ICF - Plastic ties vs Galv Steel

[Adam2]

OK so decision on ICF is being made soon. My engineer has a general affinity with metal as his view is the concrete will bond do steel so when curing will remain bonded unlike with plastic which may shrink as it cures leaving small pathways for possible water transfer.

 

The build will have 2 retaining walls so waterproofing is an important factor. Though ground is sand based and we're top of a hill so minimal risk of standing water.

 

My feelings are that the ties are encased in EPS so protected from water generally unless somehow it gets in via EPS joins after passing the external membrane and finds a route via cracks in the waterproof cement down to the ties....

 

Other factor is fixings - attaching to steel should be better than plastic as will not go brittle and possibly crack also steel may be more robust in the event of fire.

 

Final thought is concrete compaction may be expected to be better in concrete due to the slimmer nature of the ties - thin round bars Vs more complex plastic structure - though of course the plastic generally has easier fitting of rebar.

 

My view is that these are pretty marginal considerations and should be secondary to U values, experience of my preferred contractor and cost. Though I would appreciate opinions and experience from others on here.

 

Thanks

Adam

[PeterW]

15 minutes ago, Adam2 said:

My engineer has a general affinity with metal as his view is the concrete will bond do steel so when curing will remain bonded unlike with plastic which may shrink as it cures leaving small pathways for possible water transfer.

 

Your engineer is delusional ....

 

Plastic doesn’t shrink at all once moulded, so when engaged in concrete it won’t go anywhere. 

 

In the late 1970’s they made wall ties from uPVC, so if his theory was correct then a lot of buildings should have fallen down by now ... 

[jamiehamy]

I understand the concern however, when you pour, if through a line pump or boom, will likely be an over sanded mix. It should be fairly fluid and I doubt you'll have any real issues around the ties. 

 

On terms of fixing, we used Polarwall which had rails every 300mm vertically. We afixed no problem to that. In terms of fire, your protection is your plasterboard. If fire gets through that then you'll be way over by your 30mins anyway.

 

I doubt there really is any definitive answer to your questions. Each will have pro and cons, neither make them decisively better. 

 

 

 

[Adam2]

20 minutes ago, PeterW said:

Plastic doesn’t shrink at all once moulded, so when engaged in concrete it won’t go anywhere. 

 

Sorry, I probably wasn't clear, was in reference to the concrete shrinkage during curing.

[PeterW]

So it will shrink away from steel in the exact same way..? Also, you could easily damage the galvanising when the pour is underway by the abrasive concrete - that’s of a bigger concern. 

[Russell griffiths]

If your engineer is familiar with ICF then what has he worked with previously 

what ones has he had dramas with

who is building this ?

why not ask the builder what one he wants to use

 

if you are not building it, then tbh your opinion doesn’t count for much, ask the guys screwing it all together what they want in a system. 

 

Having just put over 2000 screws in my icf I’m glad I didn’t have to screw into metal webs. 

[Russell griffiths]

A funny thing happened this week, I had a lad visit my site to collect some blocks I had left over, we got chatting and he said that he has had to Change block supplier half way through his build as the quality of the blocks he was getting was so poor. 

 

This must have been a massive decision to make, and not something that was easy to achieve as the two makes where not at all compatible. 

So go and look at some builds that use the blocks you want to build with. Talk to the lads doing the build and get their opinion. 

 

Dont go by the crap in the brochure. 

[Adam2]

Thanks for the responses, I do disagree a little - seeing as I'm choosing, paying and living in the house etc etc my opinion counts for quite a lot ? 

 

I think inadvertently you agree with me then @Russell griffiths in my summary re primary factors above. For sure I am well beyond believing all that is in a glossy brochure. The builder has a preference but that is based on what he is used to - not saying that is an issue at all, but if we let builders, architects, engineers always do what they are used to we wouldn't be driving much change. Changing blocks half way through - agreed, a nightmare scenario to be avoided.

 

I was interested if any contributors with a more technical understanding could shed light on differences of metal and steel within ICF

 

 

[Russell griffiths]

So if the builder has a preference, what don’t you like about his choice? 

I agree about trying different things, but it seams as though you are going into such fine details that you may be missing some big points

usability from the people doing the build would be very high on my list. 

Imagine getting half way through and having a row with the builde, him saying I can’t stand these crappy blocks you wanted them I wanted to use the ones we had previous experience with. 

 

It happens, 

as for steel verses plastic, believe me when that concrete goes in and drops 2.5m vertically it sticks to everything 

 

i had a bit of a brain faid on mine and forgot to put in a beam pocket, so had to chop it out with a kango a week later, that wall was the most solid wall I’ve ever had to cut a hole in, the concrete was stuck fast in every nook and cranny it could find. 

 

Shrinkage away from any of the internal steel reo or plastic Webb’s completely non existent.