wall method

[95Compact]

I live in the tornado belt of NC and would like to build a weather-proof and energy-efficient home.

My plan is to pour-on-site reinforced concrete walls, 4" thick (tilt-up) with an insulation of 4" thick polystyrene and 5/8"T OSB and standing-seam panels as an exterior sheathing. The foam would be bonded to the cured concrete wall with PL polyurethane adhesive and the OSB pre-adhered to the foam (like a SIP).

Carriage bolts would further secure the insulating panels to the concrete walls on 24" centers. The interior walls would be covered with 1" foam board and drywall with wire chases routed as necc. All interior walls not requiring wiring chases would be decorative concrete, covering the exterior securing bolts and further increasing thermal mass.

Thoughts?

[95Compact]

The roof will also be of pre-cast concrete with the expectation of utilizing a 'green roof' with vegetation within the 8" or so of soil covering the roof.

[concretemasonry]

A domino-type construction connected with attachments would be worthless is a real storm, especially if they hit by a tornado.

Just look at the "safe cells" that are incorporated in the safe areas in new homes for life safety. It consists of a substantial foundation and either 8" thick reinforced (8" o.c.) concrete block or concrete walls with a cast-in-place 8" concrete roof. The safe cells can be in a basement, on salb home as a closet or bathroom or as a separate structure. The hardware (inward swinging doors and attachments) is very important. The safe cells are not usually required by code, but as a personal preference or for resale.

The biggest danger from a tornado is the debris that takes a special structure to prevent the most common form of death if the causes can be attached to any special item. Just forget about a wood structure to stand up to a real tornado.

If you have a real tornado, the house will be gone, but your neighbor's home may be untouched. - Just like roulette. We had kids a few miles away that were sucked out of a basement (no safe cell) and were drowned in a near-by pond.

Dick

[95Compact]

Thanks for the response. To be clear, it is my intention to build the entire house as a 'safe room', even though I intend to build a windowless sub-surface 'safe room' into the hill as well...

By 'domino-type' construction, do you mean tilt-up pre-cast panels as I'm describing? Is there no secure way to connect the adjacent concrete panels when they'd be installed between both a substantial poured foundation and pre-cast roof section?

I'm not at all opposed to using 8" blocks, but would that be stronger than reinforced tilt-up panels? Also, for clarification, the foam and wood sheathing would be mainly for insulation while retaining the interior thermal mass of the concrete walls.

Thanks, I'm new at this and will accept any design help you can give!

[concretemasonry]

Panels have strength problems, no matter what the strength, but because of the continuity and integrity in the resulting structure.

FEMA standards do not include precast concrete for safe cells, but only reinforced concrete block or reinforced concrete and recently 3/4" plywood panels bonded to steel plate that finally survived the tests after a few years and tries.

"Domino" construction has always had a problem with continutity and connections and that is why it is not common in high rise loadbearing structures or for structures with lateral loads that have to be connected and distributed to the rest of the structure for performance.

Dick

[ChrisVJ]

Why don't you use preformed polystyrene forms and poured concrete. It is more expensive than lumber construction but it is probably faster than laying blocks, takes almost no skill beyond regular building and of course is essentially a bunker.

The forms can come to be assembled on site or pre-assembled, ie, with the plastic connectors already in the forms. They slot together like Lego, you build wood forms for the windows and just lay and tie the rebar as you build it. You pour the concrete one floor at a time. The Polystyrene is already tied to the concrete, so you don't have to blast or screw in the ties. Easy to chase for wiring, just use a knife or hot wire.

With the effort and wet trades in putting up concrete block and then rebarring and filling I suspect solid concrete would work out cheaper. If I was building in tornado country I wouldn't even consider building any other way.