© Plateau Group
70 Middle Harbour Rd.
LINDFIELD, NSW, 2070
+61 2 9416 7458
This H4H design is available to any volunteer groups for non-commercial use, but please make a formal request.
H4H Fabrication Details
Note: The dimensions detailed given below are down to the millimetre, but the required accuracy is only within 3-4mms.
However, have the timber cut as accurately as possible.
- The floor panel uses 30x70 frame timbers standing on the vertical. It consists of a flat floor area of roughly 3.0 x 1.8 metres, with a hinged inflection panel of 1.8 x 300mm (which becomes the support for the raised floor, and a part of the room end). In some countries the longitudinal floor-support timbers are technically known as "purlins", but most countries reserve the term only for ceiling-supporting timbers in the roof,
- The main floor length is shorter than the overall unit by about 600mm, which leaves bare ground behind the inflection panel. This forms the utility cavity under the toilet and shower tray. It creates a cavity with a height from the ground of 370mm, which is sufficient to run sewerage pipes while giving them enough flow-drop to handle, say, six or more H4H units side-by-side.
- All frame joints are butt, with two 60mm countersunk screws in each.
- Note that the two end timbers are wider by 50mm on each side than the main longitudinal timber frames. This leaves 50mm tabs at the front and back, which provides stability to the box unit above (side, front and back panels). If you have offcuts of frame timber, add them to the frame sides about mid-point to provide added stability to the side frames.
- Use heavy duty (8mm to 10mm) form-work ply (the cheapest that is tolerant of occasions water spills). You will need a sheet-size of 1.8 x 3.3 m but cut to create the inflection.
The dimensions are such that allow 10mm of over-reach for the plywood floor sheet on front and two sides (back doesn't matter much). This 10mm of overlap allows glue-nailing the ply edges, and still leaves 20mm of the timber-width to carry the vertical frames.
- We suggest that the floor-panel should be painted underneath with some white-ant protection solution.
- The outside length of the floor frame is 3060mm [Sum of 3.0 m (timber length) + 60mm (two widths of 30mm)]
- The two end timbers of the frame are 1940mm in length [Sum of ply width of 1.8 + 70mm (tab projections each side)]
- Both of these outside longitudinal timbers should be inset by 50mm, to create a main frame width of 1840. Other two longitudinal frame timbers are spaced between, roughly on 616mm centres.
- The ply will now over-reach the frame timbers 10mm on both sides and the front. (The back doesn't matter)
- It may be wise to add some off-cuts half-way along the outsides of floor frame to provide extended supports.
CHECK - Frame Widths: Between longitudinals = 1.78 m / Outside 1.82 m (giving plywood edge support of 10mm each side). Tabs extend a further 50mm on each side. Front of frame to ply edge 20mm. [Note: The side and front panels sit on the floor frame, not on the floor ply.]
Floor Ply Dimensions:
- The 8-10mm formwork plywood is originally 1.8 x 3.3 m, but needs to be cut to create the main floor length of 3010mm, and a cut-off inflection width of 290mm.
[This assumes ply thickness of 10mm, for 8mm thickness increase inflection width by 2mm.]
- The inflection will be hinged upwards at a point 3000mm along ply length (This is a ply-thickness distance from the end of the main floor ply). The inflections supports the raised floor, so any weight needs to be carried on the floor ply, not on the frame. The inflections should hinge forwards, but not back past the vertical.
- The inflection height above the frame is now 290mm + 10mm ply thickness = 300. This height is needed to align with the other raised floor supports.
- A length of timber (say, 50x15 length 1.9m) strengthens the inflection and projects 50mm on each side. This provides attachment tabs to each of the side frames just below the raised floor supports. During erection, these tabs will be screwed to the bottom of stud 6 (so they are 30mm down from the top edge of the inflection panel). The tabs will need a drill hole in each for screws to attach the inflection and side walls together at the bottom of Stud 6. [Note: This also provides some diagonal stability during erection.]
CHECK - The distance of the raised inflection from the end of the whole unit is about 600mm, while the raised floor is 700mm wide. This means that the raised floor will have roughly a 100mm overhand forward of the inflection support. This is probably about ideal.
- Construct the frame as illustrated using the 30x70 timbers vertically. All joints are simple butt joints, with two countersunk 60mm screws at each joint.
- Glue and nail the main floor ply to the frame, using the 10mm over-reach on front and both sides. (The back can be flexible.)
- Hinge on the inflection panel, ensuring that it (and its tab timber) can only fold forward. Use four small gate hinges. You will need short (15mm) gutter bolts to attach the hinges to the inflection panel.
- Glue-nail a couple of 70x30mm offcuts to the sides of the floor frame for increased stability and support of the side panels.
When erected the side frames (with 30x70mm timbers on the horizontal) will overhang the floor panel by 50mm. This comes about because we need 10mms of ply over-reach for the inside ply support (to glue and nail))
Since the vertical walls have a timber width of 70, these floor-frame tabs need to extend out to the sides by 50 mms.
Inflection The inflection is hinged to the floor top forward of the cut-off point, so that it can only fold forward, and when raised the weight is carried on the floor ply, not on the frame.
The top of the inflection should be level with the top of the two side panel's raised floor support plates. So measure from the frames, not from the floor-ply surface.
The floor-ply's front-to-back length is not critical, but the point of attachment for the inflection (which supports the raised floor) is. The ideal inflection support for the raised floor should be kept well towards the back so that it is more able to carry the body-weight of someone showering. Therefore cut the 3.3 x 1.8 m floor ply across to leave an inflection section of 29cm (allowing 10mm for the thickness of the floor ply). This will leave the floor panel ply length at 3.27m.
Now add a cross-timber (this is ideally 1.9m of 75x15mm creating extended tabs which screw to stud 6.) We suggest that you screw this cross-timber onto the inflection ply, but don't glue, so that it can be adjusted up or down to match the other raised floor support levels if necessary. It needs 30mm of the inflection above the tabs (the thickness of side floor support timbers)
These dimensions should put the inflection support of the raised floor about 90-100mms behind its front edge.
Electrical feed notch:We need to bring the electrical feed into the unit (it goes initially to the box which becomes the step) so cut a small notch (10 x 10mm) into the top of the inflection at the mid-point, so that the incoming cable enters the unit at a point which is high off the ground, directly under the raised floor, and behind the Divider Cupboard.
Erection on site:
- Sheet of thick ply (possibly formwork) water-tolerant - 3.6 x 1.8 m (8-10mm thick)
- 4 lengths 70x30 at 3 metres
- 2 lengths of 1.94 m (from 2.1)
- 1 length of 75x15 cross inflection timber 1.9m
- 4 small gate hinges