ICF Queries/concerns from Architect/Structural Engineer

[Adam2]

OK - so I posted this under a more general topic in the heating as part of a discussion on heating/ventilation and it was suggested that I re-post the points below here for discussion :-) 

 

We're at the planning approval stage on a house re-build. It's a bit of a complex site as runs down a hill. We're re-building in pretty much the same foot print of the current house - will be guided by a SE on appropriate options re foundations/retaining walls. Will add a couple of pics to a blog in a minute.

 

Reason for this post is to share some concerns raised by the SE that our architect has contacted re using ICFs. We're happy with our architect's design work though they have limited and not very positive experience with ICF from a project some years back. I don't know what real experience the SE has with ICF - which is what I had expected the architect to be finding out. I'm talking to other SEs myself to select one to work with on structure/detailed design/building reg.

 

Concerns they raised are below, appreciate your thoughts on these. 

Adam

 

1. The main concern on this project would be the waterproofing system.  With an ICF product, how would the product be guaranteed?  Typically the crack widths would need to be no bigger than 0.2mm.  These are controlled by the amount of reinforcement and the cover to the reinforcement.  With ICF both the amount of rebar that can be incorporated with the wall and the cover tend to be fixed or difficult to change.  How would the walls be checked to make sure that 0.2mm crack widths have not been exceeded.
2. The house has a lot of large openings.  These could be difficult to prove using ICF due to the fixed width of wall.  There are only so many bars that can be placed within a certain width of wall.  This could mean that steel beams and or columns are required, causing further issues with detailing around the interfaces between the two.
3. Care needs to be taken when installing kitchen and bathroom units as the fixings need to be taken through the polystyrene and into the concrete.  The insulation could compress causing the units to be un level and out of alignment.
4. Detailing of structural elements can prove difficult trying to comply with the detailing code. 
5. The system is advertised as low level skill required to construct the system but in reality tying of rebar and pouring of concrete are skilled jobs and need skilled labour to carry them out.

[the_r_sole]

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Edited September 26, 2019 by the_r_sole

[ToughButterCup]

2 hours ago, Adam2 said:

[...]

1. The main concern on this project would be the waterproofing system. [...]
2. The house has a lot of large openings.[...]
3. Care needs to be taken when installing kitchen and bathroom units [...]
4. Detailing of structural elements[...]
5. The system is advertised as low level skill required to construct the system [...]

 

I offer the following; my experience is very limited indeed, it extends merely to Durisol. 

 

Our house has been 'up' after a fashion for a year now. The raw blocks - before they were parged - never leaked. The blocks are hydrophobic. When they get wet, they dry out pretty quickly. After parging (sand, cement, lime) they are bone dry (to the extent I can tell). Cloeber Permo Forte NG and cedar cladding to be added later this year.

 

Our window openings are massive. No issues have yet come to light in the terms you outline above.

 

Care in fitting  kitchen and bathroom units is a vanishing commodity in any build if my recent conversations are to be believed.  The argument presented above hints that simple shelving heavily loaded might also be a problem with ICF. Really? I mean really?

 

Our ICF supplier provides a simple (very poorly worded and structured) technical support manual.  Why should manufacturers know how to produce excellent written instructions?

 

Low level skills are fine, provided they are accompanied with personal integrity, attention to detail, persistence and the determination to do an excellent job. My skill level was nugatory. It isn't now. You can leave a five mm gap in Durisol and the concrete will seal it. Looks bloody awful, but......

 

Rebar  frameworks - I know less than nowt: our team came from Latvia. Concrete pumping companies seem to have at least some experience of working with ICFs. Locally, we had three - no four - pump sessions, each with a  different operator, each did as he was asked (including the Italian pump operator  "Eh magnifico signore, magnifico")

 

The commentary you were sent (above) seems to me to have been written by an SE that has little or no experience of the ICF under consideration. 

We asked our excellent SE (Tanners from Eire) to do  bit of work in relation to Durisol. When we submitted that work for review by an SE who works for Durisol, 50% of the rebar was removed, saving more than three quarters of the total SE bill.

 

Choose an SE who knows the product and can demonstrate a successful track record with it. Do your Due Diligence.

Edited October 17, 2018 by recoveringacademic
spelling error(s)

[Tim Alsop]

3 hours ago, Adam2 said:

1. Care needs to be taken when installing kitchen and bathroom units as the fixings need to be taken through the polystyrene and into the concrete.  The insulation could compress causing the units to be un level and out of alignment.

This is one of the reasons why I decided to use Velox instead of an ICF that uses polystyrene. The Velox product has a hydrophobic acoustic wood/cement composite board that is 35mm thick on inside walls (and also on outside for fixing cladding) and you can fix to this anywhere and no need to worry about fixing points. The Durisol product is similar since it also doesn't use polystyrene, but I preferred Velox due to having continuous concrete layer inside instead of honeycomb like would be the case with Durisol. They are both very good products though.

[Triassic]

Sounds like the architect doesn’t want you to use ICF!

[Tim Alsop]

37 minutes ago, Triassic said:

Sounds like the architect doesn’t want you to use ICF!

I found that my architect had no experience of using ICF and was asking similar questions, but when i gave him answers he was happy with the way forward. I took him to visit my chosen ICF vendor so he could see the product and understand it better.

[Mr Punter]

I think the concerns are valid.  Unlike traditional formwork, with ICF you are not able to inspect the concrete as the shuttering is never removed.  Why not get this priced in steel with concrete for the basement?  What is the preference of the SE?

 

I have done a basement in ICF and we used a type C waterproofing system (internal drained cavity membrane) with a pump.  No complaints from the owners.

[ToughButterCup]

19 minutes ago, Mr Punter said:

[...]

with ICF you are not able to inspect the concrete as the shuttering is never removed. 

[...]

 

I think I know what you mean: but in the case of Durisol - provided the contractor acts with due caution - there is no need for shuttering during the pouring process.

In the sense that the material containing the concrete (compacted , treated wood chip) is never removed, you are correct.

 

Normally a customer would never see the concrete. Normally that is...?

[Triassic]

I’ve just completed an ICF basement and we stripped the insulation from a 150mm wide area, top to bottom, in two places to inspect the poured concrete. Absolutely perfect in both cases. 

[Jeremy Harris]

1 minute ago, recoveringacademic said:

Normally a customer would never see the concrete. Normally that is...?

 

And therein lies the concern.  This is a semi-basement construction, where some of the subterranean walls need to be watertight retaining walls, I believe.  As such I share the concern about ensuring that the poured (presumably waterproof) concrete is without even the slightest flaw that might let water through.  EPS is fine when subjected to continuous damp, but are some of the other ICF materials?

 

 

[mvincentd]

If your on the same footprint do you mean the excavations already exist as required.  Is any of the existing building acting as retaining these excavations.  If so can any of this viably remain. If it is ALL to be removed what then protects the excavations.

 

It's very typical of Poole given land prices, to utilise every last inch of plot and so ‘real life buildability’ becomes a question to consider with your Principle Designer amongst others.  You could find a logistical consideration around how a builder physically achieves a task, significantly steers what tasks you should present the builder with....so you might get a great price for icf, followed by an insistance on sacrificial sheet piling to make it safe to then waterproof it externally, followed by a monumental quote to have a waterproofing system that comes with a guarantee worth its paper.  Be wary of the headline price of icf.

 

I love the concept of icf, researched it a lot, went on the Nudura course, pushed my SE at it and had my builds working drawings done based on using it, got quotes for it and for waterproofing it.  I’m definitely not against icf....but the project has to be right for it.  Walking away from it crushed my aspirations to literally self build my house, and drastically reset my budget before I’d even dug a hole.  Unfortunately most SE’s, architects etc are still quite inexperienced with it so aren’t best placed to instantly know if your project is right for it...they really need to engage with YOUR situation rather than just shoot back some generalist reticence about icf.  By the same token, and with the greatest of respect to those who have used icf above ground and express general enthusiasm for it, Its useful info but I don’t believe it gets you any further forward...below ground retaining walls are a very different kettle of fish.

 

Are you going to actually build this yourself.....do you actually need a lightweight, low skill product to get to the end result of a poured in situ concrete wall with insulation either side.  Icf is not THE way to get a poured concrete wall....it’s A way.  I used built in situ shuttered concrete, carried out by a specialist contractor, which is slow, wasteful and soul destroying, and I wouldn’t as a generalisation recommend it, but I’ve yet to be persuaded it wasn’t the best option for my project.

 

I honestly hope you can conclude that icf is good for you (but I doubt it) as I love the concept....just don’t let loving the concept lead to a blinkered determination to use it.  My build is 25 mins from yours...you are welcome to come look, just pm me....I think I can show you stuff that’s pretty relevant to your project.

[Ian]

7 hours ago, Adam2 said:

 

 

1. The main concern on this project would be the waterproofing system.  With an ICF product, how would the product be guaranteed?  Typically the crack widths would need to be no bigger than 0.2mm.  These are controlled by the amount of reinforcement and the cover to the reinforcement.  With ICF both the amount of rebar that can be incorporated with the wall and the cover tend to be fixed or difficult to change.  How would the walls be checked to make sure that 0.2mm crack widths have not been exceeded.

I'm involved with a largish commercial project which is on site at the moment. The basement was constructed using Amvic ICF using designs by a structural engineer recommended by Amvic (an engineer who is used to their system). Waterproofing of the Amvic was by Sika who designed it (it's a separate membrane system) then regularly inspected the work on site. They are providing a 20 year waterproofing guarantee.

Edited October 17, 2018 by Ian

[ToughButterCup]

1 hour ago, mvincentd said:

[...]

...below ground retaining walls are a very different kettle of fish.

[...]

 

Durisol is not appropriate for that kind of job....

[mvincentd]

37 minutes ago, Ian said:

Waterproofing of the Amvic was by Sika

@Ian if you're in conversation with the Sika inspectors it would be interesting to ask them if Sika have now "withdrawn from waterproofing icf below ground as a result of getting too many problems associated with it."  These are the precise words my Sika inspector said to me last week.

[Adam2]

So many helpful and informative responses - thanks to you all. I'll add some more info here.

 

1 hour ago, Triassic said:

I’ve just completed an ICF basement and we stripped the insulation from a 150mm wide area, top to bottom, in two places to inspect the poured concrete. Absolutely perfect in both cases. 

That's an interesting idea and we could simply re EPS it - if needed considering the ground is on the other side so probably limited value in that.

 

We are at the top of a hill and have free draining non-clay soil with a sand mix - a neighbour (not ICF) has built a place which is much larger so will also discuss with him the technique used for retaining walls.

 

1 hour ago, mvincentd said:

If your on the same footprint do you mean the excavations already exist as required.  Is any of the existing building acting as retaining these excavations.  If so can any of this viably remain. If it is ALL to be removed what then protects the excavations.

 

We will probably need some investigations pre-demolition to determine the extent to which retaining walls and foundations can/should be left in-situ to prevent earth movement. It may be that new retaining walls are built outside of the existing - a mad thought - if done with ICF possibly they could have a membrane attached and pushed back into position, as i say just a thought and will leave that to the SE. Talking of which I have an SE I am considering with significant ICF experience + some stepped builds so if engaged should add a lot of valuable experience here.

 

1 hour ago, mvincentd said:

It's very typical of Poole given land prices, to utilise every last inch of plot and so ‘real life buildability’ becomes a question to consider with your Principle Designer amongst others.  You could find a logistical consideration around how a builder physically achieves a task, significantly steers what tasks you should present the builder with....so you might get a great price for icf, followed by an insistance on sacrificial sheet piling to make it safe to then waterproof it externally, followed by a monumental quote to have a waterproofing system that comes with a guarantee worth its paper.  Be wary of the headline price of icf.

 

 

The  existing house from the 30s and the neighbouring house are fairly tight to each other - also partly a consequence of being at the end of a dead end road. Good point re costs and I am in the process of talking with builders and SEs to get a handle on how we go about this and set a budget before we get too far into this.

 

1 hour ago, mvincentd said:

Are you going to actually build this yourself.....do you actually need a lightweight, low skill product to get to the end result of a poured in situ concrete wall with insulation either side.  

No - will use a builder - if we use ICF (still the plan :-) ) then a builder with demonstrable ICF experience and as you suggest, possibly combining this with other strategies if required.

 

2 hours ago, mvincentd said:

 My build is 25 mins from yours...you are welcome to come look, just pm me..

Many thanks for the kind offer. We will take you up on that - we also have a Nudura build near us and saw the project (3rd floor concrete just in) which was very helpful though a much simpler site.

 

1 hour ago, Ian said:

I'm involved with a largish commercial project which is on site at the moment. The basement was constructed using Amvic ICF using designs by a structural engineer recommended by Amvic (an engineer who is used to their system). Waterproofing of the Amvic was by Sika who designed it (it's a separate membrane system) then regularly inspected the work on site. They are providing a 20 year waterproofing guarantee.

OK thanks for this, I will take a look at Sika, Amvic are one of the suppliers under consideration.

 

 

 

[Triassic]

6 minutes ago, Adam2 said:

We are at the top of a hill and have free draining non-clay soil with a sand mix - a neighbour (not ICF) has built a place which is much larger so will also discuss with him the technique used for retaining walls.

 

We also built into a hillside, if designed correctly the ICF and basement slab become the retaining element for the ground behind.

[Tim Alsop]

1 hour ago, recoveringacademic said:

 

Durisol is not appropriate for that kind of job....

Why is Durisol not appropriate ?

[Jeremy Harris]

8 minutes ago, Tim Alsop said:

Why is Durisol not appropriate ?

 

It's wood fibre based, so my guess is that it won't tolerate being in contact with damp all the time in the subterranean areas, such as the retaining walls.

[Tim Alsop]

17 minutes ago, JSHarris said:

 

It's wood fibre based, so my guess is that it won't tolerate being in contact with damp all the time in the subterranean areas, such as the retaining walls.

On  https://www.durisoluk.com/faqs/ you will see that it says it is approved for underground use, can be used for basements and also swimming pools. 

The same applies to Velox which is also using a wood/cement board that is waterproof and fire proof. This product is also suitable for underground, basements etc.

Obviously with any ICF product it is sensible to apply additional waterproofing since you cannot just rely on waterproof concrete in the ICF.

With Durisol the concrete layer is not continuous since the Durisol bricks have wooden tie bars between inner and outer walls. With Durisol the concrete is continuous. This is one of the reasons why I chose Velox instead of Durisol. I am planning to build a basement with it and I know it is used a lot for basement walls.

[Jeremy Harris]

On 17/10/2018 at 18:40, Tim Alsop said:

On  https://www.durisoluk.com/faqs/ you will see that it says it is approved for underground use, can be used for basements and also swimming pools. 

The same applies to Velox which is also using a wood/cement board that is waterproof and fire proof. This product is also suitable for underground, basements etc.

Obviously with any ICF product it is sensible to apply additional waterproofing since you cannot just rely on waterproof concrete in the ICF.

With Durisol the concrete layer is not continuous since the Durisol bricks have wooden tie bars between inner and outer walls. With Durisol the concrete is continuous. This is one of the reasons why I chose Velox instead of Durisol. I am planning to build a basement with it and I know it is used a lot for basement walls.

 

 

Looking at the BBA certificate, Durisol is only classed as moisture resistant when an approved external waterproofing coating is applied.

 

EPS based ICF systems won't have this limitation, as EPS is approved for use when buried underground (our foundation rests on 300mm of EPS).

 

I'd be wary of trying to use any product outside its BBA certificate limitations, because of possible problems down the line, getting building control to sign off on something that's outwith the BBA (or equivalent) approval parameters and because of possible insurance implications.  As an example, our house frame was built under the Irish approval system, which is recognised as being equivalent to BBA, but I still had to provide building control with evidence to show this.

[Alexphd1]

As mentioned above it's very hard for a individual (larger sites maybe different) to get a guarantee (silka etc) on the concrete on any ICF basement simply due to not being able to visual check the concrete after being poured. A grand design episode jumps to mind with a ICF basement  that leaked like a sive but that particular manufacture does not allow to vibrate the concrete.....

 

You could try a single sided insulated Icf designed originally for lift shafts that after the pour you remove timber from the inside and the concrete is seen. I am considering building next house entirely this way and using the extra timber sheeting for sarking the roof. All insulation on the outside sitting on the upstands of the insulated raft.

 

Since you are on hill with a 3 sided basement you start with good drainage, it's half the battle.

There are 3 options to waterproof a basement 1. External tanking. 2. Waterproof the concrete. 3. Internal drainage and sump. You can choose all 3 if you wanted, you also choose if you want to pay £££ for a insured guarantee. 

 

 

 

 

 

Edited October 17, 2018 by Alexphd1

[ToughButterCup]

37 minutes ago, JSHarris said:

Looking at the BBA certificate, Durisol is only classed as moisture resistant when an approved external waterproofing coating is applied.

 

1 hour ago, Tim Alsop said:

Why is Durisol not appropriate ?

 

In Durisol, the concrete forms a lattice, not a solid layer. There might well be a  few 'holes' in our concrete - if only because during the pour the slump varied a little. A thicker  pour increases the likelihood of an air pocket.  Scotch Broth is said to be the ideal slump. Looks disconcerting ....

[Alexphd1]

Bigger the slump more chance of a burst!! 

[Alexphd1]

@Adam2 just rereading your initial post and you have asked a few questions which have seem to be missed out above . Remember ICF is just shuttered concrete but you leave the shuttering up as insulation when finished, rest of Europe is way ahead of UK in using concrete in domestic builds.  

 

1. Guarantee, been mentioned above.

 

2.icf works well with large open spans as it's easy to integrate steel I beams with. We have poured 5m (150mm x500mm concrete core) openings with ICF and extra rebar. Possibly pour larger openings but a good SE can advise on this. Also icf can come with a range of concrete core widths from 100mm to 300mm pretty standard and larger than 300mm but starts to get slightly complicated.  US military has used of the shelf ICF for bunkers....

 

3. Within reason I don't see heavy hung items compressing on ICF being a issue. 

 

4. Not sure on this. Detailing been pretty straight forward for us apart from external join from raft to ICF but this could have been very easy if we planned better.

 

5. Agree 100%. Anybody can build a ICF wall but rebar takes a bit more and pouring concrete is tricky. Anybody thinking about diy icf, visit as many icf builds as possible esp on pour day, far better than any classroom icf day training but do this as well!

[willbish]

52 minutes ago, Alexphd1 said:

Detailing been pretty straight forward for us apart from external join from raft to ICF but this could have been very easy if we planned better. 

 

What detail did you go for here in the end @Alexphd1?