Underground drain bedding

11 Dec 2017
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United Kingdom
Hi. I’m in the process of lifting my raised decking and replacing it with a patio. The decking was built at the same time as the house in 2007 (before I bought it in 2014)
There is a foul drain pipe running under the decking and now I can see it better I’ve noticed it doesn’t seem to be bedded properly. I believe it should be bedded and covered in pea gravel. Is this correct? Is there any reason why it wasn’t when the house was built? What’s the best thing to do with it now? Should I dig the mud/stones away and surround it with pea gravel then type 1 over the top?
I’ll attach a pic.



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Because the builders were lazy or wanted to save money. Not sure what to suggest for the best, retro digging and filling with pea shingle will be a pain
Re your patio, given how shallow that pipe is you need to think about bridging the pipe (council pavers are good)
Thanks. That’s what I thought about the builders to be honest. The decking was about 350mm above the pipe and that’s roughly how high the patio will be above it once done. I really don’t want issues down the line once the patio is done so I might have to replace the mud with pea shingle unless there’s anything else that could be done?
I'm not a groundworks expert- tend to go by the Approved Docs.
Your patio (presumably no vehicles) loading will be quite low. The idea of the pea shingle is it buffers any ground movement (so the pipes stay where they are as the ground swells, freezes, gets compressed). Belt and braces would be clear 50mm plus from the sides and underneath the pipe (the underneath you'd have to do in stages) then backfill with shingle to surround and cover the pipe, then bridge the trench with council pavers (the pavers should bear on solid ground, not the shingle and not soft infill), then do what you like above. But that might be overkill for a patio.
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Thanks for that. I didn’t know about bridging over the top so I’ll look into getting some flags.

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