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.
Laying 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.
21) Other miscellany:
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.
