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

Title Page Previous Next | Conservation >Repair >Partial Renewal

5.3.1 Partial Renewal

The most frequent repair scenarios are cases where a significant proportion of a panel remains sound. The failed parts may require remedial work to the wattlework, lath, daubs, renders or, most commonly, a plaster top coat.

Plaster Coat
Where only a top coat of plaster has become loose, it may be replaced as follows:
  1. Remove cracked and loose plaster using a scraper or small trowel, being careful not to pull off secure plaster or daub.
  2. Remove dust and organic matter.
  3. Where the daub is smooth, provide a key on the daub surface by dampening with a sprayer or brush, then lightly scratch with the corner of a trowel or comb scratcher.
  4. Dress ragged edges of intact plaster using a sharp knife. Undercutting is not essential.
  5. ‘Prime’ the daub and exposed edges of plaster with limewater or a thin slurry made from fine stuff.
  6. Prepare new plaster to match existing, with sufficient hair (or straw or hay, etc) for strengthening.
  7. Dampen daub with a hand sprayer or brush. Apply plaster and finish to match existing (e.g. with wooden float, leaving an open-textured surface). Cover with sacking or cloth. Evaporation and absorption of moisture by the daub may require further dampening to ensure slow drying and proper carbonation.
  8. Dry plaster should be finished with limewash to match the existing work.

Where the plaster had been decorated, several principles of conservation can conflict. On the one hand, it is recommended that the historic decoration should not be imitated where the craft has been lost and so the plaster is left plain or an ‘impression’ of the decoration is used. Conversely, such detailing of buildings is often important to their appearance and one should endeavour to employ crafts such as decorative plastering and pargetting so they are not lost. In this case, one might re-instate the decoration, perhaps dating it to prevent confusion with regards to authenticity.

Withies and woven lath are often friable due to decay. However, the principles for the repair of wattlework are as follows:
  • the need for repair is limited to situations where wattle decay is the underlying cause of daub failure or where it is unable to withstand the applied forces during subsequent redaubing.
  • repairs should endeavour to be like-for-like: hazel withies should be repaired with green hazel; cleft oak replaced with similar.
  • the use of modern materials should be limited to only those situations where traditional methods would cause greater loss of historic fabric.

Where decay is localised, new sections of withy or lath should be ‘slipped in’ to the existing wattle so to avoid unnecessary stripping of sound daub:
  1. Test the soundness of each area of wattle using a very light pressure on the palm of the hand to emulate the forces during subsequent redaubing. Unusable wattle will either fall into dust or will crack.
  2. Evaluate remaining sound wattlework for suitability for redaubing. The occasionally spaced missing withy is unlikely to affect the soundness of a repair and may be left as found.
  3. For unsound areas of wattle, prepare replacement withies with matching materials. Repair sections should be cut to length:
    1. Where there is access across the full width of the wattle, new withies of full length can be threaded through from one end.
    2. Where access across the wattlework is limited by sound daub, access for new withies is limited to the side. The minimum length of withy that can then be used is guided by the spacing between staves. The maximum length is determined by: the access to the hollow daub ‘tube’ remaining after removal of the decayed withy; the lateral access for feeding the flexed withy into to the existing wattlework; the spacing between two adjacent staves.
  4. Tying-in should not be required If the repair withy is of sufficient length to be held in tension between staves and adjacent withies.
  5. Where a repair withy is short and loose, it should be tied into adjacent wattle work and onto staves using twine or copper wire.

When introducing new wattle or lath to a building, there is a risk of introducing a new infestation of wood-boring beetle. Where a previous infestation has been found and there are no signs of recent activity, it is likely that that the remaining timber has become unsusceptible: either the conditions are unfavourable or vulnerable wood has already been attacked and the beetles’ supply exhausted. However, where a timber frame might remain vulnerable to attack, pre-treatment of the new wood with insecticide represents a sensible precaution. With withies and laths, pre-treatment should be highly effective since the slender sections can be saturated with the active insecticide. In this situation, the treatment is perfectly targeted and the (valid) concerns relating to the treatment of historic timber are not applicable. There are many proprietary formulae, commonly using permethrin as the active ingredient, which may be water or solvent based and suitable for brush or spray application.

The approach to repairing lath is similar to that of wattlework in that replacement is limited to the need for forming a sound backing to failed daub or render. Repairs should be from similar material to existing. Sound laths that have loosened due to corroded nails can be reattached. It is essential that the laths are not re-nailed since the vibration may cause daub or friable plasters to crack. Instead, they should be secured using brass or stainless-steel screws. Splitting of the laths is not a concern in new work but movement of laths may disturb attached daub. Therefore, the drilling of pilot holes in the lath is recommended.

Cracked or loose daub should be conserved as far as practicably possible. If external daub has cracked, eroded or delaminated from its backing, then attempts to secure it should first be tried before considering replacement. Where decay only affects part of a panel, replacement can be limited to the unsound area. Cracked daub, where otherwise sound, can be consolidated using a lime mortar:
  1. Prepare the crack by removing fragments of loose daub and dust.
  2. Thoroughly dampen the edges of the crack with a sprayer or brush.
  3. For hairline cracks, fill with pure lime putty. Wider cracks to be filled with fine stuff (1 part non-hydraulic lime to 3 parts well-graded fine sand.). Large cracks can be filled with haired coarse stuff or new daub.
Where a regular programme of limewashing is established, hairline cracks may be left: the cracks are likely to be filled as part of the cycle in which a limewash of ‘creamy’ consistency should be used (e.g. 1 part mature lime putty to 5 parts water).

Where large pieces of daub have become detached, they should be replaced like-for-like using daub, rather than filling the void with lime mortar. If mortars are used habitually to replace daub then the cumulative effect will be the loss of integral wattle and daub panels and may encourage the demise the craft of daubing.
Where the detached daub has been salvaged, it can be reused to avoid unnecessary labour. It should be prepared by breaking into pieces and saturating in a bucket of water, stirred, and then left to resettle. The scum of old straw, hair and dung should be removed from the top. The daub should then be laid out until its water content is suitable for use. Hair or chopped straw and cow dung may then be added and the mix reapplied.
The preparation of new daub is described in Section 5.4.2. When replacing onto historic wattles, it may be wise to prepare the mix so it is a little wetter than compared to a daub for new work. This should make it more malleable and help prevent damage to friable withies. The risk is increased cracking of the daub, but this may be simply rectified by reworking the surface[95]hen green.95

After considering all repair options, it may occasionally be decided that a panel cannot be saved due to the poor condition of its wattlework. In this case, a panel may require complete renewal.

[95] The term ‘green’ refers to a state during drying where a daub or render has firmed up but still appears damp. It is also the state where the material is still workable with a pallet knife or modelling tool without causing the surface to break up, but does not cause the bulk of the material to shift.