Triassic

Making my own formwork

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iSelfBuild    12
2 hours ago, JSHarris said:

 

The most impressive ones I've seen were at a place a friend worked, that made cast concrete staircases, with a highly polished finish.  They used strongly reinforced plate glass moulds, with a two-part casting process, where the finish coat was applied to the glass, allowed to partly cure, then the structural layer was cast.  The glass moulds were works of art.  The place still exists, Cornish Concrete Products, but at the time my friend worked for them most of their business was in the Middle East, so he was based semi-permanently in Dubai.

 

Ha! I'm visiting them next week. They make some fantastic products. The last time I visited them they had an incredible spiral stair case in production.

 

I work with a company in Germany who make all sorts of fantastic shuttering systems and moulds for precast. They have had a concrete pump in development for the last 10 years and it's finally starting to take off in Europe. It basically injects concrete smoothly into closed moulds (which have to be incredibly strong) from the lowest point. The finish that results is like glass.

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Bitpipe    235
1 hour ago, jamiehamy said:

The slowest part was the tying - lesson for next time is to hire or by a tool for it as it was very slow. 

 

Our concrete guys used pliers to manually twist and cut the steel wire ties but moved at an incredible pace - I guess when you do it all day long you get fast :)

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Bitpipe    235
2 hours ago, PeterW said:

Polarwall, Nudura and Beco are pretty much the only ones I've seen with decent technical credentials for basements although Beco seem to be fallout by the wayside. 

 

The others can have variable core widths to allow for structural support to be correctly calculated. 

 

We looked at these guys for the basement and potentially the house when we were considering the whole build with ICF.

 

http://thermohouse.co.uk/

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Triassic    97
3 hours ago, jamiehamy said:

Has the engineer provided the details of the reinforcements? Or just a 200mm core? 

 

He's provided the reinforcing details, mind you it looks over the top given that we are in limestone, rather than loose earth.

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Triassic    97
2 hours ago, Bitpipe said:

 

We looked at these guys for the basement and potentially the house when we were considering the whole build with ICF.

 

http://thermohouse.co.uk/

I see that with this system the concrete is vibrated, whereas others don't recommend vibration. Given that others on this thread suggested steel shutter, this plastic stuff must be strong !

Edited by Triassic

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jamiehamy    182
22 minutes ago, Triassic said:

He's provided the reinforcing details, mind you it looks over the top given that we are in limestone, rather than loose earth.

Ditto - we're built into rock with soil/stone backfill. Alan at Polarwall said they'll take worse case that water pressure builds up and it has to resist a head of water. Makes sense - building could be there for 100 years +. 

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Triassic    97
18 minutes ago, jamiehamy said:

Ditto - we're built into rock with soil/stone backfill. Alan at Polarwall said they'll take worse case that water pressure builds up and it has to resist a head of water. Makes sense - building could be there for 100 years +. 

Our Build is on a hillside, if water pressure builds behind our basement we're  all doomed! 

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mvincentd    13

I did the Nudura 1 day course and wanted to build with it.  At that time the SE prelim drawings specced 200mm thick walls with modest rebar content.

....but things escalate and I end up with wall thicknesses ranging between 225 & 350mm plus a maze of steel.

Nudura do vibrate, Polarwall seemingly not.  I struggle to understand how the icf companies determine those differing approaches, particularly where waterproof additive is involved....Sika for example will turn up unannounced to check a pour and would likely not issue their guarantee on wp concrete if it wasn't properly vibrated.

Anyway, my point is that it's another complexity to choosing icf....can the final specced design accommodate (i.e. literally fit) a poker.

If concrete needs vibrating, you don't want to not have the process achieve its purpose.

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Triassic    97
7 hours ago, mvincentd said:

Sika for example will turn up unannounced to check a pour and would likely not issue their guarantee on wp concrete if it wasn't properly vibrated.

Is there a specification for vibration? How much is too much?

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Bitpipe    235
4 hours ago, Triassic said:

Is there a specification for vibration? How much is too much?

 

No idea but this is where the expertise of the crew is key - our guys vibrated a lot, both dropping the poker into the mix and running it up and down the formwork, especially internal corners  - we had window formers for light wells and these needed extra attention to make sure the concrete flowed around them well and didn't leave any air pockets.

 

When the formwork was struck, you could see the quality of the pour - virtually no 'marshmallow/popcorn' effect anywhere on the internal or external faces.

 

For me one of the few downsides of ICF is not being able to see the resultant quality of the pour.

 

They also had two pokers on the go, both to speed things up but also for redundancy in case one failed.

 

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mvincentd    13
1 hour ago, Bitpipe said:

 

For me one of the few downsides of ICF is not being able to see the resultant quality of the pour.

Precisely this...ok out of the ground maybe but in a basement situated such that there's 1 chance only, i got scared off icf.  Gutted about it, would have loved to build with it instead of handing over such a large part of my build to a specialist...spoilt some of the dream.

Look into how you'll get a waterproof guarantee on icf basement, that's actually a guarantee worth having, without installing a cavity drain inside (my quotes for this alone were circa £25k)

 

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Triassic    97
2 hours ago, mvincentd said:

Look into how you'll get a waterproof guarantee on icf basement, that's actually a guarantee worth having, without installing a cavity drain inside (my quotes for this alone were circa £25k)

The SE has specified an external land drain 200mm below the basement slab and an external water proofing  membrane, these then drains into the drain and down the slope at the front of the semi-basement. I'm currently pricing the membrane, hopefully it'll be cheaper than £25k. Also I don't need a guarantee, IF it leaks, muggins here will have to fix it !

 

Just a thought, isn't  the ICF waterproof to some extent ?

Edited by Triassic

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mvincentd    13

As far as I understand it up until a few years ago the concrete alone might have been deemed waterproof enough......but then damp leaky basements were the norm too.

its all a risk tolerance thing really. 

If you were to need to fix ICF how would you even trace the point to fix?  Your fix could end up being a cavity drain (possibly same with most systems....blocks, rc, whatever). 

Not needing a guarantee is a big help......so long as you really don't.

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Bitpipe    235
1 hour ago, Triassic said:

The SE has specified an external land drain 200mm below the basement slab and an external water proofing  membrane, these then drains into the drain and down the slope at the front of the semi-basement. I'm currently pricing the membrane, hopefully it'll be cheaper than £25k. Also I don't need a guarantee, IF it leaks, muggins here will have to fix it !

 

Just a thought, isn't  the ICF waterproof to some extent ?

 

A block of ICF may be waterproof (ish) but it's the joins between blocks where you'd have issues.

 

Waterproofing strategy really depends on your ground conditions. if you're well above the water table then waterproof concrete alone should be enough - this is what we used (warrantied by Sika). There is an admix in the concrete and waterbar at all the pour junctions. They come and inspect a few pours or ask for photos of the preparations pre-pour (depends how much they trust your crew). The admix forms a 'self healing' defence in the concrete itself and the bar prevents leakage at the horizontal and vertical joins (plus around any penetrations such as ducts etc.

 

External membranes are only as good as the quality of the application, can be a useful belt and braces but would be wary of relying on it alone.

 

External land drain (just below slab) is always best practice - back fill with 1m wide free draining clean stone also, not muck - this should prevent any water pooling against the walls. Only makes sense if you're above the water table though as it will need to drain to a soakaway above the water table.

 

If you're 'under water' then a leaky basement (regular concrete) with internal membrane, sump and pump will keep you dry but care needs to be taken to avoid ever puncturing the membrane and maintaining the pump (power cuts etc..). 

 

We have local friends near the Thames who did the full Glatthar waterproof basement system - it uses precast insulated concrete walls with additional wp/ concrete inside and a super heavy duty membrane - fully guaranteed but quite expensive. Their basement was designed to stop it floating out of the ground (massive, toed slab) as the hydrostatic pressure was so high.

 

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Edited by Bitpipe
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najem-icf    5

I'm afraid I would have to disagree with your comment "it's the joins between blocks where you'd have issues" - almost all ICF blocks available in the UK are installed break-bond - meaning the joins are held together very comfortably.  I have installed a few photos to demonstrate this.  At most you will get water seepage but concrete pours will not cause any issues. Where you have vertical stack joints (ie a vertical line of joins) you would ply this up as shown on the photo (right hand side) using the grey block - this will keep everything together during the pour.

 

While the ICF itself will not allow moisture to travel through it, we still have to comply with BS8102.
 
BS 8102 defines 3 ways of water-resistant construction:
  
   A Barrier (Membrane) protection 
   B Structurally integral protection
   C Drained protection
 
Two are recommended at minimum - three is best case if possible.  We normally use the A and B to comply.
 
The remainder of your post is absolutely bang on the money.  Just one small thing to note - I always recommend the use of a waterstop at the junction where the wall meets the foundation/slab.  The best products I have seen for this are from Kryton.  Waterproof concrete that is ordered from the plant are guaranteed so long as no water is added on site - leaks will become apparent very quickly after the concrete has cured.  We have not had any issues with water ingress in ICF so long as a waterstop is used.
 
This is my first post here - apologies if I have not followed etiquette - we all gotta start somewhere :)

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