I'm planning to make a hexagonally shaped outside pool/tank about 2400mm dia
(each side 1200mm) x 1250mm high.
The 'Splashpool 400 gallon' below is something like what I'm after, but I
want it 500mm higher:
Also, I want it a lot cheaper, and was wondering about the feasibility of
making one using 250mm x 28mm decking boards stacked on edge, a plywood base
and a lining of butyl. (I reckon that would cost c.£100 in timber or less,
if Wickes have one of their periodic '25% off decking' sales in the near
future). I think the walls would be strong enough, but am wondering about
how to connect the corner joints. I'm thinking of putting a 30 deg mitre on
the end of each board then butting them together, and securing with two
angled vertical 4" metal strips sandwiched together with bolts at each
corner. But I will have to get these made, and I was wondering if anyone
has any better ideas using off-the-shelf fixings? Any useful comments would
I would have made each layer from alternate full-length boards and short
boards. The next layer up having full-length boards over the short
boards, and vice versa.
That would give an overlap to each join below. I would use dowels* in
the overlaps, plus staggered dowels in the planks, to tie the whole lot
together. No metal strips, screws, nails or glue.
I would probably add one further layer below the (marine) plywood,
dowelled through to the layer above. That will raise the plywood above
ground level - a few offcuts would be needed under the plywood to
support the weight.
I hope that you understand what I mean! Like brickwork, the overlaps
will give incredible strength, once tied to the layers above and below.
*For dowels, I would buy hardwood rods and cut to the lengths needed. If
you have the patience and an Xacto saw, half a dozen saw cuts along
their length will make them easier to drive in.
On any particular level, the long and the short boards need not be
jointed to each other. The long board on the layer above and below
totally overlaps the whole length of the short board and the ends of the
long board above and below. It is the long boards that are joined to
each other, by vertical dowels through the overlaps.
The short boards are pushed tight against the adjacent long boards by
water pressure. They don't really need fixings but a few dowels can be
added vertically (either from long board above, or into long board
below, or both), just to keep them in place.
The corners cannot "open" as the short board will always be pushed out
into contact with the long boards and thus close the joints. As the
seasons change and all the wood expands and contracts, this manner of
construction will keep all the joints tight at all times.
If you are worried about using dowels for this, you could add a steel
stud, bolted through from top to bottom of the complete assembly, at
each corner. But hardwood dowels is all that is needed.
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