You may have heard of ICF, which stands for Insulated Concrete Forms. ICF usually come in some type of block of Styrofoam or EPS that one can stack to form the house walls and then pour full of concrete. The blocks are already engineered to fit together and provide flexibility with corners, curves and other wall features. The form becomes part of the final wall and provides a great R-value for insulating a home. Though I have not tried it, I think two people could easily setup the walls. But there are a few issues that I have with it that deterred me to try something different.
- Price - the blocks are pretty expensive
- Finishing the inside - You need to still finish the inside with another material
- Finishing the outside - You will probably want to finish the outside with another material
- More price - Even after the blocks being expensive, you still have to pay for the above interior and exterior finishes
- 16 - 4'x8' sheets at about $33 a sheet
- 2"x4'x8' at about $27 per sheet
- #4 rebar in 20' lengths
- 100 - 1/2"x2' threaded rods with two nuts and two washers per rod
- 1/2"x10' PVC pipes
- 1"x2"x8' treated wood boards (0.75" thick)
- 2"x4"x10' treated wood boards
- We drilled holes in the plyform panels to optimize the load of the concrete pressure on the forms. The horizontal spacing was 2' in the 8' length of the board (1', 3', 5', 7'). We used 16" vertical spacing (8", 24", 40") for the holes.
- We cut EPS panels and doubled them up (4") to fit between two plyform panels.
- We cut PVC peices into 5" and 2.25" lengths.
- We made straps from the 1"x2" boards and drilled wholes in them to match the vertical spacing of the plyform holes.
- We assembled the formwork in place by putting threaded rod through first plyform, a 5" PVC, a strap, the 4" of EPS, another strap, a 2.25" PVC, and then the other plyform.
- Once all 12 holes have threaded rods through, we put the 2"x4" boards laying across the rows of threaded rod on each exterior side of the plyforms.
- Then we placed another set of straps on the outside of this.
- Finally, we put washers and nuts on and tightened everything up to make it rigid.
- We tied rebar on the 5.75" side within the wall cavity both vertically and horizontally.
- We repeated this process, placing the next set off the end of the previous.
- Once the wall is formed, we put end caps on and braced it up with some metal stakes at the bottom and some 2"X4" at the top down to the ground.
- We framed a door opening inside the forms.
- We put nailers and keyways in the form cavities.
- We poured it full of concrete to a height of 48".
- We let the concrete sit a day or two and removed the 2"x4" boards, the rods, and the forms.
- We cleaned the forms up some.
- We reassembled the forms with the bottom set of holes in the plyform lined up with the top set of holes from the previous pour and repeated the process to result in an additional 32" of height.
- We repeated again (including door and window openings) for the final 32" of height to add up to 48"+32"+32"=112"
Overall, we are satisfied with the result, and saved about $7,000 fomr the price quoted by a company that pours solid concrete walls without the insulation in them. This picture peers through one window to the back walls.
I built a set of scaffolding brackets that I can fit into the threaded rod holes to support a set of planks for walking around. It gives me an idea of what the view should look like on the back deck.
That is the short of the story. It took us a period of 5 months to do it with me working full time in the prison, going to our kids' soccer games, and battling the freezing weather since November. We are now getting ready to frame the floor deck and go up higher :)