STUMBELBLOC - A guide to building with STUMBELBLOC blocks

Ideally, start on a level foundation. If not, you have to lay a mortar bed as in conventional building. However, this restricts you to only a few courses of blocks per day. On a level surface the foundation can be built using Stumbelbloc . They can be reinforced with steel rods and the cavities filled with concrete. Two courses of blocks are recommended for this and when completed an effective, strong “ring beam” is created. If the foundation cannot be built with Stumbelbloc i.e. bricks are used to create a floor slab. Usually, as a result of undulation or slope add 5mm per meter of the floor measurement to accommodate Stumbelbloc.
Use then bed mortar (In South Africa Block Grip™ is recommended) and simply dip the bottom of each block into mortar. No mortar is required on the sides or the top.
Always dry stack the first and the second course initially. This creates an equal gap on teeth of the block and sets the required tolerance. The second course should then be removed, dipped into the thin bed mortar and replaced. Ideally, the first course remains dry packed on the foundation. This eliminates cracking.

Stumbelbloc builds in modules of 200 mm. Thus a standard full block is 400 mm and a half block is 200 mm. Construction distances should therefore be planned accordingly. When building pillars or openings, rotate the flat side of the block and half block for each level. Always build in one direction i.e. flat side of block always in same direction (Left hand or the right hand).
To create bigger module door or window openings, fill hollow cavities with concrete and cut with a grinder to frame size. In areas without electricity, build the opening bigger than frame. Put hoop iron/bracing strap or wire on every second course and build up with brick castings.

To create lintels using Stumbelbloc:

a. Insert a soffit plank at the required opening and lay one course of blocks.
b. Chop off the centre teeth of blocks.
c. Lay 2 x 10 mm steel rods in horizontal cavities created on first course by removed top centred teeth.
d. Lay 2 x 10 mm steel rods in horizontal cavities created on second course by removed top centred teeth.
e. Complete building the blocks to wall plate height, fill cavities of all three courses including overhang of 200 mm per side of reveal with concrete.
f. Refer to Stumbelbloc building manual for steps from foundation to roof height.
To fit the hoop iron/bracing strap to the wall before roof construction, press cement bag four courses down into the block cavity. Bend the hoop iron/bracing straps point similar to fish hook and anchor three and a half courses deep and fill cavity with concrete. It is not ideal to plaster the dwelling on the day of construction. Thin bed mortar should cure for a minimum of two days. Finished structures should be rendered or bagged externally with waterproof “Skim Plaster™” (Product of RSA) or standard plaster for coastal areas. Internal walls may be left bare or preferably plastered or bagged.