There was some damage to the inside panels of wattle and daub during the replacement of the sole plates. The building contractors re-rendered the bottom 30 – 50cm cm or so of the outside of the wall to weatherproof it over the narrow gap that appeared, using lime mortar. But on the inside there were a number of breaks and gaps in the clay where the old panel infill fell out when the building was lifted. Some thermalite blocks, which had been used in previous repairs, also fell out.
The empty panels were filled from the inside with clay daub. After letting the work dry and crack for six weeks we put on a clay plaster made from daub mixed 2:1 with lime mortar and finally a thin coat of haired lime plaster bought ready-mixed from Anglia Lime. This was also used to plaster the thermalite blocks which had been used to fill in the old kitchen doorway, and was very effective in strengthening a section of old crumbling plaster in the kitchen.
There were two completely empty panels and a number with large holes. In all these cases, hazel ledgers were fitted to notches made on the studs and hazel sticks were tied to the ledgers with hemp string. Clay daub was pushed into and around the hazel. If these had been completely open panels, then it would have needed two people to do the job,one inside and one outside; because the outside render was intact one person could manage the infilling.
We used clay even where the broken panels proved to have been filled with thermalite blocks, on the suggestion of the wattle and daub instructor, who said this might give an early indication of whether moisture was building up behind the panel – the clay would absorb water and quickly discolour if it got damp again.
The clay inserts under the modern blocks were mixed 2:1 with lime mortar for added compression strength because they were supporting a substantial weight of material. Once dry, a clay and lime mortar mix appears to make a very strong block. In fact, at least one nearby farm outbuilding is built of clay lump – dried blocks of clay daub – without any supporting timbers. The clay blocks were very visible because of the deterioration of the wall, though it has recently been repaired and lime rendered.