Our House

One of the details to flesh out is how to get the wall upright and into place. As I research this process I’m certain it will take a variety of techniques.

In what I’ve been reading on preconstructed concrete panels I think the standard layup is outside layer, insulation, then inside layer. In the Pinkcore literature it’s the inside wythe that’s applied last and has the integrated lift bolts. This is reverse of what I intend. I want my inside walls flat and smooth so no additional finishing is required once the panels are up and connected together. I want my structural wythe layed last so my lift bolts are attached to the ferrocement reinforcing.

If I’m composing the panel on a layup table, using the table to tilt and support the panel until it is upright and supported by whatever device will support the panel until it is maneuvered into place sounds like a reasonable plan. Using the table to get the wall upright will reduces the stress on the panel and the connectors between the facia and structural wythes.

I learned a new word today. Wythe. Definition is “masonry layer”. In an insulated tiltup sandwhich the inside layer is the “facia wythe” and the external layer is the “structural wythe”.

One of my “must haves” is a non-thermally conductive connector to fasten the facia and structural wythes together through the insulating foam. It looks like Owens Corning has just the ticket. The pins made by Owens Corning are designed to have an exterior surface layer of 3″ for proper strength, but with ferrocement I don’t see that being an issue. The pins designed to be pressed through the rigid foam insulation into the initial layer of concrete. Very cool. (Installation instructions recommend vibrating or walking on the insulation at the point of the connector installation to establish good cement coverage around the point of the connector pin before the top layer of ferrocement is added).

Here’s the technical pdf link. PinkCoreXPS.pdf

I talked to Frank at our local Home Depot. Before we realized we were talking about two different things, he gave me the following prices. 3″ (R-15) sheets of Foamular (note this is not PinkCore) run $35.90, shipped in bundles of 32, 4″ (R-20) sheets are $48.11, shipped in bundles of 24. According to the PDf file the connectors are shipped separately but (I think) included in the price.

The first two pods will use 3¼ 4′x8′x3″ sheets per wall and there are 14 walls for a total of 45½ sheets. I will have 18 sheets left over at a surplus cost of $646.20 for the walls.

The amount needed for the roof equals what is needed for the walls, but in 4″ thickness. This bundling comes out about right, with two bundles equaling 48 sheets, 46 of which are required for the roof. Surplus cost on the roof is $96.22. Actually, because the pods nest the actual count for the roof will be a little more than 2 sheets less than what is required for the walls, boosting the surplus cost to $192.44.

Total cost for the Foamular, including surplus cost, is $4606.88. Update: Pinkcore (designed to be used with the connectors) isn’t Foamular and can’t be ordered from Home Depot. It’s a professional product and I’ll have to get it from a local distributor. Availability/pricing for pod insulation is now totally up in the air.

The edges of the Foamular are tongue and grooved and fit together snuggly. I don’t know if that’s the case with the Pinkcore.

I can get scrap EPS for the cost to get it here. So, say, for <$200 I can get it here and use my time and labor to cut and piece it. (I'll need to factor in the cost of the connectors which I haven't confirmed I can get.)

Can I thoroughly seal the EPS seams to eliminate any thermal break? Inquiring minds . . .

Truly, this entire process needs tested. It's possible I may not like how piecing the EPS goes. Or, I may find it a breeze and see no reason to go to the expense of purchasing Pinkcore XPS. I may piece the walls but not the roof. I may build the roof in place ala mxSteve instead of tilt-walling it and use 6″ surplus EPS as my insulation. Testing is a must. No firm decisions can be made until testing has been done.

What if . . . instead of using ferrocement for the inside layer of our home’s gross construction (remember . . . tilt-up preconstructed in layers from inside to out) I use papercrete? I really don’t need reinforcing on the inside, just a surface layer so I don’t have to do anything except run wiring, add fixtures and slap on paint. So why not papercrete? It would lighten the wall considerably and save on the cost of unnecessary reinforcing.

This SO sounds like a good plan . . .

For the interior walls that don’t need 6″ of insulation I could lay a layer of burlap on my form, run my boxes and conduit and “pour” a wall. I will have to try this . . .

I still need to find non-conductive button type connectors to fasten the inside layer of ferrocement/papercrete/fibercrete to the outside structural layer.

I get bored occasionally, or I’m on hold waiting on a client and have a few minutes to fill, so I do internet searches. Today I did a search on thin shelled structures and found some VERY interesting things.

This site has a catalog of fascinating ferrocement and other thin shelled structures. I’ve started from the bottom up and while there are a number of structures I find very appealing, so far two have captured my imagination.

In England at the Weald and Downland Museum is a green oak building that is a serious piece of craftsmanship. It is a marvelous blend of old and new technology. The use of scaffolding and the grid construction process is very interesting. Follow the construction link on the site to read through the process.

This structure (go look at the image at the link, it’s awesome) is truly a thing of beauty as well as being a serious work of craftsmanship. Here’s a picture of the inside. Isn’t that beautiful? I can see this done in ferrocement. Awesome. This is definately an mxSteve type building, on steroids. What an elegant shape!

I’ve got a friend who’s a whiz at math (masters level) and I’ve asked her to check my figures on my wall dimensions for the inset portions of my floorplan. My rough calculations put the wall height at the apex 3 foot higher on a 12 foot long wall with 4/12 pitch. 3/12 pitch would put the difference at 27″.