Housing - New Build: How good is water proof concrete?

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- CommentAuthorTriassic
- CommentTimeSep 4th 2014
We are considering using ICF to construct the walls of our basement. It has been suggested we use water proof concrete, but is it any good? Would I need an external membrane as well and would this stick to EPS?
- CommentAuthorShevek
- CommentTimeSep 4th 2014 edited
I wouldn't rely on waterproof concrete. It only takes one link in the chain to go wrong for it to turn into a disaster, whether that link is bad detailing, bad oversight, bad workmanship, etc.

Having had some experience with basements there is one method we nearly always go to at work now and that's a drain cavity membrane. Basically you assume that the basement will eventually leak in some way at some time. You do this by wrapping the inside with a kind of egg crate like membrane that allows any seepage to drain away, either by gravity on a sloping site or by pump.

The systems we've used are Triton and Delta:
http://www.tritonsystems.co.uk/pdf/Cavity_Drain_Systems_Brochure.pdf
http://www.deltamembranes.com/products/delta-drain-2/

We generally use Triton and we use the membrane that can be dot and dabbed (or plastered) directly, internally insulating with insulated plasterboard.

However I'm not sure a drain cavity system would work with ICF. Preferably you'd want to keep it dry so you'd want your membrane on the outside. Be worth having a chat to Triton and an ICF supplier.
- CommentAuthortony
- CommentTimeSep 4th 2014
No hope of it not leaking with ICF.

Put in a drain right round and lead it away to below slab in all cases, do you have ground water?
- CommentAuthorChris P Bacon
- CommentTimeSep 5th 2014
No direct experience but I remember watching an episode of Grand Designs where they did a basement in ICF and they had leaks at the cold fronts in the concrete as it hadn't been poured in one lift.

That begs the question of even if you can pour in one lift what happens at the base of the ICF wall where it comes off the foundation? The exact point where you are most likely to have water sitting.

Both of the companies that Shevek has linked to show systems for externally protecting basement walls and both show details of where the drainage membrane runs down over this joint and into the french drain. Whether you use ICF or not I would suggest that you use one of these type of drainage membrane systems and make sure that when it is being installed that no short cuts are taken with the detail at the base of the wall to foundation junction.
- CommentAuthorTriassic
- CommentTimeSep 5th 2014
Posted By: tonyPut in a drain right round and lead it away to below slab in all cases, do you have ground water?
We are located in limestone country so the ground is dry, without any signs of groundwater. We will be putting a drain right round the excavation, as we're on a slope no pump required, simply lay the drain to discharge down the slope.

As we're in dry ground I had it mind to use water proof concrete plus a membrane on the outside, with the drainage below.
- CommentAuthorShevek
- CommentTimeSep 5th 2014
The problem with externally located membranes is that repair is a major undertaking.

Internal drain cavity membranes are not only easy to repair (cut out internal wall lining, patch up, put back internal wall lining) but if they do leak the location of failure is usually directly behind the visible leak.

They're especially good if you're on sloping ground and don't need to pump, basically fail safe.

There would be a few issues to solve before using an internal membrane with ICF by the sounds of things though. You'd need to protect the ICF from backfill damage and rodents for a kick off.
- CommentAuthorChris P Bacon
- CommentTimeSep 5th 2014
Posted By: ShevekThe problem with externally located membranes is that repair is a major undertaking.

Internal drain cavity membranes are not only easy to repair (cut out internal wall lining, patch up, put back internal wall lining) but if they do leak the location of failure is usually directly behind the visible leak.

They're especially good if you're on sloping ground and don't need to pump, basically fail safe.

There would be a few issues to solve before using an internal membrane with ICF by the sounds of things though. You'd need to protect the ICF from backfill damage and rodents for a kick off.
Is it really considered best practice to allow moisture to penetrate the fabric of the building rather than than stopping it at the external surface?
- CommentAuthortony
- CommentTimeSep 5th 2014
my basement has no membranes so nothing to repair! yes and water vapour can and does pass through the walls into the ground beyond which is always cooler than the house and never dare to try come back the other way.
- CommentAuthorShevek
- CommentTimeSep 5th 2014 edited
Posted By: Chris P BaconIs it really considered best practice to allow moisture to penetrate the fabric of the building rather than than stopping it at the external surface?

Yes it is; it's considered best practice to accept that it will penetrate. Obviously it depends on the risk of moisture penetration as to which method would be sufficient, whether it be Type A = tanked protection, Type B = water resistant concrete or Type C = drained cavity, but there's usually no reason not to go with Type C off the bat, especially on a sloping site where you don't need a pump.
- CommentAuthorwillie.macleod
- CommentTimeSep 6th 2014
A lot of incorrect information about ICF and leaks in some of the posts above - no reason why a waterproof ICF basement can't be built. You are much more likely to get leaks if you decide to do a full height pour in one session. More sensible to go for 1/3 or half height pours despite what your ICF supplier says. Good concrete and properly prepared surfaces (clean and scabbed etc) well vibrated will bond just fine and you take a lot of risk out of the job, not adding additional risk.

Leaky ICF basement stories come from people thinking that you can pour concrete 3m down a 6" core with lots of rebar in the way and it that it won't get hung up and give you large holes. What happens is that the stones fall to the bottom and the cement paste goes on the sides. That's one reason it wants to leak at the bottom. Expanding strips won't do much with that problem. And there is no chance you are going to be vibrating a full height pour properly on a basement if any ICF supplier has anything to do with it.
- CommentAuthortony
- CommentTimeSep 6th 2014
In other words it has a very good chance of leaking.
- CommentAuthorwillie.macleod
- CommentTimeSep 6th 2014 edited
Posted By: tonyIn other words it has a very good chance of leaking.

Yes, if you decide to go for the cheapest and nastiest ICF box shifter supplier who reassures you that you can fill a 6" core full of rebar in full story heights and that they can sell you a magic strip to put at the bottom which will stop the bottom leaking and you won't need to vibrate it at all. They will no doubt recommend some additional potion to add to the concrete mix to make it watertight. Add all these together then you have a very good chance of a leaky ICF basement.

However if you take proper precautions and stick with BS mixes for water tanks (which funnily enough are waterproof and don't tend to leak that much despite massive pressures) then you can build yourself a watertight structure without any additional expensive bits and bobs. More cement, smaller stone, clean formwork, lower lifts, scabbed concrete surfaces, proper vibration. Just need to work within the limitations of the materials.
- CommentAuthorYanntoe
- CommentTimeSep 7th 2014
ICF?
- CommentAuthorShevek
- CommentTimeSep 7th 2014 edited
http://en.wikipedia.org/wiki/Insulating_concrete_form
- CommentAuthorEd Davies
- CommentTimeSep 7th 2014 edited
https://en.wikipedia.org/wiki/Insulating_concrete_form

[Edit: snap ]
- CommentAuthorPaulJ
- CommentTimeSep 8th 2014
I do not know of a warranty provider that would accept waterproof concrete in an ICF basement with no addition protection (membrane, sump, pumps and 3rd party insurance cover).
- CommentAuthorTriassic
- CommentTimeSep 8th 2014
Posted By: willie.macleodJust need to work within the limitations of the materials
I agree!

Baring in mind I'm on limestone, with no groundwater issues, what is the problem with water proof concrete, is there such a thing, or is waterproof concrete some sort of black art? I'd assumed it was as easy as mixing an additive to your concrete prior to the pour?
- CommentAuthorwillie.macleod
- CommentTimeSep 8th 2014
Posted By: Triassic
Baring in mind I'm on limestone, with no groundwater issues, what is the problem with water proof concrete, is there such a thing, or is waterproof concrete some sort of black art? I'd assumed it was as easy as mixing an additive to your concrete prior to the pour?

You just need to get everything right first time with poured concrete - the formwork, the concrete and the placing and vibration of the concrete. Read all of Phil Sacres basement expert website if you haven't do so yet as there is a mound of practical experience there.
- CommentAuthorTriassic
- CommentTimeSep 8th 2014 edited
Posted By: willie.macleodRead all of Phil Sacres basement expert website
Done.

If one of his teams had cover this far north I might have taken them on to do the basement.
- CommentAuthorPaulJ
- CommentTimeSep 8th 2014
Phil Sacre has gone skint a few times and there is a website dedicated to his dissatisfied clients.
- CommentAuthororangemannot
- CommentTimeSep 8th 2014
Regardless of the "waterproof" concrete, any concrete will crack or attempt to crack, given a large enough surface.
The cracks will definately NOT be waterproof.
I did attempt to argue the case for simply employing an agricultural contractor type to build me a slatted tank, sans slats, then I would simply build a normal Cavity wall house within the tank, allowing the inevatible leaks to trickle down the inside of the tank wall to a drain and sump.
And the Extra cavity bridged over at ground level.
In extremis pop down to B & Q and buy a bog standard cheap 230V submersible pump, or indeed keep one ready in a box.
Why would this not work, be a helluva sight cheaper than some of the more complicated "Engineered" solutions I have seen proposed
cheers
m
- CommentAuthorTriassic
- CommentTimeSep 8th 2014
Posted By: PaulJPhil Sacre has gone skint a few times and there is a website dedicated to his dissatisfied clients.
So there is, thanks for that. I'm beginning to realise that Tony's basement is the way to go.
- CommentAuthorSteamyTea
- CommentTimeSep 8th 2014
How about making some 8 by 4 GRP sheets, putting them on the inside of the shuttering, joining them and then poor the concrete.
- CommentAuthorwillie.macleod
- CommentTimeSep 8th 2014
Posted By: PaulJPhil Sacre has gone skint a few times and there is a website dedicated to his dissatisfied clients.

He's one man who offers to supervise jobs, you provide the labour. You provide useless labour, ignore advice and it goes pear shaped then of course you are going to get upset at him. Doesn't make it his fault. Lawyers work for those with most money, not for those in the right.

What he says on the site is information that is gold dust, it is pure experience and anyone who has experience themselves building with poured concrete will recognise that. He has a section on his site for jobs gone wrong anyway, it makes for interesting reading. Speak with both sides of the parties and see what they have to say, see who knows what they are talking about.
- CommentAuthorwillie.macleod
- CommentTimeSep 8th 2014
Posted By: orangemannotRegardless of the "waterproof" concrete, any concrete will crack or attempt to crack, given a large enough surface.

ICF done properly gives the concrete the best possible cure to help avoid cracking from moisture loss and temp changes. Just how a large a surface are you thinking this basement is likely to be?

There is nothing to stop the OP adding an external or internal drainage plane and drain/pump and backfilling with clean stone making a french drain as well.

Nothing wrong with multiple layers to stop moisture. Concrete blocks do nothing. Leave a dense concrete block in water and it is absolutely soaked in no time. The same volume of waterproof concrete - well, it won't be soaked in no time.
- CommentAuthororangemannot
- CommentTimeSep 9th 2014 edited
Willie,
Having dropped out of a Civil Engineering course in the forth final year, I remember being fasinated by the potential performance of concrete, when correctly, specified, designed, mixed, placed and cured.
The only mostly absolutly"Â£$%^&* stupid labourers who prepare for the concrete and pour/place the concrete are the problem.
Hey, thats far too stiff, ye couldnay werk way that stuff, ADD WATER.
Having seen concrete on expensive Architect supervised jobs poured indescribably wet,the reinforcing mesh being tramped in from above, and being replaced inside of 12 or 15 years ( for yards vehicle bays etc)
And nobody but me bats an eye!
Aaaraagh!
Marcus
n.b.
Interesting that Paul talks about .45W/C ratio, I still remember .4 being the absolute minimum W/C ratio, for maximium strength/final strength.
But this was not practically achievable due to the requirments of workability etc.
ps
been of few changes too since the early 1980's, in addmixtures, air entrainment, added fibre etc.
- CommentAuthorShevek
- CommentTimeSep 9th 2014
Is there any reason not to fit an internal drain cavity membrane?
- CommentAuthorTriassic
- CommentTimeSep 9th 2014 edited
Posted By: ShevekIs there any reason not to fit an internal drain cavity membrane?
Because it won't be needed !

The basement is open to the garden at the front and the geology is limestone, so no water table. All we need to do is install a French drain, around the 3 sides of the buried bit of the basement,just below the foundation slab level and an external waterproof membrane and it's job done.
- CommentAuthorShevek
- CommentTimeSep 9th 2014
That's what I mean though, if you're going to put a membrane in, why not put it on the inside?
- CommentAuthorTriassic
- CommentTimeSep 9th 2014 edited
I suppose I have a choice, however considering the risk of water penetration is low, I've come to the conclusion that a membrane outside will work just fine.

If I have a problem down the line I can easily retrofit an internal membrane.

Posted By: willie.macleodYou just need to get everything right first time with poured concrete - the formwork, the concrete and the placing and vibration of the concrete.
One thing everyone agrees on, it's all down to standards of workmanship, so I'll have to make sure I don't cut any corners.

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Housing - New Build: How good is water proof concrete?