Stitching and Major Repairs

during the actual building process and speeding up work on site.  Already, the technique has been used extensively, English Heritage and the National Trust being amongst those having done so.

In dealing with deep or through cracks, a number of stitching techniques have been tried.  Some of the published texts listed at the end of this leaflet illustrate types of stitching.  It should be noted that stitching methods serve simply as a means of reinstating the homogenous nature of the walling, forming a base for appropriate coatings where appropriate, and thereby reducing the risk of subsequent rapid deterioration.  They cannot be regarded as enhancing the structural qualities of the walling to enable it to resist additional lateral loadings arising through

former inappropriate structural alterations.  Such inappropriateloadings must be dealt with as part of the whole repair.

The principles of stitching are shown at Figure 8. As with many aspects of earth walling repairs, this is an area that is under continuing appraisal, and the approaches shown should not be seen as necessarily the only or ideal ones applicable.  One method formerly advocated involved the insertion of plain clay tiles into the existing walls as a means of providing a key and helping to spread evenly the drying shrinkage of the in-situ material applied around it.  In choosing such a method, one needs to be confident that the existing wall will be able to withstand the intrusive action of cutting chases into which the tiles are inserted.

Whilst rat holes are most commonly associated with farm outbuildings, they are sometimes found in the walls of dwellings.  Their extent will need to be assessed, since if the burrows are extensive, the structural stability of the wall may be under threat, sometimes exacerbated by excessive dampness at the base of the wall.  Unless investigative techniques such as thermal imaging are available, the probing methods themselves are likely to be intrusive, so great care is necessary during this process.  If there is any doubt about the structural stability of the wall, temporary support will be necessary.  Once the extent of the holes has been established and the cavities cleared of loose material, the repair work can be put in hand.

Various techniques have been used.  Grouting has been usedsuccessfully where the damage is confined to a few tunnels deep

within the wall.  The actual material chosen will probably have to be based on a degree of trial and error.  Whilst an hydraulic lime/ fine sand grout has proved successful in some instances, in others it has been less satisfactory.  Others using lime putty, sand and suitable aggregates have been employed successfully in some areas.

Broken bricks in a weak lime mortar have been used where there is ready access at the surface.  Firstly, the cavities are cleared of loose material and the surfaces well wetted.  Where the rat runs occupy a high percentage of the wall plan area at the base, it is likely to be necessary to prop the wall above and rebuild the lower section using blocks of reconstituted earth, completing a short section at a time.