Retaining Wall with SCIPs - Part Two

Today we built and installed the panels. Because we were building the panels ourselves we made them 36" to fit our needs and laid them on their sides. The panels are strong either way, but without a roof load to support, sideways is fine.

The panels were cut and installed. we cut the foam out where we plan to spray in columns around the rebar we installed the other day. We also cut out where the drainage pipes need to go through. We used a quick level to see where things were, but we will need to use a water or laser level to make sure everything is even.

Cutting out the foam was easy but more time consuming then I would like. Snaking the 4 pieces of rebar through the trusses had a few challanges as well, but got easier as we did a few. Normally, you would spray a column between upright panels which is a much simplier process.

At the end of the next day the panels were built and installed including pipe and rebar cut-outs.

We need to clip on a few connecting pieces and relevel and we can start shotcreting.

Retaining Wall with SCIPs - Part One - The Preparation

Over the next few weeks and next few blog postings, I'll document how to create a retaining wall using BuildFast SCIP panels.

The first step is very important. Injure your hand preventing you from doing any actual work. Indoor soccer worked for me, but there are many ways to do this.

The real first step is to lay out where you want the wall with string.

Make sure its straight, parallel to existing house and square by using 3-4-5 triangle (Pythagorean Theorem). There is plenty of info on the web on how to do this.


Next dig a shallow trench and post holes about every four feet. The trench will become the toe of the wall and the posts holes will give the wallextra bite into the ground.

QUICK TIP: Use the panel trusses as guides and support for the post rebar. It will guide the workers to center the rebar in trench, not the hole. It also makes sure they will be within the width of the wall (same as truss) without measuring.


Finally, pour the post concrete.

End of Day One - Trench dug and rebar posts are poured. Next step - install the panels.

Next

Lloyd Turner's Soap Bubble Architecture

Last weekend, I had the pleasure of meeting Lloyd Turner and seeing his beautiful home in Boulder Creek, CA. Here refers to design as "soap bubble" architecture, where the inside edges are straight and the outside is round - this is one of nature's inherently strong and efficient shapes. It is also important to note the rooms/bubbles are torispheres, not hemispheres (i.e. domes) - unlike a dome, a torisphere's walls do not arch in until they are close to the ceiling giving you full use of the floor plan below.

From the outside, only the top of partially buried domes emerge from the earth like they were grown there. Inside the rooms are warm and comfortable. A wood burning stove kept the house warm, while skylights provide plenty of light. Built in 1982, the house is in as good of condition as the day it was built thanks to its strong foundation, subterranean drainage system, and inherently strong design. Lloyd also had to design the operable skylights, round egress windows, and more.

Lloyd's construction technique:

Unlike Monolithic Dome or other air-form techniques that require extremely strong membranes, high powered fans, and airlocks, Lloyd's design uses simple Tyvek fabric and inflated with a fan - no airlock is needed for this low pressure air form. Instead he applies increasing thick layers of polyurethane foam - allowing each layer to start to set up and create the structure as he goes. In this construction photo - the first layer of foam is applied so thin the shadows of the tree branches can be seen through it. By the time he got to end he could start the next layer and within 4 layers he was able to get to 4" of foam. With 4" of foam the form is much stronger and it can hold the weight of 3/4" of shotcrete without deforming and the same layer process is continued, with a day between layers, until 2" of concrete is applied. Thus, Lloyd got the structure to "grow" with ever increasing layers until the structure was 6" of foam and concrete, all with a simple light weight air-form. Tyvek was used because it does not need to be removed after construction (the moisture can escape and it can be stuccoed over) and the gores (see airform panels design link below) can be taped together.

The airform created the concave exterior walls and roof. Temporary 1"x4" boards were used to maintain the proper arch on the top of the straight interior walls. Once the foam was sprayed onto the airform the wood framing was replaced with structural concrete insulated panels (SCIPs) similar to the ones we sell at BuildFast. Then re-bar ribbing was added at the connecting points of the airform and SCIPs to give it extra strength. The metal fiber reinforced shotcrete is then sprayed in successive thin layers to the underside of the foam domes until the required thickness is achieved. It doesn't take any longer to quickly apply several thin layers as it does to apply the full thickness while standing in one spot. Thus a a unique structure that will last for generations was built with a simple low pressure inflated form. For more info on the process check out Flying Concrete's page on the house.

Links with photos, design math, and more:

Photos

Torisphere Airform Calculations

Airform Panel Design

House Plan

Update - Lloyd asked me to add one more thing:

If you pour the foundation only (no slab) first, then spray the walls and ceiling - any concrete that falls/bounces off can be covered and incorporated into the slab when it poured at the end. Also to note, the electrical and plumbing were all put into the slab as well. Hope this helps.

Hopper Sprayers - A great tool to plaster SCIPs

There are several ways to plaster SCIP panels with a concrete/mortar mix. Hand troweling is a viable option where labor is extremely affordable. BlastCrete mortar pumps are expensive, but a great option for large scale operations. However, for most do-it-yourself projects including up to building your own house, I would recommend a hopper/stucco/mortar sprayer. One sprayer in particular is a mortar sprayer developed by Nolan Scheid. Nolan has been spraying mortar for over 15 years and has used his expertise to develop a hopper sprayer that is easy to use and very forgiving. It requires a 5HP air compressor (7-12 CFM at 90 PSI) and a mortar mixer to prepare the mix. We plan to offer these hoppers in the BuildFast store, but for now you can buy them at How to Stucco.

Back to Business

The BuildFast website will be coming out of retirement. After a short hiatus with a new baby, house construction and a lot of reflection on the business I am reopening the BuildFast website and blog. I tried to take some time to step back and reevaluate the technology. How does it stack up to other technologies and is there a business supporting the SCIP technology?

First, Structural Concrete Insulated Panels (SCIP) are still a valid technology. There are challenges with adoption (tradesman, building inspectors) and you can always build a cheaper wooden shack or mud, but this is still one of the best technologies to build a disaster resistant, rot proof, highly insulated structure that can last decades without maintenance.

However the new site is going to be more focused on how to help individuals build their own houses and other structures with SCIP panels. We want to over techniques, advices, and the tools to make the job easy and successful. We look forward to being part of the change in better building in the US and beyond.

great visit from the students at IPADE

Yesterday, executive MBA students from IPADE visited our offices in Redwood City. The 20 students and professors are visiting Silicon Valley for a few days to learn more about innovation and entrepreneurship. It is quite flattering to be on the same tour as Google and Northwest Venture Partners. They were a very sharp group and I probably learned more from them then they did from me. We talked a lot about the cultural challenges of building in Mexico (or anywhere for that matter) with a new type of building system no matter how much better it is. I hope have a great visit and I will look them up the next time I am in Monterrey or Mexico City.

CCTO

I haven't being blogging much lately; I have been busy in the shop working on changes to our panel machine. I started this blog to talk about better building techniques for the developing world and to ask people for their input. But first I want to make another plug for the California Clean Tech Open which is hosting their 2008 Official Launch tomorrow at the San Jose City Hall Rotunda. We will be there. I was also on a panel CCTO did for the Commonwealth Club at the end of February. That will be all for now about where I was or will be; we have a project in Mexico we have been asked to help with and I could use input on best practices for passive heating, composting toilets, low cost solar, etc. More to come.

Regards,
Patrick