Catenary Vaulting on Mfangano Island, Kenya: The Structural Block Walls

Last week was incredibly productive for the building team. Our task was to build a double-wythe reinforced block wall using the compressed stabilized earth blocks we made right here on-site. Due to the heavy rainfall here on Mfangano we decided to use a 10% soil-cement ratio giving us about 65-70 blocks for each 50kg bag of cement. The soil on the job site was sandy enough that we did not have to add any sand to the mixture. We produced a little over 600 blocks to make a wall that was to be about 28-36 inches tall.

Day 1: Spreading, waterproofing and first course.

laying the spreading layer of mortar and plastic for waterproofing

spreading around the rebars that will tie the wall to the foundation

laying the first blocks at the corners

masons and mixers at work...also the film crew was there

Muogah practicing is trade

Erik - not a mason - chopping blocks

one wythe of the first course in one day

Day 2: Reinforcement extension and second course.

extending the reinforcement

Muogah in deep concentration

by lunch time the entire first course was done

Gaby working on the second course

block puzzle at the buttress

good progress at the end of day two

Day 3: Third course.

moving along with the last few blocks for the second course

onwards to the third course

3rd course complete by the end of day three

Day 4: Reinforcement, fourth and fifth courses.

start the day mixing mortar - soil excavation behind

the reinforcement tied in the wall to make it strong

making quick progress

by the end of day four we had a full four courses

and the start of the fifth course

Day 5: We had only a little bit more to do on the wall, so started planning for the formwork. The idea with tile vaulting is that we use MINIMAL formwork - not a complete lack of formwork. So, we decided to make three arches - beams - using rebar. We first had to make a grid on the biggest wall we could find so we could hang a chain and find points along the curve.