ICF Concrete  Foundation Article

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ICF Insulated Concrete Forms  Problems & Leaks

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ICF Insulated Concrete Form Problems

Pros and Cons of ICF Forms The Good * The Bad * AND the Ugly!

This article is stating just the facts not to criticize or endorse ICF Insulated Concrete Forms. The results of many years of experience dealing with foundation flaws and cracking problems with this type of construction. Usually, long after, the builder is no longer taking any responsibility for their work.

Insulated concrete forms (ICF) have become popular today for many home builders because concrete professionals or contractors are not needed. Typically, the carpenter, or home builder, or homeowner on-site can assemble the forms without any outside help.

What is an ICF form?

In its simplest form, ICF Forms is two rigid polyurethane or polystyrene foam sheets separated with plastic separators. These separators set the wall thickness and are placeholders for rebar reinforcement. But still, form-work problems can occur, which translate into possible leaking issues. At NextStar we have seen many problems with ICF Form basements. We find that most home builders are unaware or in denial of any of these problems.
Picture of ICF form with some cement poured in

ICF Insulated Concrete forms Pros and Cons

Advantages of ICF construction:

  • Can be assembled without skilled labor.
  • Provides ready-to-go foundation wall insulation on both sides.
  • Can provide a continuous foundation to above-grade construction.
  • Provides internal structure to hold rebar and in most cases, more rebar than would be used in traditional foundation construction.
  • ICF Forms can be easily modified to account for changes in the plans such as windows and doors.
  • There are probably more advantages but for the purpose of this article, some are duplicates to standard concrete construction.

Disadvantages of ICF construction:

  • ICF construction foundations usually cost more to complete versus the standard wood form and pour.
  • ICF forms require extra support during setup to ensure the forms remain in place before and after pumping the concrete into the ICF forms. This additional cost needs to be factored into the overall cost. Often not done.
  • More care is needed to select the correct concrete slump and the aggregate size to ensure it meets the ICF Form manufacturer’s specifications.
  • It requires a membrane on the outside because the (snap ties) plastic separators have a wick effect, explained later.
  • The thermal mass advantage may be questionable since both sides of the foundation are insulated. In addition, some reports indicate higher energy efficiency during colder months but less energy efficiency during the warmer months. Therefore, geographical location is an essential factor in determining an ICF foundation's actual energy efficiency results.
  • The plastic separators (snap ties) results in many more penetrations through the concrete resulting in more opportunities for water to penetrate. Also, this higher volume of penetration spots may weaken the overall concrete wall in time.
  • Diagnosing ICF foundation issues is more difficult for foundation repair professionals.

icf foundation wallICF Foundation form Spall failure picture showing poor concrete pour leaving voids ICF Concrete Foundation problem, showing large voids from un vibrated concrete Closeup picture of Holes in ICF concrete foundation walls


ICF Insulated Concrete Form Problems

Wicking problem?

ICF forms have some type of polypropylene separator (snap ties) to hold the 2 sides of the form together. The smooth finish of these materials can allow water to wick inside the concrete and seep inside the foundation. The ICF forms themselves have gaps between the blocks that would allow water direct access to the concrete.

Membrane Installed?

When inspecting a problem foundation, the first thing we look is verify if a membrane has been installed. With a membrane is installed properly there should never be a leak. If Leaking, the membrane has been damaged or not installed high enough before backfilling, allowing water to get past it.

This is important because leaks are so hard to detect. Using standard crack injection methods on these foundations is comparable to the whack-a-mole game. Once one leak is injected and fixed, assured two more areas will start leaking shortly thereafter.

Building Codes

In most areas of North America, the building code now requires that ICF foundation basements have proper membranes installed. In some cases, dimple panels as well, directing water to a weeping tile drain system. However, we continue to see newly built ICF foundations with no membrane or some sort of tar roll-on coating that is not adequate. In some cases backfilled before an inspection by the building inspector.

ICF Differences

Standard concrete basement wood forms have metal snap ties every 16-24 inches horizontally and 24 inches vertically. In an ICF foundation, every block form may have 4 to 5 times more separators through the concrete to the exterior. Metal snap ties bond well with concrete, but smooth-finished plastic separators bond poorly against concrete. These will eventually allow water and moisture to wick or penetrate the foundation.

When a crack is identified, the excess foam must be removed before applying standard crack injection techniques. The IC foam makes it more difficult to identify where the leaks are located which involves more labor time. Usually, we find that a crack has originated from a plastic snap tie. It develops when the concrete shrinks during the curing process.

We always caution homeowners that crack injection in an ICF foundation is only fixing a symptom of the real problem. That is the absence of a proper membrane. Some foundations are so bad that it requires excavation and a proper membrane installed along with new weeping tile. Repairs to a cracked or faulty poured foundation can be made with polyurethane or epoxy injection. This isn't a long-term solution for an ICF foundation. Fixing one location only chases the water to the next snap tie or flaw.

An ICF foundation that has been installed properly there should be no issues. If any issues do occur, the Insulation foam hides flaws, and homeowners do not discover the problem until long after the structure is completed.

Workmanship problems:

  • Not properly supporting the forms when the concrete is poured, often from being in a rush or to save costs. They avoid using a vibrator or tamping to prevent blowouts in the form leaving many areas of the foundation with honeycombed voids. This is a large problem with many foundations we see and in some cases, the voids are so bad the groundwater easily runs through.
    ICF form blowout during concrete pour
  • Common large voids left under window or door sill plates. Wood forms around the openings installed without leaving the bottom sill plate open for concrete to be pumped into. This can leave large voids in these areas. The best option to repair this is to remove the foam. Apply grout made of Epoxy and Sand to structurally bond and fill the void area.
    Large Void in poured ICF sill plate

  • Many builders use the wrong recommended aggregate size and slump by the manufacturer of the ICF forms which contributes to many problems.


Crack in standard ICF form Foundation ExampleNon vibrated or poorly consolidated Concrete in ICF Form

Our Recommendations to Avoid problems

To avoid problems, should you decide to build with insulated concrete forms, hire experienced installers who have installed standard concrete forms. Ensure the forms are well-supported, plumb, and the concrete is vibrated. Even if it costs more to reinforce the forms it will pay for itself in the quality of the foundation.

If one of your considerations was for thermal mass to heat or to cool. May want to consider a standard foundation and only foam insulating the exterior instead. This will allow the temperature of the foundation to match the interior temperature of the structure.

Installing ICF? Then install an external membrane and secure it above grade. Install secondary membrane to the weeping tile if possible. Do this correctly you should never need help from a foundation repair contractor. Pay and do it right the first time or with an ICF Foundation pay dearly later.

What do I Do if you have a Leaky ICF Foundation?

Things to check first:

1. Is water draining out close to the exterior wall if so direct it away.

2. If your foundation has a sump pump make sure it is operating and pumping away from the foundation.

3. The soil up against the foundation is it sloped away from the walls.

4. Dig in a soil area next to the basement wall 6-10 inches deep. Determine if the wall has a membrane or the ICF Foam is exposed to the soil. If no membrane is found this is a serious deficiency, you may need to contact a local foundation contractor to examine the problem.ICF basement with dimple membrane installed

5. If you have a wet spot along the basement wall, remove any drywall and inspect. Usually, it will show dark watermarks on the ICF foam.

6. Removing foam to inspect the wall may be required to identify the problem.

Problems and solutions for your ICF Home

Cracks - Standard Polyurethane low or High-Pressure method.

Holes - Standard Polyurethane or Epoxy Injection.

Voids - Epoxy grout mixture to fill the void area.

Porous walls holes and voids everywhere. Excavate and Install or repair external membrane

Credits ©2021 NextStar Technologies Authors C Groner, N Wathen, L Frey


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ICF Insulated Concrete Forms - the many problems
The article discusses the problems with this form of foundation construction. Issues with crack repair and voids and general leaking problems.
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