Estimating construction costs

I’ll be up front about my reasons for using ferrocement. I want to be warm and dry on a budget. I want something that is functional and looks nice when I’m done. I want low/no maintenance. I have to like looking at it AND living in it and it’s got to suit the site. Being a woman, I want it all.

Per square foot house construction costs vary greatly. There’s a log home construction business on the freeway going north that was advertising homes starting at $25 a square foot. I’m pretty sure that’s only for the structure, no site prep, etc. Some papercrete people say the cost to build a papercrete home is around $1 a square foot, others say it’s more realistic to estimate the cost at $10/sf. The first probably doesn’t include the cost of windows, wiring, plumbing, foundation. The $10/sf figure might take those costs into consideration. So when it comes to figuring out what a home is actually going to cost, it’s necessary to know what is being included in the figure being quoted. For the sake of discussion, let’s assume we’re only speaking of structural materials expense. No labor, permits or professional consulting (ie: engineering), no toilets, tubs or chandeliers.

Certain costs are going to be the same per square foot regardless of the method of construction. For identical floor plans on the same site, the wiring, plumbing and foundation(+/-) should be comparable. The difference in structure cost appears when you start considering different structural materials and methods. As an example, there’s a fairly brisk span between the structural costs of log and papercrete homes.

Even in buildings with the same basic components, the method of application is going to effect cost. Papercrete and ferrocement both use concrete for construction. Ferrocement has significantly more reinforcing. Papercrete may actually use more cement.

Papercrete has a lot to offer as a building medium. The volume of paper that can be obtained at a truly minimal cost is impressive. But without established building code and accepted building practices, getting plans for a papercrete house permitted in our County could be decidedly problematic. If I were adamant to have a papercrete home I might want to push it. We’ve got domes and earthships already, so why not papercrete.

I am considered two different ways to marry ferrocement and papercrete. Neither method exposes the papercrete to our weather nor asks it to play a structural role.

The first is to use papercrete as the fascia layer. Papercrete out-performs concrete in echo suppression and insulative values, but underperforms it in thermal mass/inch of thickness. My primary concerns with papercrete are shrinkage when curing/drying and water absorption after construction is complete. What changes can I make to the papercrete making process to make it perform closer to what I want as a fascia layer?

In the process of mixing papercrete, the cement bonds with the paper and the pulping water drains away clear. Can the same be said for water proofing additives? Would the additive stay bound in the papercrete or run away with the water? If adding a water proofing agent to the pulping process isn’t an option, is it possible to add the admixture after the papercrete has drained? Can the resulting mortar be mixed with waterproofing before being applied? I haven’t heard of anyone doing this, so don’t know if it’s a viable option. Would subsequent mixing of the papercrete mortar negatively effect the good qualities of the papercrete? Inquiring minds . . .

Can papercrete water be recycled back into the process? If it can and a waterproofing agent was part of the initial papercrete making process, how would subsequent admixture amounts be determined?

Someone’s bound to say “waterproof it after it’s dried”, but I don’t see that as being an ideal option because it leaves far too much of the bulk of the papercrete free to absorb water.

Beyond its possible use as a fascia layer, papercrete has a reported R-value of 2.5 per inch. I don’t know how accurate this figure is, nor have I seen any certified test results. For the sake of projection, let’s say papercrete really is that insulative. A single 6″ layer could serve as both fascia and insulation performing multiple. (I’m ignoring the shrinkage and water retention issues for now.) So, I could spend thousands on XPS or EPS insulation and non-thermally conductive connectors to make my tiltwall sandwich, or I could use a 6″ layer (R-15) of much less expensive, but more labor intensive papercrete. If I could waterproof papercrete at the particle level and minimize shrinkage without compromising the insulative value, this would be a hugely attractive option. More research here is definately needed.

Sand reduces shrinkage but also reduces insulative values. Would replacing the sand with EPS beads minimize shrinkage while upping the insulative value? This is, of course, assuming the mortar could be mixed after the water is drained away without the subsequent mixing compromising the paper fibers. Wet the EPS beads down with dish soapy water and fold them into the papercrete mortar once it’s drained. I can see I need to talk to one of the papercrete fathers of design.

How does centrifugal water removal and compressive molding effect papercrete’s properties, separately or together? Again, inquiring minds . . .

This entry was posted in House2 Construction. Bookmark the permalink.

Leave a Reply