Posted: Tue Jul 09, 2013 1:14 pm
Hi,
Hope someone can advise me on a design consideration with my patio project, upon which I'm embarking mostly with the awesome information on this site.
I'm laying a "proper" patio on a ~10m^2 area where before there was only a loose collection of concrete flags and patches of bare top-soil.
The new patio will be riven sandstone flags and the whole area will be edged with setts.
I've included a diagram to illustrate the factors involved rather than attempt to explain everything. But I have arrived at the conclusion that patio needs to fall towards the house, due to the combination of the natural slope of the garden down to the house, the level of the concrete path (A) which I do not want to demolish, and the presence of old brick soakaway (B) which tops out relatively near the surface, all hampering efforts to direct the fall elsewhere.
I've thought of numerous drainage solutions and am considering the following options:
1) "French" / infiltration drain between path (A) and patio (as per http://www.pavingexpert.com/drain14.htm)
This would be easiest to install, probably cheapest and probably look quite aesthetically pleasing.
Also sounds like a lot of fun to build!
2a) Linear / channel drain between path (A) and patio, leading to new attenuator, probably at point ( C ).
By far the most involved to install, almost certainly the most expensive.
Would like to source something discrete like a slot-drain but finding this hard as a lowly DIY-er.
This would have the advantage that if soakaway (B) ever ceases to function it would presumably be relatively easy to redirect gully (D) to attenuator ( C ), assuming it has capacity. Probably never going to be an issue.
2b) Same idea as 2a but somehow hook up plastic outflow from channel drain to clayware pipe feeding soakaway (B).
Probably not a good idea as who knows what the performance of this old brick soakaway is.
3) Create a channel within the paving (setts) falling to a square gully in the top left corner, again to attenuator at ( C ).
Working with minimal crossfall due to level of concrete path may hamper this.
Can imagine it being fiddly to lay.
If I did it right would probably look the best though.
4) Reconsider allowing the patio to fall away from the house.
This would mean excavating an additional 100mm from the back edge, including dropping the path (which fortunately has not yet been paved) even further than it currently slopes.
Disposing of the additional spoil would almost certainly tip me over the edge of my current "hippo" allowance, thus costing another £100 give or take, which would sting a little.
Questions:
- I really do like the linear filter drain concept, but is this too close to the house and might the new water here create a problem for the property? Is an attenuator solution away from the property much preferred?
What about things like wooden fence posts near to the drain - might they deteriorate quicker?
- Would option 3 be workable given the limited cross-fall? Of course I can imagine how to build a slight fall into the in-paving channel, but not sure how to go about calculating how deep to make it, etc.
- Drainage boffins, what would you do in this situation?
Many thanks in advance for any suggestions,
Surreywill.
(EDIT: Worth noting, neighbouring properties on either side of patio)
Hope someone can advise me on a design consideration with my patio project, upon which I'm embarking mostly with the awesome information on this site.
I'm laying a "proper" patio on a ~10m^2 area where before there was only a loose collection of concrete flags and patches of bare top-soil.
The new patio will be riven sandstone flags and the whole area will be edged with setts.
I've included a diagram to illustrate the factors involved rather than attempt to explain everything. But I have arrived at the conclusion that patio needs to fall towards the house, due to the combination of the natural slope of the garden down to the house, the level of the concrete path (A) which I do not want to demolish, and the presence of old brick soakaway (B) which tops out relatively near the surface, all hampering efforts to direct the fall elsewhere.
I've thought of numerous drainage solutions and am considering the following options:
1) "French" / infiltration drain between path (A) and patio (as per http://www.pavingexpert.com/drain14.htm)
This would be easiest to install, probably cheapest and probably look quite aesthetically pleasing.
Also sounds like a lot of fun to build!
2a) Linear / channel drain between path (A) and patio, leading to new attenuator, probably at point ( C ).
By far the most involved to install, almost certainly the most expensive.
Would like to source something discrete like a slot-drain but finding this hard as a lowly DIY-er.
This would have the advantage that if soakaway (B) ever ceases to function it would presumably be relatively easy to redirect gully (D) to attenuator ( C ), assuming it has capacity. Probably never going to be an issue.
2b) Same idea as 2a but somehow hook up plastic outflow from channel drain to clayware pipe feeding soakaway (B).
Probably not a good idea as who knows what the performance of this old brick soakaway is.
3) Create a channel within the paving (setts) falling to a square gully in the top left corner, again to attenuator at ( C ).
Working with minimal crossfall due to level of concrete path may hamper this.
Can imagine it being fiddly to lay.
If I did it right would probably look the best though.
4) Reconsider allowing the patio to fall away from the house.
This would mean excavating an additional 100mm from the back edge, including dropping the path (which fortunately has not yet been paved) even further than it currently slopes.
Disposing of the additional spoil would almost certainly tip me over the edge of my current "hippo" allowance, thus costing another £100 give or take, which would sting a little.
Questions:
- I really do like the linear filter drain concept, but is this too close to the house and might the new water here create a problem for the property? Is an attenuator solution away from the property much preferred?
What about things like wooden fence posts near to the drain - might they deteriorate quicker?
- Would option 3 be workable given the limited cross-fall? Of course I can imagine how to build a slight fall into the in-paving channel, but not sure how to go about calculating how deep to make it, etc.
- Drainage boffins, what would you do in this situation?
Many thanks in advance for any suggestions,
Surreywill.
(EDIT: Worth noting, neighbouring properties on either side of patio)
