Little house, little french drain?

[stevec]

Hi

I'm after some advice on my back yard, which I am sorting out at the moment.

I need to dig a french drain, as, worse luck for me, the original sandstone flags were laid sloping downhill towards the kitchen wall (laid on clinker, so I am pretty sure they are as-built). These slabs are big, so I don't think I can lift them without breaking them (or me), so they will have to stay sloping the wrong way...

I have done some initial digging to lower the soil level to below the internal floor level and slope away from the house- original outside level was only an inch or so below the internal level, so not ideal.

Plan is to lower the inspection chamber lid by a course or 2 of bricks to get the top flush with the slabs (lots of sledge hammer fun there), reinstate missing sandstone slabs towards the house, but terminate these a foot before the kitchen wall leaving exposed gravel to stop rain splash (as per the diagram below).

So the question is: will a basic french drain sufffice (I would guess this would be the usual big geotextile 'sausage' of 20mm gravel across the 2 metre or so width of the yard), or should I go for the deluxe version with a perforated pipe that somehow connects into the inspection chamber (which would then be a further headache due to the lack of room and awkward position of the inspection chamber!)?

That said, there is a 'stub' availailable in the inspection chamber to which I can connect the land drain pipe, marked on the photo below.

I have a feeling I will be replacing and slightly re-aligning the underground soil, rain and kitchen waste pipes while I can as they are a bit of a bodge too.

 

[MikeG]

Have you exposed any of the old clay pipework in the ground? Hopefully, it will be surrounded by shingle/ loose stone, and if so, it is a neat little cheat to lead your new French drain into that shingle, rather than try to break into the side of your access chamber. An almighty amount of water follows pipes in the ground along the outside for this very reason, and you are draining such a small area that this would certainly do the trick. Unfortunately, if this isn't the case, then creating a ditch full of shingle at the low point is simply going to be creating a small water feature where you don't want one.

 

[Zebra]

It depends on the quantity of water. Those perforated pipes are probably great if you have the rainfall from an entire field saturating the ground. Then the water pressure on all sides of the pipe means it ends up in the pipe. However, if we are only talking about the water which falls in the area we can see in your photo, then I imagine that having that water disappear into the ground before it reaches the house would be sufficient (although I can see Mike's point too - you might end up with a small pond. What is the soil like? Is it clayey or sandy? How fast does it drain? Could you do an experiment now and tip a couple of buckets of water down on the ground, or run the hose for a bit, just to see what happens?.....) I don't think that the land drain in your excellent sketch will end up with more than a millimetre or two of water actually inside it.