Stem Wall Basics


I wanted to make sure that the stem wall (that hopefully all CEB block walls will be built on) was unified with the slab. You need a 3.5inch high wall above the slab floor exactly the width of the CEB block wall to prevent any floodwater (either from inside or outside) from destroying the bottom row of mud blocks and creating a threat to the integrity of the wall above them.

I constructed the stem wall form on the slab form prior to the pour. I used 1x4 clear pine that was strong and straight. You can see the bracing I used to keep it level while we filled it with concrete. This frame was easy to make exact and square. It fit over the slab to make a ledge on which I will place solid foam insulation prior to stuccoing the outside with standard stucco cement and equipment. The top of the concrete in the form was not troweled but left rough as it appeared after screeding and vibration. It is imperative to use a vibrator on this stem wall since it must be extremely strong with no bubbles or voids. It is rough on top to enable total bonding with the first course of brick mortar.

We did not try to use the concrete truck chute to fill the narrow form for the stem wall. Rather, we used the tractor bucket and it worked very well. The site was already cleared to enable the tractor to reach each wall.

The entire pour must be kept wet, and, after 24 hours, the forms can be removed and actual construction could begin. I recommend curing for at least 7 days with watering at least 3 times a day for the week before placing weight on that foundation.

You can see the ledge around the stem wall on which I will place foam insulation

prior to stuccoing it with standard stucco equipment. A 2 inch reveal of the slab is also standard so it sheds water away from the foundation. The rods provide reinforcement for the door post concrete and the board created a space for the door threshold to sit level with the final floor. A 2x8 inch treated wooden frame called a “buck” will be bonded to the concrete column to which the actual door will be fastened.

#Stemwall #CEBFoundations #CEBblocks

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