Wattle & Daub: Craft, Conservation & Wiltshire Case Study
3.6 Daub
4.1 Soils
4.1.3 Strength
4.2 Dung
4.2.2 Lignin
4.2.3 Urine
4.3 Fibre
5.4.2 Renewal

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5.2.2 Decay of Withies, Lath and Staves

The wood within the panel is susceptible to fungal rot and beetle attack. The surrounding frame may be similarly affected.[84]

Dry Rot
Dry rot is most likely to affect softwoods and usually only encroaches into hardwoods where conditions are particularly damp. Any fungus is likely to be localised to the wattle or stemming from carpentry within the building.

Wet Rot
Wood must have moisture content above 20% for the development of wet rots. The withies and staves are therefore likely to have been affected by a wet rot only if they have been exposed to prolonged periods of damp. In new wattle work or repairs, the risk of wet rot can be reduced by the use of preservatives, but such treatment does not address the root cause of damp. The benefits of treating withies and staves with preservative are therefore questionable. To compound matters, wet rot causes a structural change in the timber making it more susceptible to attack by Death Watch Beetle.

Wood-boring Insects
In the case of attack by wood-boring insects, it is essential to correctly diagnose the level of activity and the type of beetle.[85] The most common infestations are Furniture Beetle and Death Watch Beetle.[86] In historic wattles, it is unlikely that the infestation is still active due to the limited source of wood unless recent neglect has led to renewed dampness of the wattle or frame. Reducing the level of moisture should be the first course of redress. If there is no sign of recent activity, treatment is unlikely to be required. Furniture Beetle is more commonly found in softwoods, whereas Death Watch Beetle is at home in most hardwoods.
Death Watch Beetle can attack wood for many years, often unseen, and can cause severe damage to structural timbers, staves or lath before any infestation is apparent. The level of moisture in an external wattle and daub panel may enable a colony to survive until the total decay of wood exhausts their supply of nutrients. The presence of Death Watch Beetle is via the evidence of frass and flight holes. In the case of wattles, the simple technique of prodding them with a screwdriver is probably adequate to determine their condition.[87]
Common Furniture Beetle can survive at lower moisture levels than Death Watch Beetle and will attack the sapwood of most of the species of wood from which wattles and pole staves have traditionally been made. Diagnosis is by the same manner as Death Watch Beetle. Eradication is difficult without the use of chemicals and therefore an infestation localised to the wattle should probably be left to run its course. Failure of the panel is unlikely to occur due only to wood-boring insects since a residual proportion of wattle left after decay may still be sufficient to secure the daub.

Corrosion of Lath Nails
Nails that hold laths to fillets or to the frame may eventually corrode. If sufficient laths become detached from the frame, the whole panel may become loose. The problem is often not easily rectified and should be addressed using the repair techniques discussed in Section 5.3.

[84] Descriptions of rots and beetle attack are adapted from course work previously submitted by the author.
[85] Description of beetle type and its treatment are discussed in Ridout (2000).
[86] Lander (1992), pp.198-203.
[87] A control process that correlates moisture levels to beetle activity is useful in addressing the problem. Chemical treatments are available but their effectiveness is often dubious and has considerable environmental considerations. Also, the treatment of historic wattle is almost impossible without complete destruction of the panel. Where diagnosis suggests chemical treatment may be effective, recent developments using deep-penetrating ‘mayonnaise’ may be considered. For further information see Demaus (1995).