The Castle Wall: Monolithic's Other Way to Build Stemwalls
by David B. South and Freda Parker
*June 28, 2007*
Introducing the Castle Wall
Monolithic's newest method of building stemwalls uses split-face, concrete blocks that generally measure 8" x 8" x 16" and come in various attractive colors.
As the blocks are mortared together, rebar is placed both vertically and horizontally in the open cells of the blocks per structural engineering plans. Then filled -- one hundred percent -- with high strength concrete.
Result: a faux-rock exterior finish that is fully concreted and has the spectacular strength of a concrete wall.
A finished Castle Wall usually will be about 14 inches thick: 8" for the block and 6" additional for the foam, studs and drywall.
For the dome's interior, we spray the Castle Wall with two inches of insulating polyurethane foam, then line the interior with steel studs and Sheetrock.
That finishing process creates a smooth inside wall. It also gives a chase for the placement of electrical conduit and other items that must be embedded in walls.
Castle Wall vs. Orion Stemwall
Is the Castle Wall as strong as the Orion -- our original method of stemwall construction? (see "Italy High School Gladiator Coliseum")
No! But our engineering studies show that it is close and that its strength is more than adequate. Like the Orion, the Castle Wall can withstand tornadoes, hurricanes and earthquakes and is virtually firesafe.
Although its insulation is slightly reduced -- 2" of polyurethane instead of 3" -- a structure's vertical wall has very little heat conductance to the outside (see "R Fairy Tale"). Consequently, two inches of foam will seal any air movement in and out of the dome.
Note: The thermal battery of the Monolithic Dome is primarily in the roof. The walls and floor make up less than 10% of the thermal battery. For this reason the Castle Wall has little effect on the overall energy efficiency of the Monolithic Dome. See the article A Monolithic Dome's Two Batteries for more about the thermal battery.
The Castle Wall solves a lot of problems:
- It saves approximately one-third of the construction cost of an Orion stemwall.
- It creates a more attractive, colored, rock-like exterior that's tough and, unlike the Orion, requires no extra finish. Fading is minimal. Dark colors may fade up to 15% over 10 years.
- It gives dome owners the nice, smooth interior most folks want.