Home Treatment Guidance Guidance on how to: TREAT A ROOF VOID (ATTIC) TO CONTROL WOODWORM
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Guidance on how to:


roof-void2For health and safety reasons it is sensible to carry out treatment in a roof void using a water based micro emulsion timber treatment formulation. This type of treatment material is pleasant to work with within the confines of a roof void since it is virtually odour free and contains no solvent. The use of a solvent based material in a confined space or roof void should be avoided.


There is no justification, need and very little benefit to be gained from using a timber treatment material that also contains a fungicide when treating woodworm.


Roof void treatment is usually restricted to the accessible structural timber surfaces within a roof void. Other timbers often visible within a roof void such as timber laths supporting the ceiling below or slate/tile battens are not normally included in the treatment though some 'fall out' benefit of the treatment being applied may be achieved. Having assessed and established a need for treatment to take place the following sections explain how to undertake treatment of structural timbers within a roof void.


How much ready to use Woodworm Treatment fluid is needed to treat a roof?

The dimensions of timbers forming a roof structure will vary but for an approximate guide on how many litres of ready to use Woodworm Treatment fluid will be required multiply the roof 'foot print' size (in metres) by 0.75

Example: Roof 'foot print' - 6m x 9m = 54 x 0.75 = 40.5 litres (approx). If unusually large timbers are present then naturally a greater amount will be required.


Roof Void Treatment Process


RV.1 Ensure access into and out of the roof space is safe and secure.


RV.2 Before work commences display appropriate warning notices at entry points into the property and treatment area to inform others what health and safety precautions should be taken before, during and after treatment. These notices should be available from the treatment fluid manufacturer.


RV.3 Install adequate special safety lighting immune to the effects of spraying. See RV.6 below.


RV.4 ONLY walk on ceiling joists or securely fixed boarding. DO NOT walk or put any weight directly onto ceilings as damage and/or an injury might be caused. If necessary lay adequately supported temporary walk ways.

RV.5 Cover any exposed water tanks with plastic sheeting taped into position and then cover again with a dustsheet.


RV.6 Turn off at the fuse board any electrical circuits in the roof void which includes the lighting circuit for rooms directly below. Wrap any electrical junction boxes and other vulnerable fittings in plastic and tape to prevent treatment fluid from entering them. Electricity for safety lighting and if being used an electric pump should be obtained from a different circuit. Do not turn on electrical circuits in treated areas until you are satisfied that the treatment fluid is dry.


RV.7 Remove all debris, insulation and stored items likely to obstruct access to any of the structural timber surfaces.


RV.8 Carry out any necessary repairs and apply woodworm treatment by brush to any timber surfaces that will be concealed by the repairs.


RV.9 If present raise adequate boarding and remove any other moveable obstructions to gain access to concealed structural timber surfaces.


RV.10 Clean by brush and/or vacuum all exposed structural timber surfaces that are to receive treatment so that they are as far as practically possible free of dust.


RV.11 Read the label of the woodworm treatment material and material safety data sheet before use and take all precautions stipulated on the label including the wearing of personal protective equipment etc.


RV.12 If a water based concentrate is being used dilute sufficient woodworm treatment concentrate in accordance with the instructions and fix a dilute material label to the container. (Dilute material labels should be available from the manufacturer). Set up pump or make ready spray applicator.


RV.13 Start at one end of the roof and work backwards applying the woodworm treatment fluid using a coarse low pressure spray at the designated application rate to the visible surfaces of rafters and ceiling joists. Upon reaching the other end of the roof turn around and repeat the process treating the now other visible untreated surfaces of the rafters and ceiling joists. Treat all other structural timber surfaces - purlins, struts, collars etc. On vertical and the underside of timbers more than one application may be required to achieve the desired application rate


RV.14 Treat all surfaces of any boarding present and reinstate any disturbed sections.


RV.15 Allow treated timbers to dry thoroughly then remove temporary electrical junction box covers. Remove dustsheet from water tanks but leave plastic in position for removal later if necessary. Re-lay insulation, remove temporary lighting.


If House Longhorn Beetle (Hylotropes bajulus) is present:

Additional treatment procedures are likely to be required when dealing with House Longhorn Beetle (Hylotropes bajulus) infestation.


House Longhorn Beetle belongs to the Cerambycidae family and there are upwards of sixty species occurring naturally in the British Isles. Of all these House Longhorn Beetle shows a unique feature as not only is it able to complete its development in dried timber but it is also able to re-infest old dried timber. Damage is restricted to softwood ranging from minor extinct damage to the sapwood edges of timbers in old buildings to severe structurally damaging attacks in some modern properties. Most infestations are found in roof spaces.

If Death Watch Beetle (Xestobium rufovillosum) is present:

Additional treatment procedures are likely to be required when dealing with Death Watch Beetle (Xestobium rufovillosum) infestation.


Since Death watch beetle damage is mainly found in damp rotting hardwoods such as oak and elm it is essential to identify and rectify the source of moisture sustaining any associated fungal decay as well as any particular aspects of the building design contributing to dampness. The severity and rate of damage caused by Death watch beetle is greatest in damp conditions and may extend deep into the heartwood of affected timber. In less damp conditions only sapwood may be affected and in very dry conditions attack is prevented altogether.


Important notes when treating a roof void:

  1. Do not attempt to treat visible ceiling or wall laths as this could have an adverse affect upon the adhesion of the plaster to them.
  1. Take care not to flood treat ceiling joists as this could stain the ceilings below.
  1. Take extra care when walking on freshly treated ceiling joists as they will be slippery.
  1. Do not walk directly on a ceiling as you could fall through and cause damage to the ceiling and yourself.
  1. Refer to BRE Digests 327 & 371 for further guidance



Wood preservatives and wall treatment fluids are regulated under the Control of Pesticides Regulations 1986. Under these regulations it is an offence to supply, store, sell or use these chemicals unless they have the appropriate approval. Approved products are given an HSE number which must appear on the label. Essential information for the safe use of the products is also given on the label. Specifications for the supply or application of these chemicals should require that only products and processes approved under the regulations shall be used.

Contact Peter: Email - info@dampdecay.co.uk - Telephone: 015242 71794