Alterations and Key Points
If it is necessary to alter or extend an earth walled dwelling, great care is needed in ensuring that the proposed scheme will not have damaging effects on the original fabric.  The nature of in-situ earth loadbearing walling is such that it needs a generous cross-sectional area to carry the loads to the ground. Yet often, designers treat it as they would a modern cavity walled construction.  In any alteration scheme, one aim should be to minimise the loss of existing fabric.  Figure 9 illustrates some of the implications of a fairly commonly encountered end extension proposal.
Key Points

This leaflet identifies some of the problems that may be encountered with earth buildings, and a selection of repair methods that have been used successfully.  Of course, it cannot be comprehensive, and attention is drawn to the publications and organisations listed below which offer technical guidance.

Often, the problems are due to lack of maintenance, or inappropriate repairs and alterations.  Key points to remember in relation to earth walled buildings are:

    1.The roof should be well maintained and have a generous overhang.

    2.The base should extend well above ground level.  Its mortar for bedding and pointing (and rendering if applicable) should be 'breathable' - a lime mortar.

    3.The wall surface should have a well maintained surface coating both externally and internally.  Historically, not all dwellings were rendered, some having limewash applied directly to the earth wall face.  Renders and surface coatings must be moisture permeable and'giving', consisting of lime or mud mortar renders free of Portland cement together with limewash finishes.

    4.The insertion of damp-proof courses should be avoided.  They are unlikely to be of any benefit and may in themselves be harmful.

Where these basic principles have been followed, and inappropriate structural alterations are avoided or remedied, buildings of earth walling can remain very durable and offer the prospect of continuing beneficial use for many more generations.