Step-by-Step Construction Using the AMVIC Insulating Concrete Form System
Note: if you've never installed and poured an ICF wall before, it is strongly suggested that you take an appropriate installation training class and obtain onsite assistance at critical parts of the process.
Before starting to lay block:
- Rebar placement in footings or slab edge: Using a corner block and a straight block, layout and mark the rebar pattern on the footings form so that the rebar comes up approximately mid center between the webs and repeats on the same pattern (multiples of 6”) as the web. (The key here is that you do NOT want the rebar to layout so that it is hitting the webs on every block).
- Build your window and door bucks. Mark each with their size with a permanent marker.
- Materials. Gather your materials so that they are close at hand.
- If you have room bring all of the block you’ll need inside the foundation.
- Rebar. You’ll be doing a lot of rebar bending and cutting. If feasible, have the rebar delivered and dropped within the walls of the foundation. Otherwise, have it close. Put your rebar bender/cutter near the rebar.
- Bracing system. If you can, get it all inside the foundation before starting to lay block.
- 1) Check the levelness of your footings/slab … ideally you will be within ¼” all of the way around. If not, you’ll need to trim or shim. A laser level is the way to go … if you don’t have one, you can rent one from local rental companies.]
- 2) Layout and snap the lines for the interior edge of your block walls on the footing or slab. With AMVIC 6” block, the interior line will be exactly 11” from the exterior plan dimension. Use a permanent chalk or die if possible.
- 3) Layout and mark window and door openings.
- a) Use a marker and mark the centerline and dimensions of all windows and doors on the slab or footing. Measure and mark the appropriate dimension to cut the block for buck insertion (depends on type of buck being used).
- b) Using the plans, calculate the bottom height for the buck opening consistent with maintaining the specified window top height. Mark that on the slab/footing also.
- 4) First Course: Begin by placing corner blocks on each corner.
- 5) Start laying straight block from each corner toward the center of each wall segment.
- 6) Adjusting the wall sections: "stack joints". Almost always the block won't work out evenly on a wall section. Make your cut in the block in a doorway or under a window. That will minimize cutting and wasting block. Butt join the blocks at that line, and maintain that cut butt joint all the way up.
- 7) Complete the first course all of the way around the building.
- 8) Place horizontal rebar in the first course according to engineer’s specs.
- 9) Second course:
- a) Again start at the corners …. Flip the corner block over so that the long leg runs in the opposite direcition of the block below it. This starts a running bond overlap.
- b) Fill in with straight blocks.
- c) Maintain block alignment, i.e. keep the webs in line vertically so that the sheetrock installer has a straight "stud" line all the way up to fasten to without any jogs in the web alignment.
- d) Check the blocks at this point for level all of the way around. Best way is with a laser level. Second choice is a water level. If off by more than ¼”, or if there are dips or humps, then either shim or trim the bottom edge of the first course block to bring the block to level.
- 10) When level and straight, use your foam gun and insert the tip into the gap every foot or so along the bottom edge and shoot a spot of foam between the block and the concrete. Let the foam dry 1-2 hours to get a good grab on the block before you do any additional block work.
- 11) Insert horizontal rebar. Offset your rebar one web position from the rebar position in the first course. On the third course, return to the rebar position of the first course. Continue offsetting as you go up. The horizontal bars then will hold the vertical bars in place between them.
- 12) Third course. Continue up. The block layout should be the same as the first course.
- 13) Window and Door Bucks. By the third course you’ll be doing window bucks.
- a) You can use either vinyl manufactured window bucks (V-Buck) or you can build your bucks out of pressure treated wood.
- b) In either case the INSIDE dimension of your bucks, should be the appropriate required rough opening dimension specified for the windows and doors you will be installing.
- c) If using a single pressure treated buck, purchase 2x12 material and rip it down to an 11” width (for 6” blocks).
- d) Screws or galvanized nails should be inserted into the bucks so the concrete flows around them and anchors the bucks in the wall.
- e) Two 2x4’s should be used on the bottom side of the buck so that you can get a hose in to add concrete. If using vinyl bucks, you cut holes in the bottom side of the buck to achieve the same end.
- f) Before setting your buck in place, review the extra rebar requirements specified to wrap the window. Put the bottom course in before setting the buck.
- g) In some cases, you may have to cut out webs in order to fit required reinforcing steel in around door and window bucks. If so, mark that on the block so that you remember to come back and add OSB bracing where the web was removed.
- h) Ultimately, bucks need to be plumb, square and straight. When all block is laid and all the rebar is in place, then align the walls, plumb the corners, THEN plumb and square the bucks and install braces to lock that in. At the same time you need to install internal braces to make certain the weight and force of the concrete doesn’t cause the tops or sides of the bucks to bow.
- 14) Lintels. Carefully follow your plans for rebar placement in the lintels above windows. It can get crowded. Standard practice is to wire tie a 24” #4 rebar at a 45 degree angle so that 12” extends on either side of each corner of a window or door buck within the wall. The purpose of this rebar is to be a stop for cracking that is typical out of the corner of window.
- 15) Penetrations. Any through penetrations required for electrical, plumbing or HVAC should be placed at this point. Plastic pipe or wooden bucks can be used.
- 16) Floor Ledgers. There are two common ways of dealing with ledgers. In the first case, the ledger is installed before the pour, and in the second, it is done after the pour.
- a) Before the pour. If you go this way, you install the anchor bolts directly into the ledger (rather than in a scab) and hang the ledger on the block in its intended final position. To do so you have to either cut your strongbacks short to fit below the ledger, or you fir out the strongbacks to lap over the ledger. In any case, the ledger must be braced independently with kickers so that it doesn’t provide a twisting moment on the wall. A waterproof barrier must be installed on the ledger in the area where the concrete will touch the ledger.
- b) After the pour. In this case you cut out the foam and install the anchor bolts on scab pieces of OSB that are affixed by screwing the corners of the OSB into the webs of the ICF blocks. Subsequently, after the pour, you remove the OSB scabs, place the ledger on the wall below the bolts, and measure the bolt positions and drill and install the ledger. This gives you the ability to adjust the ledger to be dead level, and also doesn’t require fighting the bracing strongbacks around the ledger.
- 17) Ledger bolt installation. (The following method uses scab pieces of OSB to hold the anchor bolts in place during the pour. Subsequently the scabs are removed and the ledger installed level. There are other methods that work, and it is mostly a matter of preference.)
- a) Ledger bolts.
- i) Cut 8 X 8” squares of 7/16” OSB. This is adequate to cover a 4” wide opening by 5 or 6” high.
- ii) Bore a hole or holes in the OSB exactly corresponding to the size of the anchor bolts you are using and according to the placement specified by your plans. (In some cases there are single bolts, but staggered high and low in their placement. In other cases the bolts are all in a line. In still other cases, the engineer may specify two bolts at each location.)
- iii) Install your anchor bolts using a nut on each side of the OSB so that the bolt is held at a right angle to the OSB.
- iv) Leave enough anchor bolt protruding so that when you remove the OSB scab, and hang the ledger you will have enough bolt to go through the ledger, the anchor plate washer, and still have full thread contact on the nut.
- v) Using your plans, mark your ledger bolt layout on the foam block with a marking pen. Calculate your heights so that your finished floor comes out as specified.
- vi) Using a sharp pointed keyhole saw or pointed root pruning saw, cut openings of the size specified in your plans. Important: angle the top and the bottom of the opening at a 45 degree angle back into the block so that the concrete will fully flow into your opening around the anchor bolt.
- vii) Use drywall screws to fasten the OSB with the bolt installed into the opening. Place one screw into each corner so as to connect to the concealed web within the block. (It is imperative that all corners of the OSB scab be anchored into a web. In some cases you may have to make some larger OSB scabs to be able to reach the web.)
- 18) Alternative ledger attachment system. The Simpson Company now makes a commercial ledger attachment system that is quicker and easier to install. It is more expensive than the above system but substantially less labor to install the combined anchor and then subsequently to align the ledger level.
- 19) Bracing. There are several types of bracing that you will use. Nothing replaces expertise here. It is suggested on a first pour that having assistance from an experienced ICF builder is very important. The temporary bracing of an ICF wall prior to pouring is the trickiest part of the process. Get some help from someone who knows what they're doing.
- 20) Pouring the Walls
- a) Concrete specification. Your plans as approved should specify the concrete. AMVIC recommends 3/8” aggregate, 2500psi (min), 5 ½ sack and a 5 to 6” slump. Typically engineers in California will require 3000 psi concrete. No plasticizers are required.
- b) Pumps. Use a boom pump. Don’t even think about something else. Require a reducer to 2 ½ to 3 inches at the hose end.
- c) Vibrators. AMVIC recommends mechanical vibration. Without mechanical vibration you are most probably going to have voids in the walls. A 10-14 foot vibrator with a 1-inch pencil head is ideal. Do not use a larger head as the vibration is excessive and as well it can get stuck in the rebar. A good practice is to have two vibrators for the day of the pour. You can use one up on the scaffold and a second down at the window bucks, and also the second vibrator is a good spare.
- d) Personal equipment needed: Rubber gloves, hard hats, trowels, flat shovels.
- e) Lifts. Pour 3-5 feet at a time. Go around the structure and vibrate behind you as you pour and fill the walls. Generally, with AMVIC you can pour the walls in two lifts.
- f) Start the concrete flow in the center of wall segments and let it flow toward the corners and window bucks.
- g) In short wall segments and at T-wall junctures, be gentle in adding concrete, as when there is little room at the bottom of the wall for the concrete to spread out, the force is concentrated and excessive pressure on the block is created.
- h) Window bucks. Generally most builders find it easiest to fill the bucks first before pumping the rest of the wall.
- i) Stop the concrete at least 2 inches from the top of the block if you are going to be joining block later to pour another story. Leave the concrete deliberately rough for the next pour.
- a) Foam beads of any consequence down inside the wall are unacceptable as they create voids in the concrete when it is poured. Don’t cut block on the wall. Keep foam “sawdust” out of the wall. If you get it in, remove it either with a vacuum or by cutting temporary holes in the block and using a leaf blower to blow it out.
- b) Marking tools. Large size “Sharpie” brand permanent markers work very well for writing on dry block. If you are working in the wet, then use carpenters crayons.
- c) At the first course, if you write the dimensions for any cut block on the wall, you can then use that dimension all the way up and prevent wall growth or flare. At the same time, you can write rebar bend and cut lengths on the wall also and then repeat that as you lay each course.
Note: These are sample guidelines only. Practices will necessarily vary by locality and other requirements. In all cases, building codes, engineer and architect specifications and manufacturer’s specs and requirements take precedence over procedures referenced here. It is the builder’s responsibility to assure compliance with appropriate governing authorities for their specific project.
Pre-Install Checklist for AMVIC ICF
Except where noted, all of the following is to be on hand or completed, prior to the first day of laying block. Most of this stuff is absolutely necessary. In some cases there are alternatives that you can use but those are exceptions. Your job will go much smoother and faster if you have all of this on hand in advance. You can always return extra materials and that is preferable to running out.
Stuff to have on hand:
- q “Sharpie” indelible magic markers… full package of the large or medium. Used to write & draw on the block (carpenters pencils do not work). (If raining or heavy dew, Sharpies don’t work. In that case Carpenter’s crayons can be used).
- q Tapcon screws (0.25” diameter 1.25" hex head) and concrete drill bits (to use to anchor the feet of the alignment brace foot into the concrete. Figure 3 per foot (you’ll break some). Tapping fluid with small squirt discharge nozzle (also Dawn Dish Detergent works).
- q Other fasteners:
- Drywall screws ... 1 1/2" for screwing on OSB reinforcement sheeting
- Pan Head #8 x 1 1/2" screws. For fastening alignment bracing to the block
- q Alignment/bracing & scaffolding system.
- o Scaffold Planks in either case
- q Foam canisters (and gun)
- q Tie wire. 1 roll.
- q Sleeves (sched 20 pvc pipe) for mechanical and electrical penetrations.
- q Beam pockets and or any other structural steel and fasteners.
- q OSB – 7/16ths. Used for bracing.
- o Figure a 12” strip on each side and top of all window openings on both the inside and outside.
- o Also any “stack joints” will require a 14” or wider strip of OSB
- o If installing anchor bolts (without installing the ledger), each AB will require an 8” square of OSB with a hole drilled in the center.
- q If installing ledgers, then you need the specified anchor bolts, nuts (2 for each bolt), and square washers.
- q Sunblock, hats & dark glasses… the blast of sunlight reflecting off of the white block walls can be intense.
Tools to have on site:
- q Laser level
- q Chalkline
- q Mason’s Line
- q Plumb bob
- q 2’, 4’ and if available 6 or 8’ levels.
- q Framing square
- q Portable table saw for ripping block when required.
- q Hammer drill
- q 3/16” concrete bits for hammer drill (have at least 5)
- q Folding pruning saws or other hand saw for each crew member.
- q 4 or 4.5 inch hole saw OR a Keyhole Saw or other sharp-pointed course hand saw (drywall, pruning saw, etc.) that is suitable to plunge cut through the block to cut out 4”x5” holes in the foam to install Anchor Bolts on OSB patches.
- q Rebar bender/cutter.
- q Electric driver drills … several. Battery are handiest, but have a couple of corded versions as well. (belt hooks for driver drills are very handy).
- q Skill saw
- q Rebar tie tools
- q Hammer
- q Rebar Bender and Cutter
- q Wall Alignment System
- q Foam gun (and foam)
- q Wire needles (2). [Only required if the structure has any T-wall joints]. These are ¼ or 3/16 inch steel or stainless steel rods, three feet long, sharpened on one end with a small hole (wire tie size) drilled through the rod about 1-2 inches back from the sharp point. (These are used to thread tie wire through the wall to wrap the T-joint and hold it all in alignment.).
- q Move your rebar as close to the pad as possible. If feasible, the best location is inside the walls of the house.
- q Rebar bender setup by rebar.
- q Move all block to be used inside the walls of the footing
- q Move all bracing within the walls
- q Move all bucks within the walls.
Tasks to have completed before starting to lay block:
- q Check the footing or pad for level and note where it is not.
- q Snap a line on the pad or footing that will be the inside line of the block. Indelible chalk is best if you have it. (blue stuff wipes away pretty quickly).
- q Measure and mark the window and door layout on the pad/footing. Use a Sharpie again to mark
- o (a) the center of each window and door,
- o (b) the size of the buck, and
- o (c) for windows, the intended height of the bottom of the rough opening (the block cut line then being 1.5” below that).
- q Layout and mark any beam pockets on the pad/footing.
- q Construct all door and window bucks.
- o Rip 2x12’s to be used for bucks to 11” width.
- o Interior dimension of each buck should correspond to the required rough opening for the corresponding door /window.
- o MARK the bucks with a carpenter crayon or Sharpie as to their size, and or code of window and door schedule.
- o Drill a few 3” deck screws into the sides, top and bottom of the outside of the buck so that they are buried in the concrete when it is poured. One screw every 12-18” is adequate.
- q Build a buck for the power panel. This buck should have the inside dimension of the width of the entrance panel and should be continuous from the footing to the top plate of the house (if a single story) or up to the block level of the ledger if a multi-story. The power conduits should sweep up through the footing within this buck.
- q If you are installing anchor bolts, cut 8” squares of 7/16ths OSB with a hole drilled in the center that is the right size for the anchor bolts. Double nut the anchor bolts onto the OSB. (The threaded area of the AB must be long enough to span the nut, OSB and then leave thread out of the concrete to span the ledger, the square AB washer, and full threads on the nut. Typically this is about 2.5” of thread. Not all anchor bolts have that much thread, so verify this when you purchase the bolts). White Cap supply has a variety but they are mixed thread lengths in the same bins depending on their manufacturing source.
Stuff to have on the day of the pour
- q Concrete tools – hand floats and trowels
- q Rubber gloves for each crewmember
- q Hard hats for everyone (boom pumps and aggregate spilling off a wall top are dangerous)
- q Concrete Vibrator. Best is a vibrator with a 1” pencil head and a 12 or 14 foot shaft. (Do not exceed head size of 1 1/16ths inch. Larger head sizes can cause blowouts or hang up the vibrator on the rebar). Renting two of them is a good insurance idea… one is an on-site spare in case of failure of the first. Also you can use one in the window bucks and the 2nd up on the scaffolding. Have enough extension cord so that each vibrator can independently reach anywhere in the structure without having to change cords.
- q Blowout kit: Precut pieces of OSB, typically 24”x24”, drywall screws, battery driver drills, rubber gloves, ladder. (With the AMVIC system , if you install it properly you are unlikely to have any blowouts, however, it’s not uncommon to make a mistake in setup and so having this stuff ready makes a blowout a minor event taking 60-120 seconds to repair).
- q Spillage cleanup tools: Hose and water, trowels, flat shovels, push broom.
- q Anchor bolts and P.T. top plate for single story or top story of mult-story buildings.
- q Tip: schedule your concrete and boom pump at least one full week in advance. If doubtful, delay your pour a bit rather than rush. Always Always get the first time slot in the day on the boom pump … do not accept a schedule where the pump goes to another job before yours. Delay the pour if that is the situation. Once a pump is on another job, it can’t pull off if they have problems.