A design for small, low-cost demountable homes with full facilities (cooking, washing, shower and toilet).
© Plateau Group
This H4H design is available to any volunteer groups for non-commercial use, but please make a formal request.
H4H Fabrication Details
Electrical & Step-box
The electrical supply into the unit would be a standard hardware-shop purchased builder's cable reel/unit with a safety trip-switch. These come in different sizes and configuration; and some have four three-pin output sockets (only two are really necessary). They cost about $80 to $100 retail.
Look for the type with a relatively low profile when in use with a couple of electrical plugs projecting and the box-lid closed. It may be necessary to cut off the handles, etc. to get one of the right dimensions.
This safety switch and distribution point will be installed in the box which will become the step up to the raised floor area. While this is the simplest component in the whole construction, it is also potentially the most dangerous since it is close to the shower, and holds electrical devices.
The box-step should be 15cms in height and probably made from ply and timber off-cuts. Remember that the raised floor overhangs the inflection by 70-100mm, and the step-box will fit under this, so it needs to have about 30cms of step-width. The length of the box is not critical, but we suggest 50cms. This leaves about 30cms between it and the wall, which is probably the space needed for a Coolite fruit box, used as a food cooler.
The box will also be used to store and transport the electrical fittings and miscellaneous components, which, in addition to the feed-unit, will probably consist of:
The step-box only needs to have a 3mm ply floor, but it does need solid 150x15 sides; the step-width should be about 300mm and it needs a length of between 500 - 700mm. [Note that while the step-top itself could be made from two pieces of narrower timber with the hinge between, it would be wise to seal the joint also with builder's tape against water drips.]
The box-step should be used with the hinge side facing forwards (ie. "the wrong way around"). The opening side is then under the overhang of the raised floor, and against the inflection.
Small (20x20mm) notches should to be cut into both upper corners of the box on each side, directly under the step, and alongside the opening. These notches should be wide and deep enough to allow the entry of two-electrical cables on each side into the box interior (these entry points would be under the overhang of the raised floor).
The notch on the box-side nearest to the Divider Cupboard will be used for the entry of the incoming power cable + for an output cable feeding the bed-side wall panel. The other side of the box will use its notch for the table-side wall feed cable, and leave space for an extension cable or device cable (TV set of small fridge).
The danger here is that a cable will slip out of its notch and be cut by pressure from the step. It may be wise to add small (extended) screw on the inside of the box just below these notches so the cables can be tied down with a short piece of string or copper wire. They can't be fixed into place, but we can guard against potential damage.
Finishing touches: The box can get wet from shower drips, so you'll want to paint or lacquer it. Lacquer is best, unless you'd got some non-slip material for the top of the box. If you lacquer, dust some sand lightly over the step area before the lacquer hardens.
Electrical fittings in the side walls
There are no light fittings in the roof-ceiling panel. All electrics are in the two side walls, and are added after the frames have been lined with plywood and before any outside cladding has been attached.
Each wall's electrics consist of a single batten holder and plastic reflector embedded in the walls (therefore well protected during transport), and a double power-point with a spare switch (which is used to control the light). The switch and power-point can be separate units, but HPM (and probably the other manufacturers) make a single unit with three switches and two power sockets.
The batten-holders (use a bayonet-type, rather than a screw). To make a light-fitting the batten-holder is attached to the base of a cheap white plastic soup plate with a couple of metal threads. (Note: Melomine is highly heat resistant, some other plastics plates are not as robust. Most soup plates will handle the heat these days since people often microwave them.) Bring the feed cable in from the side rather than the back; this helps to keep cables away from the metal cladding.
Soup plates tend to have curves and sloping sides, so to embed the light-fittings in the walls you will need a template, and a scalpel-type sharp blade to carve out some of the attachment stud.
Power-point and light-switch: Using the same techniques, fix the double power-point with extra switch in place below the light. You will want the power-point to be about 100mm above any shelving to allow space for plugging-in a mobile phone charger.
The power-point unit is fed by a standard flexible three-wire electrical cable running up through the wall. During installation you will need a cable hole through Stud 5, into the wall space (between Studs 5 and 6) reserved for the water-tank and Divider Cupboard. The cable then runs (behind the cupboard) across to the Step-box. When buying plugs for this cable run, check that you have space for a conventional plug within the step-box; there's an alternative plug type which allows the cable to emerge at right-angles. (There may be potential problems with the space available in the Step-Box.)
Obviously the cable length feeding power to the Bed-side wall power-point will need to extend out from the wall by over a metre, and probably 1.2 m while that on the table side can be shorter by 0.5 m.
The connection between the power-point/switch and the batten-holder (entirely within the wall) should use the same cable type, but it actually only needs two wires (the red "active/switch wire" and the black "neutral/return"). With three-wire cable, cut off any un-used earth wire so it can't accidentally make contact with an active wire. For safety sake within these metal-clad walls the power cables need a double layer of insulation around any electrical conductor, so don't use cheap Figure 8 flex for this connection.
The electricals need a final check (probably by someone with a license) to ensure the earth wire is continuous and that the switches control the red ('active') connectors, rather than the black ('neutral') wires. You can buy a cheap electrical checking instrument at most hardware stores.
Obviously this all needs to be done before any outside cladding is added.
Mirror, paint and posters
Not strictly anything to do with electrics, but while you are embedding the light fittings, consider the possibility of adding a cheap mirror to the table-side wall. Even a small mirror will add to the impression of space. It will also be used for make-up, and for some less-particular residents their reflected image it may trigger memories of an unbearded face.
We don't think the interiors should be painted white or any very light colour. When panels are stored and transported they are sure to get dirty.
It has been suggested that many highly attractive posters are available that could be stuck up permanently to the interior ply walls. We are not convinced that everyone would like those chosen, and wall posters tend to get daggy.