Water tank foundation

[john the architect]

I also endorse Peter and his product. You can indeed drink catchment water when you store it in cement, not a plastic liner. He does some fine concrete sculpture/decorations as well. Although have not yet had the pleasure of working with Pacific Gunnite on a project, I would love to design an integrated tank and small home on top for a client. Have the perfect lot next door to our house in HPP. The design would use a domed roof on the tank, allowing for the optimal ferro cement spanning shape. A wood or bamboo floor would provide a level walking surface and leave a space to run drain lines and other utilities. The elevated structure would be steel frame with a bamboo non-structural interior lattice finish. An elevated deck would become the carport and the tank could be cement fresco mixed with surplus tile designs. Making something using the best technology and having it look island-style in the end would make this a fun and worthwhile project.

[hotinhawaii]

You appear to be responding to something in another topic. Right?

[Peter Epperson]

I like your ideas. Contrasting the concrete with wood and bamboo would make the place more livable. Don't forget to plan on a vent of some sort at the peak of the dome. If you don't let the dome breathe it will become an oven inside. With a vent you create an air current inside the building even though it may be a calm day outside with no breeze. How about just a step up to the bathroom which would allow you to run it's plumbing under the floor? The rest of the floor/tank cover could be left exposed and maybe given a saw cut and stain treatment. Lots of possibilities.

[Royall]

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Royall

[MarkP]

I have been intrigued by the concept of integrating the catchment tank with the foundation of a house for some time. I also like the idea of an elevated house (elevated on top of the tank. I am assuming that the tank is built so strongly because of the huge mass of the water that the house can only benefit from piggybacking on that both literally and figuratively. If you have to beef up the tank a bit because of the house I still think you would come out ahead versus building the tank and house foundations separately. On another post Peter Epperson said their tanks skitter around on top of the ground during an earthquake. This is exactly how I would design a house. After all, the ground is where the damaging movement is coming from. If you can build a foundation with enough strength to hold together on its own then you are better off letting it skitter than tying it down and forcing it to shake with the earthquake, but first you have to invest in that strong foundation. If the tank guys have figured that out then take advantage of that.

A major question I have is what the codes say about putting sewage lines over a water supply. Would you have to hang the bathroom and kitchen outside the footprint of the tank?

[Rob Tucker]

We have done some Castleblock homes with catchment as part of the foundation. Very doable and makes good use of space and material.

[Peter Epperson]

"A major question I have is what the codes say about putting sewage lines over a water supply. Would you have to hang the bathroom and kitchen outside the footprint of the tank?" MarkP

I have not had to deal with that question although it has crossed my mind. So far the only permitted structures built on our tanks were gazebos or rooms that didn't include plumbing. Have you run across any problems with that Rob?

[Rob Tucker]

Well, to date the Castleblock houses built upon concrete water catchment tanks have been larger than the tanks and we have avoided running waste water lines over the catchments for practical reasons. Its not hard to design the problem out.

[TrevorKane]

When you use the tank as foundation, what does the 'tank lid' look like? Is it just the joists and sub-floor, or is there some other protection?

Also, do you put an access door in the floor?

[Rob Tucker]

IF there is to be an eight foot ceiling height in the lower story the water tank is designed to hold water at a six foot depth. This allows for an access hatch above the water. I recommend a "lid" of cement panel be placed on the underside of the floor joists and a light be installed for purpose of inspecting the tank.