Drainage Headache in Small Garden Project

[zzzkr]

I'm currently in the process of laying porcelain paving across our small garden, but I've hit a wall when it comes to drainage. From the start, I was set on having the paving drain water towards the bottom of the garden — it's about 8m long — rather than towards the house. I just don't like the idea of water flowing back to the house, having read far too many horror stories about damp.

Using a 1:80 fall, this results in a 10cm drop over the 8m distance to the end of the garden. The main surface water pipe is right next to the house and quite shallow — the top of the pipe is about 15cm below the planned level of the porcelain paving. The problem is I can’t create a slope from the end of the garden back towards the house. That, and the fact the pipe would end up very shallow, essentially running through the sub-base.

I've already done some digging and removed soil to create the slope, and the next step is to add the sub-base. Unfortunately, I did this without first checking the depth of the surface water pipe.

Now I'm in a bit of a pickle and can't see a clear way out. Some possible options:

• Reverse the fall and drain water towards the house (which means moving 7 tonnes of soil back into the garden).
• Install a soakaway — but the garden is small, and I don’t really have a spot that's 5m away from any foundations. It’s either the house, the conservatory, a solid block shed, or a retaining wall.

Could I raise the floor level a bit more near the house — say, 1.5 bricks below DPC instead of 2? Could I get away with a lower slope on the surface water pipe running under the porcelain paving? Would it be acceptable for the pipe to run shallow, through the sub-base, considering it will be topped with a cement bed and porcelain?

 

[jj4091]

Getting the fall of th tiles to run downward away from the house will always be the best option.But do you have an inspection hatch or access to the drains at the rear of the property that you could connect an Aco drain to, if you could run some across the rear of the house. Some pics showing the path of the surface water drains would help.I don't know what, if anything, regulations say about the depth of drains but as long as you have some fall I don't think it would be a major issue.

 

[Koolpc]

Pics of garden would help...

 

[zzzkr]

Here are some photos for you. I've also made a drawing to try and make sense of it, not sure it's entirely accurate, though. Hopefully, it helps clarify the situation a bit.

The pencil line in the second photo marks the height where the top of the paving will start near the house. Ideally, this should be 10cm lower to allow for the slope.

 

[jj4091]

Personally I would not worry about the depth of the current surface water pipe, I presume it flows into that inspection chamber near to the white peg. And I would keep the current fall as it is, away from the house, and instal an Aco drain across the gardeen in that area so that water runs down to it and connect it into the inspection chamber. On the other side of the drain I would create a fall in the opposite direction so that basically you are creating a valley with the drain running along the botton of it. The only down side might be that it may need to be cleaned out often depending on how much fall you get on it as it flows to the inspection chamber.

 

[zzzkr]

Do you mean having the ACO drain at the bottom of the garden and then running it back along the left side? The inspection chamber you mentioned is actually for the main sewer pipe from the house, I don’t have one for surface water. I’m thinking of adding a roddable gully or something similar near the house.

There are gutter downpipes at both the conservatory and the shed, and I’m planning to connect those into the ACO drain.

Originally, I was thinking of running the surface water pipe through the middle of the garden, but having ACO drains around the edges would be much better. I could start the ACO drain from the right-hand side where the conservatory downpipe is and run it all the way across the garden.

 

[jj4091]

Yes like that but just a straight line across where the white peg is with a fall into it from both sides and no need for dog leg.