Hello
I'm hoping to get some advice on possible options for installing and draining a patio in my garden to replace the existing decking. I've researched this for a long time through forums and Paving Expert etc and it seems replacing with new decking is the only way to maintain the existing ground height and not contravene building regulations regarding height vs. DPC and drainage (at least not without extensive additional costs), but I wanted to see if anyone could help advise if that is the case or if there is a way to do it that is generally accepted and wouldn't cause issues with the surveyor if we sell the house?
I'll try to explaining what I know (or maybe misunderstand) so far as well as ask questions.
Current garden pictured below, with existing decking level with the top of the DPC. I want to maintain this level so a) we don't have a large step down from the back door, and b) so I don't have to drop the level of the rest of the garden to match (even though it is only small garden). The house was built in 2000, and the conservatory added in 2005 by Anglian Home Improvements, walls of both buildings being approx 300mm deep so I assume they're cavity walls. We bought it 5 years ago and haven't noticed any issues with the current arrangement.
I'm planning to makeover the garden similar to my design below, and believe I can put new decking against the house walls and have it drain in the same way the existing decking does now (i.e. slight fall away from house and gaps between decking with 180mm gap underneath to a gravel base), before leading into a circular paving area that can be sloped to drain into the lawn and/or the decking.
However we would ideally like to have the whole area as paved patio rather than a mix of decking and patio, for cost, aesthetic and safety reasons (the current decking is like ice in the wet and anti-slip composite decking costs a fortune). My research suggests there are two main roadblocks to achieving this, which may have suitable solutions but I don't fully understand if they're viable in my circumstance, 1) draining the water off the patio without bridging the DPC, 2) getting rid of the water somewhere once it has drained off the patio.
1) draining water off the patio without bridging the DPC.
Due to the neighbours fence along one edge of the patio (which I'm not legally allowed to drain towards?), and the total length of the patio towards the lawn being 8-9 metres, I believe my only option is to drain the patio towards the house
I believe this is ok as a last resort providing there is adequate drainage that stops water sitting against the bricks above the DPC?
Having a 200mm stone french drain between the patio and Wall B isn't desirable (I don't mind so much on Wall A) so I'd like to avoid the proposal from Paving Expert shown below
I've read people propose using a linear drain instead of the french drain proposed above, i.e. this proposal below from Paving Expert but level with the DPC instead of 75mm below. Their argument being that this would be enough to stop the DPC being bridged and 'splashing' isn't a concern because all bricks above the DPC get rained on anyway without any issues.
So it would be like using these threshold drainage designs but along all of the wall (albeit with the paving flush with the underside of the door sill and not the top surface). Is this an adequate solution, and if so could I use a slot drain along all of Wall B or would it have to be a linear channel to manage the amount of water (the width of patio draining towards Wall B is 2.75m and Wall B is approx 4m long, so approx 11sqm area to be drained)?
One added complication is an air brick along Wall A, the top of the air brick is the same height as the DPC so would be below the level of the proposed patio. Am I right in thinking neither the linear drain or the stone french drain solution would work here because they would block the air brick?
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Therefore would something similar to this shown below on Wall A be a sensible alternative and if so would I need to measure the 150mm down from the bottom of the air brick rather than the bottom of the DPC?
Assuming there is a suitable solution to draining the patio towards the house at the DPC level, and that anyone has been kind enough to still be reading this far into my War and Peace post how would I drain the drains?
2) getting rid of the water somewhere once it has drained off the patio
I'm probably more confused about this part. Am I right in thinking that all of the solutions above would need the water to then be moved and finally drained somewhere else? Either into an existing surface water drain, a french drain in the lawn, or a soakaway? If so, a soakaway seems very impractical due to cost and getting the required machinery into my back garden, so I'm discounting this idea for now (although happy to reconsider if it's easier and cheaper than I'm assuming).
The most straight forward solution would seem to be to use an existing surface water drain. The drain in the corner between Wall A and Wall B (shown in the image further up the post) seemed the perfect solution where I could run both linear channel drains into it. In fact my neighbour (in a symmetrically opposite house) had a patio installed in a similar configuration and had a linear drain connected up to this very drain. "So why are you even bothering with this post?" I hear you say. Well there are a few differences in his conservatory and garden size/shape, his patio runs away from the walls towards the lawn. There's also a question about the integrity of the people he hired to do his patio and whether they did it correctly. I'm 99% sure the drain is also connected to the kitchen waste pipes, I filled my sink and emptied it in one go and saw the water moving at the base of the external drain. My understanding is it's against regulation to empty surface water into a foul/grey water drain, is this correct? I'm still holding out some hope that I can drain a patio into this drain, otherwise why would it have been installed with an inlet from the garden/original patio if it wasn't allowed to take surface water, can anyone advise? He has since sold his house but I'm still concerned if I go down this route it will be picked up by the surveyor if we sell our house as an infringement.
If I can't use this drain the nearest guttering drain is at the front of the house and there's not enough fall to run a pipe from the patio to there without some serious excavation along the side of the house and the base of the existing downpipe. So my only other thought is installing a french drain in the lawn and connecting to this, similar to the image below. Is this an option or have I misunderstood how a french drain works? Also the corner of the lawn marked with a red hashed oval is prone to getting very wet when it rains, would the french drain help this or just make it worse by discharging more surface water in this area?
Thank you for taking the time to read this and I hope people are able to offer me some advice to close the gap between everything I've read on this topic and what I can actually apply to my circumstances.
David
I'm hoping to get some advice on possible options for installing and draining a patio in my garden to replace the existing decking. I've researched this for a long time through forums and Paving Expert etc and it seems replacing with new decking is the only way to maintain the existing ground height and not contravene building regulations regarding height vs. DPC and drainage (at least not without extensive additional costs), but I wanted to see if anyone could help advise if that is the case or if there is a way to do it that is generally accepted and wouldn't cause issues with the surveyor if we sell the house?
I'll try to explaining what I know (or maybe misunderstand) so far as well as ask questions.
Current garden pictured below, with existing decking level with the top of the DPC. I want to maintain this level so a) we don't have a large step down from the back door, and b) so I don't have to drop the level of the rest of the garden to match (even though it is only small garden). The house was built in 2000, and the conservatory added in 2005 by Anglian Home Improvements, walls of both buildings being approx 300mm deep so I assume they're cavity walls. We bought it 5 years ago and haven't noticed any issues with the current arrangement.
I'm planning to makeover the garden similar to my design below, and believe I can put new decking against the house walls and have it drain in the same way the existing decking does now (i.e. slight fall away from house and gaps between decking with 180mm gap underneath to a gravel base), before leading into a circular paving area that can be sloped to drain into the lawn and/or the decking.
However we would ideally like to have the whole area as paved patio rather than a mix of decking and patio, for cost, aesthetic and safety reasons (the current decking is like ice in the wet and anti-slip composite decking costs a fortune). My research suggests there are two main roadblocks to achieving this, which may have suitable solutions but I don't fully understand if they're viable in my circumstance, 1) draining the water off the patio without bridging the DPC, 2) getting rid of the water somewhere once it has drained off the patio.
1) draining water off the patio without bridging the DPC.
Due to the neighbours fence along one edge of the patio (which I'm not legally allowed to drain towards?), and the total length of the patio towards the lawn being 8-9 metres, I believe my only option is to drain the patio towards the house
I believe this is ok as a last resort providing there is adequate drainage that stops water sitting against the bricks above the DPC?Having a 200mm stone french drain between the patio and Wall B isn't desirable (I don't mind so much on Wall A) so I'd like to avoid the proposal from Paving Expert shown below
I've read people propose using a linear drain instead of the french drain proposed above, i.e. this proposal below from Paving Expert but level with the DPC instead of 75mm below. Their argument being that this would be enough to stop the DPC being bridged and 'splashing' isn't a concern because all bricks above the DPC get rained on anyway without any issues.
So it would be like using these threshold drainage designs but along all of the wall (albeit with the paving flush with the underside of the door sill and not the top surface). Is this an adequate solution, and if so could I use a slot drain along all of Wall B or would it have to be a linear channel to manage the amount of water (the width of patio draining towards Wall B is 2.75m and Wall B is approx 4m long, so approx 11sqm area to be drained)?
One added complication is an air brick along Wall A, the top of the air brick is the same height as the DPC so would be below the level of the proposed patio. Am I right in thinking neither the linear drain or the stone french drain solution would work here because they would block the air brick?
Therefore would something similar to this shown below on Wall A be a sensible alternative and if so would I need to measure the 150mm down from the bottom of the air brick rather than the bottom of the DPC?
Assuming there is a suitable solution to draining the patio towards the house at the DPC level, and that anyone has been kind enough to still be reading this far into my War and Peace post
how would I drain the drains?2) getting rid of the water somewhere once it has drained off the patio
I'm probably more confused about this part. Am I right in thinking that all of the solutions above would need the water to then be moved and finally drained somewhere else? Either into an existing surface water drain, a french drain in the lawn, or a soakaway? If so, a soakaway seems very impractical due to cost and getting the required machinery into my back garden, so I'm discounting this idea for now (although happy to reconsider if it's easier and cheaper than I'm assuming).
The most straight forward solution would seem to be to use an existing surface water drain. The drain in the corner between Wall A and Wall B (shown in the image further up the post) seemed the perfect solution where I could run both linear channel drains into it. In fact my neighbour (in a symmetrically opposite house) had a patio installed in a similar configuration and had a linear drain connected up to this very drain. "So why are you even bothering with this post?" I hear you say. Well there are a few differences in his conservatory and garden size/shape, his patio runs away from the walls towards the lawn. There's also a question about the integrity of the people he hired to do his patio and whether they did it correctly. I'm 99% sure the drain is also connected to the kitchen waste pipes, I filled my sink and emptied it in one go and saw the water moving at the base of the external drain. My understanding is it's against regulation to empty surface water into a foul/grey water drain, is this correct? I'm still holding out some hope that I can drain a patio into this drain, otherwise why would it have been installed with an inlet from the garden/original patio if it wasn't allowed to take surface water, can anyone advise? He has since sold his house but I'm still concerned if I go down this route it will be picked up by the surveyor if we sell our house as an infringement.
If I can't use this drain the nearest guttering drain is at the front of the house and there's not enough fall to run a pipe from the patio to there without some serious excavation along the side of the house and the base of the existing downpipe. So my only other thought is installing a french drain in the lawn and connecting to this, similar to the image below. Is this an option or have I misunderstood how a french drain works? Also the corner of the lawn marked with a red hashed oval is prone to getting very wet when it rains, would the french drain help this or just make it worse by discharging more surface water in this area?
Thank you for taking the time to read this and I hope people are able to offer me some advice to close the gap between everything I've read on this topic and what I can actually apply to my circumstances.
David
