CEB Wall Construction
The time has come to stop making cement stabilized compressed earth blocks (CEB) and mortar them into a wall and a building. We needed 2000 blocks to begin and the nice weather this spring has allowed us to make that many.
This gives you an idea of what 2000 CEB blocks look like.
We intend to use the energy building as a test unit to see how our masonry skills and back muscles handle this block work. It’s been more than 40 years since I taught block laying in Africa. Let’s hope it’s like riding a bicycle!
We have already documented how to pour a slab and a stem wall. Now for block laying.
The end product determines the process or means to that end. We’ve shown the elevation for the door to this small structure. The diagram above shows the design for the south elevation walls and window. We will plaster this building outside with wire lathe and stucco. The inside will get wire lathe and mud plaster. You won’t see the block work, so the only issue is integrity, or wall strength, in a seismic Zone 2—not fancy block work. We expect more frac’ing --this is Texas where fossil fuels do NOT contribute to global warming!
We’ll document all we do to ensure wall integrity as we go along. We will reinforce the doors and windows in a rather unique but entirely feasible manner. We do not need to reinforce the wall corners, which we would do if we were expecting a serious quake or code required it. Our window and door openings are a minimum distance from the corners so that the pier (wall section between the corner and opening) is not compromised by these openings. Mass earth walls are weak in tension and will readily crack under lateral loading. Openings must therefore be reinforced. Thus our windows and doors will have both a concrete reinforced sill and a concrete reinforced header that are both tied to the ring/bond beam that unifies the entire wall. If it rocks or rolls, it will do so as a unit. The roof is another chapter.
Enough theory. To get started I had to be sure that the foundation and stem wall were perfectly level. They were not. Using a laser level, we placed blocks of different thicknesses on each corner until they all read level. We measured down the stem wall to the foundation ledge and made a mark if the level was higher than the foundation—ie the foundation was lower in that corner than the others. I then made a plaster of cement mortar and built a ledge to the level mark so that I could use a tape measure to set each block rise—which means determine the proper depth of mortar for that course of blocks. Every evening, we lay up the next two courses by setting the corners at a set elevation so we can use a string level to ensure the walls stays plumb and level.
Speaking of mortar…we decided early on not to try to mix our own. One tiny rock (the size of a pepper corn) in the mud “pudding” or slurry and you have a “point load” which will crack the entire wall. We could not afford that, and the incredible effort to guarantee super smooth slurry was not on. Besides, no two blocks are the same dimension. So unevenness creates another point load and potential crack.
The solution to smoothing uneven blocks and avoiding stones was to use Type N lime cement mortar, which is a medium compressive strength cement to match our soft blocks. Never use stronger/stiffer mortar than the blocks you are cementing. Type N mortar also dries more slowly than Type S, so old people and amateurs have more time to work. We can use any size of block using a ½’ mortar “bed” and not worry about cracking from a point loading caused by uneven blocks. So far the Type N mortar has performed as desired.
The outside walls will get a thin coat of waste plaster. As the mortar oozes out of the joint, we just trowel it onto the wall. Later the wall will be covered with a 1” foam board—shiny side out. Then it will be lathed with standard diamond wire and stucco’d with industry technology. The CEB house need not look special. It just has to perform well.
This is what the first course with 50 blocks looks like at the end of day 1.
We’ll continue to document significant milestones in the construction of this building in the weeks to come.