Commercialisation of a low maintenance transparent coating is expected to assist wood products maintain residential market share in the face of competing materials and potentially expand markets in recreational property and non-residential applications. Testing of a range of commercial products had identified one outstanding performer and arrangements were made to work with the developer of this coating to further improve its performance, targeting a 15 year life under Canadian conditions. Exposure tests were set up to evaluate potential improvements in resistance to UV and to black stain fungi. Unusually favourable conditions for black stain fungi in the first six months of exposure provided some early results. Neither of the two reference coatings were as resistant to black stain as the experimental formulations. Furthermore, simply changing from the earlier manufacturers recommendation of one coat of step one and one coat of step two to two coats of step one and one of step two showed improvement in resistance to black stain. One of the modifications to the UV protectant system had a negative effect on resistance to black stain. None of the fungicides tested were more effective in protecting against black stain than IPBC, the fungicide in the commercial formulation. Furthermore a new formula of IPBC was not as effective as the older formula. However, two patterns of black stain were noted and there appeared to be some variation among fungicides in their resistance to these two patterns. A combination of IPBC and Propiconazole may be effective in protecting coatings from a broader range of black stain fungi. Further exposure is required to quantify any benefits to the UV protectant system or from pre-treatment with the hindered amine light stabiliser, Lignostab, with and without oxine copper.