Insulated Concrete Forms – FAQ

Building Curved Wall with Insulated Concrete Forms

2. What are the physical differences between an ICF wall and a wood frame wall?

An ICF concrete wall is stronger, more soundproof, more resistant to natural disasters, rot, and termites, better insulated (superior R-value) and, therefore, more energy efficient; it reduces air infiltration and benefits from the thermal mass of the concrete keeping inside temperatures more even.

3. Do local building departments accept Insulated Concrete Forms?

Yes, most building departments throughout North America send their inspectors on courses to learn this type of construction.

4. Can anyone do it?

This is not a “Do-It-Yourself” job. Putting the ICF formwork together is easy enough for anybody who has read the manual and achieves a shared understanding of all the sections. However, the ICF form bracing and the concrete pouring is much more demanding. Those parts should be performed by an experienced builder.

5. Is a unique concrete mix used?

Most concrete is minimum 2000 psi (20 Mpa) pre-mixed concrete (check with code). Maximum aggregate size is 3/4″ and placed at a 6″ slump using water reducing agents such as superplasticizer. Preferably, the concrete for ICF construction is pumped.

6. Do the ICF walls need to be vibrated?

Vibration is not necessary with 3/8″ aggregate and a 6″ slump. Usually rodding or taping the outside surface of the wall is enough. If a larger aggregate (maximum 3/4″) is used a pencil vibrator (maximum 1 3/8″) can be used with caution, to ensure proper consolidation of the concrete. Stay approximately 2′ away from angles, corners, T-walls, etc. when vibrating.

7. How are exterior finishes attached?

Stucco (acrylic or cement) adheres directly to the foam. Wood, plastic or metal cladding is mechanically fastened to plastic ties. Stone and brick are attached to the ICF brick ledge according to design specifications.

8. How is drywall attached?

Mechanically with drywall/gypsum screws or an EPS compatible adhesive and screws.

9. How is electrical and plumbing done?

Electrical conduit and some plumbing may be placed before the pour, otherwise, electrical, and plumbing is set into chases cut into the foam after the concrete has set.

10. Does a wall need steel reinforcement?

Concrete is strong in compression but weak in tension. Walls are usually taking a compressive load from downward forces so reinforcing steel may not be necessary unless the walls are placed under tensile stress loadings from external forces (i.e. high winds, earthquakes, ground forces, etc.). Tensile stress occurs above windows, doorways and in basement walls construction where the pressure of the earth backfill exerts a sideways load up on the basement wall; therefore reinforcement steel is needed there. However, reinforcing steel work should be designed and allowed for by your engineer.

11. Can I use ICF’s for the foundation only?

This depends on the circumstances. If you are putting 2”x 6” wood construction above it is not recommended. The difference in the ambience is such that the lower level becomes the most favorite place to be. Therefore, it is advisable for the whole house to be built out of ICFs. However, there are two exceptions. Log or timber framed SIP homes perform well on ICF foundation because of the similar level of insulation.