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Posted: Tue Dec 13, 2011 11:12 am
by peter@plotsandplants.co.u
I have a client who has a large natural pond in his garden which is 16 metres in diameter and 1 metre deep in centre. Unfortunately the only way he can access most of his garden is along a narrow strip to one side which is 1.5 metres wide and 10 metres long. In the design I have produced for him I have specified an area of paving which the client would like to be finished with Indian Sandstone to match his existing patio.
The pond fills and floods in winter and in extreme conditions the area next to the pond can be underwater. The site is heavy clay and there is no scope to drain any overflow from the pond away from the site.
I am thinking that it would be wise to finish the area in question with a permeable material such as gravel or chip pings with a substantial permeable sub base. The side next to the pond will be retained with half oak sleepers sunk into concrete.
Is there any way we could finish the area in sandstone without a risk of it eventually floating away?
Posted: Tue Dec 13, 2011 4:24 pm
by lutonlagerlout
not sure i understand you peter
sandstone will not float away
it may go very green if submerged but it is denser than water so will not float
I would use SBR in the mix and as a bond bridge on the bottom of the flags to aid adhesion
LLL 
Posted: Tue Dec 13, 2011 5:44 pm
by peter@plotsandplants.co.u
I didn't literally mean floating away. What I meant was is there away of building this area of paving so that the foundations and stone will not be liable to subsidence/cracking due to being potentially submerged part of the time. I know there will be an algae issue on the surface of the stone which is less of a problem.
Posted: Tue Dec 13, 2011 5:47 pm
by Pablo
hi Peter permeable paving over heavy clay will be a waste of time and money because the area will still flood. I'd stick with the sandstone laid as per what lll just said as long as it's one of the darker grades. Resin bonded aggregate or exposed aggregate concrete would be another option and a good way to reduce slippyness and mix the materials up without blowing the continuity out the window. Be careful the sleepers don't breach the clay or rubber lining.
Posted: Fri Dec 16, 2011 6:27 am
by mickavalon
Not a lot you can do really mate, Lll is right , just lay them normally, with a good dose of SBR, and maybe seal the Sandstone with something like "Dry Treat", would help with the Algae and water penetration. Can you not build in running a drain pipe off somewhere which could attach to the pond pump, and pump off the excess water? It doesn't even need to be permanent, just a pump and hose, easy to do and save a lot of grief. Bty the way, I'd probably look at jointing with something like Ultracrete "Flowpoint, or something else Cement based.
Posted: Fri Dec 16, 2011 11:56 am
by peter@plotsandplants.co.u
Thanks for all the good advice.
The biggest problem is that this is a truly natural pond, probably accurately called a dew pond, there is nothing man made about it and there is no scope at all to drain away from the site within the budget.
I found out on my last visit to site that the concrete surround to an old swimming pool next door but one lifted and cracked due to the degree of flooding during the winter, so even if we laid onto a thick concrete pad we might still have a problem.
I think between my landscaper, the client, and myself we have decide to go for membrane with scalps sub base, and chippings laid over. That way the water can pretty much come and go without causing a problem, the only snag with this will be algae on the chippings.
Posted: Fri Dec 16, 2011 5:17 pm
by Pablo
peter@plotsandplants.co.uk wrote:I found out on my last visit to site that the concrete surround to an old swimming pool next door but one lifted and cracked due to the degree of flooding during the winter, so even if we laid onto a thick concrete pad we might still have a problem.
you're thinking to much about this it is a physical impossibility for a narrow path to pop because of ground or flood water. The reason the pool popped is due to something that couldn't happen to properly installed paving. Algae covered gravel is about the least desirable surface you could go for at least you can clean a hard surface you couldn't even use chemicals to clean the gravel due to the nearby water.
Posted: Sat Dec 17, 2011 2:03 am
by lutonlagerlout
^^
my thoughts exactly
LLL