I wanted to experiment with flat roof structures also, and it seemed like the best way to do that would be with the Quad Deck panels (we also used these to cover the basement). This is some explanation of how we did that.
First, the video.
The Video
The Basics
Quad deck is fancy formwork (Insulated Concrete Formwork, AKA ICFs) for pouring a concrete slab over an open space. To increase strength of the final concrete structure, Quad deck shapes the concrete into Ibeams. It also includes its own internal steel structure to help it resist deflection before the concrete cures. The EPS (expanded polystyrene) foam is the tough 25 PSI stuff.
When installing, there are a few key concepts to be aware of.
First, you need to support the weight of wet concrete until it cures. This means you will need secure shoring. The brochures show fancy specialized equipment, but scaffolding and cross beams works also. These need to be strong, so do a little math and make sure that your shoring can handle the load.
Second, the concrete is going to try and push the ICFs apart. If it can separate them, it will just spill thru between them and you will have a huge mess. Toe nailing screws thru the shoring cross beams and into the steel reinforcement in the ICFs can prevent them from moving apart. The “experts” who installed my basement used drywall screws. I had a much easier time using self tapping metal screws that could easily tap into the steel reinforcement in the Quad Deck.
Third, don’t forget you will need to remove the shoring later 😉 The guys who did my basement often put screws in at angles that were only possible if the Quad Deck wasn’t there. That gave me quite a hassle. Build your shoring from below so that it can be removed from below.
Fourth, keep in mind that the concrete needs to sit on the perimeter ledge. You will be removing that shoring, so the concrete needs to be firmly distributing its weight on the ledge around the perimeter. This means you need to remove all the insulation from the edge of the QuadDeck panels. It is tempting to leave some and let the ICF overlap the edge a little, but every bit of the ledge covered by the ICF is a bit of the ledge not supporting the load.
Fifth, you will need to mind the gap. After installing the quad deck. you can use spray foam insulation to close up any gaps between the wall and the quad deck. Remember from 4 that we don’t want any insulation on the ledge.
Sixth, following your rebar specs, and especially rebar for the bond beam around the perimeter, is critical for strength. Concrete is terrible in tension, you need the rebar for any sort of flat floor to carry a load because that load inevitably creates tension, especially in the bottom of the Ibeams.
Seventh, this is a pour, so close all the sides… Also, make sure that the perimeter wall is to the correct height for easy finishing, etc. Don’t just mark the wall where they should fill to, trim it off if you can.
Maybe I’ll come back and add more later.
The Gallery
A pic is worth a thousand words and here are a bunch of pics.
These beams will both support the load of the concrete and prevent it from separating the quad deck pieces (when screwed thru to the internal steel)
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First two pieces in place.
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I cut the quad deck on saw horses in the room below.
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From this edge, you can see how the quad deck fits together
The Pink insulation is to make it easy to knock out that opening later. It basically just prevents the concrete from filling that space.
THe underside after the quad deck is in. You can see the perpendicular beams that will keep the quad deck together.
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These pics should give you an idea of the building space… One wrong step and you are headed down.
Just the quad deck
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Just a pic.
This was where one of the edges of the quad deck broke off. It was too big to fix with spray foam.
The fix was to screw a board across the hole
We are ready to shoot, but still waiting on the gunite crew
Quad-Deck is a product sold by Quad-Lock, an ICF (Insulated Concrete Forms) company. It is basically a flooring (or roofing) system that uses polystyrene as a form for concrete. The panels click together and include steel beams so they can span greater distances (with less shoring) while supporting the wet concrete. The concrete hardens to form a continuous floor over the panels and the panels are left in place as insulation.
My unique earth sheltered home design includes a basement. This increased the height of the walls holding back earth. Structurally, I needed my floor to be a sheer plane that would prevent the earth from pushing in those walls by transferring the lateral loads right thru the house into the dirt on the other side. The resulting compression would be well handled by a concrete floor. I just had to find the easiest way to build one.
I could have built a deck out of wood or steel panels supported by bracing and just poured concrete over that. There are modular systems that work pretty well and are cost effective for rectangular buildings, but my curved shape would make it quite difficult and expensive. Also, those systems generally produce a uniform concrete thickness, which adds to the expense.
ICFs had the advantage of being easy to setup and easy to trim. They also use less concrete because they can form that stronger IBeam shape. The insulation is also perfect for my in-floor radiant heating and helps with more consistent indoor temperatures and reduced sound transmission.
Unlike ICF building blocks, there are very few companies that make this sort of ICF floor system, just about the only other company with a similar product is “Lite-Deck”, but they had no distributors in my region. AMDeck is a similar product that only comes in short pieces (32 inches long) so you don’t need to order custom lengths, but you need to place the steel joists separately and then place the Insulation over them and it just seemed like more could go wrong.
The Video
The Process
1) The quad deck panels are cut to length (according to a cut sheet I provided) in the factory and shipped to the site.
2) The installers (in my case, Dan and Brian), started by setting up scaffolding spaced across the floor. Beams were placed across the scaffolding and the scaffold legs were adjusted to level the beams across the space.
3) My curved walls required both ends of every piece to be shaped to fit. This was done with a measuring tape and a saws-all. Occasionally a big cutting wheel was used.
4) Each piece was pushed up against the previous piece before being screwed in place so that they would be held tightly together. The screws were “toe-nailed” thru the wood shoring and into the steel reinforcement.
5) Spray foam was used to seal the gaps between the top edge of the wall and quad deck material.
6) Rebar was placed in the channel and across the quad deck according to the drawing. Rebar chairs were used.
7) A perimeter form, plumbing, electrical, HVAC, radiant floor PEX, etc. were added later (next post).
Surprises
In my region, it seemed like I pretty much had to go with QuadDeck if I wanted this sort of product. To make matters worse, QuadDeck only had one single installer in my region. I asked for a quote on both the quad deck and the ICF walls of the garage. The wall quote from this builder was not even in the top 3 and several times more expensive than doing FoxBlocks myself. But they were the only quote for the Quad Deck, and I thought special bracing was needed, so I decided to go with them for that portion of the build. The quote was for “Quad Deck install, labor and shoring rental.” I called for further clarification and was told it would get the quad deck ready for the pour, but did not include the actual concrete or labor to pour and finish the floor. I would need to call a separate contractor for that. The price was high, but acceptable for a company with specialty experience and equipment, so I put them in my estimate.
Later that summer, after back-filling around the basement, it was time to get the quote updated and call the crew out. I sent in pictures of the basement (including zoomed in shots of the edge of the wall), along with a cut-sheet and images from my 3D model, calculations from the QuadDeck manual (it is a pre-engineered product), etc. They updated the quote, but said they wanted an engineering stamp before they would start work.
My engineer had retired (still young, but wanted to stay home with his kids), so I contacted the builder’s engineer. He was willing to check and stamp my work and he was very affordable, but he was also very old (eighty something) and only worked face to face (no computers). I would need to take him drawings and he would hand calculate and stamp them if he approved. There was a funny telephone episode where I was asking him his address (so I could google map it), but he just kept repeating how to get to his office via landmarks. Before I could get out there (he lived 4 hours away), he had a stroke and retired. I didn’t want to pay a new engineer to learn about QuadDeck, so I began a search for someone with experience. The builder wasn’t much help. I even called quad-lock company headquarters and they just forwarded my request back to the builder. I called QuadDeck back a few times and asked for other regions until I eventually found an Engineering company in the southwest that was licensed to stamp a drawing in Michigan. It ended up adding a surprise $1200 to my estimated cost, but may have saved me some money because my version would have used twice as much rebar (I was being conservative with the Quad Deck load calculations).
I still couldn’t schedule the builder to come out. I tried to go around him, but it turned out he was also the only builder in the surrounding 4 states. He had a monopoly and ran his business that way.
Eventually, we got the quad deck panels ordered. I knew it would take weeks for my order to be cut and then delivered. They were supposed to call me with a delivery time 24 hours in advance so I could organize to unload. Instead I got an annoyed call from the driver at 6:00 in the morning wondering why there was no one at the building site. Surprise, my 10-year-old and I hopped in my car and drove the hour out to the property, but there was no way to organize any other help in that short time. When I got there a little after 7:00 AM, there was a large 18 wheeler trailer full of QuadDeck planks waiting for me. It was the closed in kind with big double doors at the back, so I could not unload with my fork lift. The panels were stacked to the roof and would need to be removed by hand, slid out one at a time. I had to get a 13 ft ladder just to reach the panels. The driver was impatient, so David and I got to work without setting up the camera. The driver complained that we were taking too long, so I told him that he could have called to let us know he was coming (as he was supposed to do) or he could help. He helped a little with a couple of pieces that David could not physically lift, but generally speaking, he just paced back and forth. Eventually we got them all out of the truck and the driver shook David’s hand before he left. I think he was impressed with David, but was also still pretty annoyed with me for not having a real crew.
We used the SkidSteer to move the blocks up behind the house and stacked them and covered them with a tarp… And then waited. Every few weeks, the builder made up some excuse and moved the date back. The list of back and forth texts is quite ridiculous. Eventually, 3 months later, he said he would be able to slot me in before the end of Sept (one week away). He asked if I had the rebar on site, I did. He asked if I had the full list of building materials he needed… I had no idea what he was talking about. He sent me a list, which added up to $1700. Surprise! The list included 4×6 beams, 35 lbs worth of screws, 3/4 inch plywood, 2x4s, 2x6s, a case of spray foam, anchor bolts, etc. I called him and asked if he was planning to build the shoring? I was obviously annoyed, which annoyed him and he said we could just call off the whole thing and I could look for another builder.
Of course, I already had the material on site and he knew he was the only builder within 1000 miles that had ever installed this stuff before… I gave in and we proceeded. He then told me that his quote did not include the perimeter forms that would also be needed before we poured, but he could do that for an extra cost. I was so annoyed, I didn’t even want to discuss the extra costs or argue that he never mentioned this before, so I told him I would take care of that myself.
I asked how many days it would take for what was included in the quote, he said 6 or 7 days for a crew of 3 people.
Anyway, as you can see from the video, it took 1 day just to set up the shoring (which turned out to be regular scaffolding and my 4×6 beams, leveled). Then 2 days to put in the quad deck. There was also a short 4th day of just a couple of hours when they finished the quad deck off and were gone by 9:00 AM to work on pouring some other wall somewhere else. Then the last day was just putting in rebar and spray foaming. The main boss never even made it out to the property.
After the job was done, he sent a final bill that included about 2000$ extra costs for “unexpected extra work” including putting in rebar and spray foam and “gasoline for the generator”, etc. I was sick of the surprises and fought him on most of it. He kept asking me to “meet him half way”. Instead I went thru my emails, texts and time-stamped-timelapse photos and wrote up what could easily have been a trial defense. For instance, I pointed out that he had estimated 7 days for 3 people, but got the job done in 4 days with mostly 2 people, how could he justify “extra costs”? He eventually gave in on most of the bogus extra charges, but still got his “36$ for gasoline for the generator”. I just wanted to move on.
Then he hit me with the scaffold rental. He wanted several thousand for that. I told him that his quote said “labor and scaffold rental”. He said that was just the first 2 weeks, I had kept the scaffolding for 3 weeks longer than that to finish getting it ready for pour and then leaving the scaffolding in for 2 weeks while the floor set. He wanted $15 per unit for those 3 weeks. I eventually agreed, but then he defined the units as half sets (so twice the cost). Arg! long story short, I ended up paying an additional 810$ to rent that scaffolding for 3 weeks. For perspective, I paid $1200 to buy my other 5 sets of scaffolding, and that included 6 decks, 8 wheels, outriggers, a grouser bar, etc.
Anyway, as much as I liked the idea of QuadDeck, I would never work with that builder again. I have some quad deck left for the roof of the mezzanine. I plan to install it myself.
Bonus fun facts…
1) The scaffolding that I rented has been stacked nicely and ready for pickup for almost 4 months with no responses to my monthly texts to the builder to come and pick ’em up. You will see it in the background of various other videos ;^) It was actually quite labor intensive to remove it from the basement (next video), so I hope the builder appreciates that that free labor. I wonder if I could surprise him with storage fees?
2) At the end of each day, the guys did a great job cleaning up the site. They used a leaf mulcher to suck up and bag the little broken bits of Styrofoam so they wouldn’t blow all over the place and they carefully stacked the other trash.
Cost
The original quote was about 4$/sqft for quad deck materials. That turned into 6$ by the time we placed the order (including freight). Then another $7/sqft for labor and shoring rental. I also budgeted about $1 for rebar and 2$ for concrete, plus 3$ for labor to pour and finish the floor. Then I had the surprise of just over 1$ for engineering plus just under 2$ for extra materials (some of which I was able to return unused and much of which I will reuse elsewhere in the build). Then, finally, that ridiculous “additional” scaffold rental at the end, which divided out to just under 1$/sqft. That comes to about ~22$/sqft by the time we were done. Quite a bit over-budget, but survivable.
At the moment, the construction schedule has 3 main paths.
1) On the east side, we are getting the steel arches rolled. We can start to erect those after the excavator comes in and sorts out the grading issue, but they are waiting on the frost laws to allow them to carry their heavy equipment on the roads.
2) On the west side, I am getting the Quonset hut ready as a work shop to build the wooden forms for the precast concrete ribs.
I probably have a months worth of work on each of these sides before the paths converge on the middle.
3) In the middle of the house, I need to get in these steel posts that will support the ring beam that will eventually support the precast concrete ribs that will eventually hold up the steel arches and shotcrete that will form the radial vaults.
This weeks video is about setting up the posts for the center section.
The Video
The Story
I’ll put the story in here to provide a little more detail and to make it text searchable for Google ;^).
Working backwards:
In this region of the earth sheltered house, the load from earth above (not shown) is directed, by the radial vaults (made of heavy shotcrete over steel arches), down onto the precast concrete ribs.
On the outside edge of the house, these radiating concrete ribs (which weigh almost 5000 lbs each) are sitting right on 4’x4′ concrete pads made of strong reinforced concrete 1 ft thick. However, at the middle of the house, the high end of these ribs are set into a central tower made of shotcrete (which will carry most of the final loads) over a steel skeleton (which will carry all the loads during construction before the shotcrete is in place). This image also shows the QuadDeck ICF floor forms. When concrete is poured over these, it will help lock the steel posts into position.
The load of those 10 heavy ribs runs thru the ring beam and down the structural steel columns into the shotcrete basement wall below.
The 3D CAD model shows a nice flat surface where these pipes attach to the top of the basement wall.
The reality is that the shotcrete guys did not do a great job of squaring off the edge of this wall, probably because it was 9 ft tall and hard to reach. I needed to fix that. I setup some cardboard forms to the level the wall should be at and backfilled with hydrolic mortar. It was thin enough that it was pretty much self leveling.
The next step was to prepare the steel bases. I bought a box of scaffold bases for $4 each, but the (nail) holes were too small to fit the anchors thru. I drilled them out using the lowest setting on my drill press and some lubrication.
Drilling steel requires low speed and lubrication. I lubricated with thread cutting oil. The smallest container I could find was much more than I would need and only cost ~4$, the drill bit was 7$, so I used the lubricant generously in order to preserve the life of the bit. I found applying it directly to the bit was the best way. If the bit started to smoke, I would stop the drill and add more oil. If the speed/pressure and lubrication are correct, long spirals of metal will come off. This indicates that the steel is being cut and not just wearing away the bit.
Then it was time to head back out and mount the bases to the wall. I was using sleeve anchors that require you to drill a hole first, and then drop the anchor in the hole. It is important that the sleeve be completely below the surface. When you tighten the nut, the sleeve is expanded and presses against the sides while the nut pulls what ever you are attaching down toward the sleeve… I was in a rush and didn’t put one of the first anchors in properly. There was probably dust in the hole. But I couldn’t pull it out again either. With the sleeve too high, the nut tightened against it before pressing the metal to the concrete, so it would never be tight. Eventually, it will be under another ft of concrete, so I was not too worried about it, but I put the rest in more carefully.
I was also careful to make sure each scaffold base was level so it would be easier to plumb the columns later.
My steel posts were ready a couple days earlier than promised (a first for me on this build), so I picked them up in my trusty trailer. They weighed about 100 lbs each and put the trailer near its official limit, but it felt like it pulled easily.
The following weekend, my parents visited with my sister.
The mission was to move the steel posts into position on the base plates, hold them steady and level and then tack them into place with my welder. The first one worked pretty well. But the welder jammed on the second one. I couldn’t untangle it, so we had to cut out all that welding wire and re-setup the machine. From then on, I always checked the wire spool every time I moved the welder to make sure that it was not tangled.
This third post was the one on the less stable base, so we added extra bracing to keep it plumb until the concrete is poured around it. We had a lot of experience pluming steel last summer, so everyone knew exactly what to do and it only took a minute or so.
My sister and I both enjoyed the welding, so we took turns welding vs holding… Some times on the same post if it was tricky to access a certain point. The most time consuming part of the process was simply adjusting the scaffolding, etc. so we could reach what ever we needed to reach.
It took us about an hour to get the first 5 posts in, but they were on the side of the circle that was easy to reach. We were expecting the back side, were we had to balance on the wall, to be more difficult, but it was pretty easy too.
After all the posts were in place, I was worried that someone may give these a good push and cause them to shift… Yes, they are welded to steel plates bolted into strong concrete with 3 inch steel anchors, but an 8ft long 100lb lever would probably be able to pry those out.
I wanted to weld the ring beam on right away, but each half was 320 lbs and I couldn’t think of a safe way to get them into position.
So we decided to weld some rebar between the posts as a temporary solution. This was nice and easy and I really liked the look of it, so it will be sad to have to cut most of it off again when we need to put the door bucks in.
I was not sure how far my tank of shielding gas (Ar and CO2 for the MIG welder) would go, so we only did tack welds. That turned out to be a good decision because it ran out just before we were done. Without the gas, the final few welds looked pretty ugly.
After that, we put in some work prepping the shop for building the forms, and I will talk about that another time.
The next step in this center section will be getting in the QuadDeck ICF (insulated concrete form) floor over the basement. I am having a painful time getting that scheduled.
The rest of the steel arches are still being rolled and I will soon start on the forms for the ribs.
