Building with cob blocks
There are no specialist skills required to construct cob block walls. General builders, bricklayers and, of course block layers, will notice that the only real difference is a little more care is required when handling these cob block products. Whilst compressive strengths are reliable and effective, tensile strengths are not so forgiving…..basically, if you drop a cob block it’ll break.
Binding mortar used for this wall was a non-hydraulic lime/coarse sand mix of 2.5 parts sand to 1 part lime. Natural hydraulic mortars can also be used (NHL2 or NHL3.5) again 2.5 parts sand to 1 part lime. Here’s a tip: we found that the non-hydraulic mortar to be more favourable because a) it has a slower set time b) it can be reconstituted and reused and c) when the bag/tub is sealed, remaining mortar can be used at a later date.