BWF members such as yourselves frequently use our Member and Technical Helplines for assistance on a wide range of Employment, Health and Safety, Contractual and Technical issues. We’re putting up a frequently asked question every Tuesday in order to help members and illustrate the type of advice we are able to provide. If you have any questions that you would like to see featured, we would be happy to assist. This question and many others like it can be found in our Question Centre. If you want further advice on any of the issues, don’t hesitate to ring the helpline or browse our extensive publications library, which includes our information on Installation, Building Regulations and Maintenance. This week: What product care instructions should I supply to my customers? Oak joinery products can consist of a variety of cross sectional details, for example, solid throughout in one piece, laminated – engineered timber, as well as veneered with a softwood core. The most common oaks used are European Oak and American White Oak and both can be used externally without preservative treatment, as long as there is no sapwood present. As American White Oak is imported with a moisture content in the region of 10%, it generally needs moisture reintroduced to bring it to external in-service conditions. ‘BS EN 942:2007 Timber in Joinery General requirements’ recommends 12 to 19%. American Red Oak and Japanese Oak are not suitable for external joinery. For the application of finishes the maximum moisture content of the oak generally needs to be no greater than 16%, but coatings’ suppliers will specify what would be compatible with their products. If the oak has a veneer over a softwood core, then the core material would, most likely, require preservative treatment. If the core material is exposed, for instance at the top and bottom ends of the door stiles, then it would be appropriate to apply a preservative to the exposed end-grain. When using a preservative, it is important to let the timber become thoroughly dry before applying any finishing coats of paint or stain otherwise the finishing coats may react with the carrier solvent in the preservative if any remains present. Exterior high-build wood stains should be used as they contain resinous binders to resist moisture movement, pigments and ultra-violet absorbers to protect against degradation by sunlight and, sometimes, biocides to protect against fungal discoloration. Some high-build finishes work best when applied over an initial coat of low-build stain that provides a key, like a primer, and colour if required. Apply finishes to all faces and edges, as well as to the cut-outs where hardware is fitted, although this may not be practical. Oak contains a relatively high level of tannins throughout the wood and when painting, a stain blocking primer should be used (not required for wood stains). You should also avoid using clear varnishes as they perform poorly on exterior wood and would require frequent maintenance. Oak will react with iron to produce strong blue-black discoloration, and so contact with mild steel tools should be minimised. Non-ferrous fixings should be used, and under no circumstances should smoothing be carried out using steel wool. When stainless steel pins are used to fix beading, occasionally staining takes place at the pin head as moisture can become trapped around the filler material and if the quality of the stainless steel pin is poor then corrosion can take place.