Spider Tie System Stem Wall Forms Complete

We finished building the stem wall forms last weekend! Personally I think they look super cool and I will be a bit sad to deconstruct them after we pour them. So much work to build them only to take them apart again and then just bury the whole thing underground.

The original plan was to pour the stem wall on Friday October 11th but our weather was once again not cooperating. We are got yet another rain storm fueled by a storm/hurricane that thankfully mostly missed us. Because of this storm we are now scheduled to pour it on Monday October 14th.

This was quite the ambitious DIY project for us. I can understand why we couldn't even get a company to put in a bid. Part of me is amazed that we pulled it off...so far. The truth will be in how it holds up to the concrete. It took almost 3000 screws to put the plywood skin on the Spider Tie towers and we cut 120 sheets of plywood! We joked that we were the Dometastic saw mill.

Watch some videos of the process. It is important to note that it was a bit different process to do the inside of the curved wall form than the outside. We had to use clamps on the inside and starter ties (Spider Tie) on the inside.
HERE is our impression of a sawmill.
HERE is a video of installing the outside of the form curve.
HERE is a video of installing the inside of the form curve.

The whole process ended up going really smoothly once we had our technique down. We found a few tricks that helped minimize the frustration of trying to tame two 8 ft long overlapping plywood sheets. Flat plywood does not like being forced onto curved forms! Oh and it is definitely NOT a one person job!

1. Use a cordless hammer drill. We have 2 and one is a hydraulic one. The hydraulic one didn't work as well as the other plain hammer drill. Not enough hammer for the drilling I guess.
2. Have many clamps to hold the 2 layers of plywood in place for the first side you put up and for the second side use the Spider Tie Starters as clamps.
3. Use a rubber mallet to get the sheets to conform. We had to really kick and pound on them to make them go in the bottom clips of the stacks.
4. Do yourself a huge favor and pre warp your plywood. We leaned our cut plywood strips up on dirt piles everywhere we could and weighted the middle with rocks to get them to warp into a curve. This helps tremendously when you are trying to make them go onto a curved structure.
5. Pre drill very tiny holes for each screw that is going into the plastic spider ties. It makes all the difference between total frustration and motoring right along through the 3000 screws you need to put in.
6. Change your screwdriver bit really often. Getting the screws properly into the ties ruins the bits really quick. We went through at least 15 bits....most likely more.

Overall the Spider Ties were well worth the cost! It made making curved forms much easier than we expected! If you want to learn more about them there are many YouTube videos and you can visit their website Spidertiesystem.com . You can also go back to my last post to see photos and video of installing the plastic ties along with all the rebar by clicking HERE.

We are trusting the advice from the company and we are NOT doing lots of external bracing of the walls. This has raised more than one eyebrow from pretty much anyone that has ever done any concrete work. We feel a bit like everyone thinks we are breaking the law of physics.

We only put up a few braces to true up the walls where they were not perfectly straight and on the outside of the big curves (just in case). In the areas where the forms are more than 30" high and in junctions between domes we put in long lag screws at the bottom of the forms. You can see these in some of the above photos if you look closely. These will come out as soon as the concrete starts to set. They are there to help with pressure at the bottom of the forms. We will be using a crane pump truck with reducers on it to minimize pressure when we fill the forms. According to Spider Tie this is all we need to do. Let's hope they are right!