Groundwork & Foundations Question

French drain vs. pea shingle


I was looking for a builder to basically lower the ground level at the back of the house as it is too high and above the existing damp proof course. It is probably contributing to damp problems but not the only reason.

The surveyor and other damp company suggested lowering the ground level around the edge of the house and back filling with pea shingle. I thought this was a french drain.

However a builder has suggested doing a below surface 4" connection to existing drainage outlets, which sounds a different things and like a lot more work. Also as it goes around the edge of the house on 2 sides, I can't see how it could be angled to drain into the one existing drain, and go around a corner?

Any ideas on what's better/more necessary - the pea shingle approach or this type of connection?

Many thanks

3 Answers

Best Answer

The pea shingle will not work in most grounds on its own it will just hold the water, you need somewhere for the water to go, we normally connect a perforated pipe to a exisitng storm drain or dig a soakaway if the ground is suitable, you do not need a great fall in the pipe 25mm over 10m is fine, flexable perforated pipe will easily go around corners ect, it is a bit more work that just pea shingle but this will work, and you will not have to do it again ! cheaper in the long run.



Answered 16th Feb 2013

Base Construction 2004 Limited

Member since 21 Jan 2013

Connecting to drains is better due to the fact that if you put pea gravel down it will help drain but only if the water has some wear to go if a foot down is solid clay then the water will be trapped

Answered 16th Feb 2013

srr property maintenance

Member since 3 Nov 2011

The pea shingle is the french drain. What your other builder is suggesting with the underground pipe sounds like a land drain. This is a perforated pipe which is laid underground and is designed to catch the ground water and divert it down the pipe which can then be connected into an existing drain. It's flexible so going around corners wouldn't be an issue. However to make sure that it works correctly it must be wrapped in a membrane which allows water through but not the soil particles as over time this would block the drain up. It is then surrounded with shingle and then backfilled over.
Benefit of this way you are actually catching the water and discharging it away.
Hope this helps.

Answered 16th Feb 2013

CGM Building Services

Member since 1 Feb 2012

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