Jan
Specialist Cob Wall Repairs in Cornwall
Most common cob wall failings:
Typically, cob wall failings in Cornwall can be found to the corners of cob walls…window and door reveals and to the corners of the building itself. These areas are vulnerable due to their ‘prominence’ ie they are no longer integral within the monolithic mass of cob that makes up the cob wall proper. Failings to the cob mass do occur, however this article is focused on the openings and corners. Further articles will address monolithic cob failures, both minor and shear, another time.[/vc_column_text][/vc_column][/vc_row]
We can see here that the reveals to this window have had historic repairs and these introductions are principally constructed of fired-brick, cement mortars and concrete. Observations tell us that this particular window opening hasn’t been ‘reduced’ in size to accommodate a new window, because the [original] slate cill length is evident. Therefore, this mish-mash of material is, without doubt, infill. So here we have a fine example of the vulnerability of these areas within a cob wall.
Removing inappropriate material/s from existing cob:
Careful and methodical removal of inappropriate material is essential. A gung-ho approach will lead to further and unnecessary disruption and/or loss of the existing, historic fabric. Delamination and/or piece by piece removal is the only effective way to remove unwanted, unnecessary and/or structurally compromising elements. Preservation and continued stabilisation of peripheral fabric/s is paramount to historic wall conservation and restoration.
Introducing a cob block and/or cob brick repair:
All specialist cob repairs in Cornwall must start at the base or the lower areas of the cob wall that are affected. There is little mileage commencing specialist cob repairs at high-level [and then continuing down] as this approach will a) almost certainly be ineffective structurally and b) the very nature of introducing cob repairs requires some (or very limited) removal of surrounding fabric to accommodate pre-formed cob blocks or cob bricks.
Render:
Commonly, all pre-formed cob block and/or cob brick repairs to cob walls in Cornwall are rendered using hydraulic or non-hydraulic lime mortars. Principally this is to achieve a protection for the exposed cob against wet weather, in particular driving rain. Whilst exposed cob walling will tolerate a degree of wet weather, cob surfacing is not comfortable with channelled water and/or saturation. Traditionally, cob walls in Cornwall would have had a lime-wash coating (more on claddings here).
Choosing the correct materials:
Earth Blocks UK have developed several unique cob products that have revolutionised the approach to and promoted effectiveness of specialist cob repairs in Cornwall. The cob product in the image was used successfully for the specialist cob repairs of these window reveals and ensured minimal loss of historic fabric. In addition, render applications thereafter were simpler and very cost effective.