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Waterproofing an ICF Basement Wall


Triassic

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I’m just about to start construction of my basement, it’s basically an open fronted box set into a hillside.

 

After much peckering and the removal of 1500 tonnes of limestone we have a flat space for the insulated slab, onto which will sit ICF (insulated concrete form) basement walls. As three different people have been involved in the basement design, architect, Structural Engineer and ICF supplier, I have three different waterproofing membranes (three different manufacturers) mentioned on the various drawings. Can anyone recommend an easy to use membrane suitable for sticking to the polystyrene ICF? In addition, I also need a protection sheet to protect the wall insulation and the waterproof membrane, Corex has been mentioned. Is it easy to fix?

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You will need to make sure that your Building Control and Warranty providers are happy with whatever system you choose.  Type C (drained cavity) systems are considered lowest risk and you have the benefit of being able to direct any water by gravity, so do not need pumps, maintenance etc.

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No warranty needed, I just need to keep BC happy. The designed method is external waterproof membrane, hence the question about which membrane is best for ICF.

 

just talked to one supplier, they no longer approve their membranes for use with ICF.

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      https://www.riw.co.uk/products/sheet-applied-systems/sheetseal-226     

Supplied by SIG  and  Bituthene  primer for the edge of concrete slab, no primer on icf as  only get one chance sticking sheet seal vertically.

For protection board bitumen based RIW  protection board joints joined with sheetseal tape.

 These were the only products that my BCO would allow as they all had  correct BS approval.

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As you know we didn't use external membranes and had Sika warrantied waterproof concrete alone approved. 

 

Reading this suggests that peel & stick membrane is the best approach for ICF  

 

https://poly-wall.com/waterproofing-system/home-stretch-icf-waterproofing-membrane/

 

Have you done a full cost comparison (materials & application cost) vs waterproof concrete? I'm guessing that if you're only using a single system and have a good land drain then water ingress is not likely a major issue for you.

 

I also used corex (or an equivalent) to protect the external EPS on my basement - very easy to fit. I tried staples initially to hold it but that was a waste of time so I switched to using leftover nails on site to secure the sheets (EPS was 200mm thick). The backfill holds it in place  - it really just stops big stones puncturing the EPS but really only gives limited protection as it's not that strong really.

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Unfortunately Sika no longer provide a warranty waterproofing system for ICF having stopped in December. According to the technical person this was because she they were unable to check the integrity of the poured concrete, hence my interest in membranes.

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13 minutes ago, Alexphd1 said:

I am planning on using the sticky membrane supplied from the ICF manufacturer. 

What about using a few sheets of eps for protection just dot and dab with adhesive using the back full to keep it on place?

 

The ICF manufacturer have recommended Grace Pre-prufe tanking membrane. Being careful with the money I’d like to get three manufacturers prices as I need to get value for money.

 

It’s a great idea to use a layer of EPS as protection for the ICF, particularly as I’m the one doing the backfilling, so I can be careful not to damage it.

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8 hours ago, Triassic said:

No warranty needed, I just need to keep BC happy.

 You need to also keep yourself happy, by feeling reassured by your chosen method...so ask yourself why those suppliers no longer offer warranty waterproof membranes for ice.

When I got quotes from companies that offered true warranties (as opposed to just material cost warranties), the prices were sending me a clear message that they didnt want to have to warranty an external membrane on icf underground.  Internal cavity drain was favoured on the basis of assuming the icf would leak and so deal with it internally.  The warrantied cavity drains were still hugely expensive.

This combined with H&s concern from the principle designer regarding how to safely put a man in a trench between an icf wall and a vertical excavation in order to tank it, caused me a total rethink of the construction method.  Obviously that’s down to site specifics that may not apply for you.

 

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One of the reasons we went away from traditional timber shuttering was to get away from the need for people to enter the space between the surrounding rock and the shuttering. By using ICF we hope to be able to apply the waterproofing membrane as we place each of the seven layers of ICF. This should be posible to do from the inside. 

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Yes, in the final analysis I felt that generally traditional shuttering did little to mitigate the 'man in trench' H&S aspect...the exception being where space was at its tightest and we used single sided shuttering.

I recall the 'apply as you go, ground up, from inside' theory being a part of our discussions.  It came down to how much confidence I wanted in the membrane system......I couldn't shut my eyes and live that process of installation and believe it was competently executed.

(I happily acnowledge I was totally paranoid about waterproofing basemented walls)

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9 hours ago, Triassic said:

One of the reasons we went away from traditional timber shuttering was to get away from the need for people to enter the space between the surrounding rock and the shuttering. By using ICF we hope to be able to apply the waterproofing membrane as we place each of the seven layers of ICF. This should be posible to do from the inside. 

We are thinking of icf and have done a lot of research on different models

i would think trying to do this how you list above will be a thorough pita, 

all the systems I have looked at come in rolls and you would want to eliminate as many joins as possible running whole strips vertically or horizontally, the thought of joining it every lift of blocks seams like hard work. 

 

Can you not batter back the sides of your excavation so you can get in there. 

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9 minutes ago, Russell griffiths said:

Can you not batter back the sides of your excavation so you can get in there. 

 

Its solid limestone rock.

 

ive removed any loose looking stuff, so I’m happy to go in and fix the waterproofing membrane.

Edited by Triassic
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1 hour ago, Triassic said:

 

Its solid limestone rock.

 

ive removed any loose looking stuff, so I’m happy to go in and fix the waterproofing membrane.

In that case there’s no need to fit it a course at a time, 

i would think you need to be guided by your icf company. 

Who did you choose in the end we are still making our mind up. 

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You can build a blockwork skin on the house side of the ICF.  This would give you the required cavity.  You will, in any case, need to finish the inside with something.  You could do a bit like the second diagram, but with drainage under the slab instead of a sump / pump.

 

Basements-Waterproofing-Protection-Type-C.aspx?width=700&height=547

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18 minutes ago, Mr Punter said:

You can build a blockwork skin on the house side of the ICF.  This would give you the required cavity.  You will, in any case, need to finish the inside with something.  You could do a bit like the second diagram, but with drainage under the slab instead of a sump / pump.

 Is not the whole point of an ICF basement to eliminate thermal bridging and provide an insulated shell, by opting for a Type C you are introducing thermal bridges and allowing water inside to then pump out.  Surely you want to opt for a Type A (Barrier Protection) and provide drainage externally to the basement!

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My design calls for a type1 waterproofing system, hence the question about which membrane is bst for  ICF. So far the architect, the SE and the ICF supplier have each made suggestions, on doing a bit of research two out of the three aren’t suitable for ICF due to the adhesives used.

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12 minutes ago, Triassic said:

My design calls for a type1 waterproofing system

 

Do you mean Grade 1?

Picture1.png.3dd506abc7f3e1e39eb0c27f9706a05b.png

I would have thought it should be Grade 3, or at least 2.

 

If you have a Grade 1 system then you will need a Type C to deal with the seepage!

 

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2 hours ago, Triassic said:

Its solid limestone rock.

So i'd imagine your geo survey states your excavations can sit near vertical in the temporary state....meaning you only have to over-dig a metre to create space that can be made viably safe to work in.  I was on chalk and lined the vertical excavation with hessian under chicken wire which proved effective at containing the small surface crumblings and gave a (possibly faux) sense of confidence to the concrete  contractors such that the boss was happy to take the job.....his workers were more circumspect but reading between their lines I think they never feel theres enough safety in place for them and it's more common than not that they find themselves woking in compromised positions.  Its a balance of viable risk and viable economics.  Even if you plan on actually doing the work yourself, get a tanking co' to quote.....if they're saying yeah we'll get in there and do that, then you can probably consider it a viable risk for yourself to do. I had a visit from HSE shortly after we'd backfilled.  He intimated that he'd not have liked what he'd seen had he visited at an earlier stage.....that could have been properly expensive for me.

I'm not trying to divert you from the main question of what membrane technology you'd prefer....just saying you should consider its real life constructibility in your specific site.  Maybe you have the space to batter back your excavations 45 degrees and the money to muck away that extra 700 tonnes, and then backfill it later.

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34 minutes ago, le-cerveau said:

 

Do you mean Grade 1?

 

 

I meant Type A Grade 3.

 

i’d just received a phone call cancelling the delivery of the MOT type1 as I was typing my last post. Can’t multi task,

 

The rock face is solid, no need to batter back.

Edited by Triassic
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