Been working on a cob wall for the past few weeks.
Cob is compacted chalk mud, built up in layers on top of a masonry plinth. Has to have a good capping to keep the water out, tiles in the case of walls and thatch if it's a cob cottage.
Main thing is, it's got to be rendered in a breathable lime mortar to let any moisture out, if it stays dry it'll last for centuries.
This wall however was rendered only a few years ago in an impermeable cement render, which very shortly after began to fail, causing damage to the cob itself.
First thing was to strip off all the cement.
Spent a couple of weeks filling the damaged areas with hydraulic lime, that will set without the need for the air to get to it.
Finished up with a 2 coat render using putty lime.
A few more days of keeping it damp till it carbonates and the job's done
Cob is compacted chalk mud, built up in layers on top of a masonry plinth. Has to have a good capping to keep the water out, tiles in the case of walls and thatch if it's a cob cottage.
Main thing is, it's got to be rendered in a breathable lime mortar to let any moisture out, if it stays dry it'll last for centuries.
This wall however was rendered only a few years ago in an impermeable cement render, which very shortly after began to fail, causing damage to the cob itself.
First thing was to strip off all the cement.
Spent a couple of weeks filling the damaged areas with hydraulic lime, that will set without the need for the air to get to it.
Finished up with a 2 coat render using putty lime.
A few more days of keeping it damp till it carbonates and the job's done
I guess this kind of work/knowledge is in short supply, so it's really nice to see long standing traditions and workmanship being carried on.
