Cob & Earth
Cob and other earth-built walls are found across the south-west, the Midlands, East Anglia and parts of Scotland and Wales, under names that change from county to county. They are thick, load-bearing, entirely vapour-open, and remarkably durable as long as they stay dry at the base and breathable on the surface. Almost all cob failure traces to two causes: cement render or modern paint sealing the wall, and water at the foot from a defective roof, blocked gutter or raised ground level. The specialists here repair, rebuild and finish earth walls using compatible materials.
What this category covers
- Cob repair, patching and rebuilding of failed sections
- Earth and lime renders, plasters and limewash finishes
- Removal of cement render and impermeable coatings
- Plinth, footing and base-of-wall repair
- Advice on drainage, ground levels and moisture management
Cob Solutions Limited
COB AND EARTH: Cob Solutions Limited is a consulting and contracting company ...
Heritage Cob & Lime
Heritage Cob & Lime manufactures lime mortars, plasters, cob blocks and associated ...
MSC Naturally
MSC Naturally supplies everything needed to build, repair or restore earth-based buildings: ...
Looking after a cob building
Keep it dry at the top and the bottom. The traditional description of a cob wall needing a good hat and a good pair of boots is accurate: a sound roof with generous overhangs and working rainwater goods above, and a dry, well-drained plinth below, prevent most of the problems specialists are called to fix.
Get cement off it. Cement render and modern masonry paint trap moisture in an earth wall, which softens it from within and causes the render to blow off in sheets, taking cob with it. Removal and replacement with lime or earth render is often the whole repair.
Work with the seasons. Cob repairs need time to dry and are damaged by frost before they have cured, so substantial work is normally carried out between late spring and early autumn, in lifts, with protection.
Avoid modern fixings and hard patches. Cement blocks, concrete lintels and rigid patches concentrate stress and moisture in a wall that works by being uniform. Repairs in matching material, keyed properly into sound cob, behave as the wall does.
Questions to ask
Why is my cob wall crumbling under the render?
Almost always trapped moisture. Cement render and modern paints stop the wall drying outwards, so water accumulates behind them and softens the earth. Removing the impermeable coating and replacing it with lime or earth render usually resolves it.
Can cob walls be repaired, or do they have to be rebuilt?
Repair is normal. Failed sections can be cut back to sound material and rebuilt in matching cob or in blocks of the same material, keyed into the existing wall. Full rebuilding is a last resort and usually needs consent on a listed building.
What paint can I use on a cob building?
Vapour-open finishes: limewash, or a clay or mineral paint compatible with the render beneath. Modern masonry paint and plastic-based coatings seal the wall and cause exactly the decay they appear to be protecting against.
All 3 businesses listed under Cob & Earth
- Cob Solutions Limited Devon
- Heritage Cob & Lime Devon
- MSC Naturally Cambridgeshire
Directory information is provided to help visitors identify potentially relevant specialists and suppliers. Inclusion does not constitute a recommendation, approval or guarantee by Tuscan Foundry Products. Please check current services, credentials, availability and suitability directly with each business.