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We've a patio next to the house which then has a ~40cm high retaining wall for the garden, which is raised above the patio. There appears to be zero drainage in place, so when it rains heavily the patio starts to fill up, and every winter the garden is waterlogged.
Said wall is collapsing, the patio has seen better days, and we'd like to extend it slightly, so we're going to get someone in to just rebuild the lot. People who know building regs better than me: what would be the minimum requirements if this was a new build, and what would be ideal? Conveniently the sewage pipe from the house does run under the patio so I could see drainage channels routing directly into that being a sensible thing to do?
First thought, I'm pretty sure you aren't supposed to be putting runoff into the drains these days and you would be expected to build some sort of soak away and divert the water to it
Not an expert but that was the advice I had when looking into a garden project
First thought, I’m pretty sure you aren’t supposed to be putting runoff into the drains these days and you would be expected to build some sort of soak away and divert the water to it
Unless you're on clay it which case you can get dispensation.
Add drainage. Dunno about what's allowed
Replace the patio with a geo-tex membrane, something like eco-tex around trees, and a permeable surface. Gravel is cheap if the furniture will cope
Replace the wall with either geo-tex and gabion baskets or a <45deg grassed slope.
Im on clay. That would have been useful to know.....
See, glad I asked!
I don't think building regs will give you much for outdoor patios etc. It is certainly the case that you shouldn't be putting rain water down into the main sewers though - it should be going into a soakaway or similar on your property.
We're on clay with a very gently sloped lawn that leads to a patio - it used to be the lawn would be a bog and the patio flooded for 3-4 months a year. I dug a french drain round the edge of the patio and put spurs out into the lawn, and its been really successful in taking the water away to our soakaways - even after sustained rain you can walk on the lawn without sinking in. The downside is that summer rain also gets drained away, so the lawn is probably drier than it used to be in july/august
<h2 style="box-sizing: border-box; margin: 0px 0px 2.85rem; padding: 0px; line-height: 1.16; font-family: Arial, Helvetica, 'Helvetica Neue', Verdana, sans-serif; color: #d50e58; font-size: 2.8rem;"><b style="box-sizing: border-box; margin: 0px; padding: 0px;">What are the rules for having a combined drainage system?</b></h2>
The only exceptions to the rules on separating surface water drainage and foul water drainage systems are for properties with septic tanks, or those that are located in areas with no access to separated drainage pipes. In certain parts of the country, the only available public sewer nearby may still be a Victorian-era combined sewer, meaning they will have no choice but to set up a combined connection.
Establishing a combined drainage system requires special permission from the local authority, who will require you to provide evidence that establishing separate foul water drainage and rainwater drains is impossible on your premises. You must be able to demonstrate the following:
<ul style="box-sizing: border-box; margin: 2.85rem 0px; padding: 0px; list-style-position: inside; color: #3c3c3c; font-family: Arial, Helvetica, 'Helvetica Neue', Verdana, sans-serif; font-size: 18px;">
<li style="box-sizing: border-box; margin: 1.425rem 0px; padding: 0px;" aria-level="1">That there are no separate foul and surface water sewers in your vicinity<li style="box-sizing: border-box; margin: 1.425rem 0px; padding: 0px;" aria-level="1">That your property is unsuitable for setting up a soakaway system as an alternative method of surface water drainage
<li style="box-sizing: border-box; margin: 1.425rem 0px; padding: 0px;" aria-level="1">That the foul water and rainwater drainage flow is kept separate up to the point where it leaves the boundary of your property, to ensure that your connection can be upgraded in future
In order to do this, the water company will ask you to provide the following, to conform with building regulations:
<ul style="box-sizing: border-box; margin: 2.85rem 0px; padding: 0px; list-style-position: inside; color: #3c3c3c; font-family: Arial, Helvetica, 'Helvetica Neue', Verdana, sans-serif; font-size: 18px;">
<li style="box-sizing: border-box; margin: 1.425rem 0px; padding: 0px;" aria-level="1">An extract from the relevant ground investigation report results<li style="box-sizing: border-box; margin: 1.425rem 0px; padding: 0px;" aria-level="1">The results of a percolation test
<li style="box-sizing: border-box; margin: 1.425rem 0px; padding: 0px;" aria-level="1">An email or letter from Building Control confirming the situation
The exacting nature of the rules surrounding surface water drainage and foul water drainage should serve to underline just how important they are to the health of the environment and the public sewer network, as well as the importance of keeping stormwater drains and sewage treatment plants properly maintained.
Can Surface Water Drain to a Foul Sewer? - Lanes Group (lanesfordrains.co.uk)
digging a soakaway seems much easier.....
As above, membrane + gravel, and if possible plant some trees/shrubs away from the house to suck the moisture out of the soil.
We've got clay soil and a gravel driveway, in torrential rain pools form but they still soak away in 30-60min once it stops.
When we had our patio done we sloped half of it into a new 'raised' bed (the patio is stepped) so only half of it points towards the existing surface drain. No idea where they connect to but I wanted to soak as much as possible both for altruistic reasons and selfishly because the grape vine is thriving on the nice warm patio with all that water draining to it 😂.
no idea what is going on with the formating....
Im on clay. That would have been useful to know…..
Some friends are on Clay, and it won't drain anything, so when they had an extension all the gutters etc drain into the main drains as a soak away would just fill and never empty. Think they just dug a test pit, filled it with water and showed Building Control, who said 'Yep, Clay!'.
Did they not just get told to build a bigger soakaway? Anyways my french drain has been working fine, and it wasn;t actually that much work. Plugging into existing drains would have been a bunch easier though!
Soakaways won't work in cohesive soils no matter how big they are.
Small patio draining into the domestic foul will be fine - thats what I did.
Now, if you were talking about discharging foul into the surface water....well you just wouldn't would you !?
well you just wouldn’t would you !?
Unless you were a water company of course.
discharging foul into the surface water
Don't lots of people connecting their "small patio draining into the domestic foul" make it more likely the above occurs?
Our house is built into a slight terrace, about a meter front to back of the house. The patio is slightly lower than the garden as well, about 10cm, so the whole house is effectively sitting in it's own lake when we have very heavy rain. the previous patio/front path was open gravel around the edge, but on investigation the water didn't run anywhere, so was getting under the house (poor foundations, another story!).
I've managed to pick up the road drain outside our house on the high side, so i can get some surface water in to that from the front, but the patio to the rear i need to put a soakaway in to get the water away from the house. We are on a mixed soil, not heavy clay but pretty poor on the percolation test pits.
Anyway, i vaguely remember reading somewhere that any soakaway pits or outlets for French drains should be a recommended minimum of 5mtrs away from the house if at all possible, but more importantly not closer than 5mtrs from any neighbouring properties.
Soakaways won’t work in cohesive soils no matter how big they are.
True but you can and should be building a rain garden or a treepit instead.
The biggest issue with rainwater runoff is the speed in which it enters the system. There are two ways you can feasibly address this at home.
1. Rain garden tree pit or bio retention arrangements. Providing storage and attenuating the run off ( and you get a nice healthy plants bed aswell)
2. Rain butts. Again, useful to water the garden but when it's going to rain hard you draw it down to create storage capacity and then let it refill and you store that. Control can be automatic or manual... Manual works if you put in the effort.
You should not be stuck any direct run off into a drain, whether it's permitted or not ( and England is lagging way behind the rest of the UK in this regard).
This mainly applies to new construction but honestly we are getting to the stage now where the more people who take quite simple measures can really ease the pressure on systems that simply cannot function with the additional pressures we are putting on them via climate change and ever increasing impermeability of our built environments.
The guidance is pretty good, and very readable on the matter, worth a look. It doesn't cover just drainage, the main point is water should stay where it lands as a resource for aslong as possible.
https://www.susdrain.org/resources/SuDS_Manual.html
I will field any questions on the matter if I can.
As for retaining wall... Gabions or my personal favourite. Flex MSE can both look lovely and work well, both very within DIY able skills aswell.