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
Front Panel and Door.
[Highest Skill Level]
The front panel requires a higher level of skill than most of the other panels, simply because it involves fitting and swinging a door, and the door needs locks. This wall panel also needs a number of hoop-iron cross-braces to keep the whole unit square, whereas the other panels are lined with large single-sheets of plywood which do this job more effectively.
In a cluster of H4H cabins outdoors, the front panel will inevitably face the wind and weather, and it has less cladding protection (because of the door) than the other panels. We use water-tolerant polystyrene foam (discarded fruit-box) insulation, so it will tend to lose a slightly disproportionate amount of the heat in winter. It also needs a way to hold-down the roof since wind can easily get under the (fairly narrow) roof overhang.
For this reason, special attention needs to be paid to the corner gal angle-iron locking and strap cross-bracing system, and also to the way in which the roof panel is tied to the sides; because these sides are tied to the floor, and the floor panel will need to be locked down to the ground.
The side-walls and front panel are tied together using strips of 2.1 m lengths of 20x20 gal angle-iron [blue on diagram]. These angles are permanently fixed to the Front Wall panel with, say, a half-dozen screws on the outside (the cladding side) of the Front Wall's corner studs A and D. Note that allowance must be made for the fact that Stud A is 70x30, while Stud D is 30x30. Another strip of the same gal angle across the bottom of the frame holds the door-opening in place during transport (since the bottom plate doesn't go the full width), and this also seals the air-gap between the vertical wall and the horizontal floor.
Another noteworthy solution worth mentioning is the use of an L-shaped Bed Support for a secondary purpose. This ties the door into the frame during transit, and it requires hinging (just alongside Stud B) after the panel has been ply-lined and otherwise finished. (See the note on the L-panel for dimensions).
The wooden frame of the Front Panel is 1.8 metres wide, which matches the width of the interior plywood used for the floor panel. Both the Table-side and Bed-side panels sit alongside (not on top of!) the thicker (15mm) floor ply. This adds another 2 x 70mm (plus 3mm ply each side) of width to the building when the panels are assembled, creating a total exterior dimension of 1946mm + cladding.
We plan to use a 70x30 x 2140m Studs A and B as both framing and door-jambs. These will be rebated at the top to accept the top wall plate (30x30) which slots into the center of each. This creates a door-width opening of 750mm.
Slotting the top plate into these two door-jamb timbers is a bit of a nuiscance (you need to saw down, then drill a series of holes to break out the 30x030 excess), but the result are much stronger face-screwed joints at the two points where the wall structure is weakest during transport.
This approach might also save costs, since extra door-jam timber no longer needs to be added on the sides if you have a door that fits this 750 gap; the door can be directly hinged to the stud itself. Alternately, if you have a narrower door, you can add a jamb timber on one or both sides to narrow this doorway gap.
We have settled here on a 750mm door width, because it allows the bed-plank (which occupies most of the other side) to be the standard 900mm mattress width and still leave 150mm of space for Door Jambs (2 x 30).
Strict definition: A door jamb is the flat surface that runs vertically up either side of the door frame. ... This is where you attach the hinges to hang the door, and also if holds the 'striker plate' on the opposite jamb which protects the timber from the lock mechanism when you to open, close and lock your door.
Dressed and routed timbers like this are expensive and unnecessary in a small cabin. The door frame we use here (usually just the wall studs) has all these elements combined, and it serves to keep wind and weather out. We will use tacked-on narrow battens to create an air-gap seal.
Doors and security.
Security is often a major consideration with the homeless in shelters and so it will likely be a problem here unless adequate security is provided; remember that one-third of the homeless these days are women. So doors, locks and fittings are important.
Commercial front-doors sold at hardware stores vary in size from 700 to 900mm in width, and are 1900 to 2000mm in height. The costs are astronomical.
The older inch-feet standards have resulted in second-hand door sizes which are commonly 750x1950mm, but there's a lot of variation. You could widen the door gap by 30-50mm if you need to, but smaller is better here.
The width of the front frame we propose has been set by the sizes of available second-hand doors, but there is a bit of flexibility here. You can make your own from scratch, but you need considerable joinery skills and some specialised equipment such as bench saws and routers. Ideally the door would be made with fairly heavy timbers (usually 35mm) and use two perspex lites.
By using a style of door with a middle timber division, and two frosted perspex lites (rather than fragile glass), a door can be created which is both difficult to break into, and strong enough to transport on the back of a truck.
Second-hand doors are one of the few recovered building materials that are widely sold in building junk-yards, and you also see them on street piles during suburban throw-outs. Most are the old 'Federation'-style inside panel doors which were made by craftsmen from quality timber in the past, and they are easily converted.
Anyone can replacing the upper-panels of a Federation door with perspex which is easily cut to size and frosted with sandpaper (or by adding an adhesive frosting sheet). The main problem you might face with the older doors is that the joinery often morticed (slotted-in) their door latches to produce a door with only the knobs or levers protruding on either side): the catch was embedded within the timber. This 'mortised slot' weakens the door precisely at the point where you want strength and to fit the new lock.
However you can:
The point is; don't be afraid to use an old door as the foundation upon which to build a new stronger door. You can add strengthening material also to the panels and to any of the main door timbers; you can add reinforcement to both the front surface and to the back. If you make these additions carefully and symmetrically, it will appear to be a deliberate design.
Note in the drawing that if you need to add height to the door, attach a wider timber at the bottom with a chamfered edge to provide a drip-edge for rain run-off.
The main point here is to buy or modify your door before you make your Front Wall Panel.
Adjusting for different door widths.
The easiest way to adjust to accommodate door widths less or more than 750mm is to leave the main wall structure as is, and shift Stud A with the door hinges in or out.
You can gain an extra 15mm of door width by replacing the 70x30 stud with a 70x15 plank without sacrificing much strength, but only do this if you can't easily trim down the door itself.
If your door is narrower than 750mm then the priority would be to add a solid packing batten (or even another 30x30 frame timber) behind Stud A (between it and the side wall). Next in priority would be to add 15x40 timbers inside the door-frame area.
Overall, you probably have a width adjustment range from 15mm wider, to 60mm narrower without needing to think about changing the main frame area. [But ...Remember to make an adjustment of the locking batten on the Long L-shaped Bed support.]
You can, of course, move the whole panel section between Stud B and C either way and reduce or expand the size of the noggin between Studs C and D. The dimensions of the lining ply and the bed and shelf battens will then need adjustment.
Also choose your door locks. Commercial front doors are usually pre-drilled for the standard cylinder locks, but these are expensive. Be aware that a lock for a front-door can cost as much as the door itself.
You can now buy mortice locks that can (with a bit of adjustment) replace the normal indoor-mortice latch mechanism to convert it for front-door use. They have a cylinder key mechanism. [We have had no experience with these, and they look expensive.]
The problem with home-made or second-hand doors is that ideally you want the lock-mechanism on the inside, but you need the key mechanism to be on the outside -- and that requires a large hole penetrating the timber and often special tools for creating mortice slots.
Latch vs. Lock: When talking to the hardware people, the terminology supposedly is "latch" for the door-catch mechanism widely used only on inside doors, usually with levers or knobs on both sides (sometimes with an old-fashioned key slot also), while "lock" implies a higher level of security for an outside door which needs a lock-smith to cut a spare key.
Unfortunately the terms are used almost interchangeably. Some of the "Night Latches" can be purchased with a cylinder-style key unit. And there are also "Double Cylinder Deadlatches" and "Double Cylinder Deadlocks". The 'double cylinder' is just a way of signifying that you'll pay through the nose to have an extra key cut. The term 'striker' refers to the metal plate (with a curved edge) which provides the fixed side of the lock, and is permanently attached to the door-frame. It is also called a 'strike plate' or known in some ads as a door's 'bolt plate'.
Don't forget the lock is only as secure as the "post" that secures the door-frame into the wall. You might also consider adding a pad bolt and/or a 'slip-chain' security device that allows people to open the door enough to see out and accept deliveries without becoming vulnerable. There are combination pad-bolts + chain units, but they aren't cheap.
You might consider a few different types of seperate key-type security locks also. There are tumbler-type padlock which require an outside bolt of course, and there are also both basic inside "bolts" and the more elaborate "deadbolt" types which must be difficult to fit into the thickness of most second-hand doors. You need to check out costs and suitability at a good hardware store. Possibly a good and secure type of fixed deadlock for this application is a Yale or Lockwood standard Deadlock like the one illustrated here which is often used for sliding doors. Note that it has interlocking fingers that only retract when opened with a key. These can be bolted to the outside of what was a second-hand latched door, now reinforced, and such security devices are probably as secure as the door itself.
Constructing the Wall Frame
Apart from the two Door Jambs, the Front Frame is made from 30x30mm rough pine. The top plate of the Front Wall panel is 1770 long and it sits above three of the four vertical studs ...designated A to C (with A and B being the 70x30 door jams) and Stud C being shorter than the others by 60mm.
The top and bottom plates butt against Stud D which is the full height of 2140 and is held into the frame by screw from the sides. This change allows a full-length gal angle-iron (blue in the diagram) joiner to be secure for almost the full height. Remember that this front panel is probably the weakest point in the whole design for a couple of reasons, and it is also likely to come under the most sustained wind-pressures and general weather attacks.
The two wider Studs A and B will need to be slot-rebated to accept the horizontal 30x30 top-plate. So for reasons of strength, we think it best to leave both sides of these Stud timbers intact and create a 30-by-30mm slot in the top-center of each jamb.
Note that while you are cutting the rebates into Studs A and B, these timbers are wider than the others at the base, so they need a 15x15 notch to handle the 15mm floor thickness.
The shorter bottom plate should be 960mm in length (allowing 750mm for the door and three timber thicknesses.
These calculations set the standard-sized ply liner dimensions to the full 2.1m in height with a a width of 990mm. This also gives the ply a 10mm share (an "overhang") of the frame timber at top and bottom, for gluing and tacking, the full 30mm of overlap on corner, but it leaves no attachment to the 70mm wide lock-side door frame.
This stud needs a 30mm batten on the wall side just to give the ply some attachment. But before you do this you'll need to fit the Letter/Delivery Box.
We believe that a fixed address is vitally important for people who have been experiencing homelessness. Therefor a letter delivery slot is an important facility; they need an address to get some government support and services, and they must be encouraged to retain contacts with family and friends.
We suggest that the Letter/Delivery slot also should be large enough for a Pizza, which means it is also potentially an entry point for an arm, and also for driving rain. It is best placed high in the wall (at least 1220) and it needs both shielding against wind-intrusion and some indication of deliveries.
We are suggesting a flat framed box, 60mm in it's interior height and 400mm wide. It would need to project, say 40mm outside the cladding to create an overhang, and about 30mm into the room for a hinged self-supporting drop-down tray. It would be fixed between Studs B and C at the cross-over points of the wall bracing (above 1220). To further strengthen this section of the wall, a noggin should be added alongside it between Studs C and D.
The diagram here has a hinged front flap which would provide closure to the main wind-gap but still be easy for the Postie to lift to open. The drop-down tray inside the room could be 100-150mm wide. The base should be given a distinctly downward slope in case water does get in.
It then needs a hinged hanging door of about 65 x 400 (wide enough to give coverage from rain coming from the sides). A screwed down piece of gal-angle offcut might be the best way to seal the top at the cladding edge, and this can be behind the cladding.
Inside the room the box base would extending into the room by, say, 50-100mm, with the top cut back to the ply-level. You would need to round the corners off this tray-extension so that it doesn't present a dangerous corner to someone entering through the door or getting out of bed. The tray will probably prove to be useful as a bed-side table also.
Somewhere immediately alongside or above the outside face of the Letter/Delivery box you need a 'plate' area for an address house number, and perhaps the name of the occupant. Each cabin also needs some sort of identification number for all its components.
Door Jambs and fitting
The Door Jambs (also called 'Door-jams') are on both sides of the door opening ie. Studs A and B. A 30mm batten has been added to Stud B for interior ply fixing, and this is also needed for the outside cladding; both indoor and outside linings butt tightly against the back of the jamb and the batten gives them a lock-down point, and so provides a reasonable seal. In areas with torrential rain, an extra cover-strip might need to be added here outside the cladding to keep the junctions water-tight.
The door opens inwards, so the jambs should project inside the room by about 15mm, and therefore outside by between 20 and 30mm (depending on the door thickness). Hinges are always located with their pivot point in line with the back of the door jamb. This sets the door back in its jambs, and almost fully over the floor ply.
You will probably need to set the hinge into the jamb by the depth of the metal by carefully chiselling the wood our for a millimetre or two, but check first that the hinge hasn't already been embedded too much in on the door side.
Before adding Stud A to the main frame, consider adding the door hinges, and virtually fitting the door to this stud before it is integrated into the frame. This makes the rest of the frame less cumbersome to handle also.
You now know where the 15mm floor ply fits into the bottom of the Stud, so someone can work independently on checking-in and screwing in the door hinges, confident that the door will be able to swing open. They should stand the door with its lock-side down, and clamp Stud A and door together with Stud A on its side (as per illustration). Both hinge surfaces are clamped tightly together at the same height with just a thin piece of cardboard between (in case the door swells). Also check that the door is a millimeter or two above the rebate cut you made for the 15mm floor.
Lay the open butterfly hinges across between the two surfaces, and mark their positions. Use a scalpel to cut around the hinge shape, then with a sharp chisel, "check the hinge in" by removing only a millimetre or so of wood on both door and Stud - but never so much that the metal of the hinge is below the wood surface (unless you have a particularly thick hinge when closed). This way, you can work on the two sides of both hinges together and match the check-in on each in depth and position.
Also, this Stud A timber also carries the angle-iron joiner which links the front and table-side wall together. So add this angle while you are fixing the hinges. The free tongue of this angle needs to be positioned 20mm back from the front edge of the timber (and that distance should be exactly the amount you notched from the top to carry the top plate).
Later, when the door is on its hinges and integrated into the wall frame you will also need to add a narrow door batten on Stud A to block any air-gaps which may still exist around the hinges. Also you will need a matching batten on Stud B for the same reason to stop air entering around the locks, and also to limit the door's outward swing. It is remarkable how much cold air can come through these junctions because they often swell and shrink over time.
Keep the door with Stud A separate until you have done the bulk of the work on the main front frame.
You need to add the cross-bracing of the main frame. This is best added to the outside, under the cladding. There is a problem here because potential heavy weather requires strong cross-bracing, and there is no easy way to fix the two bracings to the mid-point of Stud B (above and below the Letter/Delivery slot).
The timber here is 70mm wide while the rest of the frame is 30mm (and you wouldn't screw the cross-brace to a batten). So the best idea is to bend the ends of both strap iron braces, and fasten them with long screws through the batten into the solid timber of Stud B.
The top fixing points for the cross-bracing are not a problem because the wall's top plate (30x30) is the full 1.8m width and so drilling and screwing the hoop iron on to the plate rather than the Stud is not a problem. Somewhere close to the B Door Jamb is perfectly adequate.
The bottom fixing points are a moderate problem because the timber doesn't continue across the Door-sill, but fixing the straps to the bottom plate next to the Stud B Door Jamb in the same way is probably adequate.
Before fixing the other ends of these cross-bracing straps you need to check the whole frame for squareness by using a sheet of plywood. Also check that the slight gaps around the door are even top and bottom.
You can now bring these two diagonal bracing straps together at about the mid-point on Stud D near to the noggin, and drill a single screw-hole through them both and into the timber. From this point on the frame should remain square, and the plywood will add even more to this diagonal rigidity.
As before, always drill and screw the straps to any frame timber crossed over.
Add ply and supporting battens
We assume that you've already made and installed the Letter/Delivery box as a unit. So now cut out the necessary opening in the ply, then nail and glue the ply in place while everything is square. You should then add the two horizontal support battens: one is for the Bed (450 + floor thickness from frame) and the other for the high-shelf (1550).
We also need to add a vertical batten to carry the hinges for the longer of the L-shaped 'double' bed support panels. This batten is actually needed mainly for its thickness, to hold the panel away from the wall, so that it can fold flat over the door jambs and lock the door frames in place during transport.
Gluing this vertical batten to the ply is probably adequate, but it won't hurt to add a short screw or two through the ply from behind before the cladding is fixed.
You will probably find it best to use short gutter-bolts to fix the hinges on the the 8mm ply of the L-shaped supports, and wood screws elsewhere.
The lower hinge for this L-shaped support panel can be screwed directly to the bottom wall plate with its pivot-point 800mm from the wall.The top hinge should be of the "T" type (standard garden) because the top of the "T" can then be used to tie together the horizontal and vertical battens. Strength isn't a major consideration here.
Above Door Gap
These will be variable depending on the door you used. You can fill in any gaps, of course, with Marine Ply or cladding offcut, and possibly a 750 length of heavy batten/framing timber. The Marine Ply is the best solution since it adds diagonal strength to the door opening.
Another alternative is to span the gap with a 750 piece of (say) dressed 15x100, and drive a long screw through both Door-jambs into the two end/mid-points, in effect creating a stiff-but-moveable louvre which can be opened or closed for summer or winter. This will be immediately under the roof overhang, so it shouldn't be a problem with rain penetration if positioned outside the door line (since the door hinges inwards).
Doorstep - Sill
Note: that this applies only at the time of erection. However you should make the decision, then include the solution you propose in the Step-Box so it is included automatically and arrives at the erection site.
In use, the gal angle iron tie used along the bottom of the Front Frame will present a safe edge to people stepping through the doorway. However rain will likely be a problem if it drives into, or onto, the end of the Floor Ply. You might consider a few different possibilities: