Be grateful for your thoughts, we're on a small patio (30m2) and i had planned to install a linear drain to take the water and then onto a soakaway. We've dug a trial put to see how the water drains, on first look the soil seems OK, not too much clay which is a surprise for us in Essex.
But whilst double checking construction for the soakaway on the site I came across:
http://www.pavingexpert.com/drain14.htm
I've used this type of design before in other situations but wondered if it would be an option for this job. would certainly save us some time rather than building the soakaway.
Only thought was whether this would be sufficient for our surface area?
Many thanks for any advice/thoughts.
Best choice for small patio
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lutonlagerlout
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Tony McC
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The edge drain (a variation on a fin drain) shown on the page you quote is fine for a 30m² patio as long as the drain *isn't* against the house. It needs to be adjacent to an unpaved area and as far from the house as practical.
I know splash strips (gravel-filled gaps between paving and masonry) are popular but I would never recommend their use for draining anything more than a single flag width.
I know splash strips (gravel-filled gaps between paving and masonry) are popular but I would never recommend their use for draining anything more than a single flag width.
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bigwest
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ntaylor83
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Hi,
Sorry to jump on the OPs post but thought it best to keep this here as its pretty much identical. Any help would be greatly appreciated as I am out of my depth with this one.
New patio being laid (has been halted until the drainage problem gets sorted). The whole patio is around 34m2, and it snakes to the left of the picture and out into the lawn. The lawn will be around 500mm raised once the sandstone patio is fully laid.
We were originally to run off to an exisiting drainage hole (that went nowhere - nice) back to the main drain that sits against the house. Long story short the way that its been laid so far makes it near impossible to get back to the drain.
Sorry for the long winded intro....
My original idea was to dig under the new brick wall footings, use the aco drains to collect the water, dig a huge hole into the lawn another 2m away from the wal into a polystrom crate
Having come across the OPs alternative solution http://www.pavingexpert.com/drain14.htm I'm wondering if you very helpful people think it would be possible to drain the proposed area into a trench, hence not needing the soakaway?
There would be two trenches at the two ends of the new wall (one to the left of the photo which cannot be seen.) in this case it would be more like 15-20m2 for each trench.
No signs of clay at the moment and no previous waterlogging on old paving.
Again any help much appreciated!
Sorry to jump on the OPs post but thought it best to keep this here as its pretty much identical. Any help would be greatly appreciated as I am out of my depth with this one.
New patio being laid (has been halted until the drainage problem gets sorted). The whole patio is around 34m2, and it snakes to the left of the picture and out into the lawn. The lawn will be around 500mm raised once the sandstone patio is fully laid.
We were originally to run off to an exisiting drainage hole (that went nowhere - nice) back to the main drain that sits against the house. Long story short the way that its been laid so far makes it near impossible to get back to the drain.
Sorry for the long winded intro....
My original idea was to dig under the new brick wall footings, use the aco drains to collect the water, dig a huge hole into the lawn another 2m away from the wal into a polystrom crate
Having come across the OPs alternative solution http://www.pavingexpert.com/drain14.htm I'm wondering if you very helpful people think it would be possible to drain the proposed area into a trench, hence not needing the soakaway?
There would be two trenches at the two ends of the new wall (one to the left of the photo which cannot be seen.) in this case it would be more like 15-20m2 for each trench.
No signs of clay at the moment and no previous waterlogging on old paving.
Again any help much appreciated!
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Mikey_C
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how deep was the footing for the retaining wall? you don't want to undermine it with the drainage. on the subject of the wall, has it got any weep holes in it (can't see from this photo), I ask but I'm absolutely sure in needs them, someone with much greater knowledge than will confirm or deny my thoughts.
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ntaylor83
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Thanks for the reply Mikey. Ive had a chat with a pal and he concurs that method may undermine the footings, so the soakaway crates it is. He also mentioned the weep holes in the retaining wall so I'll check with the brickie.
On the soakaway front. The installation guides on this site show a 110mm pipe going into the crate. I have 110mm pipes but all the installation guides on polypipe/aquacell show only a 160mm "knock out". Im guessing theres a smaller knock out within that can be used for the 110mm pipe, or will I need the adaptor for those products?
Also, I'll be need 3 crates but at a bit of a dilemna how to arrange.
The drainage pipe will be ~900m below the lawn surface, and to me it would make sense to place them side by side but that will require around 3m3 dig out(1.4 deep x 1.7 wide x 1.3 length). Silly question but does it matter if the pipe goes into the top of the crate as shown on this site or can the crate be laid to have the inlet pipe at the bottom?
The other option is 3 stacked on top with the pipe going into centre crate gives a much deepr hole but much smaller dig out ~1.5m3, given that I'll need to go down 900m to get to the pipe...If they are stacked vertically can the pipe go into middle crate or does it need to go in the top one?
Sorry for all the questions, as I said before very much out of my depth (no pun intended)
On the soakaway front. The installation guides on this site show a 110mm pipe going into the crate. I have 110mm pipes but all the installation guides on polypipe/aquacell show only a 160mm "knock out". Im guessing theres a smaller knock out within that can be used for the 110mm pipe, or will I need the adaptor for those products?
Also, I'll be need 3 crates but at a bit of a dilemna how to arrange.
The drainage pipe will be ~900m below the lawn surface, and to me it would make sense to place them side by side but that will require around 3m3 dig out(1.4 deep x 1.7 wide x 1.3 length). Silly question but does it matter if the pipe goes into the top of the crate as shown on this site or can the crate be laid to have the inlet pipe at the bottom?
The other option is 3 stacked on top with the pipe going into centre crate gives a much deepr hole but much smaller dig out ~1.5m3, given that I'll need to go down 900m to get to the pipe...If they are stacked vertically can the pipe go into middle crate or does it need to go in the top one?
Sorry for all the questions, as I said before very much out of my depth (no pun intended)
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Tony McC
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ntaylor83
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Tony McC
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You've miscalculated horribly and then some! But it all gets terribly complicated.
That equation is the 'old' method of calculating soakaway volumes, but given that the preferred methodology (BRE Digest 365*) is a complete headfecker, and that the old method works OK for patios and driveways under 200m², I usually stick with it, but it really is rather crude and tends to produce hugely over-big soakaways.
* - I've been trying for three very long years to turn this document into understandable English and publish a simplified method on the website, but I've become convinced that it's deliberately over-complicated so that drainage engineers can sell you over-priced software to solve what should be a simple Input less Outflow calculation!
Very generally speaking, on free draining sites, you will be OK with one crate per 50m². Now I know someone will shoot me down over this over-simplification, but there are a number of variables to consider, not least of which is the permeability of the ground (percolation rate, Vp), and on sites where soakaways are viable, the rate of outflow is generally sufficient to cope with an inflow from a 10 year storm event onto a <50m² pavement that can be stored in a single 200-250 litre crate.
If your trial pit is emptying in less than 2 hrs, then a single crate will be fine.
That equation is the 'old' method of calculating soakaway volumes, but given that the preferred methodology (BRE Digest 365*) is a complete headfecker, and that the old method works OK for patios and driveways under 200m², I usually stick with it, but it really is rather crude and tends to produce hugely over-big soakaways.
* - I've been trying for three very long years to turn this document into understandable English and publish a simplified method on the website, but I've become convinced that it's deliberately over-complicated so that drainage engineers can sell you over-priced software to solve what should be a simple Input less Outflow calculation!
Very generally speaking, on free draining sites, you will be OK with one crate per 50m². Now I know someone will shoot me down over this over-simplification, but there are a number of variables to consider, not least of which is the permeability of the ground (percolation rate, Vp), and on sites where soakaways are viable, the rate of outflow is generally sufficient to cope with an inflow from a 10 year storm event onto a <50m² pavement that can be stored in a single 200-250 litre crate.
If your trial pit is emptying in less than 2 hrs, then a single crate will be fine.
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ntaylor83
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Thanks Tony,
I've unfortunately ordered 3 already after looking here:
http://www.pavingexpert.com/drain13.htm
As the digging has already commenced I'll probably install 2 knowing that in your expert opinion 1 is probably enough, unless you think this is massive overkill.
Thanks again, this is realy helpful
I've unfortunately ordered 3 already after looking here:
http://www.pavingexpert.com/drain13.htm
As the digging has already commenced I'll probably install 2 knowing that in your expert opinion 1 is probably enough, unless you think this is massive overkill.
Thanks again, this is realy helpful