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Frequently Asked Questions

 

  1. What are ICF's?
  2. What are the advantages of building with ICF's?
  3. Do the AMVIC forms stay in place after the concrete is poured?
  4. How are doors and windows installed?
  5. What Is EPS (Expanded Polystyrene)?
  6. Is the AMVIC ICF easy to use?
  7. How do you run the electrical or plumbing?
  8. When you use the AMVIC ICF below grade, should you waterproof the ICF?
  9. Do I need to worry about Termites?
  10. How high can I build with AMVIC ICFs?
  11. How is drywall attached?
  12. How do you hang pictures?
  13. How are exterior finishes attached?
  14. What are the physical difference between an AMVIC wall and a stick frame wall?
  15. Is building with Insulating Concrete Form an experimental construction form?
  16. Is a special concrete mix used?
  17. What method should be used to pour the concrete?
  18. What kind of vibrator should be used?
  19. I’m confused --- some ICF manufacturers recommend vibration of the concrete, others say to rod it or tap the outside of the form, and others say none of the above. What’s right?
  20. Why haven’t we seen more ICF construction on the West Coast?
  21. What will ICF construction mean for the future value of my home?
  22. Will I be able to find contractors and subcontractors who are familiar with and capable of building with ICFs?
  23. Are their limitations on what kind of house you can build with ICFs?
  24. Does an ICF-built house look different than others?
  25. Do local building departments accept AMVIC?
  26. Do I need an engineer to review my building plans?
  27. Can I construct radius and angled walls using AMVIC ICFs?
  28. Can I leave this product exposed to ultraviolet rays for extended periods of time?
  29. Does Expanded polystyrene (EPS) present a serious fire hazard?
  30. I am concerned about mold and mildew in my new building. Will building with AMVIC block reduce or eliminate this problem?
  31. How much does it cost to build with AMVIC compared to other building materials?
  32. How does AMVIC compare to concrete block or poured wall construction?
  33. Can I see an actual AMVIC project?

 

1. What are ICF's?

ICF is the acronym for Insulating Concrete Forms. There are multiple types of ICF's but in general ICF's are rigid plastic foam forms that are filled with reinforced concrete to create structural walls. They hold concrete in place during curing and remain in place afterwards to provide thermal insulation. ICF's are used to make structural concrete walls, and can be used to make either foundation or above-grade walls. The forms are typically made from pure foam-plastic insulation but may also be made from a composite of cement and foam insulation or a composite of cement and processed wood. The foam is typically either expanded polystyrene (EPS). In addition to holding the concrete in place while curing, ICF's usually provide a web system to hold rebar in place properly spaced so that ties are avoided, and also a system is provided in most (not all) ICF's to mechanically attach interior and exterior wall finishes.
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2. What are the advantages of building with ICF's?

The building will use 35 up to 70% less energy to heat and cool; it will be quieter and will keep out more unwanted noise than a conventionally constructed home; the house will have superior wind and fire resistance; the exterior walls are essentially impervious to rot and decay, and overall you will experience a much more comfortable living environment.
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3. Do the AMVIC forms stay in place after the concrete is poured?

Yes. The AMVIC forms are used to allow builders to pour a solid concrete wall. However, upon completion, the forms are designed to provide insulation, nailing surfaces, and a vapor barrier, all in one step.
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4. How are doors and windows installed?

A wooden or vinyl buck is built to the desired rough opening size and incorporated into the AMVIC wall as it is being stacked prior to pouring the concrete. Once the concrete cures, doors and windows are installed as usual into this opening.
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5. What Is EPS (Expanded Polystyrene)?

EPS is constructed from millions of tiny air cells fused in manufacturing to form a rigid material. EPS contains no CFC's or HCFC's and has a zero ozone depletion rating. In fact, it is totally inert and considered one of the best insulating materials available.
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6. Is the AMVIC ICF easy to use?

AMVIC ICF’s are the most recently designed blocks on the market, and builders are consistently giving them strong reviews for ease of use and enhanced speed of assembly. The design of the AMVIC blocks makes them the easiest to use of any system available. The blocks arrive on site pre-assembled, and the straight block and 90 deg and 45 deg blocks provide for almost all shape requirements. If additional angles or curves are required, they can be constructed on-site using straight blocks. Little to no taping is required, extra reinforcement is reduced, and the 6 inch spacing of internal webbing makes it possible to trim the blocks to any length without requiring additional bracing as is recommended with other manufacturer’s blocks. AMVIC ICF's are lightweight and there is very little cleanup on the job site once the project is complete. AMVIC provides ongoing training classes and optional on-site technical support helping the project run smoothly.
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7. How do you run the electrical or plumbing?

Some of the utilities are placed prior to the pour, and others are done afterwards. Services access cavities need to be cut before the pour. Just use a saw, utility knife or hot knife to cut through the blocks. Then place the service pipes (or sleeves) in the openings. The gaps should be foamed to prevent concrete leakage during the pour. Wiring and Plumbing Once the pour is complete cavities for wiring and plumbing can be cut into the surface using a router, chainsaw, or hot knife. Place the services in chase. Generally, the Romex will be a friction fit into the groove. Occasionally a drop of foam is used to hold it in place much like a staple. Make sure to observe all code requirements. If vents have to be run in exterior walls, they may need to be placed in the cavity of the block prior to the pour. Generally, it is easiest to plan the layout of utilities to minimize use of the exterior walls.
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8. Should you waterproof the blocks when you use the AMVIC ICF below grade?

Yes. There are three parts to the below grade waterproofing: French drain (foundation drain), waterproofing, and a drain board – protection course. An ICF approved spray-on or roll-on liquid waterproofing membrane such as AquaSeal Eco-Flex is recommended from 6 inches above the finished grade to 6” down the footing. A French drain tile system should be installed at the base of the footing and covered with coarse drain rock. A dimpled drain board product such as ProtectoWrap’s Protecto Drain 2000-V or System Platon should be installed over the waterproofing to provide protection for the waterproofing and to create an air space between the backfill and the waterproofing. When a dimple board product is used, you can backfill with native soil. Alternatively, there are membrane systems such as Polyguard 650 that can be used instead of the liquid waterproofing, which are proven systems that work well, although with more labor to install.
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9. Do I need to worry about termites?

Maybe/probably/depends. This is very dependent on the area of your building site. If termites are a concern for conventional buildings in your area then they are a concern with ICF construction. While termites don't feed on EPS like they do wood, they can tunnel through EPS to reach a food source. While this is infrequent, and probably a low threat in our Northern California environment there are several ways of installing the block to create termite barriers that should satisfy building inspectors. We can assist you with alternative considerations.
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10. How high can I build with AMVIC ICFs?

A: Multi-story structures can be built with AMVIC, one story at a time. Each story is stacked 9' to 12' and poured in 2' - 4' lifts in a continuous pour.
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11. How is drywall attached?

Mechanically with drywall / gypsum screws or an EPS compatible adhesive and screws.
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12. How do you hang pictures?

Normal to lightweight pictures can typically be hung using a picture hanger with a nail driven anywhere into the sheetrock just like in frame construction. Heavier weight objects will need to be hung by screwing or nailing into the imbedded web, one of which is imbedded in the block running floor to ceiling spaced every six inches. The webs can be located much the same as in frame construction using either a magnetic stud finder (find the screws), or a sensitive electronic stud finder. Once you’ve located one web the other webs will be easy as they are in multiples of exactly 6” from there. If you need to hang something between the webs, you can use a molly type anchor into the sheetrock just like you would in frame construction. (If necessary in extreme cases you can use a concrete drill and go back into the concrete and set a concrete anchor).
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13. How are exterior finishes attached?

Stucco (acrylic or cementitious) is adhered directly to the foam. Wood, plastic or metal cladding is mechanically fastened to the imbedded plastic ties. Stone and brick are attached according to design specifications.
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14. What are the physical differences between an AMVIC wall and a stick frame wall?

An AMVIC wall is stronger, more soundproof, more resistant to natural disasters, better insulated, has a superior R-value, is more energy efficient, reduces air infiltration and benefits from the thermal mass of the concrete.
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15. Is building with Insulating Concrete Form an experimental construction form?

Definitely not. Residential structures have been being built in the U.S. of formed concrete since the turn of the century. Thomas Edison built several homes of formed concrete in the 1900's that are still occupied today. Stay-in-place concrete form construction began in Europe in the 50’s and has been widely practiced in Eastern Canada and Eastern U.S. since the 70’s.
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16. Is a special concrete mix used?

Generally walls will require 3000 psi concrete or as specified by your engineer or code. Maximum aggregate size is 3/4" and placed at a 5-6" slump.
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17. What method should be used to pour the concrete?

Concrete can be placed using any one of several methods; concrete pump, conveyer belt, crane and bucket or by a chute directly from the truck. A pump is the easiest method using a 3" or 2.5" reducer in the hose to reduce the concrete velocity.
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18. What kind of vibrator should be used?

An electric vibrator with a 1-inch pencil head and a 12-14 foot shaft. Frequently these can be rented for 30-35 dollars per day. Many contractors rent a second vibrator as a spare and to use in doing windows while the second vibrator is up on the scaffold.
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19. I’m confused—Some ICF manufacturers recommend vibration of the concrete, others say to rod it or tap the outside of the form, and others say none of the above. What’s right?

The word here is to "consolidate" the concrete, which eliminates air pockets and voids. Elimination of these voids is required for the concrete wall to take on its full design strength. It is required by code and general good construction practice. Consolidation has three basic accepted methods, internal vibration with a concrete vibrator (this works the best), rodding (simply using a rod or piece of rebar and poking through the concrete multiple times, or tapping (tapping the forms with a hammer or other item). According to the CSA and American Standards, "all site placed concrete is to be consolidated sufficiently". Some manufacturers suggest you use the tapping method, and fill with a more fluid concrete (5-6" plasticizer induced slump). The problem is that an inexperienced crew often does not remove all the voids using this method. A reason that manufacturers make different recommendations regarding vibration is their concern for blowouts. There are variations in the relative strength of the block systems (during the pour and setting up of the concrete) from one manufacturer to another. Those manufacturers who suggest not to vibrate their forms in part stems from this blowout concern.

 

AMVIC ICF blocks were specifically designed to be strong and tight enough to resist blowout when they are mechanically vibrated with an internal vibrator. Mechanically vibrating the concrete in your AMVIC wall provides assurance that the wall will assume its full design strength. AMVIC recommends appropriate vibration.
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20. Why haven’t we seen more ICF construction on the West Coast?

The construction industry is generally slow to change and evolve. ICF got its start in more severe climates of the Northeast U.S. and Canada where the energy savings were obvious and overwhelming. Milder weather, abundant wood and business-as-usual made the west coast slower to adapt this new technology. Rising energy costs, cost and quality of lumber, and consumer demand have been changing this. ICF has been gradually moving west, particularly into areas with significant needs for air conditioning where the thermal mass of ICF drastically reduces electric bills for A/C.
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21. What will ICF construction mean for the future value of my home?

As energy costs continue to rise, and as ICF construction is more widely understood and appreciated it is reasonable to project that ICF houses will command a 10-15% premium over comparable stick-built homes in the not too distant future.
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22. Will I be able to find contractors and subcontractors who are familiar with and capable of building with ICFs?

There are contractors throughout the area that have built with ICF’s and others that are eager to adapt to the technology. We maintain a listing of contractors that are familiar with ICF and AMVIC. In addition we provide training for builders, that combined with site assistance from one of our consultants should overcome any problems associated with a first-time ICF build.

Selection of subcontractors will require a bit more screening than normal ... some are willing to learn new systems, and others may be inclined to avoid the job by "high bidding" their bid. A little shopping around should find subs who will work at prices comparable to conventional construction. The only subs that have to do anything different are electrical, and to some extent plumbing.
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23. Are their limitations on what kind of house you can build with ICFs?

No. Virtually any design that can be built with conventional framing can be built with ICFs with almost no limitations. There are special engineering requirements however, to cantilever out upper floors in a “garrison” style construction and it remains simpler to contain all ICF walls directly over the wall below.
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24. Does an ICF-built house look different than others?

From the exterior, there is no distinguishable difference in appearance. On the inside, the interior windows will be recessed deeper due to the 11 inch walls and have more interior design articulation.
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25. Do local building departments accept AMVIC?

Yes, however some local officials may have more experience with this than others. Most of the Northern California and Nevada counties have approved ICF projects recently. Most building departments have dealt with ICF construction previously and are knowledgeable about it. AMVIC's system has been approved by the ICBO Evaluation Service, the primary construction product certification organization in the country. The ICBO report number is ER-5948. Download this ICBO Report. If your onsite inspector is dealing with his first ICF project, it may take a little education and Amvic Pacific will assist you in that.
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26. Do I need an engineer to review my building plans?

ICF construction within seismic zones 3 & 4 (all of California and Northern Nevada) require that an engineer specify the structural elements of the design plan. Proper engineering will ensure that your construction project meets with local code requirements as well as ensuring proper design loads for hurricanes, earthquakes and other natural environmental conditions.

Our listing of AMVIC ICF-experienced structural engineers has qualified engineers for California, Nevada, and most other western states. Engineers can perform all of the calculations, or can use the HUD Prescriptive Tables for ICF Construction, 2nd Edition.
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27. Can I construct radius and angled walls using AMVIC ICFs?

Yes. Radius walls are constructed by removing sections from the inside side panel and bending the ICF into the required shape. Similarly, any angle can be made by miter cutting the form at the proper angle and using foam to join the edges. Ninety-degree and 45-degree corners are manufactured to speed construction since they are the most commonly used corner angle.

A newly introduced product/service from AMVIC is custom manufactured curved blocks to build curved walls. Available in three standard radii, if a custom radius is required, this is also available. Contact Amvic-Pacific if you are interested in this.
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28. Can I leave this product exposed to sunlight for extended periods of time?

Exposure of up to a year should not pose a significant problem. However, the ultraviolet light of sunlight will produce a light oxidation layer on the surface of the forms after extended periods of exposure. This oxidation does not indicate any detrimental effects to the wall form. If the proposed finish is to be a stucco (or other hard coat material), it is recommended that the oxidized layer be brush away to provide a clean bonding surface for the stucco materials. Ultimately the product needs to be protected with a covering coat of material.
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29. Does Expanded polystyrene (EPS) present a serious fire hazard?

The potentially flammable material in ICF walls is the foam. AMVIC is manufactured with a flame-retardant additive; these foams, unlike lumber, will not support combustion. Tests have shown that in the event of fire, EPS does not emit any gases any more harmful than those emitted by burning wood.
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30. I am concerned about mold and mildew in my new building. Will building with AMVIC block reduce or eliminate this problem?

Mold and mildew are not a problem when building with the AMVIC wall system. Mold and mildew are fungi that grow in a moist atmosphere. They tend to form on the interior/exterior of walls where moisture condenses as a result of surface/air temperature differences. (For example, interior warm air contacting relatively cool spots on a surface becomes colder, increases in relative humidity and condenses.) Once the fungus forms, it can discolor the materials beneath it, deteriorate the materials' structures, and emit particles that cause unpleasant odors or affect the health of the building occupants. The AMVIC block will not allow condensation and resultant mold or mildew growth on either side of a wall as there are no thermal breaks in the wall; the inside wall remains at room temperature and the outside wall remains at the outside ambient temperature. The AMVIC ICF form the perfect air and thermal barrier.

When used below grade, the inside of exterior walls should have a coating applied that allows moisture to pass through it should any moisture make its way behind the surface. Water based latex paints "breath" and allow any trapped moisture to ventilate.
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31. How much does it cost to build with AMVIC compared to other building materials?

This isn’t a simple question to answer. Best case is that it the same or slightly cheaper than framing with 2X4 construction. The worst case is up to a 4% greater project cost. The walls themselves cost more than equivalent wood framed walls. That’s only a part of the story however. With an experienced crew, the walls will go up faster than stick framing. There are construction savings on insulation, prepping for an exterior hard coat, reduced waste, and on sizing heating and air conditioning equipment, which can be reduced due to the thermal efficiency of the AMVIC building. If you are building on a hillside and would need to form a retaining wall, then building with the AMVIC system will be the same cost or even slightly lower than building conventionally. Probably the best working assumption is to assume either the same cost as stick frame up to a 1-2% increase in cost to go with AMVIC, and slightly higher to use other ICF block systems.

Building with AMVIC is comparable in cost to building with 2x6 wall construction. The AMVIC wall will give you an effective insulation value of R32—much greater than a 2x6 wall—allowing you to save 50-80% on your heating and cooling costs and rapidly becoming cheaper than stick framing over a very few years. Contact your local rep, Amvic-Pacific for assistance in estimating your project.

 

This article features an excellent discussion of the issues.


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32. How does AMVIC compare to concrete block or poured wall construction?

When cured, the concrete in AMVIC walls is 50% stronger and use 30% less concrete than traditionally poured walls. While the cost of a bare block or poured wall is less, AMVIC provides insulation and furring strips, and is ready to finish, making it a cost effective and less labor-intensive choice. AMVIC also is far less labor intensive to use where there are frequent openings and/or popouts as are frequently the case in residential construction.
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33. Can I see an actual AMVIC project?

Yes. Contact Amvic-Pacific 530-265-9085 ... we will let you know when the next project will be going up in your area.
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