Red Kite

Basement - ICF vs Shuttered Reinforced Concrete

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Hi, we are looking at a basement into a slope in clay soil - front out of the ground. I am trying to decide how to build it and seem to have a choice of ICF versus RC (Reinforced Concrete) - anyone any thoughts about Pro's and Con's? Here I am only considering external tanking and waterproof concrete - to my mind an internal membrane and sump is admitting defeat!

 

I like RC because you can see the concrete and any defects when you take the shuttering away - and my GW does basements like this all the time and is prepared to guarantee waterproofing for 10 yrs (not sure if that is really worth much!).

 

However I am hearing that ICF may be cheaper / quicker - and as I need to insulate anyway seems like a neat way to go. Would I need external tanking to an ICF basement?

 

I am looking at an insulated raft slab under the basement and TF above - and also having the discussion of a concrete 'top' to the basement (cast in situ / hollow core beams etc) versus an 'open box' with a posijoist type roof - again any sage advice would be welcome.

 

It would seem there is no 'best way' and the SE's I have talked to say the reinforcing / concrete for the walls is much the same for ICF and RC 

 

Any thoughts?

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16 minutes ago, Red Kite said:

Hi, we are looking at a basement into a slope in clay soil - front out of the ground. I am trying to decide how to build it and seem to have a choice of ICF versus RC (Reinforced Concrete) - anyone any thoughts about Pro's and Con's? Here I am only considering external tanking and waterproof concrete - to my mind an internal membrane and sump is admitting defeat!

will probably be mandatory in some parts of uk  for BC 

 

16 minutes ago, Red Kite said:

I like RC because you can see the concrete and any defects when you take the shuttering away - and my GW does basements like this all the time and is prepared to guarantee waterproofing for 10 yrs (not sure if that is really worth much!).

 

However I am hearing that ICF may be cheaper / quicker - and as I need to insulate anyway seems like a neat way to go. Would I need external tanking to an ICF basement?

take a look at VELOX system  maybe.

and yes --again will be mandatory in some parts of uk . and a perimeter french drain as well

 

16 minutes ago, Red Kite said:

my GW does basements like this all the time and is prepared to guarantee waterproofing for 10 yrs (not sure if that is really worth much!).

that's like  a durex  warranty-- too late when you need to claim on it and so much will depend on your ground conditions and water table 

 

16 minutes ago, Red Kite said:

I am looking at an insulated raft slab under the basement and TF above - and also having the discussion of a concrete 'top' to the basement (cast in situ / hollow core beams etc) versus an 'open box' with a posijoist type roof - again any sage advice would be welcome.

 again check Velox and also  isotex system --both do them and you use rebar from walls to tie it in .

 

using std shuttering --you got pay to rent it -then remove it --seems a waste compared to an ICF system  to  me 

if you want to use poly type go look at Isodom 2000. 

loads to chose from 

 

Edited by scottishjohn

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Our BC was happy with just waterproof concrete (Sika warrantied system) in our basement and the shuttering crew were quite fast as they built one corner piece, one flat piece and rotated them around the site, minimising the joinery time.

 

My warranty is with Sika, not contractor. 15 years.

 

We also have a perimeter land drain at the foot of the basement slab draining to a soak away and  there is a 1m wide backfill of clean stone between the exterior insulation and the excavation.

 

I've no doubt that ICF would perform as well, however it would still have needed additional insulation on the outside as I needed 200mm. I also liked seeing the pour quality post striking and ensuring the water bar detail was correct..

 

If you're paying a contractor to do this then they're providing all the kit anyway (and the expertise).

 

Be wary of external tanking - it's only as good as the crew that install it and if you get an issue it will be hard to isolate it. With warrantied concrete if it leaks, it's their fault and can be fixed from inside.

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Have you considered precast concrete? I built a very large reinforced block work retaining wall... never again. Took us months to get out of the ground, it burst on us in the first pour. Loads of photos here: https://www.facebook.com/pg/iSelfBuild/photos/?tab=albums

 

I'm a consultant within precast concrete (the manufacturing side of things) and a lot of manufacturers are starting to offer retaining wall units with waterproof tanking pre-installed. Mainly used on commercial projects for now. That is the way I would go if I do another retaining wall.

 

Image may contain: bridge and outdoor

 

 

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6 minutes ago, iSelfBuild said:

Have you considered precast concrete? I built a very large reinforced block work retaining wall... never again. Took us months to get out of the ground, it burst on us in the first pour. Loads of photos here: https://www.facebook.com/pg/iSelfBuild/photos/?tab=albums

 

I'm a consultant within precast concrete (the manufacturing side of things) and a lot of manufacturers are starting to offer retaining wall units with waterproof tanking pre-installed. Mainly used on commercial projects for now. That is the way I would go if I do another retaining wall.

 

 

 

 

Is that the system I saw on a job last year?

 

An old leaning garden retaining wall, holding back about a metre of soil.  the replacement "wall" seemed to comprise H profile steel beams concreted quite deep into the ground, and then pre cast concrete panels lowered into the beams.

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More like this, you can see a T + G profile in the edge, these can have connection wire ropes embedded and filled with grout for high load situations which make it monolithic. 

 

Retaining_wall_carousel-4_x980_y420.jpg.856ab11bd539d246783c555d47ad90a5.jpg

 

Also exposed rebar can be left at the edges for additional casting on site to make it monolithic. 

precast-concrete-wall.jpg.b323dfb07c17408c3c1980bf185f99d1.jpg

 

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34 minutes ago, iSelfBuild said:

More like this, you can see a T + G profile in the edge, these can have connection wire ropes embedded and filled with grout for high load situations which make it monolithic. 

 

Retaining_wall_carousel-4_x980_y420.jpg.856ab11bd539d246783c555d47ad90a5.jpg

 

Also exposed rebar can be left at the edges for additional casting on site to make it monolithic. 

precast-concrete-wall.jpg.b323dfb07c17408c3c1980bf185f99d1.jpg

 

and how much each are those pieces ?

before you tell me i know now no self builder could afford them or use them to build a basement with them .

ICF will do anything you need for a domestic build at affordable prices 

Edited by scottishjohn

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I have absolutely no idea on price, it would depend on so many job specific factors. I know a few precasters welcome residential projects.

Edited by iSelfBuild

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I think you'd struggle to get a waterproof join between those.

 

The contractor I used knocked out my 110m2 basement with 42 liner metres of 2.5m high walls in about 3 weeks and not even the slightest sign of a breakout but they were using industrial quality shuttering and were very experienced.

 

Rebar work was impeccable too (all 14t of it)  they even spotted a few mistakes in the SE drawings which they sheepishly acknowledged when I called them up about it. The BCO turned up for a pre-pour inspection and left after 10 mins saying he didn't need to see any more :)

 

Cost was about £1000/m2 - i.e about £100k for the whole basement including excavation, muck away, drainage, the basement itself and backfill with clean stone.

Edited by Bitpipe
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Are you planning to diy or contract in a specialist company? 

 

The big advantage of ICF is that a competent DIY can do a build himself. If you go DIY shuttering the heavy duty metal stuff is very expensive and experience is the key with timber shuttering. 

 

Yes icf needs extra waterproofing, I plan to use waterproof concrete, external tanking and a French drain. Its a 3 sided basement (front open) so that's help! 

 

If you want to check concrete after pour then there is always the icf you remove one side originally developed for lift shafts. 

http://www.nudura.com/divisions/nudura-products/one-series

 

There is always this product that looks very interesting but I don't know if I have the b***s to build a whole house out of it.

http://spidertiesystem.com

 

Interesting figures £1000m2 for a basement, if I was getting figures like that I wouldn't be building a basement ground is cheap up here I would just build a bigger house above ground. I may think  different if ground was scare or expensive. 

 

A lot of different ICF on the market some good some not so good. Do your own research and be very wary of the sales patter, plenty of it! 

 

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If you have a good Groundworks team who are familiar with reinforced concrete then it seems like a no brainer 

asking them to use something they are not familiar with will rock the boat. 

And ICF is not cheap to buy, I would go traditional route then waterproof the outside and insulation on the inside. 

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Idon,t see ICF forms as being more expensive than a lot of joiners time and wood to make forms ,when so many simple ICF systems YOU can build  the basement or retaining walls required in a couple of days .

excavation will be same what ever system you go for ,

woodcrete type need no or very minimal bracing up to 2m  per pour,velox say 3m with internal wall braces built in(triangular rebar structure ) for strength and to keep vertical 

see Velox +durisol +Isotex --can be with or without insulation 

just don,t see reusable metal forms with crane hire  you would need or purpose built wood shuttering being cheaper --concrete  will be the same as will re -bar  if needed

step bloc is another type of CF just concrete blocks with holes you fill

you want to go poly type+insulated then check izodom 2000 system- 2m lengths of wall with variable tie length so you can have  thickness you want

how much quicker than this do you want to build a wall!!

Edited by scottishjohn

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If only icf was as easy as that video! (Still a simple build method). What system did you use john?

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Totally agree that a major consideration is if if you want to DIY or get a contractor to handle it. 

 

Standard formwork and shuttering is definitely not for the faint hearted and looked to require a lot of experience and equipment.

 

Also a 3 sided basement will be more manageable than our four sided big hole in the ground. 

 

Regarding the economics that I experienced, I would not have been allowed to build any bigger above ground as was restricted by ridge height and already was exceeding the original house footprint by a significant margin. Planners did not blink at basement, which increased the internal floor area by almost 50%.

 

Being in SE England, the land prices are such that £1000/m2 is quite good value.

 

Also, I should really offset the cost of the basement against a passive slab or traditional strip foundations (we have 1m of clay on gravel and chalk) so the incremental figure is less than that. Doesn't include fit out though but that was not a huge number as it got rolled into the rest of 1st/2nd fix and finish.

 

Edited by Bitpipe

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Local friends who build a basement practically in the Thames used the Glatthar Fertigkeller system which is precast, pre-insulated and also waterproof. I think they use WPC for the sections, a special grout for the joins and a thick membrane which may have been sprayed on (or sprayed over, can't recall). Their main design challenge was stopping hydrostatic pressure pushing the basement out of the ground, as a result their slab was ginormous.

 

Full turnkey service, design and build, comprehensive warranty but very expensive (we got quotes).  

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2 hours ago, Alexphd1 said:

If only icf was as easy as that video! (Still a simple build method). What system did you use john?

not got there yet -still plot problems +arguing on final design allowed .

but If going poly ICF  it would be Isodom2000  no doubt -like the locking pin shapes compared to others

-loads of different elements off the shelf + less joins has to be  big plus 

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59 minutes ago, scottishjohn said:

not got there yet -still plot problems +arguing on final design allowed .

but If going poly ICF  it would be Isodom2000  no doubt -like the locking pin shapes compared to others

-loads of different elements off the shelf + less joins has to be  big plus 

 

Rome wasn't built in a day! 

 

A few houses up here have been built with isodom2000 (ekonect) nice product. Wasn't keen on the eps ties but they do it with plastic ties aswell. 

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38 minutes ago, Alexphd1 said:

 

Rome wasn't built in a day! 

 

A few houses up here have been built with isodom2000 (ekonect) nice product. Wasn't keen on the eps ties but they do it with plastic ties aswell. 

makes a difference when the agent also is builder and can do a turn key if you want -they not going to sell stuff they don,t like building

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6 hours ago, cherryfountain said:

Has anyone on here used Stepoc blocks for basement walls?  What are the pros and cons for this system?

Yep !

Worked great !

Simply bed the first course then off you go . I had to add rebar in as I went . I shuttered any corners before the pour . Poured the whole lot in 1 go ! ; few minor issues but no real problems 

 

I insulated on the outside . Also land drain at base . Internally I will have membraned walls going into an internal drain then out to sump .

 

The main thing is that stepoc is an easy diy approach - Christ ; I did it so it must be ! .

 

 

EC80BF5B-F12C-4AE3-A353-EE7C87DDFE6C.jpeg

Edited by pocster
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I usually find agents/builders use/sell what they can get best margins on not what they want to sell. If it is the ekonect guys from glasgow the father and son actually are nice guys👍

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1 hour ago, Alexphd1 said:

I usually find agents/builders use/sell what they can get best margins on not what they want to sell. If it is the ekonect guys from glasgow the father and son actually are nice guys👍

yep,   thats them used to be Durisol agent .

 

I checked price of the stepbloc --dearer than any of the ICF  systems -

-thats why we dont, see an insulated version being sold for house building  I am guessing

,other wise its basically  same idea  as any ICF system .maybe it will come 

Edited by scottishjohn

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I have circa 155sqm of rc walls containing 47.5cu, and 212sqm of slab containing 63.5cu Sika waterproof concrete.  All shuttering was bespoke timber and fair faced ply.  Sikaproof-A membrane was placed in the shuttering and is therefore bonded to the rc (external face) by the pour.

There's near 1200sqm of A393 mesh and 170sqm of A142 in that lot.

172sqm of slab was powerfloated, concrete was pumped 35 metres, 8 separate days of 40 ton crane hire.  Contractor was a respected specialist.

£117k

 

Independent quotes to waterproof the structure using external membranes and internal cavity drains (so replacing Sikaproof-A and Sika waterproof additive) were circa £27k...or if I chose to build icf they went up by £15k, for little better reason than them not wanting to have to waterproof subterranean icf.

 

Are you considering a concrete 'top' because the wall/top junction is underground?  If you have such a detail then ensure it is impeccably detailed and stick to a single manufacturer system of waterproofing solution...have them detail it.  This will force you into a very early commitment which you might not fancy, ...but suck it up, if you value peace of mind.

 

 

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