On 2 Apr, 22:32, Martin wrote:
On Wed, 2 Apr 2008 04:35:04 -0700 (PDT), Adam Aglionby
wrote:



On 31 Mar, 17:10, Martin wrote:
On Mon, 31 Mar 2008 08:47:02 -0700 (PDT), wrote:
On Mar 31, 3:35 pm, Martin wrote:
On Mon, 31 Mar 2008 05:36:10 -0700 (PDT), wrote:
You have all been most helpful!

I've been thinking about this on my lunchtime stroll to the shops.

I think I will build a box the rough height and width I want out of
bricks. This allows me to fill the box with logs. A space to be used
by critters at some point I hope.

I can then shape around this with concrete. Once the rough shape is
done, I can put down some of the underlay, some thick liner (I found
1mm rubber one) and then another layer of underlay, then finally more
concrete to hold the rocks in place. Enough [real] rocks and pebbles
and you will not see the main structure.

What about concrete cracking? Would the fact that the liner is between
two sheets of underlay resist tearing? Small cracks I would imagine
would survive. Greater than 1mm I have a bigger problem.

Some build boat hulls using a matrix of chicken wire covered with waterproof
cement. The result is very strong and completely waterproof.
Chicken wire ferro cement -http://www.green-trust.org/2003/ferrocement/default.htm
--

Martin

Martin,

What makes this waterproof? I'm kinda lost.
I get the chicken wire idea. is the cement special? An additive maybe?

They seem to use Portland Cement. Ask at a builders supply place.

http://en.wikipedia.org/wiki/Ferrocement
--

Martin

Try http://ferrocement.com

Artificial rock used to be a major Victorian curiosity, nothing like a
grotto for getting one up on the Jones`s on the next estate.

Schloss Linderhof has a complete underground grotto, complete with wood fired
heated pool for local nymphs, made out of ferro cement.
--

Martin

Pulhamite was the stuff was trying to remember:

http://www.pulham.org.uk

http://www.english-heritage.org.uk/s...show/nav.18750

For the OP came across this basic instructable:

http://www.artificialrock.ca/form.html

Having watched prop builders turn unpromising blocks of poly into
perfect replica sphinxes and things , the building part is a skill
that you can learn, the abilty to turn it into what you can envision
is a talent that you cannae.

There was a touring replica of some French show caves built from
polystyrene a few years ago.

Adam