwing the metal-clad box to the OSB wall. Screwing a Box to the Wall. 5th October 2015.

The metal-clad box is easily securely screwed to the 18mm thick OSB sheathing of the workshop wall.

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Securing the plastic conduit to the OSB wall. Fixing Conduit to the Wall. 5th October 2015.

These photographs show how the Spacer Bar Saddles are used for fixing the plastic conduit to the OSB sheathing of the wall. The right photograph shows the base of the saddle being attached with a single screw to the 18mm thick OSB sheathing of the wall. The left photograph shows the conduit held in place by a saddle which is screwed to the spacer bar base with two self tapper screws. These self tapper screws do not extend into the underlying OSB sheathing.

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Work in progress installing sockets with conduit. Work in Progress. 5th October 2015.

The double-socket on the left has been completely installed. The metal box of the next double socket is shown on the right with the conduit connecting the two sockets secured in place.

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View of completed socket cabling (in part). View of Completed Cabling (in part). 23rd October 2015.

View looking towards the window end of the workshop, showing the completed conduit enclosed cabling for the metal-clad double sockets.

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Using flexible electrical conduit. Using Flexible Conduit. 9th October 2015.

Where cable conduit needs to change direction and angles it is sometimes easier to use a short length of flexible 20mm diameter conduit as shown here. This interfaces in exactly the same way with the metal clad sockets (and switches), but is easier than using rigid conduit with 90o elbows (which are also shown in the photograph).

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Fluorescent Lighting Installation.

This outlines how the four 4 foot (1,220mm) long fluorescent lights were installed (Three in the workshop and one at the back of the mezzanine floor).

Fluorescent light showing the dimension needed between the two wooden support battens, 18th July 2015. Fluorescent Light Fitting. 18th July 2015.

Fluorescent light unit to be used in the workshop showing the dimension needed between the mid points of the two wooden support battens (above the ceiling, see photograph below).

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A pair of fitted battens, 18th July 2015. Fluorescent Light Support Battens. 18th July 2015.

A pair of fitted wooden fluorescent light support battens showing the correct dimension of 600mm between their mid points to enable the lights to be screwed in place, after construction of the plasterboard ceiling.

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Wooden battens for lighting attachment.

Wooden Fluorescent Light Support Battens, 18th July 2015.
The three pairs of battens (arrowed in red) for supporting the new fluorescent light units. These battens were simply screwed to the joists. It is easiest to install these before the ceiling plasterboard is put in place. 5mm diameter holes were then drilled through the centre of each batten and when the plasterboard ceiling was attached, the holes were extended through the plasterboard. With the holes in the ceiling visible from below, it was easy to see the location for the screws securing the lights through the plasterboard and into the wooden battens above.

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Installing the fluorescent lighting, 12th August 2015.

Workshop Fluorescent Lighting Installation, 12th August 2015.
Work in progress installing the fluorescent lights in the workshop, attached to the wooden battens shown in the picture above. Note the conduit used for the wiring. The cabling was surface mounted and not installed above the plasterboard as it is against Building Regulations to install electric cabling in a thermally insulated area, as there is a risk of the cable over-heating and causing a fire.

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Conduit delivering cable to a fluorescent light.

Interface Between Conduit & Fluorescent Light.
Photograph showing how 20mm plastic conduit is easily attached to a fluorescent lamp via a screwed adaptor passing through a knock-out hole at the end of the lamp.

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Wiring the double gang light switch, 27th August 2015.

Wiring a Light Switch, 27th August 2015.
A single, metal-clad double gang light switch, located by the main door of the garage, was used for controlling both the mezzanine/vestibule and workshop lighting circuits. The photograph shows the four brown (live) cables from the two lighting circuits. To make it easier to get the wiring correct, the two brown cables from the mezzanine/vestibule lighting circuit have had red insulation tape stuck on the ends of the cables. The other ends of the cables (not shown in the photograph), were also flagged with red insulation tape. The metal-clad switch was also earthed (an essential requirement), using the green & yellow sleeved cable (earthing not shown). Note how the conduit fits easily to the switch via a threaded plastic adaptor, which enters a knock-out hole in the top of the switch

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Wiring the light switches, completed.

Light Switch Wiring Completed.
Light switch cabling completed, switch ready to use. Left hand switch operates the three workshop fluorescent lights whilst the right hand switch operates the two fluorescent lights in the vestibule and at the back of the mezzanine floor.

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Workshop Lighting Completed, 27th September 2015.

Workshop Lighting Completed, 27th September 2015.
The three workshop fuorescent lights installed and operating correctly.

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Mezzanine floor lighting completed.

Mezzanine floor lighting completed, 29th August 2015.
Mezzanine floor fluorescent light completed and operational.

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Vestibule lighting completed.

Vestibule lighting completed, 17th August 2015.
Vestibule fluorescent light completed and operational.

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Re-wiring completed October 2015. Inspected and approved by a professional electrician on 23rd June 2016.

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