
Bricks unloaded

Stones unloaded
To avoid damp getting into cob walls, it is necessary to build a plinth wall at least 450mm above ground level on the foundations, on top of which the cob walls will be built. ((Technically a plinth wall might not be necessary. Some old cob houses don’t have them, and they are clearly situated in such a way that ground water isn’t an issue and hasn’t ‘melted’ the walls over the years. What we don’t know is how many old cob houses without plinth walks did fall down over the years. It is certainly highly advisable to build a plinth wall to keep the cob from sitting directly on the ground.)) To save money, the bulk of the plinth walls have been built in brick. S looked for second-hand bricks. Most ‘modern’ second-hand brick can’t be reused because it tends to be mortared with Portland cement. The binding strength of Portland cement is stronger than the material of the brick itself, so it’s difficult-to-impossible to clear the mortar off a brick without breaking it. You can find older second-hand bricks, but because it’s labour intensive to clean them off properly (even with older mortars) and tend to be used by people who need to match existing bricks when repairing or extending an existing building, they are expensive.
What S did find is brick seconds from a brick manufacturer in Glasgow. They are cosmetic seconds – bricks that aren’t the right colour or are slightly burned — but structurally sound. Normally they would be broken up for use in aggregate and concrete so as well as using a product that would otherwise be degraded, they are a lot less expensive than ‘normal’ bricks. A win-win!
Continue reading →