Narrow Garden - Patio Drainage Question

[senzubeansoup]

Hello everyone,

I'm considering installing a patio in my back garden, about two metres from the back door of my house. My house is a typical Victorian/Edwardian mid-terrace with a characteristically long and narrow garden. The patio would ideally be around 3.5m wide (the approximate width of my garden), and approximately 4m in length.

There is currently a very tired looking, uneven patio where I intend on laying the new one, and following heavy downpours I have noticed standing water, so drainage is certainly a priority for me, especially as I intend on laying a small lawn beyond the patio. However, having looked into the various drainage options, none of them seem appropriate in light of the particular qualities of my garden.

I considered installing a channel drain or French drain where the water collects. However, the only drain to which I can direct the water to is right in front of my kitchen window, meaning that, having sloped the patio away from the house, rainwater would then have to be redirected back towards the house, which to me seems to be asking for trouble, not to mention laborious.

Given how narrow my garden is, a soakaway does not appear to be an option either. There is nowhere in the garden which is 2.5m away from a boundary, and as I understand it installing one would fall foul of regulations.

There isn't enough space in the immediate vicinity of where the patio will go to put enough plants to soak up the excess water.

I looked into underground water storage, but it's far too expensive.

Leaving gaps between the paving slabs to allow for water to permeate also sprung to mind, but I would prefer to be able to fill the joints between the slabs as it makes weed intrusion less likely and jet-washing the slabs will be less messy.

Does anyone have any ideas? After hours of research I'm at my wits end! Thanks in advance.

 

[Why Not Indeed]

If the only way you can reach the drain is running it back towards your house because that's where the drain is, then that is what you have to do. Make sure the drainage is installed in such a way that you can inspect it and maintain it easily. That way, the "trouble" that you think is being invited can be averted.

Leaving gaps between the paving slabs to allow for water to permeate also sprung to mind

It sounds like this is what you already have, right [tired looking, uneven patio]? And it doesn't fix the problem.

 

[senzubeansoup]

If the only way you can reach the drain is running it back towards your house because that's where the drain is, then that is what you have to do. Make sure the drainage is installed in such a way that you can inspect it and maintain it easily. That way, the "trouble" that you think is being invited can be averted.

I suppose it is.

It sounds like this is what you already have, right [tired looking, uneven patio]? And it doesn't fix the problem.

Having not yet pulled up all of the slabs I'm not sure what lies beneath, but if there was something problematic, I would remedy it.

 

[JohnD]

Run it away from the house, with a good fall. One inch per yard will let the rain wash away dirt.

If the patio was not there, the rain would soak into the ground. You can dig a drainage ditch at the edge of the patio, filling it with large stones (not shingle) and protecting it from mud intrusion with fabric.

To avoid undermining the patio you can lay a small brick wall, or cast a concrete lip, in the ground before laying the patio.

Remember that the house end must be at least two courses of bricks below the original DPC. You may need to dig out the old paving to achieve this.

It is very likely that any gullies or drains at the back of the house will be cracked and leaking, so dig to examine and replace them during your preparations.

You are not allowed to run ground water into the public drains.

 

[senzubeansoup]

If the patio was not there, the rain would soak into the ground. You can dig a drainage ditch at the edge of the patio, filling it with large stones (not shingle) and protecting it from mud intrusion with fabric.

I take it that this ditch would remain open, rather than be covered over in the same manner as a soakaway? I was hoping to create some continuity from the patio to the lawn, rather than a hard border.

Remember that the house end must be at least two courses of bricks below the original DPC. You may need to dig out the old paving to achieve this.

Does this apply even where the house end of the patio is two metres away from the house and appropriately sloped?

 

[JohnD]

You can fill it with pebbles so there is a flat surface you can't fall into. It is possible to put a couple of paving slabs where you would walk on and off. Pebbles drain very freely and do not permit capillarity due to the large and irregular gaps.

What will be next to the house wall? And how high?

 

[senzubeansoup]

You can fill it with pebbles so there is a flat surface you can't fall into. It is possible to put a couple of paving slabs where you would walk on and off. Pebbles drain very freely and do not permit capillarity due to the large and irregular gaps

That's doable.

What will be next to the house wall? And how high?

There is currently brick paving next to the house - it looks like it's at least 150mm below the DPC, so no concerns there.

That brick paving continues for about two metres, at which point there is a step up, which is where the knackered patio I'm looking to replace starts.