Because of the damp climate in Ireland, even on a hot summer’s day, wet rot is still at work on the sub-structure of your deck, due to the moisture that is trapped between the deck boards and sub-frame. In addition to this, the quality of pressure-treated wood in Ireland is inferior to that in other countries, as the ACQ chemical used to preserve the timber is only a coating and does not penetrate to its centre. Deck flashing is the process of protecting the sub-structure of your deck using a water-proof membrane.  I recommend a self-adhesive rubber membrane applied to the tops of the joists before fitting the deck boards. This will add a minimum of 10 years to the life of your sub-structure, yet at present this procedure is seldom used in Ireland. On an average-sized deck (12’x16’) the cost of deck-flashing would be an extra €100. Remember that your flashing must be self-sealing (reseals itself when penetrated by screws) and that is why we recommend rubber. DPC or plastic will not self-seal. If you have spent time and effort researching a quality decking product, it would be a shame not to give some thought to protecting the sub-frame beneath it.

A.Mullen BetterDeck