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The Contractor’s Guide to Insulated Concrete Forms

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Insulated Concrete Forms

You’ve probably seen them (if not used them yourself), foundations constructed with extruded polystyrene (type 2 Styrofoam) that gets filled with concrete.  This type of foundation is more common than you may think and it’s being used more and more for houses and small commercial buildings.  As a contractor, you need to be aware of this growing trend to use what are commonly known as Insulated Concrete Forms (ICFs).

Insulated Concrete Forms Ground Installation

Insulated concrete forms aren’t new – they’ve been around for more than 20 years.  However, ICFs have become more prevalent because builders, engineers and architects want their structures to be stronger, more energy efficient and sound proof.  This increase in usage has resulted in more companies now manufacturing insulated concrete forms including ARxx, QuadLokIntegraspec and Nudura. Personally, Nudura is the brand I use for both new construction and renovation projects, which I referenced in my article about how to choose the right home addition.

An Inside Look at Insulated Concrete Forms

ICFs consist two Styrofoam panels that vary in thickness depending on the manufacturer; the most common size is 2-1/2’.  The two panels are connected by plastic webs.  These webs are available in different widths depending on the thickness of wall being built.  This compares to traditional foundations built using heavy plywood panels locked together using metal form ties, bars and stabilized with walers.

Insulated Concrete Forms Plastic Webs robinsonconstructioninc

Image from robinsonconstructioninc.com

One of the main reasons insulated concrete forms are so popular is because of their R-value. Fortunately, the thickness of the walls doesn’t affect the R-value.  Walls that are going to be under greater amounts of lateral pressure – whether from being below grade or high winds – require 8-10” thick concrete walls.  A standard residential wall only needs six inches of concrete.  Traditional foundations usually have 10” of concrete, which provides more strength, but if the same foundation uses insulated concrete forms and only has six inches of concrete it needs more rebar to prevent contractions that can cause cracks.  Most ICF manufacturers have detailed reference charts that show rebar details based on the height and thickness of the wall.  The manufacturers also may provide guides about how to construct rebar headers over rough openings.  This can be done by building a buck to hold back wet concrete during the concrete placement stage.

Besides a good R-value, insulated concrete forms also come in a variety of different panel types to achieve different architectural details.  For example, 90- and 45-degree corner pieces are used for both inside and outside corners.  You also can order corner pieces that can be adjusted for unique angles.  If the building has a brick face, you can use brick check panels designed to step out the form.   In addition to connecting the panels, the plastic webs act as a stud and enable you to hang drywall directly on the face of the foam.  This eliminates the need to frame wood or steel stud walls inside the structure.  The webs also allow you to fasten plywood or furring strips, which then provide a nailing surface for siding.

Insulated concrete forms are much less labor intensive to both install and strip.  As with any form, you need to brace the forms for pouring wet concrete.  Most ICFs dealers sell a bracing system that both plumbs up and aligns the wall and acts as staging to work from while pouring concrete.  When you start to strip the forms, all that has to be removed is the bracing.  The foam in ICFs is permanent, but when using plywood panels you have to strip the panels, scrape them down and oil them.

Insulated Concrete Forms Bracing quadlock

Image from quadlock.com

Insulated concrete forms help with energy efficiency.  Buildings constructed with ICFs are much more energy effiencient compared to traditional wood frames.  For example, I recently worked on a 4,000 square foot vetrinary  clinic. The clinic was upgraded from 800 square feet.  We built

the clinic with insulated concrete forms; the owner said the heating expenses after the build were one-third of what she paid in her old space, even though the space was less than 25 percent of the size of the current building!

Insulated Concrete Forms Installation   Insulated Concrete Forms Installation Complete

Insulated Concrete Forms Installation Work   Insulated Concrete Forms Interior

One final note about ICFs:  They’re classified as “engineered,” which means there are strict engineering specifications that need to be followed in order for it to perform to a set standard.  To ensure that the strict installation guidelines are met, whoever installs the forms must be licensed for that specific brand through training courses.  If a licensed installer isn’t used on the build local building authorities can fail the project. Fortunately, dealers who sell insulated concrete forms offer the training courses.

Feel free to ask any questions about ICFs in the comments below and I’ll see if I can provide an answer.

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About

Jeff Kirk is a Red Seal journeyman carpenter in Halifax, Nova Scotia. He completed a 4-1/2 year apprenticeship in 2008. His work has been focused on high end residential renovation and custom new home construction... Read more

66 comments on “The Contractor’s Guide to Insulated Concrete Forms

  1. Kurt

    The new energy codes that are coming to Minnesota will be a great boost to ICF foundations. I really believe that the biggest gains are when you go above grade with the ICF’s

  2. Ben

    Great article! Thanks for posting! The ICF’s have intrigued me, but I have yet to work with them. Hopefully will get a chance to try them out sometime soon.

  3. John S

    Lego has got to have some sort of copyright on ICF 🙂

    Honestly though – how tricky is it to use as a building material?

    Also (and this may be a stupid question) – but in the clinic example you provided, was there any additional insulation besides the ICF?

  4. Jeff Post author

    nope. the icf is the form and the insulation. if far out performs a traditional wood framed wall, As for working with it , there is a short learning curve after about 3 builds youll have hte basics down.. its when you get into full icf builds with odd window opening shapes and pouring gable end walls it starts to get tricky

  5. mark

    On basements, do you still insulate the framed walls in front of the ICF? Also, how do they waterproof the exterior below grade? I’m thinking tar wouldn’t work on ICF’s.

  6. Jeff Post author

    for basements. zero framing is required around the perimeter for insulation. the only time its needed is for pipes that might be exposed. its merely to bury them. like i mentioned the foam is the insulation. if you build a full house with it the only real difference is the thickness of the wall below grade solely for strength to withstand hydrostatic pressure from caving the wall in

    for waterproofing below grade its a two stage process. the 1st thing that goes on is a peel and stick membrane, some manufactures make their own which you buy from the icf supplier or you can simply buy blueskin.. from there the dimpled plastic thats now used on most foundations that creates a drainage plan between the back fill and the foundation itself. from there your good to go.. any exposed foam above grade either gets parged or housewrap then siding

  7. Jeff Post author

    its nothing overly complicated. is like anything else if you take to time how to do it properly the build will go well, and teh more you do it you will learn little tricks to do it faster and more precisely to make it go smoother

  8. Heidi

    My house was built with ICFs way back in 1994 and they have been great. My heating bills are almost non-existent. The one trouble I’ve had, however, is that the waterproofing stuff they put below grade is cracking and falling off. The house is split-level on a hill, and it looks like some kind of a membrane along with the concrete stuff they covered it with is just falling off around most of the house right above where it meets the ground. I’ve asked local contractors, but none of them seem familiar with this stuff. Do I repair this with the same stuff you mentioned above for waterproofing below-grade areas?

    Thanks!
    Heidi

  9. Jeff Post author

    pretty much, its possible that the product that they used might have been an earlier version of it which wasnt latex modified which makes it more resisiliant. or even it might have been exposed to some chemical thats causing it to crumble like you mention..

    if the peel and stick membrane was above grade and exposed to uv for too long it will dry out and crack

  10. Jeff

    Used it a number of years ago (when it was in its infancy) to build my brothers house. Basement and first floor (above grade) were ICF. At the time 45 degree corners didn’t exist, we had to make our own. Bracing was also a little hairy, we had to build it. One corner started to have a blowout so we used the skidsteer to push it back in place. Has graphite foam made it to ICF yet?

    I should run the numbers between a poured wall with rigid applied after the fact vs icf. All of our commercial foundations are poured wall and rigid foam but also have a warehouse full of form panels in every size and shape. The nice thing about ICF is a builder doesn’t need all of the possible form combinations.

    1. Jeff Post author

      i haent heard anything about hte graphite foam.. as for different types of corners ARXX was making a form that you can change the angle of it. if memory serves correct it acts like hinge, but bracing is very very important on corners no matter what type of corner.. thye are hte weakest point in the whole assembly

  11. Jeff Post author

    locally s.i.p`s are extremely rare.. i have officially done one.. the closest thing to a s.i.p ive done was to build a giant fridge for a farmer who sells veggies at the local farmers market.. same sorta theory in the way we built it

  12. Jon

    I grew up in the 1990s in a home that was built this way. It was fascinating to see them build the house out of giant, white “Legos” and pour in the concrete. My parents increased the size of ALL of the windows on the home which partially offset the energy efficiency of the foam construction, but it was about 50% larger than our previous home and the utilities were the same. I think the only complaint we ever had is that there were no studs in external walls when we wanted to hang picture frames & such. We had to rely on drywall anchors for everything.

  13. Casey R

    Polystyrene ICFs are not, as someone suggested, foolproof. Blowouts and voids are very possible. Another problem is insect infestation – they don’t eat it but carpenter ants love to nest in the stuff and termites tunnel through it. A couple of vendors use borax in their formulation to deter insects, but last time I checked, most did not.

    My main problem with Polystyrene ICFs is that I live on the edge of a state forest where a brush fire is inevitable. ICFs are not inherently fire resistant. When subject to a wildfire, the foam can melt, even if covered. The area is also a gather spot for masses of carpenter ants.

    There are other types of insulated concrete forms which encapsulate the insulation in concrete and generally are shaped and stacked more like concrete masonry units. The one that has a production facility within driving distance of my place is Faswall, which coats wood chips with concrete. Faswall has some similarities to Durisol as both use specially processed wood as the insulating agent. How they get the rated R value from wood and concrete, is beyond me however, they do use rockwool inserts in the block to increase the R value.

    The other two are Cempo and Rastra which use (reportedly) recycled polystyrene rather than wood chips that are coated with concrete.

    In the marketing materials of the concrete/wood or concrete/polystyrene they like to use an inflated value based on thermal mass. This value may be valid under certain conditions, but certainly not for winter in my area. Still, I will probably go this route as these ICFs are fire resistant (although the polystyrene beads could still melt under extreme temperatures, leaving a porous concrete block) and insect resistant. I will plan on augmenting the blocks with additional insulation, however.

    1. Jeff Post author

      wow casey i didnt know that, those products arent locally available as far as i know. are they more commonly used where you are or is required. i could very easily see it being required in commercial construction such as interior bearing walls for fire reasons.

      its required to use peel and stick membranes for waterproofing below grade and then parged above grade with a stucco type product which will help. also cladding it with fibre cement siding will increase a buildings fire rating on the outside as it will not burn

  14. Mike

    Let’s say I agree with the insulating value of ICF for the moment  and ignore some of its issues, none of which are deal breakers. 

    I usually build with concrete block, stucco exterior, injected foam inside the block cells with reflective foil and furring strips on the inside. This is typical in our Florida area. 

    According to our energy rater:

    ICF has an R- 22

    CMU with injected foam and foil. R-8

    CMU vs. ICF amounts to a 5 point HERS score difference if the house is a 1 story. With a 2 story home the HERS score differential is 2 points. 

    So here’s my point, clients always ask, what can I do to lower my energy bill for the least amount of cost?

    Client is willing to spend $20,000 today in anticipation of potential savings over the next few years. A payback period of 10 years or less is acceptable. 

    Even if I build a 1 story home for them and their HERS score improves all of 5 points there are lots of other products or energy efficient options that will lower heir HERS score with a faster payback period. 

    For example, raising the SEER level of an HVAC system costs $1,500 and lowers the HERS score by 5 points with a 5 years payback. 

    Logically, why would a client select ICF unless they would be willing to raise their energy reduction budget of payback period? 

    Am I missing something?

  15. George

    I have studded in front of my basement walls for ease of wiring. Would there be a problem with insulating these walls. I’m worried about moisture and mold. I know there is no reason to do this but it is a small area and a lot is for sound. Thank you
    .

  16. Jeff Post author

    insulating the stud cavities wont hurt anything. it will take up the space so stale moisture laden air cant sit in there. also it will stop the transfer of sound from room to room

  17. mark wolschlager

    I am building a 2 story house with basement approx.1400 sf on first floor,am thinking of using 8inch in basement and 4 inch in the first floor walls. is this good thinking or should I go 10 and 6 inch ( I want the extra ledge for 1st floor placement and brick ledge ) the project is in Anthony new mexico thanx mark

  18. Jeff Post author

    depending on what brand your using some of them actually make a brick ledge panel you can use . as for wall thickenss ive never heard of a 4″ wall from any of the manufacturers. they typically start at 6″

    as for having a thicker basement wall. its generally only required depending on what the soil conditions are and how the property is graded.. the deeper the basement it typically requires thicker walls to resist the soil pressure

  19. Tanya Belland

    We’ve recently purchased a home built with icf walls from basement to rooftop. We are trying to hang a 50″ tv on an outside wall but we aren’t sure if the webbing things are strong enough to support the tv or if we should attempt to drill into the concrete. Can you give us some help?

    Thanks

    Tanya Belland

  20. Jeff Post author

    one option is to cut out a section of drywall behind where the tv will be and replace it with 1/2″ plywood and put quite a few screws in it attaching to the webs.. from there you can mount the mounting plate to the plywood

  21. Howard

    Has anyone ever had a completed ICF wall that you covered the exposed above grade portion with a peel-n-stick that had a finished look to it? I am looking for some that can cover my existing peel-n-stick, which has an exterior like rubber (it is Hydroseal 3000). Thanks Carl

    1. Jeff Post author

      there is no such product that im aware of. peel and stick membranes arent meant to be a finish cladding product. they are there to seal the below grade portion of icf`s or for flashing details. above grade the icf should be covered with either a parging product or with siding

  22. Clayton

    Hi,
    We are building a home and the contractor has used ICF foundation walls. The basement floor was poured a week ago and on the weekend it rained significantly. The basement now has water that has seeped in and still seems to be coming in. We don’t know if it’s coming in thru the floor or the wall. The contractor has removed about 2 feet of the styrofoam and we have discovered that the concrete has voids in it – approx 2 in this 2 feet that has been uncovered measuring approx 4in x 2in. Are these voids normal? Do you think this may be where the water is coming from? We cannot see thru to the outside, but upon placing finger in void seems wet with rusted type dampness, also rebar seems rusted. I also have photos..thank you very much!

    1. Jeff Post author

      how far along is the house in construction.. is there a roof on it yet. did they backfill around the foundation as well.. im curious as to if they water proofed the outside of the icf with peel and stick or another form of water proofing..

      as for teh voids.. that is not normal thats a very poor job of consolidating the concrete there should be no voids at all. the rusted dampness is happening do to the water passing through and running along the rebar which has rusted .. i wouldnt worry so much about the rust as much as what the source of hte water is..

      also im curious as to if they installed a weeping tile at the footing to help with drainage or if there will be a sump pump

  23. Brandi

    Our house was built 4 years ago with an icf foundation. We now have a horizontal crack running along the top of one of our basement walls. We have someone wanting to buy our house but is afraid it is a foundation problem. We are hoping it is just the drywall cracking or buckling.Is that common with icf?

    1. Jeff Post author

      how big is the crack.. are there any doors on the floor directly above that are jamming up. it coiuld just be a flexing drywall seam. or it could be a bad footing hard to tell without seeing it

  24. Joel

    We are thinking about purchasing a home that was made with ICF. All of the interiors of the exterior walls were finished with stucco… poorly. I saw lots of spiderweb hairline cracks and there aren’t any corners. It’s the one thing I don’t like about the home.
    Is it possible to remove the stucco from the foam without destroying the foam?

    Thanks,
    Joel

    1. Jeff Post author

      to be honest i really dont know. i have virtually zero experience with stucco.. its extrmelely rare in my neck of the woods because im in a environment that goes through a severe freeze thaw cycle which destroys stucco pretty easily

  25. Eric Schwab

    We bought a house almost a year ago now, and the basement has the ICF as the walls. I’ve been doing a lot of research because I want to start the process of finishing the basement myself. My biggest questions are about the electrical and framing. Do I need to frame or can I just put the drywall straight against the wall? If I do this, how do I go about running the electrical through the walls? My last question is about a vapor barrier. I’ve read that when you finish your basement, you need to install a vapor barrier. With these ICF forms, is there already a barrier in them? This will save me alot of money if I don’t need to frame and insulate. Thanks for the info.

    1. Jeff Post author

      for installing drywall you can fasten the drywall directly to the icf. there are embedded plastic studs in the foam block, the location of them will be marked directly on the foam on nudura they have a diamond shape every 8″ you will need to use a minimum of 1 5/8″ screws

      for running wiring in the block its as simple as carving out the foam, or if you really want to you can frame up stud walls in front of the foam.. the latter is required to run plumbing as pipes are too thick to fit within the foam

      and for vapor barrier some manufacturers of icf, their foam has a perm rating high enough to classify as a vapor barrier, if not you can apply poly over the foam or use vapor barrier primer which gets applied to the drywall after its hung

  26. Marnie

    We recently had a fire and part of our basement needs to be renovated. The process of removing the insulation from a part of the wall has been difficult. My concern is the renovation build back. Can this stuff just be ripped out in a portion and put back in??

    1. Jeff Post author

      any sections of the icf`s foam that was damaged should be removed completely and disposed of.. expanded polystyrene releases harmful gases when it burns.
      as for replacing it.. you wont be able to fully replace the icf as its locked into the concrete as well. have the contractor simply patch the missing foam with sheets of new rigid foam which should glued either with foam adhesive or spray foam.. in conjuction with some framing materials which will provide a surface to attach new drywall

  27. Cindy Shaurette

    Hello
    We did a large basement with styro-block. Loving it, do we need to tuck tape all the seems or can we just drywall overtop without it. We were at a dilemma weather to vapor barrier it or not as well.

    Thank you
    Cindy

    1. Jeff Post author

      it depends on the region your in. in warm climates vapor barrier needs to be on the outside of a wall. and in cold climates it goes to the inside. check with your local building office as to what they reccomend

  28. C

    Hi, have a icf basement built and putting in the vapour barrier for the basement slab. What kind of adhesive should we use to seal the poly to the foam? Thanks!

    1. Jeff Post author

      for sealing the poly, accoustical caulking is the standard. it can be used for poly anywhere in the house and it does not react with the foam in the sense that polyeurathane based adhesives and sealants do where they actually eat the foam

  29. Ryan Albert

    I want to put stone veneer on the outside my walk out basement (basement is made of icf’s), how do I attach the lath for the scratch coat? I cannot find any links, that are not broken, to help me. Any help would be appreciated, thank you.

    1. Jeff Post author

      your best bet is to check directly on the icf manufacturers website if you can, or consult the dealer who sold it they should be able to help you out.

      we dont do much with stone veneer however back in the fall we did have a company install stone on a icf. we fastened concrete board to icf first screwing into the webs.. from there it provided a better base to apply the stone

  30. Dean Renner

    Jeff, I am planning on building with ICF’s in the near future. I would like a rock exterior. I know a brick/rock ledge is required. my question is whether or not the ledge needs to be lower than the slab? As i plan to do as much of the work myself, a same level ledge would be easier for me to finish the slab on. Plan to build in central Tx. I also understand that no vapor barrier is needed on walls? Thanks for your response

    1. Jeff Post author

      Most manufacturer actually have a brick ledge block which works directly with the regular block. I would check with your local suppliers first though to see which brands are available and if they sell the brick ledge. The other thing is most regions require a licensed installer on the build as ICF is a engineered product, you might be able to get the supplier to send out a rep or a licensed installer to work with you

  31. David Dirth

    I built my basement with ICF’s. I now want to attach a garage to the side of my house and this will require a footing of 40″. Do I need to remove the foam in order to attach to the concrete, or can I just install the rebar thru the foam and into the concrete?

    1. Jeff Post author

      david,

      you will have to cut the foam out in order to properly tie in the new garage foundation. if not there will be a weakend joint, plus added strain on the rebar. easiest way to remove it is to markout exactly where the garage ties in with a permanent marker, then cut the inner and outer line with a recip or circ saw. from there simply chip out the foam with the claw of a hammer

      1. Vance

        I just did the same thing as david but im now wondering do I really need to put on blueskin on the garage foundation

        1. Jeff Post author

          it depends on the situtation.. is the garage attached or dettached… if its attached its a good idea as it will to keep ground water from infiltrating to teh inside of the foundation as it can slowly create moisture problems in teh garage or even make its way into hte house.

          if its dettached it shouldnt be a big deal as there should be a plastic moisture barrier underneath the concrete slab

  32. Mike

    I bought a house with Icf foundation. It previously had frozen and cracked pipes. All the foam on the interior walls have been removed, the hangers are still in tact. I’m wondering if I can spray foam it and hang the drywall on the hangers? Or what other options I would have. Thanks

    1. Jeff Post author

      theres a couple options there,, you can cut 2″ rigid foam and glue it back to the concrete using foam adhesive or you could get someone to spray foam yes.. i dont quite under stand why the foam was removed though,

      if the plastic webs are fully intact you can fasten new drywall directly to them . if the webs are destroyed you can remove all of them and attach ” truewall” foam which has a channel in it for wood strapping to go in then drywall to that

      1. Mike

        Thanks Jeff, I think it was all removed cause if the flood and how long the water sat in there. There was mold.
        What rout would you personally go. I have a guy that can come in tomorrow to spray foam it. All the hangers are in tact except for maybe 2. Also I live in Alberta probably simalar to the climate your in as I seen your on the east coast of Canada. Do I need a vapour barrier or air gap with spray foam or just 2″ of spray foam and then drywall
        Thanks
        Mike

  33. Jeff Post author

    vapor barrier is required in canada no matter what if inspected. with spray foam there are two different weights.. 4 lb and 6lb foam, the 6 lb has both a higher r -value and can act as a vapor barrier at the same time.
    thats probably your best option as attaching vapor barrier tight will be ticky…

    just make sure the foam installer does very light coats so that it doesnt come out past the face of the webs… if it does its a hateful job trimming it all back ,, not to mention you might get billed for that wasted material

  34. Mark

    I am looking at building in the future and I’m thinking ICF for basement and 1st floor walls. Basement I would use 10″ thick wall and on the 1st floor I would use 6″ thick wall. How do you create the transformation between the to different thicknesses and do you pour this all at one time or at two different times?

    1. Jeff Post author

      Typically when you step down the thickness of the wall you don’t go from a 10-inch down to a 6. it would be an 8in thick to a 6 unless otherwise spect by an engineer

      Most manufacturers of ICF block have transition blocks to make that switch from the thicker downed of thinner wall

  35. Pingback: 3 Tips to Safely and Successfully Install Eco-Friendly ICFs In Your Home’s Foundation | Sweet Greens

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