H.C.L Knowledge Base

Here at Heritage Cob & Lime we don't just care about the buildings we work on daily.

We believe that to safeguard the beauty of these traditional buildings into the future we should pass on some of our knowledge.

Guide Sheets...

Free and helpful information sheets:

You're welcome to click on any of the sheets below to read and download for free if needed.
Guide Sheets for Building with Cob
Guide Sheets for NHL
Guide Sheets for Laths
Guide Sheets for Lime Pointing
Guide Sheets for Lime Rendering
Guide Sheets for Lime Safety
Guide Sheets for Lime Washing
Guide Sheets for Plastering
'The Cob Buildings Of Devon 2' Maintenance and repair guide
If you have any further questions or more information needed please don't hesitate to get in touch.

or call us: 01237 477 431



Failing External Cement Render


A common problem on many old houses is that they have a cement render on the exterior walls, which doesn’t allow the substrate (cob/stone/stone rubble/brick) to breathe and flex. This gives rise to all sorts of problems one of which is the cement render begins to crack. Water then gets into the render, and starts eroding the substrate. Cold weather causes the water to freeze under the surface of the cement and then as the weather warms up and the ice melts, the cement begins to crack and fall off the wall. All the time this is happening, the interior walls are also suffering as the damp in the substrate begins to seep through. The problem will continue to get worse and the render start to fall off the wall. If the cement is covering a cob wall, then the cob will begin to fail.


Solution: Remove the cement render, make good any damage to the substrate and then re-render with lime mortar, finishing with either lime wash or mineral silicate paint, both of which are breathable.


Interior Damp Issues


Internal damp is usually caused by inappropriate render on the exterior walls and/or inappropriate gypsum & all other modern day non breathable plasters on interior walls. The problem with using modern plasters on older properties is that like their counterpart, cement, they are not a breathable medium to use on cob, stone/stone rubble/brick construction. Damp can’t escape once it penetrates gypsum and so stays in the plaster causing it to deteriorate. Common sights are paint and plaster bubbling and flaking off onto the floor, followed by larger swathes parting company with the substrate.


Solution: Remove gypsum plaster and re-plaster with breathable lime mortar, finishing with a coat of fine lime plaster to give a smooth finish. This can then be painted with a choice of breathable paint - lime wash, casein paint or mineral silicate.

Common Problems With Older Properties.


01237 477 431