ICF Insulated Concrete Form Problems

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

This article states 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 in below-grade basements. Usually, long after, the builder no longer takes 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, 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 are two rigid polyurethane or polystyrene foam sheets separated with plastic separators. These separators set the wall thickness and are placeholders for rebar reinforcement. However, form-work problems can occur, translating 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 give a continuous foundation for above-grade construction.
It provides an internal structure to hold rebar and, in most cases, more rebar than used in traditional foundation construction.
ICF Forms can be easily modified for plan changes such as windows and doors.
There are probably more advantages, but for this article, some are duplicates of standard concrete construction.

Disadvantages of ICF construction:

ICF construction foundations usually cost more than 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.
Selecting the correct concrete slump and aggregate size requires more care to ensure it meets the ICF Form manufacturer’s specifications.
During the concrete pour, the concrete mix tends to stick to the foam, preventing it from flowing, especially in the cold.
It requires a membrane 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 essential in determining an ICF foundation's actual energy efficiency results.
The plastic separators (snap ties) cause many more penetrations through the concrete, which provides more opportunities for water to penetrate. This higher volume of penetration spots may weaken the overall concrete wall over time.
Diagnosing ICF foundation issues is more difficult for foundation repair professionals.

ICF 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 polypropylene separators (snap ties) to hold the two 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 have gaps between the blocks that enable direct water access to the concrete.

Membrane Installed?

When inspecting a problem foundation, the first thing we look for is to verify if a membrane has been installed. With a membrane appropriately installed, 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. Standard crack injection methods on these foundations are comparable to the whack-a-mole game. Once one leak is injected and fixed, two more areas will start leaking shortly afterward.

Building Codes

In most areas of North America, the building code now requires that ICF foundation basements have proper membranes installed. Sometimes, dimple panels also direct water to a weeping tile drain system. However, we continue to see newly built ICF foundations with no membrane or some 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 determine where the leaks are located, requiring more labor time. Usually, we find that a crack 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 only fixes a symptom of the real problem. That is the absence of a proper membrane. Some foundations are so bad that they require excavation, a proper membrane, and new weeping tile. A cracked or faulty poured foundation can be repaired 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 correctly should have no issues. If any problems occur, the Insulation foam hides flaws, and homeowners do not discover the problem until long after the structure is completed.

Workmanship problems:

They do not properly support the forms when the concrete is poured, often because they are in a rush or to save costs. They avoid using a vibrator or tamping to prevent blowouts, leaving many areas of the foundation with honeycombed voids. This is a significant problem with many foundations we see, and in some cases, the voids are so bad that groundwater easily runs through.
Common large voids left under a 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 space.
Many builders use the wrong aggregate size and slump recommended by the ICF form manufacturer, contributing to many problems.

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

Our Recommendations to Avoid Problems

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

If one of your considerations was whether thermal mass would heat or cool, you may want to consider a standard foundation and only foam insulation for the exterior instead. This will allow the foundation's temperature to match the structure's interior temperature.

Are you installing ICF? Then, install an external membrane and secure it above grade. If possible, install a secondary membrane directed to the weeping tile. 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 close to the exterior wall? If so, direct it away.

2. If your foundation has a sump pump, ensure it operates and pumps away from the foundation.

3. The soil against the foundation is 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 if the ICF Foam is exposed to the soil. If no membrane is found, this is a severe deficiency, you may need to contact a local foundation contractor to examine the problem. ICF basement with dimple membrane installed