I think the previous thread described why XPS was not necessary. Essentially EPS will let water in but also let it out. XPS may find it harder to let out but since water almost always finds a way in it may be problematic. Lots of people seem to use it for this application so perhaps this is all theoretics. I would hope that with a french drain we are not talking standing water but just a bit of moisture. In previous discussion people have said not to cover it at all with render. Some have tried a paving slab to ?prevent rats etc.
My intention presently is to run 200mm EPS70 directly down the walls and as deep into the founds as is safe. I will then put down landscape fabric and fill the hole with Leca. The fabric will fold over the top and be back filled with soil in which to plant some pretty flowers etc. I will probably leave a 6 inch wide Leca 'path' around the perimeter.

I intend to take the render to ground level or very slightly below. I do not intend to put anything else on the below ground EPS.

Thanks FosterTom, yes I did read with enthusiasm another thread where you argued in favour of EPS. Got it now, thanks for explaining the difference between EPS and XPS!
If you've installed it exposed without any finish, I take it you're using the silver grey stuff, not the white!? If it is breathable, then it seems counter-productive to cover it with a cement render as pmgowan suggests, at least in my case, where the wall has no dpc and needs to breathe.
Would you apply a backing coat of some sort on brickwork first to prevent there being little air gaps behind it? Or would it not matter that much? I'd prefer not to, as it's hard to do underground! And because although I want to insulate the wall, really I'm more concerned with the welfare of my very old brickwork than with gaining the last little bit of U-value!
Thanks for the leca suggestion. I read another thread where you talked about using leca as the aggregate. I'm a little concerned because the leca stones are quite small, and what I've found with the gravel that's in there now is that it doesn't drain properly, is still moist inside the french drain, and I'm still getting damp patches indoors. I was wondering whether those soakaway crates, wrapped in a geotextile, would allow a bit more air in the french drain?.... Or would it make little difference as the EPS will stop the moisture from getting to the wall?
Many thanks for your input!

Posted By: zebraI take it you're using the silver grey stuff, not the white

No, the white, but might use grey next time - no durability issue with either.

Posted By: zebraWould you apply a backing coat of some sort on brickwork first to prevent there being little air gaps behind it?

Isolated air pockets parallel with the wall (transverse to direction of heat flow) are not a problem, provided they're limited in size e.g. the size of one EPS board divided airtight from the next, to prevent extensive convection transferring heat across the face of the wall, from warmer to cooler bits. What is essential is no air voids running parallel with the direction of heat flow i.e. between the board edges; conversely to make sure no fixing adhesive in those same joints. Either air or adhersive will provide a convective or conductive shortcut for the heat flow.

Posted By: zebraI'm a little concerned because the leca stones are quite small

You can buy them in 3 size grades.

The drain arrangement that I have now, which I built in the summer, has somewhere to drain to, but is not working because I'm still getting damp patches indoors. It is a perforated drain pipe 150mm below internal floor level, backfilled with gravel wrapped in geotextile, up to 400mm above internal floor level. I think the reason it's failing is that the gravel is too dense, there's no air down there, and the water can still travel sideways through the drain, which is only 250mm wide. I can't go wider, and unfortunately, can't create an open gully like yours Pugliese, although it seems a very good solution if it were possible, because it's not on my land. The back wall of the house is the boundary of the plot and I'm doing all this in the churchyard!
I was concerned that leca would have the same issues as the gravel - too dense, doesn't drain readily, still damp in the drain, damp finds its way into the wall??
To what extent would the EPS create a barrier against the ingress of dampness from the drain to the wall? I had an architect recommend a system where a bitumen layer would be applied to the brickwork first, but I'm loathe to paint my 400 year old bricks with bitumen! I could apply a polythene layer first, but it's the trade-off between waterproofness and breathability!
(The walls will be able to breathe inwardly - at the moment it's bare brick but will be a lime plaster finish, one day!)

Posted By: zebraSo what are you going to finish it with, as the white stuff can't look good externally!

We were talking about finish below ground level - I said none - but of course render or other finish where visible above ground.

EPS EWI is customarily finished with patent (acrylic usually) render, part of the EWI system, which is (or can be) breatheable.

Correct countryman about the geotex but if you are clever then you leave access points so you can flush the pipe on a regular basis.

Posted By: zebraThe drain arrangement that I have now, which I built in the summer, has somewhere to drain to, but is not working because I'm still getting damp patches indoors.

In heavy rain the gravel might become saturated before it drains away.

paraphrase <<French drains don't work.>> !!???
Now you have me worried as I'm committed to this one ( in photo ) using 20mm shingle, terram 1B1 ( 2-layers with a net matrix in the middle ) and 80mm perforated pipe . . . . designed to reduce the water table around the walls and keep the clay off the brickwork below the dpc.

Posted By: countrymanGeotex membrane is only good for one thing and that is stopping roots blocking the drain/pipe/whatever.

They do stop the fine soil blocking up the rain. They do it very well. So well, in fact, that the fine soil blocks up the geotex membrane

Posted By: JontiCorrect countryman about the geotex but if you are clever then you leave access points so you can flush the pipe on a regular basis.

This is a shock! So forget the geotex (gladly) but commit client to flushing out? But on its way to being flushed out, won't fines eventually clog up the sharp stone in the trench? Is there no solution, other than excavating and renewing the sharp stone every decade?

It's the digging out that's daunting! Still, we now have permission to simply leave out the geotex?!

Because

Posted By: countrymanYou are wasting your time adding a geotex membrane if you are thinking that your French drain is going to be hunky dory and keep working for a long time. Geotex membrane is only good for one thing and that is stopping roots blocking the drain/pipe/whatever.

They do stop the fine soil blocking up the rain. They do it very well. So well, in fact, that the fine soil blocks up the geotex membrane in a matter of months and so you are back to square one as the water cannot now get at your French drain.

So, get the digger greased!

If land Drain is so bad then how come old septic tanks with little more than an out fall into maybe 1/2m2 of broken brick, they seem to plug on for years. This I suspect is due to the water waste finding its own route through tiny holes in the soil structure. We have a route for water of 80mm diameter with the land drain. I don't think we will have a problem

What methods have you guys used to fix the EPS to the wall, (mine would be rubble stone)
and if I want to lime render the EPS do I need to have fixed some mesh in place, if so what type please?

Thanks